Zoom lens, imaging apparatus having the same, and imaging system

Abstract

To provide a zoom lens that can obtain high optical performance despite its small size and large diameter.SOLUTION: A zoom lens has a first lens group having a positive refractive power, a front group including one or two lens groups and having a negative refractive power, and a rear group including an aperture diaphragm and one or more lens groups, which are arranged in order from an object side to an image side, wherein an interval between the adjacent lens groups changes in zooming. The first lens group is immovable in focusing. The first lens group includes a positive lens arranged on the most object side. When the refractive powers from the positive lens to a lens on the most image side of the front group are combined at a telephoto end, the composite refractive power is negative. A distance on an optical axis from the aperture diaphragm to an image surface at a wide-angle end, the total length of the zoom lens at the wide-angle end, the maximum refractive index of the lens included in the first lens group, the maximum value of an air interval in the first lens group in the entire zoom area, and the maximum value of an air interval in the front group in the entire zoom area, are each appropriately set.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens, which is suitable for digital video cameras, digital still cameras, broadcast cameras, cameras for silver halide film, surveillance cameras, and the like. [Background technology]

[0002] In recent years, there has been a demand for a telephoto lens with a zoom function, which is small and has a large aperture, yet has high optical performance. Patent Document 1 discloses an optical system having a plurality of converter lenses, which is composed of a first to third lens group with positive, negative, and positive refractive powers, and a subsequent group including one or more lens groups, which are arranged in order from the object side to the image side, in order to achieve weight reduction and telephotography. Patent Document 2 discloses an optical system having a first and second lens group with positive and negative refractive powers, and a subsequent group including one or more lens groups, which are arranged in order from the object side to the image side, in order to achieve both size reduction and weight reduction and high image quality, in which the first lens group is composed of a plurality of subgroups. Patent Document 3 discloses an optical system having a first lens group with positive refractive power, a second lens group, and a subsequent group including one or more lens groups, which are arranged in order from the object side to the image side, in order to achieve both improved optical performance and weight reduction, and which ensures an air gap in the first lens group. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-120746 A [Patent Document 2] Patent Publication No. 2022-26392 [Patent Document 3] International Publication No. 2022 / 124184 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the optical system of Patent Document 1, the refractive power of the first and second lens groups is optimized to achieve compactness, and it is also possible to achieve telephotography using multiple converter lenses, but it is difficult to achieve compactness when the image sensor is large. In the optical system of Patent Document 2, the spacing between the main variable magnification groups can be changed during zooming, or the number of lenses in the main variable magnification groups can be increased to achieve high image quality, but it is difficult to achieve a large aperture. In the optical system of Patent Document 3, the configuration of each lens group is optimized to achieve both weight reduction and suppression of chromatic aberration, but it is difficult to achieve compactness when the aperture is large.

[0005] An object of the present invention is to provide a zoom lens that is small in size and has a large aperture, yet provides high optical performance. [Means for solving the problem]

[0006] A zoom lens according to one aspect of the present invention has, arranged in order from the object side to the image side, a first lens group having positive refractive power, a front group including one or two lens groups and having negative refractive power overall, and a rear group including an aperture stop and one or more lens groups, and the spacing between adjacent lens groups changes during zooming, the first lens group is fixed with respect to the image plane during focusing, and includes a positive lens arranged closest to the object side, and at the telephoto end, when the refractive powers from the positive lens to the lens of the front group arranged closest to the image side are combined, the combined refractive power becomes negative, and when the distance on the optical axis from the aperture stop to the image plane at the wide-angle end is dsw, the total length of the zoom lens at the wide-angle end is Ldw, the maximum refractive index of the lenses included in the first lens group is nd1max, the maximum value of the air spacing in the first lens group over the entire zoom range is d1a, and the maximum value of the air spacing in the front group over the entire zoom range is dUa, 0.10 <dsw / Ldw<0.50 1.45 <nd1max≦1.80 3 <d1a / dUa<300 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 and has a large aperture, yet provides high optical performance. [Brief description of the drawings]

[0008] [Figure 1] 1A to 1C are cross-sectional views of a zoom lens according to a first embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Diagram 2] 4A, 4B, and 4C are aberration diagrams of the zoom lens of Example 1 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Diagram 3] 11A to 11C are cross-sectional views of a zoom lens according to a second embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 4] 5A, 5B, and 5C are aberration diagrams of the zoom lens of Example 2 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Diagram 5] 11A to 11C are cross-sectional views of a zoom lens of a third embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 6] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 3 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 7] 11A to 11C are cross-sectional views of a zoom lens according to a fourth embodiment at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 8] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 4 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 9] 13A to 13C are cross-sectional views of a zoom lens of Example 5 at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 10] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 5 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 11] 13A to 13C are cross-sectional views of a zoom lens of Example 6 at a wide-angle end, at a middle zoom position, and at a telephoto end. [Figure 12] 13A, 13B, and 13C are aberration diagrams of the zoom lens of Example 6 at the wide-angle end, at the intermediate zoom position, and at the telephoto end. [Figure 13] FIG. 1 is a schematic diagram of an imaging device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same reference numerals are given to the same members, and duplicated explanations will be omitted.

[0010] 1, 3, 5, 7, 9, and 11 are cross-sectional views of the zoom lenses of Examples 1 to 6 at the wide-angle end (short focal length end), at an intermediate zoom position, and at the telephoto end (long focal length end), respectively. The zoom lenses of the respective Examples are used in imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide cameras, and surveillance cameras, as well as optical devices including interchangeable lenses. The zoom lenses of the respective Examples can also be used as projection optical systems for projection devices (projectors).

[0011] In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lens of each embodiment is configured to have multiple lens groups. In this specification, a lens group is a group of lenses that move or stand still as a unit during zooming. That is, in the zoom lens of each embodiment, the distance between adjacent lens groups changes during zooming. Note that the lens group may be configured of one lens or multiple lenses. The lens group may also include an aperture stop.

[0012] In each cross-sectional view, Li represents the i-th lens group (i is a natural number) counted from the object side among the lens groups included in the zoom lens.

[0013] Also, SP is an aperture stop that determines (limits) the light flux of the open F-number (Fno). IP is an image plane, on which the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed when used as the photographing optical system of a video camera or digital still camera. Also, when the zoom lens of each embodiment is used as the photographing optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is placed on the image plane IP.

[0014] The arrows relating to focus and floating indicate the direction of movement of the lens groups during focusing from infinity to a close distance.

[0015] A protective glass for protecting the lens may be arranged on the object side of the first lens group L1. Furthermore, a protective glass or a low-pass filter may be arranged between the lens arranged on the most image side of the zoom lens and the image surface IP. Such optical members with extremely weak refractive power, such as protective glass or a low-pass filter, are not considered to be lenses constituting the zoom lens. An optical member with extremely weak refractive power is an optical member whose absolute focal length is three or more times the focal length of the zoom lens.

[0016] Fig. 2(A), Fig. 4(A), Fig. 6(A), Fig. 8(A), Fig. 10(A), and Fig. 12(A) are aberration diagrams at the wide-angle ends of the zoom lenses of Examples 1 to 6, respectively. Fig. 2(B), Fig. 4(B), Fig. 6(B), Fig. 8(B), Fig. 10(B), and Fig. 12(B) are aberration diagrams at the intermediate zoom positions of the zoom lenses of Examples 1 to 6, respectively. Fig. 2(C), Fig. 4(C), Fig. 6(C), Fig. 8(C), Fig. 10(C), and Fig. 12(C) are aberration diagrams at the telephoto ends of the zoom lenses of Examples 1 to 6, respectively.

[0017] In the spherical aberration diagram, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, ΔS shows the amount of astigmatism on the sagittal image plane, and ΔM shows the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the imaging half angle of view (°), which is the angle of view calculated by paraxial calculation.

[0018] Next, the characteristic configuration of the zoom lens of each embodiment will be described.

[0019] The zoom lens of each embodiment includes a first lens group L1 having a positive refractive power (optical power=the reciprocal of the focal length), a front group U including one or two lens groups and having a negative refractive power overall, an aperture stop SP, and a rear group including one or more lens groups, which are arranged in this order from the object side to the image side. Since the variation in spherical aberration and coma aberration due to manufacturing errors increases in the telephoto range, the zoom lens of each embodiment is a so-called positive lead type zoom lens in which the first lens group L1 has a positive refractive power. This makes it possible to reduce the height of incidence of an on-axis ray to a lens element arranged on the image side of the front group U, and to satisfactorily correct various aberrations such as chromatic aberration and spherical aberration over the entire zoom range while achieving a compact zoom lens.

[0020] In the zoom lenses of each embodiment, the first lens group L1 is fixed relative to the image plane during focusing. Also, in the zoom lenses of embodiments 1, 2, 4, and 5, the first lens group L1 is fixed relative to the image plane during zooming. By fixing the first lens group L1 relative to the image plane during zooming, it is possible to suppress changes in the overall lens length during zooming. In addition, it is possible to reduce the number of movable groups, which leads to simplification of the mechanical parts. Simplification of the mechanical parts can reduce the generation of dust and the like. Furthermore, it is possible to ensure strength when accessories such as a front filter and a converter lens are attached.

[0021] In the zoom lens of each embodiment, the first lens group L1 includes a positive lens L arranged closest to the object. The first lens group L1 converges on-axis light rays, preventing the zoom lens from becoming larger due to telephoto shooting or a larger aperture. By arranging the positive lens L closest to the object in the first lens group L1, the zoom lens can be made compact and spherical aberration can be easily corrected. In addition, by converging on-axis light rays with the positive lens L and arranging other lenses with an appropriate air gap between them, the diameter of each lens can be made smaller, making it easier to reduce the weight.

[0022] In the zoom lens of each embodiment, when the refractive powers of the positive lens to the lens arranged closest to the image side of the front group U are combined at the telephoto end, the combined refractive power becomes negative. The front group U is a lens group (main variable magnification group) that mainly performs the variable magnification function. In order to obtain a predetermined zoom ratio, it is necessary to strengthen the refractive power of the front group U or to increase the amount of movement during zooming. In the zoom lens of each embodiment, the configuration of the front group U is simplified while suppressing the image plane fluctuation during zooming, which makes it easy to reduce the weight of the zoom lens. By making the front group U have a simple configuration, it is possible to correct the field curvature in the wide-angle range and the spherical aberration in the telephoto range, while suppressing the fluctuation of the chromatic aberration of magnification during zooming and the variation due to manufacturing errors in the spherical aberration and coma aberration in the telephoto range due to decentering.

[0023] The zoom lens of each embodiment satisfies the following conditional expressions (1) to (3).

[0024] 0.10 <dsw / Ldw<0.50 ···(1) 1.45 <nd1max≦1.80 ···(2) 3 <d1a / dUa<300 ···(3) Here, dsw is the distance on the optical axis from the aperture stop SP to the image plane IP at the wide-angle end. Ldw is the total length of the zoom lens of each embodiment at the wide-angle end (total lens length; the distance on the optical axis from the lens surface closest to the object to the image plane IP). nd1max is the maximum refractive index of the lenses included in the first lens group L1. d1a is the maximum air spacing (lens spacing) in the first lens group L1 over the entire zoom range. dUa is the maximum air spacing in the front group U over the entire zoom range.

[0025] Conditional formula (1) specifies the distance on the optical axis from the aperture stop SP to the image plane IP at the wide-angle end and the overall length of the zoom lens at the wide-angle end. By satisfying conditional formula (1), it is possible to shorten the overall length of the zoom lens and suppress the occurrence of various aberrations, particularly chromatic aberrations such as distortion and chromatic aberration of magnification. If the lower limit of conditional formula (1) is not satisfied, the overall length of the zoom lens increases, which is undesirable. If the upper limit of conditional formula (1) is exceeded, the aperture diameter and the diameter of the rear group increase, making it difficult to reduce the weight, particularly the weight of the focus lens group.

[0026] Conditional formula (2) specifies the maximum value (maximum refractive index) of the refractive index at the d-line of the lens included in the first lens group L1. By satisfying conditional formula (2), it is possible to achieve both weight reduction and chromatic aberration correction. In the lens included in the first lens group L1, a composite optical element such as a replica resin layer (called a hybrid aspheric surface or a replica aspheric surface) is defined as a single lens element including the resin layer. Specifically, for example, an element including a resin layer with a thickness of 0.3 mm or less on the optical axis is defined as a single lens element. In addition, when the material is specified, the resin layer is not taken into consideration for calculation. In general, the Abbe number tends to decrease as the refractive index of the lens material increases. In addition, the partial dispersion ratio θgF tends to increase as the refractive index increases, and the specific gravity tends to increase. If a material below the lower limit of conditional formula (2) is used, the refractive index becomes low, making it difficult to arrange a lens with a small Abbe number, and the achromatism in the first lens group L1 is likely to be insufficient. In addition, if an attempt is made to ensure the achromatism effect, it is not preferable because it leads to insufficient correction of spherical aberration, especially on the telephoto side. If a material with a refractive index exceeding the upper limit of conditional formula (2) is used, the refractive index will be high, and lenses with a small Abbe number and a large partial dispersion ratio θgF will be arranged. This is not preferable because it leads to insufficient correction of axial chromatic aberration over the entire zoom range in the first lens group L1 and lateral chromatic aberration on the telephoto side. In addition, even if a high refractive index lens is used to reduce the number of lenses, it is not preferable because it tends to lead to an increase in lens mass.

[0027] Conditional expression (3) specifies the maximum value of the air gap in the first lens group L1 and the front group U. By satisfying conditional expression (3), it is possible to suppress various aberrations and reduce the weight of the zoom lens at the same time. If the lower limit of conditional expression (3) is not satisfied, it becomes difficult to position the principal point of the front group U on the image side at the telephoto end. In order to achieve compactness while maintaining a desired zoom ratio, it is necessary to increase the refractive power of the first lens group L1 and the front group U, which tends to increase the number of lenses. If the upper limit of conditional expression (3) is exceeded, the thickness on the optical axis of the first lens group L1 becomes large, which leads to an increase in the radial direction of the positive lens L, making it difficult to reduce the weight. In addition, it becomes difficult to suppress coma aberration at the telephoto end.

[0028] With the above-described configuration, it is possible to realize a zoom lens that is small in size and has a large aperture, yet provides high optical performance.

[0029] It is preferable that the numerical ranges of the conditional expressions (1) to (3) are set to the numerical ranges of the following conditional expressions (1a) to (3a).

[0030] 0.20 <dsw / Ldw<0.49 ···(1a) 1.55 <nd1max≦1.80 ···(2a) 3.5 <d1a / dUa<50.0 ···(3a) It is further preferable that the numerical ranges of the conditional expressions (1) to (3) be the numerical ranges of the following conditional expressions (1b) to (3b).

[0031] 0.30 <dsw / Ldw<0.49 ···(1b) 1.60 <nd1max≦1.80 ···(2b) 3.8 <d1a / dUa<10.0 ···(3b) Next, a description will be given of configurations that are preferably satisfied in the zoom lens of each embodiment.

[0032] It is preferable that the first lens group L1 is composed of four or less lenses. By reducing the number of lenses that make up the first lens group L1, which has a large lens diameter, it is possible to achieve a reduction in size and weight. In addition, the height of the light beam emerging from the first lens group L1 can be reduced, and off-axis aberrations such as coma aberration and field curvature can be effectively corrected.

[0033] The first lens group L1 is preferably composed of one negative lens and two or three positive lenses. This configuration makes it easy to effectively correct axial chromatic aberration and lateral chromatic aberration over the entire zoom range, and to effectively correct spherical aberration and axial chromatic aberration on the telephoto side that accompanies a large aperture.

[0034] The front group U is preferably composed of three or four spherical lenses, including at least one positive lens. This makes it possible to suppress surface shape errors (so-called astigmatism and quirk component errors) that tend to occur in aspherical lenses. In addition, it is possible to simultaneously correct lateral chromatic aberration and field curvature in the wide-angle range and spherical aberration in the telephoto range while increasing the refractive power of the second lens group L2.

[0035] The rear group is disposed closest to the object and has a lens unit LA with positive refractive power, and it is preferable that the lens unit LA is fixed relative to the image plane IP during zooming. This makes it easier to ensure the accuracy of the decentering position associated with larger apertures and shorter overall lengths of the zoom lens, and makes it possible to reduce decentering coma aberration and decentering astigmatism during zooming that occur due to manufacturing errors. In addition, the number of movable groups can be reduced during zooming, making it possible to miniaturize the zoom lens and simplify its configuration, making it easier to ensure the imaging performance of the zoom lens.

[0036] It is preferable that the lens group LA has at least three positive lenses, which allows for excellent correction of the axial chromatic aberration and the spherical aberration caused by the increase in the aperture for each wavelength.

[0037] It is preferable that the lens group arranged closest to the image side be fixed relative to the image plane IP during zooming, which can reduce the generation of dust and other particles when the zoom lens is removed, and makes it easier to ensure durability.

[0038] It is preferable that the lens positioned closest to the image side of the zoom lens is a lens with a convex shape toward the image side, which makes it relatively easy to ensure the back focus and also makes it possible to suppress the collection of unwanted light (ghosts) caused by the image sensor.

[0039] It is preferable that the aperture stop SP is disposed closer to the image side than the lens group LA, which makes it easier to prevent the size of the stop member from increasing as the aperture diameter increases.

[0040] The lens arranged adjacent to the image side of the aperture stop SP is preferably made of an element (single lens or cemented lens) that is convex toward the object side. This makes it easier to suppress spherical aberration that accompanies a large aperture and to correct off-axis aberrations in the wide-angle range. Furthermore, if the convex element is a cemented lens, it is easier to correct spherical aberration, coma aberration, and field curvature at the same time.

[0041] It is preferable that the zoom lens of each embodiment does not include a diffractive optical element, since the inclusion of a diffractive optical element is undesirable because it would cause diffraction flare.

[0042] It is preferable to perform zooming so that the distance between the first lens unit L1 and the front unit U at the telephoto end is wider than that at the wide-angle end, and the distance between the front unit U and the rear unit is narrower. This makes it possible to achieve a large aperture while reducing weight.

[0043] When the front group U is made up of two lens groups, it is preferable to change the spacing of the front group U during zooming, which makes it possible to effectively correct variations in spherical aberration and curvature of field that occur during zooming.

[0044] Next, conditions that the zoom lens of each embodiment should preferably satisfy will be described. The zoom lens of each embodiment should preferably satisfy one or more of the following conditional expressions (4) to (12).

[0045] 1.75 <ndUv<2.40 ···(4) 0.56<θgFUv<0.68 (5) 56<νd1a<100 (6) -35.00<βUt<-0.45 (7) 1.7<βUt / βUw<20.0 (8) 2.4 <f1 / fLA<10.0 ···(9) -0.35 <fU / ft<-0.05 ···(10) 0.01 <skt / ft<0.35 ···(11) -9.0 <f1 / fU<-1.6 ···(12) Here, ndUV is the refractive index of the lens made of the material with the highest refractive index among the lenses included in the front group U. θgFUv is the partial dispersion ratio of the lens made of the material with the highest refractive index among the lenses included in the front group U. νd1a is the average value of the Abbe number at the d-line of the lenses included in the first lens group L1. βUt is the lateral magnification of the front group U at the telephoto end (composite lateral magnification when the front group U is composed of multiple lens groups). βUw is the lateral magnification of the front group U at the wide-angle end (imaging magnification. Composite lateral magnification when the front group U is composed of multiple lens groups). f1 is the focal length of the first lens group L1. fLA is the focal length of the lens group LA arranged closest to the object side of the rear group. fU is the focal length of the front group U at the telephoto end (composite focal length when the front group U is composed of multiple lens groups). ft is the focal length of the zoom lens at the telephoto end. skt is the back focus at the telephoto end (the distance on the optical axis from the lens surface closest to the image side to the image surface IP).

[0046] Conditional formula (4) specifies the refractive index of the lens made of the material with the maximum refractive index among the lenses included in the front group U. Due to the characteristics of glass, as the refractive index increases, the Abbe number decreases while the partial dispersion ratio tends to increase. When a material with a high refractive index is used for the positive lens of the front group U, which has a negative refractive power overall, it becomes easier to achromatize the front group U and correct the secondary spectrum of the axial chromatic aberration and lateral chromatic aberration of the zoom lens. In addition, by using a material with a high refractive index, the curvature becomes small (the radius of curvature becomes large), making it easier to correct spherical aberration. In addition, it becomes easier to reduce the number of lenses constituting the front group U, which has a relatively large diameter, while satisfactorily correcting the curvature of field and the astigmatic difference. If the lower limit of conditional formula (4) is exceeded, the refractive power of the front group U needs to be weakened to correct the curvature of field, which results in an increase in the overall length of the zoom lens and an increase in the amount of movement of the front group U, which is not preferable. If the upper limit of conditional formula (4) is exceeded, the variation (curvature) of the lateral chromatic aberration at each image height increases.

[0047] Conditional formula (5) specifies the partial dispersion ratio of the lens made of the material with the maximum refractive index among the lenses included in the front group U. By satisfying conditional formula (5), it is possible to achieve a good balance between suppressing the fluctuation of chromatic aberration, including chromatic aberration of magnification and axial chromatic aberration during zooming, and suppressing chromatic aberration of magnification in the telephoto range. If the lower limit of conditional formula (5) is not met, the effect of correcting axial chromatic aberration of the positive lens in the front group U is weakened, and it becomes necessary to strengthen the convergence action of the first lens group L1 and suppress the height of the light ray incident on the second lens group L2 arranged on the image side of the first lens group L1. This increases the refractive power of the first lens group L1, and the number of lenses and the mass are increased, which is undesirable. If the upper limit of conditional formula (5) is exceeded, the fluctuation of axial chromatic aberration during zooming and the variation of spherical aberration and coma aberration for each wavelength increase, which is undesirable.

[0048] Conditional expression (6) specifies the average value of the Abbe number at the d-line of the lenses included in the first lens group L1. By satisfying conditional expression (6), it becomes possible to effectively correct various aberrations including chromatic aberration while reducing the weight of the zoom lens. If the lower limit of conditional expression (6) is not satisfied, the amount of chromatic aberration generated in the first lens group L1 becomes too large, making it difficult to correct various aberrations including chromatic aberration in a well-balanced manner in the entire zoom lens. If the upper limit of conditional expression (6) is exceeded, it becomes difficult to ensure the transmittance of the glass material constituting the lens.

[0049] Conditional formula (7) specifies the lateral magnification of the front group U at the telephoto end. If the lower limit of conditional formula (7) is exceeded, it becomes difficult to obtain a desired zoom ratio, and the rear group must share the zoom ratio, resulting in an increase in size of the zoom lens. If the upper limit of conditional formula (7) is exceeded, it is advantageous for ensuring a high zoom ratio, but the magnification of the front group U at the telephoto end becomes too large, making it difficult to suppress curvature of field and distortion in the wide-angle range.

[0050] Conditional formula (8) specifies the relationship between the lateral magnifications of the front group U at the telephoto end and the wide-angle end. By satisfying conditional formula (8), a high zoom ratio can be ensured. If the lower limit of conditional formula (8) is exceeded, the zoom effect of the front group U is small and it is necessary to ensure the zoom effect with the rear group, making it difficult to suppress lateral chromatic aberration of magnification and distortion in the telephoto range and making it difficult to achieve compactness. If the upper limit of conditional formula (8) is exceeded, the image plane fluctuation during zooming becomes large, making it difficult to maintain high optical performance.

[0051] Conditional expression (9) specifies the relationship between the focal length of the first lens group L1 and the focal length of the lens group LA arranged closest to the object in the rear group. By satisfying conditional expression (9), it is possible to achieve a large aperture while effectively suppressing spherical aberration and coma aberration. If the lower limit of conditional expression (9) is not satisfied, it is undesirable because it is difficult to correct spherical aberration and coma aberration. If the upper limit of conditional expression (9) is exceeded, it is undesirable because the refractive power of the first lens group L1 is small and it is difficult to shorten the overall length of the zoom lens. In addition, it is difficult to achieve a high zoom ratio.

[0052] Conditional formula (10) specifies the relationship between the focal length of the front group U at the telephoto end and the focal length of the zoom lens at the telephoto end. By satisfying conditional formula (10), both high zoom ratio and compact size can be achieved. Below the lower limit of conditional formula (10), the Petzval sum becomes negatively large, which is undesirable as it leads to an increase in the curvature of field. Above the upper limit of conditional formula (10), in order to achieve high zoom ratio, it is necessary to increase the amount of movement of the second lens group L2 or to increase the zooming effect of the lens group arranged on the image side of the second lens group L2. Increasing the amount of movement of the second lens group L2 increases the overall length of the zoom lens, which is undesirable. In addition, increasing the zooming effect of the lens group arranged on the image side of the second lens group L2 increases the overall length of the zoom lens or increases the number of lenses, which is undesirable.

[0053] Conditional expression (11) defines the relationship between the back focus at the telephoto end and the focal length of the zoom lens at the telephoto end, the so-called retro ratio. If the lower limit of conditional expression (11) is exceeded, it becomes difficult to arrange the shutter members, etc. If the upper limit of conditional expression (11) is exceeded, it becomes difficult to correct distortion and curvature of field, and this leads to an increase in the number of lenses, which is not preferable.

[0054] Conditional expression (12) specifies the relationship between the focal length of the first lens group L1 and the focal length of the front group U at the telephoto end. In a zoom lens with a relatively bright telephoto side, if the refractive power of the first lens group L1 is not appropriately secured within a range where aberrations can be corrected, the overall length of the zoom lens on the telephoto side will increase, and furthermore, the diameter of the front lens will be increased in order to secure peripheral light. By satisfying conditional expression (12), it is possible to maintain an appropriate zoom ratio and to make the zoom lens compact. If the lower limit of conditional expression (12) is not satisfied, it becomes difficult to correct spherical aberration on the telephoto side. If the upper limit of conditional expression (12) is exceeded, the aberration fluctuation of the first lens group L1 and the front group U during zooming becomes large, making it particularly difficult to suppress curvature of field.

[0055] It is preferable that the numerical ranges of the conditional expressions (4) to (12) be the numerical ranges of the following conditional expressions (4a) to (12a).

[0056] 1.78 <ndUv<2.10 ···(4a) 0.570<θgFUv<0.675 (5a) 60<νd1a<100 (6a) -31.00<βUt<-0.50 (7a) 1.8<βUt / βUw<14.0 (8a) 2.5 <f1 / fLA<8.0 ···(9a) -0.30 <fU / ft<-0.10 ···(10a) 0.03 <skt / ft<0.30 ···(11a) -7.5 <f1 / fU<-2.2 ···(12a) It is further preferable that the numerical ranges of the conditional expressions (4) to (12) be the numerical ranges of the following conditional expressions (4b) to (12b).

[0057] 1.80 <ndUv<2.00 ···(4b) 0.575<θgFUv<0.670 (5b) 62<νd1a<100 (6b) -30.50<βUt<-0.52 (7b) 1.9<βUt / βUw<12.0 (8b) 2.6 <f1 / fLA<6.8 ···(9b) -0.25 <fU / ft<-0.15 ···(10b) 0.05 <skt / ft<0.25 ···(11b) -6.0 <f1 / fU<-2.8 ···(12b) Next, the zoom lens of each embodiment will be described in detail.

[0058] The zoom lenses of Examples 1 to 3 are configured with a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, and a rear group, which are arranged in this order from the object side to the image side. In the zoom lenses of Examples 1 to 3, the second lens group L2 corresponds to the front group U. The zoom lenses of Examples 4 to 6 are configured with a first lens group L1 having positive refractive power, a second lens group L2 having negative refractive power, a third lens group L3, and a rear group, which are arranged in this order from the object side to the image side. In the zoom lenses of Examples 4 to 6, the second lens group L2 and the third lens group L3 correspond to the front group U.

[0059] The zoom lens of the first embodiment has a zoom ratio of 1.4 and an aperture ratio of about 2.9 to 4.1. In the first embodiment, the rear group is composed of the third lens group L3 to the eighth lens group L8, which are arranged in order from the object side to the image side, and have positive, positive, negative, positive, negative, and positive refractive powers. In a reference state where the object distance is infinite, the first lens group L1, the third lens group L3, the sixth lens group L6, and the eighth lens group L8 are fixed with respect to the image surface IP during zooming from the wide-angle end to the telephoto end. The second lens group L2 moves toward the image side, the fourth lens group L4 moves along a locus convex toward the object side, and the fifth lens group L5 and the seventh lens group L7 move toward the object side. During focusing on a close-distance object, the fifth lens group L5 and the seventh lens group L7 move toward the image side.

[0060] The zoom lens of the second embodiment has a zoom ratio of 1.9 and an aperture ratio of about 2.9 to 4.6. In the second embodiment, the rear group is composed of the third lens group L3 to the eighth lens group L8, which are arranged in order from the object side to the image side, and have positive, positive, negative, negative, positive, and negative refractive powers. In a reference state where the object distance is infinite, the first lens group L1, the third lens group L3, the sixth lens group L6, and the eighth lens group L8 are fixed with respect to the image surface IP during zooming from the wide-angle end to the telephoto end. The second lens group L2 moves toward the image side, the fourth lens group L4 moves along a locus convex toward the object side, the fifth lens group L5 moves toward the object side, and the seventh lens group L7 moves toward the image side. During focusing on a close-distance object, the fifth lens group L5 moves toward the image side, and the seventh lens group L7 moves toward the object side.

[0061] The zoom lens of Example 3 has a zoom ratio of 4.0 and an aperture ratio of about 4.1 to 4.1. In Example 3, the rear group is made up of a third lens group L3 to a fifth lens group L5, which are arranged in this order from the object side to the image side, and which are positive, negative, and positive. In a reference state where the object distance is infinity, each lens group moves during zooming from the wide-angle end to the telephoto end. During focusing on a close-up object, the fourth lens group L4 moves toward the image side.

[0062] The zoom lens of Example 4 has a zoom ratio of 1.9 and an aperture ratio of about 2.9 to 4.6. In Example 4, the rear group is composed of the fourth lens group L4 to the ninth lens group L9, which are arranged in order from the object side to the image side, and have positive, positive, negative, negative, positive, and negative refractive powers. In a reference state where the object distance is infinite, the first lens group L1, the fourth lens group L4, the seventh lens group L7, and the ninth lens group L9 are fixed with respect to the image surface IP during zooming from the wide-angle end to the telephoto end. The second lens group L2 and the third lens group L3 move toward the image side, the fifth lens group L5 moves along a locus convex toward the object side, the sixth lens group L6 moves toward the object side, and the eighth lens group L8 moves toward the image side. During focusing on a close-distance object, the sixth lens group L6 moves toward the image side, and the eighth lens group L8 moves toward the object side.

[0063] The zoom lens of the fifth embodiment has a zoom ratio of 1.4 and an aperture ratio of about 2.9 to 4.1. In the fifth embodiment, the rear group is composed of the fourth lens group L4 to the ninth lens group L9, which are arranged in order from the object side to the image side, and have positive, positive, negative, positive, negative, and positive refractive powers. In a reference state where the object distance is infinite, the first lens group L1, the fourth lens group L4, the seventh lens group L7, and the ninth lens group L9 are fixed with respect to the image surface IP during zooming from the wide-angle end to the telephoto end. The second lens group L2 and the third lens group L3 move toward the image side, the fifth lens group L5 moves along a locus convex toward the object side, the sixth lens group L6 moves toward the object side, and the eighth lens group L8 moves toward the object side. During focusing on a close-distance object, the sixth lens group L6 and the eighth lens group L8 move toward the image side.

[0064] The zoom lens of Example 6 has a zoom ratio of 2.9 and an aperture ratio of about 4.1 to 4.1. In Example 6, the rear group is made up of a fourth lens group L4 to a sixth lens group L6, which are arranged in this order from the object side to the image side, and which are positive, negative, and positive. In a reference state where the object distance is infinity, each lens group moves during zooming from the wide-angle end to the telephoto end. During focusing on a close-distance object, the fifth lens group L5 moves toward the image side.

[0065] In the zoom lens of each embodiment, any of the lens groups may be moved as a vibration-proof group so as to include a component in a direction perpendicular to the optical axis, or may be rotated (rocked) in a plane direction including the optical axis, to perform vibration prevention. For example, in the zoom lens of the first embodiment, the 16th to 18th lenses may be moved so as to include a component in a direction perpendicular to the optical axis, to perform vibration prevention. There is no particular restriction on the number or shape of the lenses in the vibration-proof group. In addition, it is preferable that the vibration-proof group has a negative refractive power as a whole.

[0066] Numerical examples 1 to 6 corresponding to the first to sixth embodiments, respectively, are shown below.

[0067] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. In addition, nd represents the refractive index of each optical member with respect to the d-line, and νd represents the Abbe number of the optical member. The Abbe number νd and partial dispersion ratio θgF of a certain material are given by the following, when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), C-line (656.3 nm), and g-line (435.8 nm) of the Fraunhofer lines are Nd, NF, NC, and Ng, respectively: νd=(Nd-1) / (NF-NC) θgF=(Ng-NF) / (NF-NC) It is expressed as:

[0068] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the zoom lens of each example is focused on an object at infinity. "Back focus" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image surface expressed as an air-equivalent length. When an optical element with extremely weak refractive power is disposed between the zoom lens and the image sensor, the back focus is the value obtained by converting the optical element with extremely weak refractive power disposed between the zoom lens and the image sensor into an air-equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object) of the zoom lens to the final surface. "Lens group" is not limited to a case where it is composed of multiple lenses, but also includes a case where it is composed of one lens.

[0069] If the optical surface is aspheric, a * symbol is added to the right of the surface number. The aspheric shape is expressed as follows, where X is the displacement from the apex of the surface in the optical axis direction, H is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, K is the conic constant, and A4, A6, A8, A10, and A12 are the aspheric coefficients of each order:

[0070]

number

[0071] In addition, "e±XX" in each aspheric coefficient is "×10± XX " It means.

[0072] [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd θgF 1 730.9556 5.892 1.51860 69.89 0.5318 2 -6243.5126 0.500 3 198.7095 16.104 1.43387 95.10 0.5373 4 -3325.1197 79.136 5 155.0904 9.320 1.43387 95.10 0.5373 6 1493.6041 1.635 7 -1752.4247 2.500 1.65412 39.68 0.5737 8 198.0530 (variable) 9 411.1739 4.561 1.89286 20.36 0.6393 10 -443.2523 1.800 1.75700 47.82 0.5565 11 111.4148 10.005 12 -125.4127 1.800 1.61772 49.81 0.5603 13 -376.7073 (variable) 14 323.1596 9.629 1.43387 95.10 0.5373 15 -143.7175 0.300 16 174.5820 7.144 1.49700 81.54 0.5375 17 -610.1252 0.300 18 102.2907 12.593 1.43875 94.66 0.5340 19 -170.4620 1.500 1.85150 40.78 0.5695 20 288.0578 (variable) 21 122.2879 6.365 1.49700 81.54 0.5375 22 -891.3501 (variable) 23 (Aperture) ∞ (Variable) 24 -1838.6951 1.000 1.77250 49.60 0.5520 25 63.1863 (variable) 26 67.3791 1.000 1.89286 20.36 0.6393 27 45.1355 7.018 1.61772 49.81 0.5603 28 -148.0674 1.000 29 617.5001 4.586 1.66565 35.64 0.5824 30 -59.6998 1.200 1.55200 70.70 0.5421 31 45.6096 4.496 32 -116.6098 1.200 1.49700 81.54 0.5375 33 68.7125 2.622 34 53.7871 6.809 1.58144 40.75 0.5774 35 -91.7944 (variable) 36 290.3730 1.300 1.49700 81.54 0.5375 37 81.1764 7.199 38 -38.3664 1.350 1.85896 22.73 0.6284 39 -44.9029 (variable) 40 54.6122 4.669 1.54814 45.79 0.5686 41 225.7345 5.070 42 -77.3223 1.500 1.49700 81.54 0.5375 43 -337.7382 39.500 Image plane ∞ Various data Zoom ratio 1.424 Wide Angle Mid-Telephoto Focal length 409.335 505.051 582.738 F-number 2.880 3.553 4.100 Half angle of view (°) 3.025 2.453 2.126 Image height 21.635 21.635 21.635 Lens total length 475.002 475.002 475.002 BF 39.500 39.500 39.500 d 8 75.292 102.470 123.027 d13 51.451 24.274 3.716 d20 16.196 12.309 16.151 d22 4.395 8.282 4.440 d23 21.740 11.632 5.653 d25 20.779 30.887 36.866 d35 5.522 3.808 2.263 d39 17.024 18.738 20.283 Zoom lens group data Group starting plane focal length 1 1 410.021 2 9 -130.744 3 14 133.646 4 21 216.820 5 23∞ 6 24 -79.059 7 26 120.226 8 36 -135.543 9 40 326.087 Focus 24-25 / 36-39 Wide Angle Mid-Telephoto INF 0 / 0 0 / 0 0 / 0 10m 4.425 / 1.194 6.260 / 1.702 7.991 / 2.188 5m 8.968 / 2.466 12.783 / 3.570 16.500 / 4.678 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd θgF 1 570.3427 5.308 1.55397 71.76 0.5389 2 4110.5896 0.500 3 180.9086 14.162 1.43387 95.10 0.5373 4 -16508.0671 79.751 5 139.9369 7.584 1.43387 95.10 0.5373 6 653.8269 1.766 7 -4831.6176 2.500 1.65412 39.68 0.5737 8 174.5670 (variable) 9 518.2941 2.000 1.75500 52.32 0.5475 10 122.9643 8.588 11 -110.2774 2.000 1.43875 94.66 0.5340 12 580.4461 2.754 1.94594 17.98 0.6546 13 -1719.8627 (variable) 14 542.7184 9.491 1.43875 94.66 0.5340 15 -140.9845 0.300 16 214.1095 8.022 1.43875 94.66 0.5340 17 -340.1080 0.300 18 119.2253 13.087 1.43875 94.66 0.5340 19 -160.9653 1.800 1.88300 40.76 0.5667 20 422.5642 (variable) 21 101.4565 8.513 1.43875 94.66 0.5340 22 -706.5165 (variable) 23 (Aperture) ∞ (Variable) 24 272.7897 2.275 1.86966 20.02 0.6434 25 1503.3424 1.200 1.85150 40.78 0.5695 26 63.1952 (variable) 27 56.6311 6.531 1.58313 59.38 0.5434 28 -168.5178 1.400 1.98612 16.48 0.6657 29 416.0912 1.895 30 12335.3111 4.342 1.72047 34.71 0.5834 31 -66.3850 1.200 1.43875 94.66 0.5340 32 42.4384 5.451 33 -79.6923 1.200 1.61800 63.40 0.5395 34 164.6449 4.073 35 158.9082 3.926 1.89286 20.36 0.6393 36 -104.0776 1.882 37 3107.5060 6.177 1.51680 64.20 0.5342 38 -38.1010 1.500 1.69350 53.21 0.5473 39 -76.7167 14.040 40 -2495.0850 1.802 1.98612 16.48 0.6657 41 289.7081 4.371 42 -55.9357 1.487 1.83400 37.34 0.5790 43 -224.9602 (variable) 44 425.8906 5.874 1.65160 58.54 0.5390 45 -57.2522 (variable) 46 -72.2123 1.500 1.43875 94.66 0.5340 47 -228.1975 41.785 Image plane ∞ Various data Zoom ratio 1.902 Wide Angle Mid-Telephoto Focal length 306.239 400.502 582.535 F-number 2.900 3.284 4.600 Half angle of view (°) 4.041 3.092 2.127 Image height 21.635 21.635 21.635 Lens total length 475.001 475.001 475.001 BF 41.785 41.785 41.785 d 8 30.863 63.518 113.126 d13 86.178 53.524 3.916 d20 16.045 5.554 14.429 d22 4.870 15.361 6.486 d23 25.268 12.546 3.652 d26 14.363 27.084 35.979 d43 6.069 8.177 12.155 d45 9.007 6.899 2.922 Zoom lens group data Group starting plane focal length 1 1 412.353 2 9 -136.937 3 14 152.746 4 21 202.855 5 23∞ 6 24 -97.865 7 27 -222.023 8 44 77.826 9 46 -241.489 Focus 24-25 / 44-45 Wide Angle Mid-Telephoto INF 0 / 0 0 / 0 0 / 0 10m 2.604 / -1.258 4.033 / -1.909 7.881 / -3.525 5m 5.322 / -2.473 8.265 / -3.676 16.515 / -6.419 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd θgF 1 117.8476 10.117 1.59410 60.47 0.5550 2 -727.8101 18.200 3 94.9790 8.242 1.49700 81.61 0.5386 4 -252.5833 1.800 1.78800 47.37 0.5559 5 94.7236 (variable) 6 157.5616 1.500 1.79500 45.29 0.5600 7 39.1088 6.013 8 -383.4067 1.500 1.49700 81.61 0.5386 9 35.7445 7.507 1.83400 37.34 0.5790 10 -23201.6288 3.000 11 -63.2907 1.500 1.77250 49.63 0.5508 12 -264.1072 (variable) 13 79.9982 5.382 1.43700 95.10 0.5326 14 -193.1021 0.200 15 78.6173 5.052 1.49700 81.61 0.5386 16 -278.0686 0.200 17 61.2944 8.872 1.49700 81.61 0.5386 18 -60.7345 1.300 1.83481 42.72 0.5650 19 117.9451 2.700 20(Aperture) ∞ 18.024 21 163.3512 1.200 1.83400 37.16 0.5776 22 40.5008 8.022 1.51823 58.90 0.5457 23 -84.0400 0.200 24 78.6064 3.008 1.83481 42.72 0.5650 25 1019.6835 (variable) 26 -288.7482 2.342 1.80518 25.46 0.6156 27 -60.1020 4.557 28 -49.2539 1.000 1.77250 49.60 0.5520 29 42.3947 (variable) 30 -45.0423 1.400 1.75211 25.05 0.6190 31 -62.7141 0.200 32 76.8156 3.984 1.83481 42.72 0.5650 33 -47317.2031 39.493 Image plane ∞ Various data Zoom ratio 4.047 Wide Angle Mid-Telephoto Focal length 71.997 136.486 291.389 F-number 4.120 4.120 4.120 Half angle of view (°) 16.725 9.007 4.246 Image height 21.635 21.635 21.635 Lens total length 276.801 306.083 332.801 BF 39.493 58.857 64.844 d 5 2.000 49.361 107.654 d12 82.955 43.367 1.534 d25 3.802 5.786 15.562 d29 21.532 21.691 16.186 d33 39.493 58.857 64.844 Zoom lens group data Group starting plane focal length 1 1 357.575 2 6 -59.668 3 13 53.274 4 26 -45.937 5 30 153.963 [Numerical Example 4] Unit: mm Surface Data Surface number rd nd νd θgF 1 509.4253 5.145 1.55397 71.76 0.5389 2 1908.1748 0.500 3 172.6878 14.918 1.43387 95.10 0.5373 4 -6542.9443 79.356 5 151.3594 7.360 1.43387 95.10 0.5373 6 1005.1306 1.834 7 -1171.2363 2.500 1.65412 39.68 0.5737 8 185.1693 (variable) 9 390.5571 2.000 1.75500 52.32 0.5474 10 126.1889 8.294 11 -115.1194 2.000 1.45860 90.19 0.5354 12 256.0979 (variable) 13 337.6115 2.846 1.94594 17.98 0.6546 14 1629.6846 (variable) 15 453.0790 10.195 1.43875 94.66 0.5340 16 -135.6192 0.300 17 202.0520 8.211 1.43875 94.66 0.5340 18 -356.3936 0.300 19 112.1278 13.346 1.43875 94.66 0.5340 20 -167.8601 1.800 1.88300 40.76 0.5667 21 351.9034 (variable) 22 102.2878 8.157 1.43875 94.66 0.5340 23 -848.5635 (variable) 24 (Aperture) ∞ (Variable) 25 236.4199 2.191 1.86966 20.02 0.6434 26 648.7493 1.200 1.83481 42.74 0.5648 27 63.6631 (variable) 28 56.2840 6.407 1.58313 59.38 0.5434 29 -150.1497 1.400 1.98612 16.48 0.6657 30 512.0374 1.816 31 -4546.1831 4.028 1.72047 34.71 0.5834 32 -67.7594 1.200 1.43875 94.66 0.5340 33 40.8618 5.154 34 -81.0754 1.200 1.61800 63.40 0.5395 35 151.7764 3.690 36 155.9681 3.892 1.89286 20.36 0.6393 37 -89.4509 1.793 38 846.1126 6.168 1.51680 64.20 0.5342 39 -37.8113 1.500 1.69350 53.21 0.5473 40 -83.0137 8.168 41 -273.1606 1.495 1.98612 16.48 0.6657 42 962.3575 3.565 43 -62.5689 1.489 1.85540 36.56 0.5782 44 2447.8470 (variable) 45 211.7513 6.420 1.67790 50.72 0.5557 46 -56.4512 (variable) 47 -65.0196 1.500 1.43875 94.66 0.5340 48 -161.4072 47.957 Image plane ∞ Various data Zoom ratio 1.904 Wide Angle Mid-Telephoto Focal length 305.975 400.455 582.520 F-number 2.900 3.300 4.600 Half angle of view (°) 4.045 3.092 2.127 Image height 21.635 21.635 21.635 Lens total length 475.001 475.001 475.001 BF 47.957 47.957 47.957 d 8 30.113 61.786 109.903 d12 3.056 2.446 2.230 d14 82.767 51.705 3.803 d21 17.440 5.739 16.238 d23 4.813 16.515 6.016 d24 23.683 10.524 3.768 d27 18.180 31.340 38.095 d44 6.384 7.913 10.725 d46 7.269 5.740 2.928 Zoom lens group data Group starting plane focal length 1 1 416.444 2 9 -99.882 3 13 449.682 4 15 145.221 5 22 208.601 6 24∞ 7 25 -106.379 8 28 -128.199 9 45 66.388 10 47 -249.342 Focus 23-24 / 35-38 Wide Angle Mid-Telephoto INF 0 / 0 0 / 0 0 / 0 10m 2.633 / -1.267 4.081 / -1.877 8.230 / -3.552 5m 5.386 / -2.429 8.377 / -3.607 17.333 / -6.404 [Numerical Example 5] Unit: mm Surface Data Surface number rd nd νd θgF 1* 233.5210 14.201 1.59349 67.00 0.5361 2 -3860.7690 75.218 3 167.5081 9.741 1.43387 95.10 0.5373 4 1366.7274 2.895 5 -907.6191 2.500 1.61340 44.27 0.5633 6 134.9541 10.172 1.43387 95.10 0.5373 7 733.9326 (variable) 8 418.4886 2.923 1.98612 16.48 0.6657 9 2855.5393 1.800 1.51680 64.20 0.5342 10 91.7731 (variable) 11 -158.0234 1.800 1.75500 52.32 0.5474 12 -1095.0250 (variable) 13 274.5113 9.678 1.43387 95.10 0.5373 14 -157.2093 0.300 15 147.8952 8.122 1.43387 95.10 0.5373 16 -581.1844 0.300 17 105.1297 12.023 1.43875 94.66 0.5340 18 -187.0741 1.500 1.85150 40.78 0.5695 19 289.7811 (variable) 20 123.0396 5.946 1.49700 81.54 0.5375 21 -2854.4014 (variable) 22 (Aperture) ∞ (Variable) 23 613.1779 1.000 1.77250 49.60 0.5520 24 56.2042 (variable) 25 53.9825 1.000 1.89286 20.36 0.6393 26 37.6134 7.374 1.61340 44.27 0.5633 27 -207.9132 0.981 28 1552.5249 4.375 1.66565 35.64 0.5824 29 -58.2642 1.200 1.55200 70.70 0.5421 30 47.9290 3.954 31 -144.3128 1.200 1.49700 81.54 0.5375 32 59.0492 2.499 33 57.9347 6.233 1.58144 40.75 0.5774 34 -94.1465 (variable) 35 220.2090 1.400 1.49700 81.54 0.5375 36 66.0540 7.287 37 -38.9405 1.400 1.75211 25.05 0.6190 38 -45.3811 (variable) 39 53.4770 3.715 1.54814 45.79 0.5686 40 112.3255 6.030 41 -77.1110 1.500 1.49700 81.54 0.5375 42 -105.0245 39.500 Image plane ∞ Aspheric Data Front page K = 0.00000e+00 A 4= 7.18492e-10 A 6= 2.58156e-14 A 8= 1.34636e-18 Various data Zoom ratio 1.424 Wide Angle Mid-Telephoto Focal length 409.422 505.057 582.860 F-number 2.880 3.553 4.100 Half angle of view (°) 3.025 2.453 2.126 Image height 21.635 21.635 21.635 Lens total length 475.002 475.002 475.002 BF 39.500 39.500 39.500 d 7 78.590 105.041 124.799 d10 13.095 14.557 15.911 d12 51.821 23.907 2.796 d19 14.645 11.584 15.115 d21 4.855 7.917 4.386 d22 21.855 11.025 3.911 d24 19.450 30.279 37.393 d34 6.280 4.664 1.976 d38 14.644 16.260 18.948 Zoom lens group data Group starting plane focal length 1 1 385.915 2 8 -293.729 3 11 -244.803 4 13 132.759 5 20 237.492 6 22∞ 7 23 -80.161 8 25 127.025 9 35 -128.916 10 39 257.818 Focus 23-24 / 35-38 Wide Angle Mid-Telephoto INF 0 / 0 0 / 0 0 / 0 10m 4.312 / 1.809 6.062 / 2.617 7.603 / 3.365 5m 8.687 / 3.911 12.273 / 5.837 15.524 / 7.739 [Numerical Example 6] Unit: mm Surface Data Surface number rd nd νd θgF 1 377.2064 4.992 1.55200 70.70 0.5421 2 -308.8554 23.000 3 102.6869 7.325 1.43700 95.10 0.5326 4 -936.2210 1.800 1.80000 29.84 0.6017 5 358.7290 (variable) 6 491.2972 1.500 1.75500 52.32 0.5474 7 45.1559 6.008 8 -111.6719 1.500 1.49700 81.61 0.5386 9 45.1084 7.173 1.83400 37.34 0.5790 10 -305.1587 (variable) 11 -56.4522 1.500 1.59349 67.00 0.5361 12 -506.1690 (variable) 13 115.0689 5.104 1.43700 95.10 0.5326 14 -142.5829 0.200 15 87.5168 4.562 1.49700 81.61 0.5386 16 -379.5702 0.200 17 57.4849 7.714 1.49700 81.61 0.5386 18 -106.7474 1.300 1.83481 42.72 0.5650 19 129.8218 2.700 20(Aperture) ∞ 12.700 21 86.0973 1.200 1.74951 35.33 0.5818 22 32.4825 9.408 1.49700 81.61 0.5386 23 -144.5309 0.200 24 76.8445 2.747 1.85150 40.78 0.5695 25 265.6436 (variable) 26 -137.4492 4.251 1.72047 34.71 0.5834 27 -34.4731 1.000 1.59282 68.62 0.5458 28 42.2743 (variable) 29 -40.2811 1.400 1.59270 35.45 0.5927 30 -66.3445 0.200 31 82.0262 4.137 1.71300 53.87 0.5459 32 5947.4920 (variable) Image plane ∞ Various data Zoom ratio 2.886 Wide Angle Mid-Telephoto Focal length 101.052 149.599 291.652 F-number 4.120 4.120 4.120 Half angle of view (°) 12.084 8.229 4.242 Image height 21.635 21.635 21.635 Lens total length 279.187 298.229 308.962 BF 39.496 46.458 52.523 d 5 15.457 41.395 71.518 d10 4.243 5.452 5.454 d12 50.522 34.089 1.454 d25 4.624 5.350 8.335 d28 51.023 51.663 55.855 d32 39.496 46.458 52.523 Zoom lens group data Group starting plane focal length 1 1 205.720 2 6 -116.803 3 11 -107.192 4 13 49.219 5 26 -63.658 6 29 330.139 Various values ​​in each numerical example are summarized in Table 1 below.

[0073] [Table 1]

[0074] [Imaging device] Next, an embodiment of a digital still camera (imaging device) using the zoom lens of each embodiment as an imaging optical system will be described with reference to Fig. 13. In Fig. 13, 10 denotes a camera body, and 11 denotes an imaging optical system constituted by any of the zoom lenses described in the first to sixth embodiments. 12 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor that is built into the camera body and receives an optical image formed by the imaging optical system 11 and photoelectrically converts it. The camera body 10 may be a so-called single-lens reflex camera having a quick-turn mirror, or may be a so-called mirrorless camera having no quick-turn mirror.

[0075] In this way, by applying the zoom lens of each embodiment to an imaging device such as a digital still camera, it is possible to obtain an imaging device with a small lens. [Imaging system] An imaging system (surveillance camera system) may be configured that includes the zoom lens of each embodiment and a control unit that controls the zoom lens. In this case, the control unit can control the zoom lens so that each lens group moves as described above during zooming, focusing, and image blur correction. In this case, the control unit does not need to be configured integrally with the zoom lens, and the control unit may be configured separately from the zoom lens. For example, a configuration may be adopted in which a control unit (control device) that is disposed far away from a drive unit that drives each lens of the zoom lens includes a transmission unit that sends a control signal (command) for controlling the zoom lens. With such a control unit, the zoom lens can be remotely operated.

[0076] In addition, the control unit may be provided with an operation unit such as a controller or buttons for remotely operating the zoom lens, so that the zoom lens is controlled in response to a user's input to the operation unit. For example, a zoom-in button and a zoom-out button may be provided as the operation unit. In this case, the control unit may be configured to send a signal to a drive unit for the zoom lens so that the magnification of the zoom lens increases when the user presses the zoom-in button, and decreases when the user presses the zoom-out button.

[0077] The imaging system may also have a display unit such as a liquid crystal panel that displays information (movement state) related to the zoom of the zoom lens. The information related to the zoom of the zoom lens is, for example, the zoom magnification (zoom state) and the movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing the information related to the zoom of the zoom lens displayed on the display unit. In this case, the display unit and the operation unit may be integrated by adopting, for example, a touch panel.

[0078] The disclosure of this embodiment includes the following configurations and methods.

[0079] (Configuration 1) A zoom lens having, in order from an object side to an image side, a first lens group having positive refractive power, a front group including one or two lens groups and having negative refractive power as a whole, and a rear group including an aperture stop and one or more lens groups, wherein the distance between adjacent lens groups changes during zooming, the first lens group is fixed with respect to an image plane during focusing; the first lens group includes a positive lens arranged closest to the object, At the telephoto end, when the refractive powers of the positive lens to the lens located closest to the image side of the front group are combined, the combined refractive power becomes negative, Let dsw be the distance on the optical axis from the aperture stop to the image plane at the wide-angle end, Ldw be the total length of the zoom lens at the wide-angle end, nd1max be the maximum refractive index of the lenses included in the first lens group, d1a be the maximum value of the air spacing in the first lens group over the entire zoom range, and dUa be the maximum value of the air spacing in the front lens group over the entire zoom range. 0.10 <dsw / Ldw<0.50 1.45 <nd1max≦1.80 3 <d1a / dUa<300 A zoom lens characterized by satisfying the following conditional expressions: (Configuration 2) Let ndUv be the refractive index of the lens made of a material having the maximum refractive index among the lenses included in the front group. 1.75 <ndUv<2.40 2. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 3) Let θgFUv be the partial dispersion ratio of the lens made of a material having the maximum refractive index among the lenses included in the front group. 0.56<θgFUv<0.68 3. The zoom lens according to claim 1, wherein the following condition is satisfied: (Configuration 4) When the average Abbe number at the d line of the lenses included in the first lens group is νd1a, 56<νd1a<100 4. The zoom lens according to any one of configurations 1 to 3, wherein the following condition is satisfied: (Configuration 5) Let βUt be the lateral magnification of the front group at the telephoto end, -35.00<βUt<-0.45 5. The zoom lens according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) When the lateral magnification of the front group at the telephoto end is βUt and the lateral magnification of the front group at the wide-angle end is βUw, 1.7<βUt / βUw<20.0 6. The zoom lens according to any one of configurations 1 to 5, wherein the following condition is satisfied: (Configuration 7) Let f1 be the focal length of the first lens group, and fLA be the focal length of the lens group in the rear group that is located closest to the object side. 2.4 <f1 / fLA<10.0 7. The zoom lens according to any one of configurations 1 to 6, wherein the following condition is satisfied: (Configuration 8) Let fU be the focal length of the front group at the telephoto end, and ft be the focal length of the zoom lens at the telephoto end. -0.35 <fU / ft<-0.05 8. The zoom lens according to any one of configurations 1 to 7, wherein the following condition is satisfied: (Configuration 9) When the back focus at the telephoto end is skt, 0.01 <skt / ft<0.35 9. The zoom lens according to any one of configurations 1 to 8, wherein the following condition is satisfied: (Configuration 10) Let f1 be the focal length of the first lens group, and fU be the focal length of the front lens group at the telephoto end. -9.0 <f1 / fU<-1.6 10. The zoom lens according to any one of configurations 1 to 9, wherein the following condition is satisfied: (Configuration 11) 11. A zoom lens according to any one of configurations 1 to 10, wherein the lens group arranged closest to the object side in the rear group is fixed with respect to the image plane during zooming. (Configuration 12) 12. The zoom lens according to any one of configurations 1 to 11, wherein the first lens group is composed of four or less lenses. (Configuration 13) 13. A zoom lens according to any one of configurations 1 to 12, wherein the first lens group L1 is composed of one negative lens and two or three positive lenses. (Configuration 14) 14. The zoom lens according to any one of configurations 1 to 13, wherein the front group is composed of three or four spherical lenses including at least one positive lens. (Configuration 15) 15. The zoom lens according to any one of configurations 1 to 14, wherein the lens group arranged closest to the image side of the zoom lens is fixed with respect to the image plane during zooming. (Configuration 16) 16. The zoom lens according to any one of configurations 1 to 15, wherein the lens arranged closest to the image side of the zoom lens is a lens having a convex shape facing the image side. (Configuration 17) 17. A zoom lens according to any one of configurations 1 to 16, wherein the aperture stop is disposed closer to the image side than the lens group disposed closest to the object side in the rear group. (Configuration 18) 18. A zoom lens according to any one of configurations 1 to 17, wherein the lens disposed adjacent to the image side of the aperture stop is made of an element having a convex shape facing the object side. (Configuration 19) A zoom lens according to any one of configurations 1 to 18, characterized in having, arranged in order from the object side to the image side, the first lens group, a second lens group having negative refractive power, and the rear group. (Configuration 20) The zoom lens according to configuration 19, wherein the rear group comprises a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, a sixth lens group having positive refractive power, a seventh lens group having negative refractive power, and an eighth lens group having positive refractive power. (Configuration 21) The zoom lens according to configuration 19, wherein the rear group comprises a third lens group having positive refractive power, a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, a sixth lens group having negative refractive power, a seventh lens group having positive refractive power, and an eighth lens group having negative refractive power. (Configuration 22) 20. The zoom lens according to configuration 19, wherein the rear group comprises a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. (Configuration 23) A zoom lens according to any one of configurations 1 to 18, characterized in having, arranged in order from the object side to the image side, the first lens group, a second lens group having negative refractive power, a third lens group, and the rear group. (Configuration 24) The zoom lens according to configuration 23, wherein the rear group comprises a fourth lens group having positive refractive power, a fifth lens group having positive refractive power, a sixth lens group having negative refractive power, a seventh lens group having negative refractive power, an eighth lens group having positive refractive power, and a ninth lens group having negative refractive power. (Configuration 25) The zoom lens according to configuration 23, wherein the rear group comprises a fourth lens group having positive refractive power, a fifth lens group having positive refractive power, a sixth lens group having negative refractive power, a seventh lens group having positive refractive power, an eighth lens group having negative refractive power, and a ninth lens group having positive refractive power. (Configuration 26) 24. The zoom lens according to configuration 23, wherein the rear group comprises a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power. (Configuration 27) 27. An imaging device comprising: the zoom lens according to any one of configurations 1 to 26; and an imaging element that receives an image formed by the zoom lens. (Configuration 28) 27. An imaging system comprising: a zoom lens according to any one of configurations 1 to 26; and a control unit that controls the zoom lens during zooming. (Configuration 29) 29. The imaging system according to configuration 28, wherein the control unit is configured as a separate entity from the zoom lens and has a transmission unit that transmits a control signal for controlling the zoom lens. (Configuration 30) 30. The imaging system according to configuration 28 or 29, wherein the control unit is configured as a separate entity from the zoom lens and has an operation unit for operating the zoom lens. (Configuration 31) 31. The imaging system according to any one of configurations 28 to 30, further comprising a display unit that displays information related to the zoom of the zoom lens.

[0080] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0081] L positive lens L1 First lens group U front group

Claims

1. A zoom lens having, arranged in order from the object side to the image side, a first lens group having positive refractive power, a front group including one or two lens groups and having negative refractive power as a whole, and a rear group including an aperture stop and one or more lens groups, wherein the spacing between adjacent lens groups changes during zooming, During zooming, at least four lens groups move, the first lens group is fixed relative to an image plane during focusing; the first lens group includes a positive lens arranged closest to the object, At the telephoto end, when the refractive powers of the lenses from the positive lens to the lens arranged closest to the image side in the front group are combined, the combined refractive power becomes negative, Let dsw be the distance on the optical axis from the aperture stop to the image plane at the wide-angle end, Ldw be the total length of the zoom lens at the wide-angle end, nd1max be the maximum refractive index of the lenses included in the first lens group, d1a be the maximum value of the air gap in the first lens group over the entire zoom range, and dUa be the maximum value of the air gap in the front lens group over the entire zoom range. 0.10<dsw / Ldw<0.50 1.45<nd1max≦1.80 3<d1a / dUa<300 A zoom lens characterized by satisfying the following conditional expressions:

2. Let ndUv be the refractive index of the lens made of a material with the largest refractive index among the lenses included in the front group. 1.75<ndUv<2.40 2. The zoom lens according to claim 1, wherein the following condition is satisfied:

3. When the partial dispersion ratio of the lens made of the material with the largest refractive index among the lenses included in the front group is θgFUv, 0.56<θgFUv<0.68 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

4. When the average value of the Abbe numbers at the d-line of the lenses included in the first lens group is νd1a, 56<νd1a<100 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

5. When the lateral magnification of the front group at the telephoto end is βUt, -35.00<βUt<-0.45 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

6. When the lateral magnification of the front group at the telephoto end is βUt and the lateral magnification of the front group at the wide-angle end is βUw, 1.7<βUt / βUw<20.0 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

7. When the focal length of the first lens group is f1 and the focal length of the lens group located closest to the object side in the rear group is fLA, 2.4<f1 / fLA<10.0 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

8. When the focal length of the front group at the telephoto end is fU and the focal length of the zoom lens at the telephoto end is ft, -0.35<fU / ft<-0.05 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

9. When the back focus at the telephoto end is skt, 0.01<skt / ft<0.35 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

10. When the focal length of the first lens group is f1 and the focal length of the front group at the telephoto end is fU, -9.0<f1 / fU<-1.6 3. The zoom lens according to claim 1, wherein the following condition is satisfied:

11. 3. A zoom lens according to claim 1, wherein the lens unit in the rear group arranged closest to the object side is fixed relative to the image plane during zooming.

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

13. 3. The zoom lens according to claim 1, wherein the first lens unit L1 is composed of one negative lens and two or three positive lenses.

14. 3. A zoom lens according to claim 1, wherein the front group is made up of three or four spherical lenses, including at least one positive lens.

15. 3. The zoom lens according to claim 1, wherein the lens group arranged closest to the image side of the zoom lens is fixed relative to the image plane during zooming.

16. 3. The zoom lens according to claim 1, wherein the lens element arranged closest to the image side of the zoom lens is a lens element having a convex shape facing the image side.

17. 3. The zoom lens according to claim 1, wherein the aperture stop is arranged closer to the image side than the lens group arranged closest to the object side in the rear group.

18. 3. The zoom lens according to claim 1, wherein the lens arranged adjacent to the image side of the aperture stop is made up of an element having a convex shape on the object side.

19. 3. A zoom lens according to claim 1, comprising, in order from the object side to the image side, the first lens group, a second lens group having negative refractive power, and the rear lens group.

20. 20. The zoom lens according to claim 19, wherein the rear group consists of a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a positive refractive power, a seventh lens group having a negative refractive power, and an eighth lens group having a positive refractive power.

21. 20. The zoom lens according to claim 19, wherein the rear group comprises a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, a sixth lens group having a negative refractive power, a seventh lens group having a positive refractive power, and an eighth lens group having a negative refractive power.

22. 20. The zoom lens according to claim 19, wherein the rear group comprises a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power.

23. 3. The zoom lens according to claim 1, comprising, arranged in order from the object side to the image side, the first lens group, a second lens group having negative refractive power, a third lens group, and the rear lens group.

24. 24. The zoom lens according to claim 23, wherein the rear group consists of a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, a sixth lens group having a negative refractive power, a seventh lens group having a negative refractive power, an eighth lens group having a positive refractive power, and a ninth lens group having a negative refractive power.

25. 24. The zoom lens according to claim 23, wherein the rear group consists of a fourth lens group having a positive refractive power, a fifth lens group having a positive refractive power, a sixth lens group having a negative refractive power, a seventh lens group having a positive refractive power, an eighth lens group having a negative refractive power, and a ninth lens group having a positive refractive power.

26. 24. The zoom lens according to claim 23, wherein the rear group comprises a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power.

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

28. 3. An imaging system comprising: the zoom lens according to claim 1; and a control unit that controls the zoom lens during zooming.

29. 29. The imaging system according to claim 28, wherein the control unit is configured as a separate unit from the zoom lens and includes a transmission unit that transmits a control signal for controlling the zoom lens.

30. 29. The imaging system according to claim 28, wherein the control unit is configured as a separate unit from the zoom lens and has an operation unit for operating the zoom lens.

31. 29. The imaging system according to claim 28, further comprising a display unit that displays information related to the zoom of the zoom lens.

Images