Zoom lens and imaging apparatus

Abstract

To provide a zoom lens that is small-sized, has a wide angle of view, and has a parallax that is well corrected over a wide wavelength range from a visible region to a near-infrared region within the entire zoom range.SOLUTION: A zoom lens of the present invention has one or more lens groups having a negative refractive power, and a lens group having a positive refractive power, which are arranged in order from an object side to an image side. The one or more lens groups having a negative refractive power include a lens group BN including at least one negative lens BNn. The refractive index, Abbe number, and partial dispersion ratio of the negative lens BNn are appropriately set.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] 2. Description of the Related Art Wide-angle zoom lenses capable of capturing a wide range of images are in demand for surveillance cameras, digital still cameras, video cameras, and broadcast cameras. Imaging devices such as surveillance cameras use visible light for imaging during the day and near-infrared light for imaging at night. For example, surveillance cameras often use near-infrared light with a wavelength of 800 nm to 1000 nm for imaging at night to facilitate imaging under low illumination. For this reason, there is a demand for surveillance cameras and the like to use zoom lenses with well-corrected aberrations in a wide wavelength range from the visible range (wavelength of about 400 nm to 700 nm) to the near-infrared range.

[0003] Furthermore, from the standpoint of improving ease of handling and installation, it is desirable to reduce the size of the entire camera, which in turn requires a reduction in the size of the zoom lens. Conventionally, negative lead type zoom lenses have been known as compact zoom lenses with a wide angle of view (Patent Documents 1 and 2). In addition, negative lead type zoom lenses in which various aberrations are well corrected over a wide wavelength range from the visible region to the near infrared region are also known (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-120822 A [Patent Document 2] JP 2008-65051 A [Patent Document 3] JP 2019-61005 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a zoom lens used in a security camera or the like, it is important to have high optical performance with good correction of various aberrations, especially chromatic aberration, over a wide wavelength range from the visible region to the near infrared region. In a negative-lead zoom lens, in order to obtain high optical performance by good correction of axial chromatic aberration and lateral chromatic aberration over a wide wavelength range, it is important to appropriately set the lens configuration and the glass material of the lenses used in the lens group. If these configurations are inappropriate, it becomes very difficult to obtain a zoom lens with high optical performance over a wide angle of view while miniaturizing the entire system. SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a zoom lens that is small in size, has a wide angle of view, and has excellent correction of aberrations over the entire zoom range and across a wide wavelength range from the visible region to the near infrared region. [Means for solving the problem]

[0006] In order to achieve the above object, a zoom lens of the present invention has, in order from the object side to the image side, one or more lens groups having negative refractive power and a lens group having positive refractive power, the one or more lens groups having negative refractive power include a lens group BN including at least one negative lens BNn, and when the refractive index of the negative lens BNn is nd_BNn, the Abbe number is νd_BNn, and the partial dispersion ratio is θCt_BNn, 1.60 <nd_BNn<2.00 25.0<νd_BNn<55.0 0.4958<θCt_BNn-0.00417×νd_BNn<0.5508 The present invention is characterized in that the following conditional expression is satisfied: Effect of the Invention

[0007] According to the present invention, it is possible to provide a zoom lens that is small in size, has a wide angle of view, and has aberrations well corrected over the entire zoom range and across a wide wavelength range from the visible region to the near infrared region. [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 when focused on infinity. [Diagram 2] 4A to 4C are aberration diagrams of the zoom lens according to Example 1 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Diagram 3] FIG. 11 is a cross-sectional view of a zoom lens according to a second embodiment at the wide-angle end when focused on infinity. [Figure 4] 8A to 8C are aberration diagrams of the zoom lens according to Example 2 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Diagram 5] FIG. 11 is a cross-sectional view of a zoom lens according to Example 3 at the wide-angle end when focused on infinity. [Figure 6] 11A to 11C are aberration diagrams of the zoom lens according to Example 3 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 7] FIG. 11 is a cross-sectional view of a zoom lens according to Example 4 at the wide-angle end when focused on infinity. [Figure 8] 11A to 11C are aberration diagrams of the zoom lens according to Example 4 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 9] FIG. 11 is a cross-sectional view of a zoom lens according to Example 5 at the wide-angle end when focused on infinity. [Figure 10] 13A to 13C are aberration diagrams of the zoom lens according to Example 5 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 11] FIG. 13 is a cross-sectional view of a zoom lens according to Example 6 at the wide-angle end when focused on infinity. [Figure 12] 13A to 13C are aberration diagrams of the zoom lens according to Example 6 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 13] FIG. 13 is a cross-sectional view of a zoom lens according to Example 7 at the wide-angle end and focused on infinity. [Figure 14] 13A to 13C are aberration diagrams of the zoom lens according to Example 7 at the wide-angle end, at the intermediate focal length, and at the telephoto end. [Figure 15] 1 is a schematic diagram of an imaging device equipped with a zoom lens in each embodiment. [Figure 16] 1 is a schematic diagram of an imaging device equipped with a zoom lens in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The zoom lens of the present invention will now be described. The zoom lens of the present invention is a negative-lead zoom lens including, in order from the object side to the image side, one or more lens groups having negative refractive power and a lens group having positive refractive power, the one or more lens groups having negative refractive power including a lens group BN having negative refractive power.

[0010] The lens group BN includes at least one negative lens BNn that satisfies the following conditional expressions (1), (2), and (3). 1.60 <nd_BNn<2.00 ···(1) 25.0<νd_BNn<55.0 (2) 0.4958<θCt_BNn-0.00417×νd_BNn<0.5508 (3) Here, nd_BNn, νd_BNn, and θCt_BNn respectively indicate the refractive index, the Abbe number, and the partial dispersion ratio of the negative lens BNn.

[0011] Here, when the refractive indices at the d-line, C-line, t-line, and F-line of the Fraunhofer lines are nd, nC, nt, and nF, respectively, the Abbe number νd and the partial dispersion ratio θCt are given as follows: νd=(nd-nt) / (nF-nC) θCt=(nC-nt) / (nF-nC)

[0012] Conditional formula (1) defines the range of the refractive index of the negative lens BNn. If the upper limit of conditional formula (1) is exceeded, there is practically no choice of glass material. If the lower limit of conditional formula (1) is exceeded, the refractive index of the glass material is too small, so the curvature becomes large in order to maintain the refractive power of the negative lens BNn, which undesirably worsens various aberrations.

[0013] Conditional formula (2) specifies the range of the Abbe number of the negative lens BNn. Since the lens group BN has negative refractive power, it is desirable that the negative lens BNn included in the lens group BN has low dispersion in order to reduce chromatic aberration. If the upper limit of conditional formula (2) is exceeded, a glass material having a higher refractive index in the near infrared region than in the visible region is selected, which is undesirable because the chromatic aberration of magnification in the near infrared region is worsened compared to the visible region when the chromatic aberration of magnification in the visible region is corrected. If the lower limit of conditional formula (2) is exceeded, the dispersion becomes too high, which is undesirable because the chromatic aberration of magnification in the visible region is worsened.

[0014] Conditional formula (3) defines the range of the partial dispersion ratio of the negative lens BNn. If the upper limit of conditional formula (3) is exceeded, the partial dispersion ratio value becomes too large, which is undesirable because it becomes difficult to obtain a sufficient correction effect for lateral chromatic aberration in the near infrared region. If the lower limit of conditional formula (3) is exceeded, there is essentially no choice of glass material.

[0015] It is more preferable to restrict conditional expressions (1), (2), and (3) as follows: 1.65 <nd_BNn<1.93 ···(1a) 29.0<νd_BNn<53.0 (2a) 0.5108<θCt_BNn-0.00417×νd_BNn<0.5508 (3a)

[0016] Moreover, it is more preferable to further restrict conditional expressions (1a), (2a), and (3a) as follows: 1.69 <nd_BNn<1.87 ···(1b) 32.0<νd_BNn<52.0 (2b) 0.5208<θCt_BNn-0.00417×νd_BNn<0.5508 (3b)

[0017] In order to reduce the size of the entire system, the zoom lens of the present invention includes a total of five or less lens groups. The zoom lens of the present invention also includes, in order from the object side to the image side, two or less lens groups with negative refractive power and a lens group with positive refractive power.

[0018] In order to ensure a wide angle of view while miniaturizing the entire system, it is preferable to arrange a lens group with a strong negative refractive power as close to the object as possible, and such a strong negative lens group contributes greatly to the occurrence of various aberrations such as field curvature and chromatic aberration of magnification. Therefore, the lens group BN is the lens group with the largest (strongest) negative refractive power among the negative lens groups (the one or more lens groups with negative refractive power) arranged closer to the object than the lens group with positive refractive power arranged closest to the object. The occurrence of various aberrations is suppressed by defining the negative lens BNn as in the above conditional expressions (1), (2), and (3).

[0019] Furthermore, in order to reduce various aberrations throughout the entire zoom range, it is effective to reduce the curvature of each negative lens by including multiple negative lenses in the lens group BN. The more negative lenses included in the lens group BN, the easier it is to reduce the amount of various aberrations, but it becomes difficult to achieve compactness, so it is necessary to select an appropriate number of lenses while taking into account the balance between these two. Therefore, in order to achieve both the suppression of various aberrations and compactness, the number of negative lenses included in the lens group BN is set to between two and four.

[0020] Moreover, the lens unit BN has at least one positive lens BNp that satisfies the following conditional expression (4). 20.0<νd_BNp<40.0 (4) Here, νd_BNp indicates the Abbe number of the positive lens BNp.

[0021] Conditional formula (4) defines the range of the Abbe number of the positive lens BNp. Since the lens group BN has a negative refractive power as a whole, it is desirable that the positive lens included in the lens group BN has high dispersion in order to reduce chromatic aberration. If the upper limit of conditional formula (4) is exceeded, the positive lens BNp will have too low dispersion, which is undesirable as it will worsen the lateral chromatic aberration in the visible range. If the lower limit of conditional formula (4) is exceeded, a glass material with a smaller refractive index in the near-infrared range than in the visible range will be selected, which is undesirable as it will worsen the lateral chromatic aberration in the near-infrared range compared to the visible range when the lateral chromatic aberration in the visible range is corrected.

[0022] It is more preferable to restrict condition (4) as follows: 23.0<νd_BNp<38.0 (4a) Moreover, it is more preferable to further restrict condition (4a) as follows: 24.0<νd_BNp<37.5 (4b)

[0023] When the distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the lens group BN is D_BN and the focal length of the lens group BN is f_BN, the following conditional expression (5) is satisfied. 0.5<|f_BN / D_BN|<3.0 (5) Condition (5) is intended to reduce the size of the entire system and to widen the angle of view. If the upper limit of condition (5) is exceeded, the absolute value of the refractive power of lens unit BN becomes too small, making it difficult to achieve a wide angle of view. If the lower limit of condition (5) is exceeded, the thickness of lens unit BN increases, making it difficult to achieve a compact size.

[0024] It is more preferable to restrict condition (5) as follows: 0.5<|f_BN / D_BN|<2.6 (5a) Moreover, it is more preferable to further restrict condition (5a) as follows: 0.5<|f_BN / D_BN|<2.3 (5b)

[0025] Among lens groups having three or more lenses and positive refractive power, the lens group arranged closest to the object side is designated as lens group BP, and lens group BP has at least one negative lens BPn that satisfies the following conditional expressions (6), (7), and (8). 1.40 <nd_BPn<2.00 ···(6) 15.0<νd_BPn<61.0 (7) 0.5408<θCt_BPn-0.00528×νd_BPn<0.5808 (8) Here, nd_BPn, νd_BPn, and θCt_BPn respectively indicate the refractive index, the Abbe number, and the partial dispersion ratio of the negative lens BPn.

[0026] Conditional formula (6) defines the range of the refractive index of the negative lens BPn. If the upper limit of conditional formula (6) is exceeded, there is practically no choice of glass material. If the lower limit of conditional formula (6) is exceeded, the refractive index of the glass material is too small, so the curvature becomes large in order to maintain the refractive power of the negative lens BPn, which undesirably worsens various aberrations.

[0027] Conditional formula (7) defines the range of the Abbe number of the negative lens BPn. Since the lens group BP has a positive refractive power as a whole, it is desirable that the negative lens included in the lens group BP has low dispersion in order to reduce chromatic aberration. If the upper limit of conditional formula (7) is exceeded, the positive lens becomes too highly dispersed, which is undesirable as it worsens the axial chromatic aberration in the visible range. If the lower limit of conditional formula (7) is exceeded, a glass material with a smaller refractive index in the near-infrared range than in the visible range is selected, which is undesirable as it worsens the axial chromatic aberration in the near-infrared range compared to the visible range when the axial chromatic aberration in the visible range is corrected.

[0028] Conditional formula (8) defines the range of the partial dispersion ratio of the negative lens BPn. If the upper limit of conditional formula (8) is exceeded, there is practically no choice of glass material. If the lower limit of conditional formula (8) is exceeded, the partial dispersion ratio value is too small, making it difficult to obtain a sufficient correction effect for axial chromatic aberration in the near-infrared region, which is undesirable.

[0029] It is more preferable to restrict conditions (6), (7), and (8) as follows: 1.55 <nd_BPn<1.93 ···(6a) 21.0<νd_BPn<60.0 (7a) 0.5408<θCt_BPn-0.00528×νd_BPn<0.5628 (8a)

[0030] Moreover, it is more preferable to further restrict conditional expressions (6a), (7a), and (8a) as follows: 1.60 <nd_BPn<1.87 ···(6b) 24.0<νd_BPn<59.0 (7b) 0.5408<θCt_BPn-0.00528×νd_BPn<0.5508 (8b)

[0031] In order to achieve compactness while reducing various aberrations throughout the entire zoom range, the lens group BP contains two or less negative lenses.

[0032] The lens unit BP has at least one positive lens BPp that satisfies the following conditional expression (9). 70.5<νd_BPp<100.0 (9) Here, νd_BPp indicates the Abbe number of the positive lens BPp.

[0033] Conditional formula (9) defines the range of the Abbe number of the positive lens BPp. Since the lens group BP has positive refractive power as a whole, it is desirable for the positive lens BPp included in the lens group BP to have low dispersion in order to reduce chromatic aberration. If the upper limit of conditional formula (9) is exceeded, there is essentially no choice of glass material. If the lower limit of conditional formula (9) is not satisfied, the positive lens BPp will have too high dispersion, which undesirably worsens axial chromatic aberration in the visible range.

[0034] It is more preferable to restrict condition (9) as follows: 75.0<νd_BPp<98.0 (9a) Moreover, it is more preferable to further restrict condition (9a) as follows: 81.5<νd_BPp<95.0 (9b) The lens group BP has a variable magnification function, and by moving toward the object side during zooming from the wide-angle end to the telephoto end, various aberrations are reduced while the overall system is made compact. Note that in this specification, the wide-angle end and the telephoto end refer to the zoom positions when the optical system that moves for zooming is located at both ends of the range in which it can move mechanically in the direction along the optical axis.

[0035] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1, 3, 5, 7, 9, 11, and 13 are lens cross-sectional views at the wide-angle end of Numerical Examples 1 to 7 described below. In each lens cross-sectional view, B1 to B5 are first to fifth lens groups, FC is a focus group, AP is an aperture stop, G is a glass block such as a CCD or CMOS cover glass, a low-pass filter, or an IR (infrared) cut filter, and IM is an image plane.

[0036] The arrows in the lens cross-sectional view indicate the movement locus of each lens group during zooming from the wide-angle end to the telephoto end. When focusing from infinity to a close distance, the focus group FC is moved on the optical axis in the direction indicated by the left and right arrows in the drawing. Among the movement loci of the lens groups in the lens cross-sectional view, the solid curve indicates the movement locus for correcting the image plane fluctuation accompanying zooming from the wide-angle end to the telephoto end when focusing on an object at infinity, and the dotted curve indicates the movement locus for correcting the image plane fluctuation accompanying zooming from the wide-angle end to the telephoto end when focusing on an object at close range. In addition, the aperture stop AP is fixed in Numerical Examples 1 and 2, and moves in the direction indicated by the arrows during zooming from the wide-angle end to the telephoto end in Numerical Examples 3, 4, 5, 6, and 7.

[0037] In addition, in a surveillance camera or the like, there are cases where a daytime shooting mode and a nighttime shooting mode are switched. An IR cut filter may be inserted or removed according to the shooting mode using an insertion / removal mechanism (not shown), or the IR cut filter may be switched to another filter (for example, a filter that cuts visible light) using a switching mechanism (not shown).

[0038] 2, 4, 6, 8, 10, 12, and 14 are aberration diagrams of the respective numerical examples at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C). In each aberration diagram, d, g, and 940 represent the d-line, g-line, and wavelength 940 nm, M and S represent the meridional image plane and sagittal image plane, distortion is shown for the d-line, and lateral chromatic aberration is shown for the g-line and wavelength 940 nm. Numerical data of the numerical embodiments of the present invention will be described in Numerical Embodiment 1 to Numerical Embodiment 7. In each numerical example, the paraxial radius of curvature r (mm) of each surface from the object side, the distance d (mm) between each surface and the next surface, the refractive index nd of each glass material for the d line, the Abbe number νd, and the partial dispersion ratio θCt are given.

[0039] A surface with an * to the right of the surface number has an aspheric shape expressed by the following formula.

number

[0040] FIG. 1 is a cross-sectional view of a zoom lens according to a first embodiment at the wide-angle end when focused on infinity. The zoom lens of the first embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, an aperture stop AP, and a second lens group B2 with positive refractive power. During zooming, the distances between adjacent lens groups and the aperture stop AP change. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11, a negative lens L12, a positive lens L13, and a negative lens L14. The second lens group B2 is composed of, in order from the object side to the image side, a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, and a negative lens L25.

[0041] When zooming from the wide-angle end to the telephoto end, the first lens unit B1 moves toward the image side, and the second lens unit B2 moves toward the object side. The aperture stop AP does not move for zooming. Also, when focusing from infinity to a close distance, the first lens unit moves toward the object side. In the zoom lens according to the first embodiment, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L11, the lens group BP is the second lens group B2, the negative lens BPn is the negative lenses L23 and L25, and the positive lens BPp is the positive lenses L21 and L22.

[0042] Table 1 shows the relationships between various numerical values ​​in Numerical Example 1 corresponding to Example 1 and each conditional expression. Conditional expressions (1), (2), and (3) show values ​​for the negative lens L11. Conditional expression (4) shows values ​​for the positive lens L13. Conditional expression (5) shows values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) show values ​​for the negative lens L25. Conditional expression (9) shows values ​​for the positive lens L22. The zoom lens of Numerical Example 1 satisfies all of the conditional expressions.

[0043] 2 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 1. It can be seen that the zoom lens of Numerical Example 1 has excellent aberration correction. As described above, the zoom lens of Numerical Example 1 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible region to the near infrared region over the entire zoom range. EXAMPLES

[0044] FIG. 3 is a cross-sectional view of the zoom lens according to the second embodiment at the wide-angle end when focused on infinity. The zoom lens of the second embodiment is composed of, from the object side to the image side, a first lens group B1 with negative refractive power, an aperture stop AP, a second lens group B2 with positive refractive power, and a third lens group B3 with negative refractive power. During zooming, the mutual distances between the adjacent lens groups and the aperture stop AP change. The first lens group B1 is composed of, from the object side to the image side, a negative lens L11, a negative lens L12, a positive lens L13, and a negative lens L14. The second lens group B2 is composed of, from the object side to the image side, a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, and a negative lens L25. The third lens group B3 is composed of, from the object side to the image side, a negative lens L31 and a positive lens L32.

[0045] When zooming from the wide-angle end to the telephoto end, the first lens group B1 moves toward the image side, and the second lens group B2 moves toward the object side. The aperture stop AP and the third lens group B3 do not move for zooming. When focusing from infinity to a close distance, the first lens group B1 moves toward the object side.

[0046] In the zoom lens according to the second embodiment, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L11, the lens group BP is the second lens group B2, the negative lens BPn is the negative lenses L23 and L25, and the positive lens BPp is the positive lenses L21 and L22.

[0047] Table 1 shows the relationships between various numerical values ​​in the second numerical embodiment corresponding to the second embodiment and each conditional expression. Conditional expressions (1), (2), and (3) indicate values ​​for the negative lens L11. Conditional expression (4) indicates values ​​for lens L13. Conditional expression (5) indicates values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) indicate values ​​for the negative lens L23. Conditional expression (9) indicates a value for the positive lens L22. The zoom lens of Numerical Example 2 satisfies all of the conditional expressions.

[0048] 4 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 2. It can be seen that the zoom lens of Numerical Example 2 has excellent aberration correction. As described above, the zoom lens of Numerical Example 2 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible region to the near infrared region over the entire zoom range. EXAMPLES

[0049] FIG. 5 is a cross-sectional view of the zoom lens according to the third embodiment at the wide-angle end and focused on infinity. The zoom lens of the third embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, an aperture stop AP, a second lens group B2 with positive refractive power, and a third lens group B3 with positive refractive power. During zooming, the mutual distances between the adjacent lens groups and the aperture stop AP change. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11, a negative lens L12, and a positive lens L13. The second lens group B2 is composed of, in order from the object side to the image side, a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, and a negative lens L25. The third lens group B3 is composed of a positive lens L31.

[0050] During zooming from the wide-angle end to the telephoto end, the first lens group B1 moves toward the image side and then toward the object side, and the aperture stop AP and the second lens group B2 move toward the object side. The third lens group B3 does not move for zooming. During focusing from infinity to a close distance, the first lens group B1 moves toward the object side.

[0051] In the zoom lens of Example 3, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L12, the lens group BP is the second lens group B2, the negative lens BPn is the negative lenses L23 and L25, and the positive lens BPp is the positive lenses L21, L22, and L24.

[0052] Table 1 shows the relationships between various numerical values ​​in Numerical Example 3 corresponding to Example 3 and each conditional expression. Conditional expressions (1), (2), and (3) indicate values ​​for the negative lens L12. Conditional expression (4) indicates values ​​for the positive lens L13. Conditional expression (5) indicates values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) indicate values ​​for the negative lens L25. Conditional expression (9) indicates a value for the positive lens L22. The zoom lens of Numerical Example 3 satisfies all of the conditional expressions.

[0053] 6 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 3. It can be seen that the zoom lens of Numerical Example 3 has excellent aberration correction. As described above, the zoom lens of Numerical Example 3 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over the entire zoom range over a wide wavelength range from the visible range to the near infrared range. EXAMPLES

[0054] FIG. 7 is a cross-sectional view of the zoom lens according to the fourth embodiment at the wide-angle end and focused on infinity. The zoom lens of the fourth embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, a second lens group B2 with negative refractive power, an aperture stop AP, a third lens group B3 with positive refractive power, and a fourth lens group B4 with positive refractive power. During zooming, the mutual distances between the adjacent lens groups and the aperture stop AP change. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11 and a negative lens L12. The second lens group B2 is composed of, in order from the object side to the image side, a negative lens L21, a negative lens L22, and a positive lens L23. The third lens group B3 is composed of, in order from the object side to the image side, a positive lens L31, a positive lens L32, a negative lens L33, a positive lens L34, and a negative lens L35. The fourth lens group B4 is composed of a positive lens L41.

[0055] During zooming from the wide-angle end to the telephoto end, the second lens group B2 moves toward the image side and then toward the object side, and the aperture stop AP and the third lens group B3 move toward the object side. The first lens group B1 and the fourth lens group B4 do not move for zooming. During focusing from infinity to a close distance, the second lens group B2 moves toward the object side.

[0056] In the zoom lens of Example 4, the lens group BN having negative refractive power is the second lens group B2, the negative lens BNn is the negative lens L21, the lens group BP is the third lens group B3, the negative lens BPn is the negative lenses L33 and L35, and the positive lens BPp is the positive lenses L31, L32 and L34.

[0057] Table 1 shows the relationships between various numerical values ​​in the fourth numerical embodiment corresponding to the fourth embodiment and each conditional expression. Conditional expressions (1), (2), and (3) indicate values ​​for the negative lens L21. Conditional expression (4) indicates values ​​for the positive lens L23. Conditional expression (5) indicates values ​​calculated for the second lens group B2. Conditional expressions (6), (7), and (8) indicate values ​​for the negative lens L35. Conditional expression (9) indicates a value for the positive lens L32. The zoom lens of Numerical Example 4 satisfies all of the conditional expressions.

[0058] 8 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 4. It can be seen that the zoom lens of Numerical Example 4 has excellent aberration correction. As described above, the zoom lens of Numerical Example 4 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible region to the near infrared region over the entire zoom range. EXAMPLES

[0059] FIG. 9 is a cross-sectional view of the zoom lens according to the fifth embodiment at the wide-angle end when focused on infinity. The zoom lens of the fifth embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, a second lens group B2 with positive refractive power, a third lens group B3 with negative refractive power, and a fourth lens group B4 with positive refractive power. During zooming, the interval between adjacent lens groups changes. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11, a negative lens L12, and a positive lens L13. The second lens group B2 is composed of, in order from the object side to the image side, an aperture stop AP, a positive lens L21, a positive lens L22, a negative lens L23, a negative lens L24, and a positive lens L25. The third lens group B3 is composed of a negative lens L31. The fourth lens group B4 is composed of, in order from the object side to the image side, a positive lens L41, a negative lens L42, and a positive lens L43.

[0060] When zooming from the wide-angle end to the telephoto end, the second lens group B2 moves toward the object side, the third lens group B3 moves toward the object side and then moves toward the image side, and the fourth lens group B4 moves. The first lens group B1 does not move for zooming. Also, when focusing from infinity to a close distance, the third lens group B3 moves toward the image side.

[0061] In the zoom lens of Example 5, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L11, the lens group BP is the second lens group B2, the negative lens BPn is the negative lens L24, and the positive lens BPp is the positive lenses L22 and L25.

[0062] Table 1 shows the relationships between various numerical values ​​in Numerical Example 5 corresponding to Example 5 and each conditional expression. Conditional expressions (1), (2), and (3) show values ​​for the negative lens L11. Conditional expression (4) shows values ​​for the positive lens L13. Conditional expression (5) shows values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) show values ​​for the negative lens L24. Conditional expression (9) shows values ​​for the positive lens L22. The zoom lens of Numerical Example 5 satisfies all of the conditional expressions.

[0063] 10 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 5. It can be seen that the zoom lens of Numerical Example 5 has excellent aberration correction. As described above, the zoom lens of Numerical Example 5 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible range to the near infrared range over the entire zoom range. EXAMPLES

[0064] FIG. 11 is a cross-sectional view of the zoom lens according to the sixth embodiment at the wide-angle end and focused on infinity. The zoom lens of the sixth embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, a second lens group B2 with positive refractive power, a third lens group B3 with negative refractive power, a fourth lens group B4 with negative refractive power, and a fifth lens group B5 with positive refractive power. During zooming, the interval between adjacent lens groups changes. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11, a negative lens L12, a negative lens L13, a positive lens L14, and a negative lens L15. The second lens group B2 is composed of, in order from the object side to the image side, an aperture stop AP, a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26. The third lens group B3 is composed of, in order from the object side to the image side, a negative lens L31, and positive lenses L32, L33, and L34. The fourth lens group B4 is composed of a negative lens L41, and the fifth lens group B5 is composed of a positive lens L51.

[0065] During zooming from the wide-angle end to the telephoto end, the second lens group B2 moves toward the object side, the third lens group B3 moves toward the object side, and the fourth lens group B4 moves toward the object side and then moves toward the image side. The first lens group B1 and the fifth lens group B5 do not move for zooming. During focusing from infinity to a close distance, the fourth lens group B4 moves toward the image side.

[0066] In the zoom lens of Example 6, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L11, the lens group BP is the second lens group B2, the negative lens BPn is the negative lenses L23 and L25, and the positive lens BPp is the positive lenses L24 and L26.

[0067] Table 1 shows the relationships between various numerical values ​​in Numerical Example 6 corresponding to the sixth embodiment and each conditional expression. Conditional expressions (1), (2), and (3) indicate values ​​for the negative lens L11. Conditional expression (4) indicates values ​​for lens L14. Conditional expression (5) indicates values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) indicate values ​​for the negative lens L23. Conditional expression (9) indicates a value for the positive lens L24. The zoom lens of Numerical Example 6 satisfies all of the conditional expressions.

[0068] 12 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 6. It can be seen that the zoom lens of Numerical Example 6 has excellent aberration correction. As described above, the zoom lens of Numerical Example 6 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over the entire zoom range over a wide wavelength range from the visible region to the near infrared region. EXAMPLES

[0069] FIG. 13 is a cross-sectional view of the zoom lens according to the seventh embodiment at the wide-angle end and focused on infinity. The zoom lens of the seventh embodiment is composed of, in order from the object side to the image side, a first lens group B1 with negative refractive power, a second lens group B2 with positive refractive power, a third lens group B3 with positive refractive power, a fourth lens group B4 with negative refractive power, and a fifth lens group B5 with positive refractive power. During zooming, the interval between adjacent lens groups changes. The first lens group B1 is composed of, in order from the object side to the image side, a negative lens L11, a negative lens L12, a negative lens L13, a positive lens L14, and a negative lens L15. The second lens group B2 is composed of, in order from the object side to the image side, a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26. The third lens group B3 is composed of, in order from the object side to the image side, a negative lens L31, a positive lens L32, a positive lens L33, and a positive lens L34. The fourth lens group B4 is composed of a negative lens L41, and the fifth lens group B5 is composed of a positive lens L51.

[0070] During zooming from the wide-angle end to the telephoto end, the second lens group B2 moves toward the object side, the third lens group B3 moves toward the object side, and the fourth lens group B4 moves toward the object side. The first lens group B1 and the fifth lens group B5 do not move for zooming. During focusing from infinity to a close distance, the fourth lens group B4 moves toward the image side.

[0071] In the zoom lens of Example 7, the lens group BN having negative refractive power is the first lens group B1, the negative lens BNn is the negative lens L11, the lens group BP is the second lens group B2, the negative lens BPn is the negative lenses L23 and L25, and the positive lens BPp is the positive lenses L24 and L26.

[0072] Table 1 shows the relationships between various numerical values ​​in Numerical Example 7 corresponding to the Seventh Embodiment and each conditional expression. Conditional expressions (1), (2), and (3) show values ​​for the negative lens L11. Conditional expression (4) shows values ​​for the positive lens L14. Conditional expression (5) shows values ​​calculated for the first lens group B1. Conditional expressions (6), (7), and (8) show values ​​for the negative lens L23. Conditional expression (9) shows values ​​for the positive lens L24. The zoom lens of Numerical Example 7 satisfies all of the conditional expressions.

[0073] 14 is aberration diagrams at the wide-angle end (A), at the intermediate focal length (B), and at the telephoto end (C) of the zoom lens of Numerical Example 7. It can be seen that the zoom lens of Numerical Example 7 has excellent aberration correction. As described above, the zoom lens of Numerical Example 7 realizes a zoom lens that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible region to the near infrared region over the entire zoom range.

[0074] (Imaging device) Next, an embodiment of an image pickup apparatus using the zoom lens of the present invention as a photographing optical system will be described with reference to FIGS. 15 and 16, reference numeral 16 denotes a photographing optical system constituted by the zoom lens of the present invention. Reference numerals 10 and 11 denote a surveillance camera (imaging device) body, and reference numeral 12 denotes an imaging element such as a CCD or CMOS that receives a subject image formed by the photographing optical system 16. Reference numeral 13 denotes a recording means for recording information corresponding to the subject image received by the imaging element 12, reference numeral 14 denotes a transfer means for transferring information corresponding to the subject image received by the imaging element 12, and reference numeral 15 denotes a cover for protecting the surveillance camera body 11 and the photographing optical system 16.

[0075] In this way, by applying the zoom lens of the present invention to an imaging device such as a surveillance camera, it is possible to realize an imaging device that is small in size, has a wide angle of view, and has excellent aberration correction over a wide wavelength range from the visible to the near-infrared region over the entire zoom range. The imaging device is not limited to a surveillance camera, but may also be a video camera, a digital camera, or the like. In addition to the above, the imaging device of the present invention may also have an aberration correcting means, such as a circuit for electrically correcting aberration.

[0076] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and variations are possible within the scope of the gist of the present invention. For example, the number of lenses in each group may be changed, the number of aspherical lenses may be increased, or the number of subsequent lens groups may be changed, as long as the requirements of the present invention are satisfied.

[0077] (Numerical Example 1) Unit: mm Surface Data Surface number rd nd vd θct 1 29.721 0.70 1.85920 33.0 0.686 2 7.274 7.00 3 -16.563 0.90 1.49700 81.5 0.826 4 16.369 1.07 5 17.278 3.00 1.73800 32.3 0.715 6 -18.856 0.70 1.52841 76.5 0.818 7 37.024 (variable) 8 (Aperture) ∞ (Variable) 9* 9.154 2.52 1.55332 71.7 0.816 10* -20.215 0.42 11 15.422 3.50 1.43875 94.7 0.841 12 -10.031 0.10 13 19.606 0.49 1.85478 24.8 0.674 14 6.039 1.01 15* 12.915 2.43 1.76802 49.2 0.789 16 -4.994 1.60 1.67300 38.3 0.748 17 19.706 (variable) 18 ∞ 1.96 1.51400 70.0 19∞0.50 Image plane ∞ Aspheric Data 9th page K = 0.00000e+00 A 4=-3.79778e-04 A 6=-1.16991e-06 A 8=-2.22422e-07 Side 10 K = 0.00000e+00 A 4= 3.78175e-04 A 6=-3.65070e-06 Page 15 K = 0.00000e+00 A 4=-1.98800e-04 A 6=-1.09240e-05 Various data Zoom ratio 2.30 Wide-angle end Mid-range Telephoto end Focal length 2.68 4.07 6.16 F-number 1.24 1.49 1.85 Half angle of view 73.09 43.69 28.13 Image height 3.04 3.04 3.04 Lens length 49.38 40.72 36.27 BF 4.46 5.89 8.03 d 7 15.81 7.14 2.70 d 8 3.67 2.24 0.10 d17 2.67 4.09 6.23 Zoom lens group data Group starting plane focal length 1 1 -8.79 2 9 9.00 Single lens data Lens starting surface focal length 1 1 -11.37 2 3 -16.42 3 5 12.66 4 6 -23.54 5 9 11.75 6 11 14.46 7 13 -10.38 8 15 4.98 9 16 -5.77

[0078] (Numerical Example 2) Unit: mm Surface Data Surface number rd nd vd θct 1 35.601 0.70 1.85920 33.0 0.686 2 7.631 7.00 3 -21.129 0.90 1.49700 81.5 0.826 4 13.533 1.76 5 17.429 3.12 1.78880 28.4 0.694 6 -20.334 2.36 1.83481 42.7 0.756 7 139.125 (variable) 8 (Aperture) ∞ (Variable) 9* 10.838 2.48 1.55332 71.7 0.816 10* -13.130 0.67 11 11.079 4.00 1.43875 94.7 0.841 12 -13.213 0.10 13 25.581 0.44 1.85478 24.8 0.674 14 5.534 0.60 15 25.701 1.67 1.76385 48.5 0.769 16 -7.634 0.50 1.73800 32.3 0.715 17 -28.550 (variable) 5.64 18 -23.690 0.50 1.65412 39.7 0.756 19 36.392 0.37 20 -25.682 1.23 1.85150 40.8 0.739 21 -11.726 2.44 22∞1.96 1.51400 70.0 23∞0.50 Image plane ∞ Aspheric Data 9th page K = 0.00000e+00 A 4=-3.96779e-04 A 6=-1.76656e-06 A 8=-3.17779e-07 Side 10 K = 0.00000e+00 A 4= 2.33037e-04 A 6=-4.60764e-06 A 8=-1.97114e-07 Various data Zoom ratio 2.30 Wide-angle end Mid-range Telephoto end Focal length 2.74 4.17 6.30 F-number 1.50 1.76 2.16 Half angle of view 72.72 42.57 27.40 Image height 3.04 3.04 3.04 Lens length 53.87 44.24 39.16 BF 4.24 4.24 4.24 d 7 17.07 7.44 2.36 d8 3.63 2.22 0.10 d17 0.53 1.94 4.06 Zoom lens group data Group starting plane focal length 1 1 -8.72 3 9 9.36 4 18 -700.01 Single lens data Lens starting surface focal length 1 1 -11.44 2 3 -16.46 3 5 12.35 4 6 -21.11 5 9 11.14 6 11 14.46 7 13 -8.35 8 15 7.88 9 16 -14.26 10 18 -21.86 11 20 24.36

[0079] (Numerical Example 3) Unit: mm Surface Data Surface number rd nd vd θct 1 52.948 0.70 1.49700 81.5 0.826 2 7.674 4.00 3 -11.208 0.50 1.69930 51.1 0.760 4 10.502 0.10 5 11.227 2.13 2.00330 28.3 0.684 6 -134.899 (variable) 7 (Aperture) ∞ (Variable) 8* 7.080 2.99 1.55332 71.7 0.816 9* -21.235 0.10 10 7.704 1.94 1.49700 81.5 0.826 11 -14.948 1.16 1.73800 32.3 0.715 12 7.791 2.75 13* 7.514 3.00 1.55332 71.7 0.816 14* -8.856 0.56 15 -4.697 0.50 1.65160 58.5 0.852 16 26.274 (variable) 17 17.346 1.55 1.95906 17.5 0.626 18 -97.671 0.89 19 ∞ 0.80 1.51000 60.0 20∞0.50 Image plane ∞ Aspheric Data Side 8 K = 0.00000e+00 A 4=-2.41442e-04 A 6=-2.93273e-06 A 8=-1.31398e-07 9th page K = 0.00000e+00 A 4= 1.46781e-04 A 6=-4.13146e-06 Page 13 K = 0.00000e+00 A 4=-4.04672e-05 A 6=-2.25562e-06 Side 14 K = 0.00000e+00 A 4=-2.01018e-04 A 6= 1.00971e-05 A 8=-6.79161e-06 Various data Zoom ratio 4.89 Wide-angle end Mid-range Telephoto end Focal length 4.41 9.89 21.55 F-number 1.85 2.88 5.09 Half angle of view 46.53 18.41 8.40 Image height 3.20 3.20 3.20 Lens length 39.92 35.15 41.55 BF 1.92 1.92 1.92 d 6 14.76 4.98 0.70 d 7 0.75 0.77 0.80 d16 0.50 5.51 16.15 Zoom lens group data Group starting plane focal length 1 1 -11.09 3 8 8.42 4 17 15.46 Single lens data Lens starting surface focal length 1 1 -18.15 2 3 -7.68 3 5 10.41 4 8 9.97 5 10 10.53 6 11 -6.79 7 13 7.86 8 15 -6.08 9 17 15.46

[0080] (Numerical Example 4) Unit: mm Surface Data Surface number rd nd vd θct 1 22.667 0.60 1.88300 40.8 0.734 2 22.127 0.12 3 24.339 0.60 1.89190 37.1 0.720 4 17.554 (variable) 5 17.408 0.60 1.75106 43.1 0.710 6 7.209 4.00 7 -17.254 0.50 1.49700 81.5 0.826 8 11.783 0.10 9 11.210 1.31 1.96300 24.1 0.661 10 39.197 (variable) 11 (Aperture) ∞ (Variable) 12* 8.568 1.39 1.55332 71.7 0.816 13* -22.436 0.10 14 5.750 2.21 1.49700 81.5 0.826 15 -29.870 2.50 1.73800 32.3 0.715 16 5.021 1.84 17* 8.599 3.00 1.55332 71.7 0.816 18* -5.745 0.35 19 -3.705 0.50 1.61340 44.3 0.783 20 229.578 (variable) 21 11.411 1.02 1.95906 17.5 0.626 22 80.414 0.97 0.626 23 ∞ 0.80 1.51000 60.0 24∞0.50 Image plane ∞ Aspheric Data Side 12 K = 0.00000e+00 A 4=-8.52142e-05 A 6=-2.98726e-06 A 8=-1.35718e-07 Page 13 K = 0.00000e+00 A 4= 1.37104e-04 A 6=-5.89903e-06 Page 17 K = 0.00000e+00 A 4=-5.77343e-04 A 6=-7.87271e-05 Side 18 K = 0.00000e+00 A 4=-1.47624e-03 A 6=-9.72761e-05 A 8=-1.26067e-05 Various data Zoom ratio 4.89 Wide-angle end Mid-range Telephoto end Focal length 4.35 9.15 21.26 F-number 1.85 2.88 5.09 Half angle of view 41.58 19.50 8.40 Image height 3.20 3.20 3.20 Lens length 41.00 41.00 41.00 BF 2.00 2.00 2.00 d 4 1.11 6.81 0.97 d10 16.54 5.81 0.98 d11 0.10 0.32 0.80 d20 0.50 5.30 15.49 Zoom lens group data Group starting plane focal length 1 1 -72.10 2 5 -14.20 4 12 8.49 5 21 13.77 Single lens data Lens starting surface focal length 1 1 -2199.05 2 3 -73.66 3 5 -16.81 4 7 -14.01 5 9 15.94 6 12 11.39 7 14 9.91 8 15 -5.65 9 17 6.73 10 19 -5.94 11 21 13.77

[0081] (Numerical Example 5) Unit: mm Surface Data Surface number rd nd vd θct 1 201.037 2.64 1.75106 43.1 0.710 2 19.452 13.35 3 -38.541 2.98 1.49700 81.5 0.826 4 106.807 0.15 5 56.207 5.00 1.85478 24.8 0.674 6 33866.841 (variable) 7(Aperture) ∞ 1.00 8* 32.079 6.00 1.58313 59.4 0.827 9* -67.427 1.43 10 17.359 4.99 1.49700 81.5 0.826 11 852.564 1.00 1.51742 52.4 0.800 12 14.743 2.78 13 63.102 1.00 1.73800 32.3 0.715 14 17.160 4.74 1.49700 81.5 0.826 15 -35.791 (variable) 16 -47.590 1.00 1.51633 64.1 0.869 17 64.651 (variable) 18 26.098 4.90 1.80400 46.5 0.772 19 -274.816 1.80 1.65412 39.7 0.755 20 19.160 1.21 21 24.911 5.00 1.49700 81.5 0.826 22 -69.372 (variable) 23∞1.20 1.51400 70.0 24∞1.00 Image plane ∞ Aspheric Data Side 8 K = 0.00000e+00 A 4=-6.25545e-06 A 6= 6.40561e-09 A 8=-4.09596e-11 9th page K = 0.00000e+00 A 4= 4.36302e-06 A 6= 4.11537e-09 A 8=-3.34407e-11 Various data Zoom ratio 3.90 Wide-angle end Mid-range Telephoto end Focal length 12.30 21.47 48.01 F-number 1.75 2.65 4.00 Half angle of view 55.56 29.16 12.79 Image height 10.75 10.75 10.75 Lens length 123.99 123.99 123.99 BF 14.31 7.14 7.14 d 6 41.99 25.60 1.01 d15 3.13 10.75 36.01 d17 3.59 19.53 18.87 d22 12.52 5.35 5.35 Zoom lens group data Group starting plane focal length 1 1 -27.14 2 7 29.76 3 16 -52.93 4 18 40.61 Single lens data Lens starting surface focal length 1 1 -28.85 2 3 -56.60 3 5 65.86 4 8 38.12 5 10 35.58 6 11 -29.01 7 13 -32.24 8 14 24.05 9 16 -52.93 10 18 29.86 11 19 -27.32 12 21 37.54

[0082] (Numerical Example 6) Unit: mm Surface Data Surface number rd nd vd θct 1 948.059 1.50 1.69930 51.1 0.760 2 22.397 4.09 3 45.106 1.50 1.49700 81.5 0.826 4 23.025 12.00 5 -40.318 3.00 1.49700 81.5 0.826 6 31.763 7.11 1.89190 37.1 0.720 7 -40.840 0.15 8 -38.276 1.40 1.49700 81.5 0.826 9 35.582 (variable) 10 (Aperture) ∞ 0.95 11 124.389 1.33 1.96300 24.1 0.661 12 6096.891 0.10 13 26.572 2.05 1.75500 52.3 0.801 14 89.724 8.48 15 24.426 3.00 1.78880 28.4 0.694 16 15.238 0.59 17 20.999 3.28 1.49700 81.5 0.826 18 -25.731 0.30 19 -22.473 1.00 1.61340 44.3 0.783 20 19.686 0.10 21 17.717 5.00 1.49700 81.5 0.826 22 -33.352 (variable) 23 -44.951 1.00 1.78880 28.4 0.694 24 28.560 2.73 1.49700 81.5 0.826 25 -58.326 3.96 26 51.986 2.06 1.49700 81.5 0.826 27 -226.122 3.52 28 25.936 1.07 1.95906 17.5 0.626 29 28.747 (variable) 30 -35.042 1.00 1.48749 70.2 0.892 31 -53.245 (variable) 32 31.656 3.17 1.95906 17.5 0.626 33 101.261 11.36 34 ∞ 1.20 1.54000 70.0 35∞1.00 Image plane ∞ Various data Zoom ratio 1.56 Wide-angle end Mid-range Telephoto end Focal length 12.00 15.29 18.73 F-number 2.61 2.97 3.25 Half angle of view 58.13 42.90 34.24 Image height 10.75 10.75 10.75 Lens length 128.66 128.66 128.66 BF 13.14 13.14 13.14 d 9 28.15 20.54 13.92 d22 0.10 3.16 5.47 d29 10.00 4.02 11.06 d31 1.41 11.94 9.21 Zoom lens group data Group starting plane focal length 1 1 -19.54 2 10 29.73 3 23 -1799.62 4 30 -214.11 5 32 46.97 Single lens data Lens starting surface focal length 1 1 -32.82 2 3 -96.82 3 5 -35.26 4 6 21.00 5 8 -36.87 6 11 131.84 7 13 49.31 8 15 -60.00 9 17 23.82 10 19 -16.95 11 21 24.06 12 23 -22.01 13 24 38.98 14 26 85.26 15 28 233.14 16 30 -214.11 17 32 46.97

[0083] (Numerical Example 7) Unit: mm Surface Data Surface number rd nd vd θct 1 151.965 1.50 1.75106 43.1 0.710 2 23.277 9.39 3 -47.393 3.00 1.49700 81.5 0.826 4 28.852 5.72 5 -110.789 3.50 1.49700 81.5 0.826 6 56.583 10.00 1.95375 32.3 0.699 7 -49.847 0.14 8 -46.250 3.50 1.49700 81.5 0.826 9 282.758 (variable) 10 (Aperture) ∞ 0.95 11 32.470 5.00 2.00330 28.3 0.684 12 -1082.761 0.69 13 31.495 3.05 1.69930 51.1 0.760 14 465.195 0.32 15 -128.211 3.00 1.73800 32.3 0.715 16 18.792 0.86 17 24.232 2.75 1.49700 81.5 0.826 18 -39.876 2.23 19 -39.734 1.35 1.73800 32.3 0.715 20 21.710 0.10 21 21.469 2.79 1.49700 81.5 0.826 22 -36.329 (variable) 23 -22.351 2.50 1.85478 24.8 0.674 24 36.740 3.12 1.49700 81.5 0.826 25 -30.262 0.49 26 -447.249 1.83 2.00330 28.3 0.684 27 -51.036 0.10 28 42.369 7.89 1.43875 94.7 0.841 29 -28.443 (variable) 30 -32.682 1.00 1.51633 64.1 0.869 31 216.335 (variable) 32 38.262 3.40 1.95906 17.5 0.626 33 1197.540 13.13 34 ∞ 1.20 1.54000 70.0 35∞1.00 Image plane ∞ Various data Zoom ratio 1.50 Wide-angle end Mid-range Telephoto end Focal length 12.00 14.98 18.00 F-number 2.22 2.54 2.81 Half angle of view 56.94 43.20 35.21 Image height 10.75 10.75 10.75 Lens length 129.19 129.19 129.19 BF 14.91 14.91 14.91 d 9 22.75 15.13 8.52 d22 1.55 4.61 6.92 d29 1.83 1.06 1.85 d31 7.99 13.31 16.82 Zoom lens group data Group starting plane focal length 1 1 -23.92 2 10 32.38 3 23 45.66 4 30 -54.91 5 32 41.15 Single lens data Lens starting surface focal length 1 1 -36.78 2 3 -35.62 3 5 -74.84 4 6 29.12 5 8 -79.69 6 11 31.49 7 13 48.17 8 15 -22.02 9 17 30.77 10 19 -18.85 11 21 27.59 12 23 -15.95 13 24 33.91 14 26 57.29 15 28 40.15 16 30 -54.91 17 32 41.15

[0084] [Table 1]

[0085] The disclosure of this embodiment includes the following configuration. (Configuration 1) The optical system has one or more lens groups having negative refractive power and one or more lens groups having positive refractive power, which are arranged in this order from the object side to the image side, The one or more lens groups having negative refractive power include a lens group BN including at least one negative lens BNn, When the refractive index of the negative lens BNn is nd_BNn, the Abbe number is νd_BNn, and the partial dispersion ratio is θCt_BNn, 1.60 <nd_BNn<2.00 25.0<νd_BNn<55.0 0.4958<θCt_BNn-0.00417×νd_BNn<0.5508 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) 2. The zoom lens according to configuration 1, wherein the zoom lens includes five or fewer lens groups. (Configuration 3) 3. The zoom lens according to configuration 1 or 2, wherein the one or more lens groups having negative refractive power are composed of one or two lens groups having negative refractive power. (Configuration 4) 4. The zoom lens according to any one of configurations 1 to 3, wherein the lens group BN is a lens group having the largest negative refractive power among the one or more lens groups having negative refractive power. (Configuration 5) The zoom lens according to any one of configurations 1 to 4, wherein the lens group BN includes two to four negative lenses. (Configuration 6) When the Abbe number of the lens group BN is νd_BNp, 20.0<νd_BNp<40.0 6. The zoom lens according to any one of configurations 1 to 5, comprising at least one positive lens that satisfies the following condition: (Configuration 7) When the distance from the lens surface closest to the object side to the lens surface closest to the image side in the lens group BN is D_BN and the focal length of the lens group BN is f_BN, 0.5<|f_BN / D_BN|<3.0 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) the zoom lens has a lens group having a positive refractive power composed of three or more lenses, Among the lens groups having positive refractive power and composed of three or more lenses, the lens group BP arranged closest to the object side has at least one negative lens BPn, and when the refractive index of the negative lens BPn is nd_BPn, the Abbe number is νd_BPn, and the partial dispersion ratio is θCt_BPn, 1.40 <nd_BPn<2.00 15.0<νd_BPn<61.0 0.5408<θCt_BPn-0.00528×νd_BPn<0.5808 8. The zoom lens according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) The zoom lens according to configuration 8, wherein the lens group BP has two or less negative lenses. (Configuration 10) When the Abbe number of the lens unit BP is νd_BPp, 70.5<νd_BPp<100.0 10. The zoom lens according to claim 8, further comprising at least one positive lens which satisfies the following condition: (Configuration 11) 11. The zoom lens according to any one of configurations 8 to 10, wherein the lens unit BP moves toward the object side during zooming from the wide-angle end to the telephoto end. (Configuration 12) 12. An imaging device comprising: the zoom lens according to any one of configurations 1 to 11; and an imaging element that receives an image formed by the zoom lens. [Explanation of symbols]

[0086] B1: First lens group B2: Second lens group B3: Third lens group B4: Fourth lens group B5: Fifth lens group

Claims

1. The optical system has one or more lens groups having negative refractive power and a lens group having positive refractive power, which are arranged in this order from the object side to the image side, The one or more lens groups having negative refractive power include a lens group BN including at least one negative lens BNn, When the refractive index of the negative lens BNn is nd_BNn, the Abbe number is νd_BNn, and the partial dispersion ratio is θCt_BNn, 1.60<nd_BNn<2.00 25.0<νd_BNn<55.0 0.4958<θCt_BNn−0.00417×νd_BNn<0.5508 A zoom lens characterized by satisfying the following conditional expressions:

2. 2. The zoom lens of claim 1, wherein the zoom lens includes five or fewer lens groups.

3. 2. The zoom lens according to claim 1, wherein the one or more lens groups having negative refractive power are composed of one or two lens groups having negative refractive power.

4. 2. The zoom lens according to claim 1, wherein the lens group BN is a lens group having the largest negative refractive power among the one or more lens groups having negative refractive power.

5. 2. The zoom lens according to claim 1, wherein the lens unit BN includes two to four negative lenses.

6. When the Abbe number of the lens unit BN is νd_BNp, 20.0<νd_BNp<40.0 2. The zoom lens according to claim 1, comprising at least one positive lens which satisfies the following condition:

7. When the distance from the lens surface closest to the object side to the lens surface closest to the image side in the lens unit BN is D_BN and the focal length of the lens unit BN is f_BN, 0.5<|f_BN / D_BN|<3.0 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. the zoom lens has a lens group having a positive refractive power composed of three or more lenses, The lens group BP arranged closest to the object side among the lens groups having positive refractive power composed of the three or more lenses has at least one negative lens BPn, and when the refractive index of the negative lens BPn is nd_BPn, the Abbe number is νd_BPn, and the partial dispersion ratio is θCt_BPn, 1.40<nd_BPn<2.00 15.0<νd_BPn<61.0 0.5408<θCt_BPn−0.00528×νd_BPn<0.5808 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. 9. The zoom lens according to claim 8, wherein the lens unit BP has two or less negative lenses.

10. When the Abbe number of the lens unit BP is νd_BPp, 70.5<νd_BPp<100.0 9. The zoom lens according to claim 8, comprising at least one positive lens which satisfies the following condition:

11. 9. The zoom lens according to claim 8, wherein the lens unit BP moves toward the object side during zooming from the wide-angle end to the telephoto end.

12. 12. An imaging device comprising: the zoom lens according to claim 1; and an imaging element that receives an image formed by the zoom lens.

Images