Zoom lens and imaging device

Abstract

To provide a large-aperture, compact zoom lens which offers superior optical performance, and to provide an image capturing device having the same.SOLUTION: A zoom lens and an image capturing device having the same are provided, the zoom lens comprising a first lens group G1 with negative refractive power located on the most object side and, on the image side of the first lens group G1, a positive lens group Pa (G3) with positive refractive power, a negative lens group N (G4) with negative refractive power, and a positive lens group Pb (G5) with positive refractive power arranged in the described order from the object side. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, while the positive lens group Pa and the positive lens group Pb move toward the object side on the same trajectory. Zooming is accomplished by changing distances between adjacent lens groups along an optical axis, and focusing from infinity to an object at a finite distance is accomplished by moving the negative lens group N toward the image side. The zoom lens satisfies given conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens and an imaging device suitable for a small imaging device using a solid-state imaging element or the like. [Background technology]

[0002] Conventionally, imaging devices using solid-state imaging elements such as digital still cameras and digital video cameras have been widely used. As an optical system of an imaging device, for example, a wide-angle or standard zoom lens having, in order from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power is known (for example, see Patent Documents 1 to 3). By adopting such an optical configuration, it is possible to configure the entire device compactly while satisfactorily correcting various aberrations.

[0003] In addition, in the above zoom lenses, the second lens group and the fourth lens group are moved along the same path during magnification change. Therefore, in these zoom lenses, it is possible to configure these two positive lens groups as one unit. By configuring both lens groups as a unit, it is possible to suppress the occurrence of decentering errors during assembly, reduce manufacturing errors, and improve yields. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-21258 A [Patent Document 2] JP 2014-26211 A [Patent Document 3] JP 2009-169051 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, compared to a fixed focal length lens, a zoom lens tends to be a dark lens because it is made up of a large number of lenses. Also, when the two positive lens groups are configured as one unit during zooming, it is advantageous in reducing decentering errors and manufacturing errors as described above, but it creates restrictions in increasing the aperture and reducing the size while maintaining high optical performance. For example, the zoom lenses disclosed in Patent Documents 1 and 2 have an Fno of about 5.8 at the telephoto end, and do not have a large aperture. On the other hand, the zoom lens disclosed in Patent Document 3 has an Fno of 2.8 and a large aperture. However, in this zoom lens, multiple lens groups are moved during focusing, and the mechanism for moving the lens groups during focusing and zooming is complicated. Therefore, this zoom lens is not sufficiently compact.

[0006] An object of the present invention is to provide a wide-angle or standard zoom lens and an image pickup apparatus that are large in diameter, small in size, and have high optical performance. [Means for solving the problem]

[0007] In order to solve the above problem, the zoom lens of the present invention has a first lens group having negative refractive power closest to the object side, and has a positive lens group Pa having positive refractive power, a negative lens group N having negative refractive power, and a positive lens group Pb having positive refractive power, in this order from the object side, closer to the image side than the first lens group, and when varying magnification from the wide-angle end to the telephoto end, the first lens group moves toward the image side, and the positive lens group Pa and the positive lens group Pb move toward the object side along the same locus, varying magnification by changing the distance on the optical axis between adjacent lens groups, and focusing from infinity to a finite distance object by moving the negative lens group N toward the image side, and is characterized in that the following conditions are satisfied: 0.80<(Rnf+Rnr) / (Rnf-Rnr)<1.40 ···(1) -1.20< fn / ft <-0.50 (2) however, Rnf: radius of curvature of the surface in the negative lens group N closest to the object Rnr: radius of curvature of the surface in the negative lens group N that is closest to the image side fn: focal length of the negative lens group N ft: focal length of the zoom lens at the telephoto end

[0008] In order to solve the above problem, the imaging device of the present invention is characterized in that it includes the above zoom lens and an imaging element on the image side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal. [Brief description of the drawings]

[0009] [Figure 1] 1 is a lens cross-sectional view of the zoom lens of Example 1 when focused at infinity, where the upper row shows the wide-angle end, the middle row shows the intermediate focal length, and the lower row shows the telephoto end (the same applies below). [Diagram 2] 4A to 4C are aberration diagrams of the zoom lens of Example 1 when focused on an object at infinity at the wide-angle end. [Diagram 3] 4A to 4C are aberration diagrams of the zoom lens of Example 1 when focused on infinity at an intermediate focal length. [Figure 4] 4A to 4C are aberration diagrams of the zoom lens of Example 1 when focused on an object at infinity at the telephoto end. [Diagram 5] FIG. 11 is a lens sectional view of the zoom lens of Example 2 when focused on an object at infinity. [Figure 6] 8A to 8C are aberration diagrams of the zoom lens of Example 2 when focused on an object at infinity at the wide-angle end. [Figure 7] 11A to 11C are aberration diagrams of the zoom lens of Example 2 when focused on infinity at an intermediate focal length. [Figure 8] 8A to 8C are aberration diagrams of the zoom lens of Example 2 when focused on an object at infinity at the telephoto end. [Figure 9] FIG. 11 is a lens sectional view of the zoom lens of Example 3 when focused on an object at infinity. [Figure 10] 11A to 11C are aberration diagrams of the zoom lens of Example 3 when focused on an object at infinity at the wide-angle end. [Figure 11] 11A to 11C are aberration diagrams of the zoom lens of Example 3 when focused on infinity at an intermediate focal length. [Figure 12]11A to 11C are aberration diagrams of the zoom lens of Example 3 when focused on an object at infinity at the telephoto end. [Figure 13] FIG. 11 is a lens sectional view of the zoom lens of Example 4 when focused on an object at infinity. [Figure 14] 11A to 11C are aberration diagrams of the zoom lens of Example 4 when focused on an object at infinity at the wide-angle end. [Figure 15] 11A to 11C are aberration diagrams of the zoom lens of Example 4 when focused on infinity at an intermediate focal length. [Figure 16] 11A to 11C are aberration diagrams of the zoom lens of Example 4 when focused on an object at infinity at the telephoto end. [Figure 17] FIG. 13 is a lens sectional view of the zoom lens of Example 5 when focused on an object at infinity. [Figure 18] 13A to 13C are aberration diagrams of the zoom lens of Example 5 when focused on an object at infinity at the wide-angle end. [Figure 19] 13A to 13C are aberration diagrams of the zoom lens of Example 5 when focused on infinity at an intermediate focal length. [Figure 20] 13A to 13C are aberration diagrams of the zoom lens of Example 5 when focused on an object at infinity at the telephoto end. [Figure 21] FIG. 13 is a lens sectional view of the zoom lens of Example 6 when focused on an object at infinity. [Figure 22] 13A to 13C are aberration diagrams of the zoom lens of Example 6 when focused on an object at infinity at the wide-angle end. [Diagram 23] 13A to 13C are aberration diagrams of the zoom lens of Example 6 when focused on infinity at an intermediate focal length. [Figure 24] 13A to 13C are aberration diagrams of the zoom lens of Example 6 when focused on an object at infinity at the telephoto end. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the zoom lens and the imaging device according to the present invention will be described. However, the zoom lens and the imaging device described below are one aspect of the zoom lens and the imaging device according to the present invention, and the zoom lens and the imaging device according to the present invention are not limited to the following aspects.

[0011] 1. Zoom Lens 1-1.Optical configuration The zoom lens of this embodiment has a first lens group having negative refractive power closest to the object, and has, on the image side of the first lens group, a positive lens group Pa having positive refractive power, a negative lens group N having negative refractive power, and a positive lens group Pb having positive refractive power, in that order from the object side.

[0012] By adopting the above-mentioned refractive power arrangement, the zoom lens can easily correct aberrations during zooming while widening the angle of view at the wide-angle end, thereby realizing a wide-angle or standard zoom lens that is small in size and has high optical performance.

[0013] Here, the zoom lens may include the first lens group, and a positive lens group Pa, a negative lens group N, and a positive lens group Pb that are adjacently arranged in order from the object side on the image side of the first lens group. The zoom lens may be substantially composed of these four lens groups, or may include other lens groups. For example, various configurations may be adopted, such as a four-group configuration having a negative-positive-negative-positive refractive power arrangement in order from the object side, a five-group configuration having a negative-negative-positive-negative-positive refractive power arrangement in order from the object side, or a six-group configuration having a negative-negative-positive-positive-negative-positive refractive power arrangement in order from the object side, or a negative-positive-positive-negative-positive refractive power arrangement in order from the object side, or a negative-positive-positive-negative-positive refractive power arrangement in order from the object side. In any configuration, by changing the distance on the optical axis between adjacent lens groups when changing the magnification, aberration correction becomes easy, and a zoom lens with high optical performance over the entire magnification range can be realized. However, from the viewpoint of miniaturizing the zoom lens, it is preferable that the number of lens groups that substantially constitute the zoom lens is six or less.

[0014] (1) First lens group The first lens group is the lens group arranged closest to the object in the zoom lens, and moves toward the image side when zooming from the wide-angle end to the telephoto end. A so-called negative-first type zoom lens, in which a lens group having a negative refractive power is arranged closest to the object, can shorten the close-up shooting distance and relatively easily achieve a wide angle of view. Since it is relatively easy to ensure a back focus in such a negative-first type refractive power arrangement, it is suitable as an optical system for a single-lens reflex camera. On the other hand, in an optical system for an imaging device that does not require a reflex mirror, such as a mirrorless single-lens camera, the back focus may be shorter than that of an optical system for a single-lens reflex camera. In an optical system for an imaging device that may have a short back focus, a lens configuration close to symmetrical can be adopted even when a negative-first type refractive power arrangement is adopted. In an asymmetrical lens configuration, when an aperture is increased, the lens design becomes complicated in order to satisfactorily correct various aberrations such as distortion, and it may be difficult to achieve a large aperture while maintaining a small size and good imaging performance. On the other hand, with a lens configuration that is close to symmetrical, it is relatively easy to correct distortion and other aberrations even when the aperture is increased. Therefore, by using the zoom lens in the optical system of a mirrorless single-lens camera or the like, it becomes easy to increase the aperture while maintaining a small size and good imaging performance.

[0015] As long as the first lens group has a negative refractive power, the specific lens configuration is not particularly limited. In a wide-angle or standard zoom lens having a first lens group with a negative refractive power closest to the object side, the ray height of the maximum off-axis light beam incident on the first lens group, i.e., the incident position of the maximum off-axis light beam on the first lens group, becomes high, so that the off-axis light beam is incident on the periphery of the lens. Therefore, in order to realize a wider angle of view at the wide-angle end while maintaining the zoom lens compact, it is preferable to configure the zoom lens using multiple lenses with negative refractive power. In particular, it is preferable that at least one lens, preferably two or more lenses among the lenses with negative refractive power constituting the first lens group are meniscus lenses with a concave shape toward the image side. By adopting such a configuration, it is possible to prevent the off-axis light beam from being strongly bent when passing through each surface constituting the first lens group while disposing a strong negative refractive power in the first lens group. Therefore, it is possible to reduce the occurrence of curvature of field, distortion aberration, etc., and obtain a zoom lens with good image surface characteristics. In order to improve the image surface characteristics, it is preferable that at least one of the lenses in the first lens group has one or more aspheric surfaces.

[0016] In order to effectively correct various aberrations such as spherical aberration and coma, it is preferable that the first lens group has at least one lens having positive refractive power.

[0017] An optical element having no refractive power or an extremely small refractive power may be disposed on the object side of the first lens group. Examples of such an optical element include a protection filter for protecting the lens from dirt and scratches, an ND filter used to reduce the amount of incident light, and various filters such as a PL filter for adjusting color.

[0018] (2) Positive lens group Pa and positive lens group Pb The positive lens group Pa and the positive lens group Pb each have a positive refractive power. In addition, the positive lens group Pa and the positive lens group Pb move toward the object side along the same trajectory when zooming from the wide-angle end to the telephoto end. By moving the positive lens group Pa and the positive lens group Pb, which have positive refractive power, along the same trajectory, it is possible to configure the positive lens group Pa and the positive lens group Pb as one unit. Therefore, compared with the case where the positive lens group Pa and the positive lens group Pb are moved along separate trajectories, it is possible to simply configure a zoom mechanism for moving each lens group when zooming. Furthermore, it is possible to suppress the occurrence of decentering errors during assembly, thereby reducing manufacturing errors and improving yields.

[0019] The positive lens group Pa and the positive lens group Pb are not particularly limited in their specific lens configurations as long as they each have a positive refractive power. In the zoom lens, they are arranged on the image side. With the zooming operation of the zoom lens, the ray height of the maximum off-axis light beam incident on the positive lens group Pb varies. That is, the ray height of the maximum off-axis light beam incident on the positive lens group Pb differs between the wide-angle end and the telephoto end. Therefore, in order to satisfactorily correct coma aberration, curvature of field, etc., it is preferable that the positive lens group Pb includes at least one aspherical surface.

[0020] (3) Negative Lens Group N The negative lens group N has a negative refractive power, and is disposed between the positive lens group Pa and the positive lens group Pb adjacent to these lens groups, and the specific lens configuration is not particularly limited as long as the distance on the optical axis between the positive lens group Pa and the negative lens group N and the distance on the optical axis between the negative lens group N and the positive lens group Pb change during magnification. For example, it is preferable that the negative lens group N is composed of one lens element. Here, the lens element refers to one single lens, or a cemented lens in which multiple single lenses are integrated without an air gap. That is, the single lens element referred to here refers to a lens having multiple optical surfaces, in which only the most object-side surface and the most image-side surface are in contact with air, and the other surfaces are not in contact with air. In addition, in this specification, the single lens may be either a spherical lens or an aspherical lens. In addition, the aspherical lens also includes a so-called composite aspherical lens having an aspherical film attached to its surface.

[0021] By configuring the negative lens group N from one lens element, various manufacturing errors such as decentering errors and errors in the air gap between multiple lens elements can be reduced. This makes it possible to reduce degradation of optical performance caused by manufacturing errors, and to reduce variations in performance between products. This makes it possible to manufacture zoom lenses with high optical performance with a good yield.

[0022] During zooming, by changing the axial distance between the negative lens group N and the positive lens group Pa, and the axial distance between the negative lens group N and the positive lens group Pb, it is possible to satisfactorily correct various aberrations throughout the entire zoom range, and to realize a zoom lens with a large zoom ratio. Furthermore, by changing the axial distance between the negative lens group N and the positive lens group Pa, and the axial distance between the negative lens group N and the positive lens group Pb, it is possible to maintain good image surface quality during zooming.

[0023] Furthermore, in this zoom lens, the negative lens group N is used as a focusing group, and the negative lens group N is moved along the optical axis to focus from infinity to a nearby object. As described above, when the positive lens group Pa and the positive lens group Pb are configured as one unit, the negative lens group N is supported movably relative to the unit, so that even when the negative lens group N is directly driven by a stepping motor or an ultrasonic piezo motor during zooming and focusing, decentering error caused by the movement of the negative lens group N can be suppressed. Therefore, even if the shooting distance changes depending on the position of the subject, aberration fluctuation caused by decentering error can be suppressed, and a beautiful subject image can be obtained regardless of the shooting distance.

[0024] Furthermore, by configuring the negative lens group N from a single lens element as described above, the focusing group can be made lighter, the controllability of the focusing group can be improved, and quick autofocusing can be achieved.

[0025] (4) Aperture diaphragm In the zoom lens, the arrangement of the aperture diaphragm is not particularly limited, but in order to reduce the size and increase the aperture of the zoom lens, it is preferable to arrange the aperture diaphragm between the first lens group and the positive lens group Pa. The zoom lens includes the first lens group having negative refractive power, which is closest to the object side. Therefore, if the aperture diaphragm is arranged closer to the image side than the positive lens group Pa, the entrance pupil position will be located on the image side in the entire zoom lens system. If the entrance pupil position is located on the image side, the front lens diameter will be large, making it difficult to reduce the size of the zoom lens. In this case, it is also difficult to sufficiently pass off-axis light beams, making it difficult to increase the aperture of the zoom lens while ensuring the peripheral light amount.

[0026] When one or more lens groups are disposed between the first lens group and the positive lens group Pa, the aperture diaphragm may be disposed between the lens surface of the first lens group closest to the image side and the lens surface of the positive lens group Pa closest to the object side, and the position of the aperture diaphragm is not particularly limited as long as it is disposed between these two positions. However, in this case, in order to obtain the above-mentioned effect, it is more preferable to dispose the aperture diaphragm between the lens group disposed immediately before the object side of the positive lens group Pa and the positive lens group Pa.

[0027] (5) Operation when changing magnification In this zoom lens, the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this case, as described above, when changing the magnification from the wide-angle end to the telephoto end, the first lens group moves toward the image side, and the positive lens group Pa and the positive lens group Pb move toward the object side along the same trajectory. Apart from these points, the direction and amount of movement of each lens group during the magnification change are not particularly limited. Also, as long as the distance on the optical axis between adjacent lens groups changes, each lens group may be a moving group that moves along the optical axis during the magnification change, or a fixed group that is fixed with respect to the imaging surface.

[0028] 1-2.Conditional Expressions In the zoom lens, it is preferable that the above-mentioned configuration is adopted and that one or more of the following conditional expressions are satisfied.

[0029] 1-2-1.Conditional expression (1) 0.80<(Rnf+Rnr) / (Rnf-Rnr)<1.40 ···(1) however, Rnf: radius of curvature of the surface closest to the object in the negative lens group N Rnr: radius of curvature of the surface closest to the image side in the negative lens group N

[0030] Conditional formula (1) is a formula that specifies the shape of the entrance surface and the exit surface of the negative lens group N. By satisfying conditional formula (1), it is possible to suppress the fluctuation of spherical aberration, curvature of field, and distortion during zooming, and to perform favorable correction of these various aberrations. Therefore, even when the positive lens group Pa and the positive lens group Pb arranged in front of and behind the negative lens group N are moved along the same locus during zooming, it is possible to obtain a zoom lens with high imaging performance by suppressing the fluctuation of aberration. In addition, when the negative lens group N is used as a focusing group, it is possible to suppress the fluctuation of spherical aberration when focusing on a nearby object, and it is possible to realize a zoom lens with high optical performance over the entire focusing range.

[0031] On the other hand, when the value of conditional formula (1) is equal to or less than the lower limit, the effect of the light beam converged by the positive lens group Pa being bounced up at the entrance surface of the negative lens group N becomes large. In this case, the variation of spherical aberration during magnification and focusing becomes large, so that it becomes difficult to move the positive lens group Pa and the positive lens group Pb on the same trajectory during magnification in order to obtain a zoom lens with high optical performance. Therefore, it becomes impossible to configure the positive lens group Pa and the positive lens group Pb as one unit, and the mechanism for moving each lens group during magnification becomes complicated, and the configuration of the lens barrel also becomes complicated, making it difficult to miniaturize the entire zoom lens unit. On the other hand, when the value of conditional formula (1) is equal to or more than the upper limit, the effect of the off-axis light beam being bounced up at the exit surface of the negative lens group N becomes large. In this case, the variation of field curvature and distortion during magnification and focusing becomes large. Therefore, it becomes impossible to move the positive lens group Pa and the positive lens group Pb along the same locus during magnification change, and for the same reason as above, it becomes difficult to reduce the size of the entire zoom lens unit.

[0032] In order to obtain the above effect, the lower limit of conditional formula (1) is preferably 0.85, and more preferably 0.90. The upper limit of conditional formula (1) is preferably 1.35, more preferably 1.30, and even more preferably 1.25. In conditional formula (1), the above-mentioned preferable numerical values ​​of the lower limit and upper limit can be appropriately selected, and in that case, the inequality sign (<) in conditional formula (1) may be changed to an inequality sign with an equal sign (≦). The same applies to the other conditional formulas.

[0033] 1-2-2.Conditional expression (2) -1.20< fn / ft <-0.50 (2) however, fn: focal length of negative lens group N ft: focal length of the zoom lens at the telephoto end

[0034] Conditional formula (2) defines the ratio between the focal length of the negative lens group N and the focal length of the zoom lens at the telephoto end. By satisfying conditional formula (2), the refractive power of the negative lens group N falls within an appropriate range, and the amount of movement of the negative lens group N during zooming can be kept within an appropriate range, making it possible to realize a compact zoom lens with high optical performance over the entire zoom range.

[0035] On the other hand, when the value of conditional expression (2) is equal to or less than the lower limit, the refractive power of the negative lens group N becomes weak, and in order to perform good aberration correction over the entire zoom range, it is necessary to increase the amount of movement of the negative lens group N during zooming. This is undesirable because it is difficult to achieve a compact zoom lens while maintaining high optical performance. On the other hand, when the value of conditional expression (2) is equal to or more than the upper limit, the refractive power of the negative lens group N becomes strong, and it is possible to reduce the amount of movement of the negative lens group N during zooming. However, when the refractive power of the negative lens group N becomes strong, the aberration fluctuation accompanying the movement of the negative lens group N becomes large. In order to obtain a zoom lens with high optical performance, it is difficult to move the positive lens group Pa and the positive lens group Pb on the same trajectory during zooming, and for the same reason as above, it is difficult to reduce the size of the entire zoom lens unit.

[0036] In order to obtain the above-mentioned effects, the lower limit of conditional expression (2) is preferably -1.10, and more preferably -1.00, and the upper limit of conditional expression (2) is preferably -0.55, and more preferably -0.60.

[0037] 1-2-3.Conditional expression (3) -5.40 <(1-βnt 2 )×βrt 2 < -2.40 ···(3) however, βnt: lateral magnification of negative lens group N at the telephoto end βrt: the combined lateral magnification at the telephoto end of all lens groups located on the image side of the negative lens group N

[0038] Conditional formula (3) is a formula for defining the sensitivity of the negative lens group N. Here, the sensitivity represents the amount of movement of the image plane when the lens group moves a unit amount. When the negative lens group N is used as a focusing group, by satisfying conditional formula (3), the amount of movement of the negative lens group N when focusing from infinity to a close object can be kept within an appropriate range, making it easier to control the movement position of the negative lens group N when focusing and to make the zoom lens more compact.

[0039] On the other hand, when the value of conditional formula (3) is equal to or less than the lower limit, the sensitivity of the negative lens group N becomes high. Therefore, when the negative lens group N is used as a focusing group, the amount of movement of the negative lens group N when focusing on a nearby object becomes small, so that it becomes necessary to control the movement position of the negative lens group N when focusing with extremely high precision, which may make the control difficult. On the other hand, when the value of conditional formula (3) is equal to or more than the upper limit, the sensitivity of the negative lens group N becomes low, so that when the negative lens group N is used as a focusing group, the amount of movement of the negative lens group N when focusing on a nearby object becomes large. Therefore, it becomes difficult to achieve a compact zoom lens.

[0040] In order to obtain the above-mentioned effects, the lower limit of conditional formula (3) is preferably -5.00, and more preferably -4.60, and the upper limit of conditional formula (3) is preferably -2.55, and more preferably -2.70.

[0041] 1-2-4.Conditional expression (4) When the negative lens group N is composed of one lens element, it is preferable that the following condition is satisfied. vdn > 50 ···(4) however, vdn: Abbe number of the lens element constituting the negative lens group N (when the lens element is composed of a single lens, it is the Abbe number of the single lens at the d-line. When the lens element is composed of a cemented lens, it is the Abbe number of the lens having the largest negative refractive power at the d-line among the multiple single lenses constituting the cemented lens.)

[0042] Conditional formula (4) is a formula that specifies the Abbe number of the lens element for the d-line when the negative lens group N is composed of one lens element. By satisfying conditional formula (4), the occurrence of chromatic aberration in the negative lens group N can be suppressed. In addition, in a zoom lens, for example, at the wide-angle end, the axial chromatic aberration can be corrected well, but the lateral chromatic aberration becomes large, and at the telephoto end, the lateral chromatic aberration can be corrected well, but the axial chromatic aberration becomes large. In other words, it may be difficult to correct the axial chromatic aberration and the lateral chromatic aberration in a well-balanced manner. By satisfying conditional formula (4), it becomes easy to correct both the axial chromatic aberration and the lateral chromatic aberration in a well-balanced manner at both the wide-angle end and the telephoto end. Furthermore, in the zoom lens, the negative lens group N is used as a focusing group, and by satisfying the above conditional formula (4), the occurrence of the axial chromatic aberration caused by the change in the shooting distance can be suppressed, and the chromatic aberration can be corrected well over the entire focusing range.

[0043] On the other hand, when the value of conditional formula (4) is equal to or smaller than the lower limit, it becomes difficult to correct axial chromatic aberration and lateral chromatic aberration in a well-balanced manner because the chromatic dispersion of the lens elements constituting the negative lens group N becomes large. Furthermore, when the negative lens group N is used as a focusing group to focus on a nearby object, it becomes difficult to correct axial chromatic aberration, which is not preferable.

[0044] In order to obtain the above effect, the lower limit of conditional expression (4) is preferably 60, more preferably 65, and even more preferably 70. On the other hand, the above effect can be obtained by satisfying conditional expression (4), and there is no need to specify the upper limit of conditional expression (4). However, glass materials with large Abbe numbers are more expensive than glass materials with small Abbe numbers. To effectively correct chromatic aberration, it is preferable to use glass materials with large Abbe numbers, but the larger the Abbe number, the less cost-effective it is. From this viewpoint, therefore, the upper limit of conditional expression (4) is preferably 100 or less, more preferably 95, and even more preferably 85.

[0045] 1-2-5.Conditional expression (5) -1.60 ≦ XF / XR ≦ -0.30 (5) however, XF: Distance traveled on the optical axis by the first lens group when changing magnification from the wide-angle end to the telephoto end XR: The distance traveled on the optical axis when the positive lens group Pa changes magnification from the wide-angle end to the telephoto end

[0046] Conditional formula (5) is a formula that specifies the ratio of the moving distances of the first lens group and the positive lens group Pa (and the positive lens group Pb) when changing magnification from the wide-angle end to the telephoto end. As described above, when changing magnification from the wide-angle end to the telephoto end, the first lens group moves toward the image side, and the positive lens group Pa and the positive lens group Pb move toward the object side along the same trajectory. At this time, XF is a positive value, and XR is a negative value. The moving distances refer to the distances between the positions of each lens group at the wide-angle end and the positions of each lens group at the telephoto end.

[0047] In recent years, imaging devices are held or mounted on gimbals (stabilizers) or drones to capture video. In a zoom lens, each lens group moves during magnification change, so the center of gravity is likely to change. In a negative-first optical system, the incident position of the maximum angle of view ray with respect to the front group (for example, the first lens group) becomes higher, especially when the refractive power arrangement is of a retrofocus type at the wide-angle end. Therefore, the lens diameter of the front group is larger than that of the rear group, and the weight ratio of the front group in the entire optical system of the zoom lens becomes large. In addition, in the zoom lens, when the positive lens group Pa, the negative lens group N, the positive lens group Pb, and the driving mechanism for focusing are unitized as described above, the weight ratio of these in the entire product also becomes large. Therefore, by moving the first lens group toward the image side and the positive lens group Pa and the positive lens group Pb toward the object side within a range that satisfies conditional formula (5), the change in the center of gravity during magnification change can be suppressed. Therefore, even when capturing video by holding the imaging device on a gimbal or the like, it is possible to suppress image blur and tilt and rotation of the zoom lens due to changes in the center of gravity position.

[0048] On the other hand, if the numerical value of conditional formula (5) is outside the above range, it becomes difficult to adjust the balance between the weight of each lens group, the first lens group and the positive lens group Pa (and the positive lens group Pb), and the amount of movement of each lens group during zooming, and it becomes difficult to suppress changes in the position of the center of gravity during zooming.

[0049] In order to obtain the above-mentioned effects, the lower limit of condition (5) is preferably -1.50, and more preferably -1.40, and the upper limit of condition (5) is preferably -0.35, and more preferably -0.40.

[0050] 1-2-6.Conditional expression (6) 0.70 < Ymax / BFw < 1.60 (6) however, Ymax: The maximum image height of the zoom lens BFw: Back focus of the zoom lens when focused at infinity at the wide-angle end

[0051] Conditional formula (6) is a formula that specifies the ratio between the maximum image height of the zoom lens and the back focus of the zoom lens at the wide-angle end. The back focus is the distance on the optical axis from the lens surface located closest to the image side in the zoom lens to the image surface. The lens surface located closest to the image side is the lens surface located closest to the image side among the lens surfaces that substantially constitute the zoom lens. The lens surfaces that substantially constitute the zoom lens do not include a cover glass or the like. If an optical element that does not have substantial refractive power, such as a cover glass, is included between the lens surface located closest to the image side and the image surface, the thickness of the optical element is converted to an air equivalent length. By satisfying conditional formula (6), the zoom lens can be made compact and have a wide angle, while ensuring an appropriate back focus for an interchangeable lens of an imaging device that employs an interchangeable lens system such as a mirrorless camera.

[0052] On the other hand, if the value of conditional expression (6) is equal to or less than the lower limit, the back focus of the zoom lens becomes too long, making it difficult to miniaturize the zoom lens. In this case, the refractive power arrangement at the wide-angle end is of a retrofocus type, and the asymmetry becomes strong. As a result, barrel distortion occurring on the object side becomes large. On the other hand, if the value of conditional expression (6) is equal to or more than the upper limit, the back focus of the zoom lens becomes too short, making it difficult to ensure an appropriate back focus for the interchangeable lens.

[0053] In order to obtain the above-mentioned effects, the lower limit of conditional formula (6) is preferably 0.85, more preferably 0.95, and even more preferably 1.10, and the upper limit of conditional formula (6) is preferably 1.55, more preferably 1.50, and even more preferably 1.45.

[0054] 1-2-7.Conditional Expression (7) 0.50 < βprt / βprw < 1.70 (7) however, βprw: lateral magnification of the positive lens group Pb at the wide-angle end βprt: lateral magnification of the positive lens group Pb at the telephoto end

[0055] Conditional formula (7) defines the ratio between the lateral magnification of the positive lens group Pb at the wide-angle end and the lateral magnification of the positive lens group Pb at the telephoto end. As described above, the height of the maximum off-axis light beam incident on the positive lens group Pb varies with the magnification change of the zoom lens. By satisfying conditional formula (6), coma aberration and curvature of field can be effectively corrected, and a zoom lens with high optical performance over the entire magnification change range can be realized. In this case, it is more preferable that the positive lens group Pb is configured to include at least one aspherical surface.

[0056] On the other hand, when the value of conditional expression (7) is equal to or smaller than the lower limit, or equal to or larger than the upper limit, the difference in height of the maximum off-axis light beam incident on the positive lens group Pb at the wide-angle end and the telephoto end becomes large, making it difficult to satisfactorily correct coma and field curvature at both the wide-angle end and the telephoto end.

[0057] In order to obtain the above-mentioned effects, the lower limit of condition (7) is preferably 0.6, and more preferably 0.7, and the upper limit of condition (7) is preferably 1.4, and more preferably 1.3, and even more preferably 1.2.

[0058] 2. Imaging device Next, an image pickup device according to the present invention will be described, which is characterized by including the zoom lens according to the present invention and an image pickup element provided on the image plane side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal.

[0059] Here, the imaging element is not particularly limited, and solid-state imaging elements such as a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The imaging device according to the present invention is suitable for imaging devices using such solid-state imaging elements, such as digital cameras and video cameras. The imaging device may be a fixed-lens imaging device in which a lens is fixed to a housing, or may be an interchangeable-lens imaging device, such as a single-lens reflex camera or a mirrorless single-lens camera.

[0060] It is more preferable that the imaging device has an image processing section that electrically processes the captured image data acquired by the solid-state imaging element to change the shape of the captured image, and an image correction data storage section that stores image correction data, image correction programs, etc., used to process the captured image data in the image processing section. When a zoom lens is made smaller, distortion (curvature) of the captured image shape formed on the imaging surface is likely to occur. In such a case, distortion correction data for correcting the distortion of the captured image shape is stored in advance in the image correction data storage section, and the image correction data is stored in the image processing section. In the image processing unit, it is preferable that the distortion of the captured image is corrected by using the distortion correction data stored in the image correction data storage unit in the image processing unit. According to this imaging device, the zoom lens can be made even more compact, and a beautiful captured image can be obtained while the imaging device as a whole can be made more compact.

[0061] Furthermore, in the imaging device according to the present invention, it is preferable that the image correction data storage unit stores magnification chromatic aberration correction data in advance, and the image processing unit performs magnification chromatic aberration correction of the captured image using the magnification chromatic aberration correction data stored in the image correction data storage unit. By correcting the magnification chromatic aberration, i.e., chromatic distortion aberration, by the image processing unit, it is possible to reduce the number of lenses constituting the optical system. Therefore, with such an imaging device, it is possible to further reduce the size of the zoom lens, obtain a beautiful captured image, and reduce the size of the entire imaging device.

[0062] Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. EXAMPLES

[0063] (1) Optical configuration of zoom lens 1 is a lens cross-sectional view showing the lens configuration of a zoom lens according to Example 1 of the present invention, in which the upper row shows the wide-angle end, the middle row shows the intermediate focal length state, and the lower row shows the telephoto end state.

[0064] The zoom lens is composed of, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this embodiment, the third lens group G3 is the positive lens group Pa in the present invention, the fourth lens group G4 is the negative lens group N in the present invention, and the fifth lens group G5 is the positive lens group Pb in the present invention.

[0065] The configuration of each lens group will be described below. The first lens group G1 is composed of, from the object side, a negative meniscus lens concave on the image side, and a cemented lens consisting of a biconcave lens and a positive meniscus lens concave on the image side.

[0066] The second lens group G2 is composed of, in order from the object side, a biconvex lens and a negative meniscus lens having a convex shape facing the image side.

[0067] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens formed by cementing a negative meniscus lens having a concave shape on the image side and a biconvex lens.

[0068] The fourth lens group G4 is composed of a negative meniscus lens having a concave shape facing the image side, that is, the fourth lens group G4 is composed of one single lens element.

[0069] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0070] In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 and the fifth lens group G5 move toward the object side along the same trajectory, and the fourth lens group G4 moves toward the object side with respect to the image surface. Also, when focusing from infinity to a close object, the fourth lens group G4 moves toward the image side.

[0071] "IP" in Fig. 1 is an image plane, specifically an imaging surface of a solid-state imaging element such as a CCD sensor or a CMOS sensor, or a film surface of a silver halide film. In addition, a parallel plate having no substantial refractive power, such as a cover glass CG, is provided on the object side of the image plane IP. These points are the same in the lens cross-sectional views shown in the other embodiments, so the explanation will be omitted below.

[0072] (2) Numerical examples Next, a numerical example in which specific numerical values ​​of the zoom lens are applied will be described. The following shows the "surface data", "aspheric data", "magnification data (when focusing on an object at infinity)", "magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens. In addition, the values ​​of each formula (values ​​corresponding to the conditional formulas) are summarized after Example 6.

[0073] In the "surface data", the "surface number" is the order of the lens surface counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the distance on the optical axis of the lens surface, "nd" is the refractive index for the d-line (wavelength λ=587.6 nm), and "vd" is the Abbe number for the d-line. The "*" next to the surface number indicates that the lens surface is aspheric, and "S" represents the aperture stop. Furthermore, "d5", "d9", etc., in the column for the distance on the optical axis of the lens surface mean that the distance on the optical axis of the lens surface is a variable distance that changes when the magnification is changed. In each table, the unit of length is all "mm", and the unit of the angle of view is all "°". In addition, "∞" in the column for the radius of curvature means a flat surface. In Table 1, the 24th and 25th surfaces are surface data for the cover glass CG.

[0074] "Aspheric data" indicates the aspheric coefficients of each aspheric surface, where x is the amount of displacement from the vertex of the surface in the optical axis direction and is defined by the following formula: x=(h 2 / r) / [1+{1-(1+k)×(h / r) 2} 1 / 2 )] +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 In the above formula, h is the height from the optical axis, r is the paraxial radius of curvature, k is the conic coefficient, and An is the n-th order aspheric coefficient. In the [Aspheric Data] section, "E±XX" represents exponential notation, and "×10 ±XX " means.

[0075] "Magnification data (when focusing on infinity)" indicates the focal length of the zoom lens when focusing on infinity at the wide-angle end, intermediate focal length, and telephoto end, "Fno" (F-number), "image height," and each variable interval. "Magnification data (when focusing on a finite object)" indicates each variable interval when focusing on a finite object at a specified shooting distance. "Focal length data of each lens group" indicates the focal length of each lens group that constitutes the zoom lens. The matters related to these tables are the same in the tables shown in the other examples, so explanations will be omitted below.

[0076] 2, 3, and 4 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity. The longitudinal aberration diagrams shown in each diagram are, from the left side of the drawing, spherical aberration (mm), astigmatism (mm), and distortion (%), respectively. In the spherical aberration diagram, the solid line shows spherical aberration at the d-line (wavelength 587.6 nm), and the dashed line shows spherical aberration at the g-line (wavelength 435.8 nm). In the astigmatism diagram, the vertical axis shows half angle of view (ω) and the horizontal axis shows defocus, the solid line shows the sagittal image plane (dS) of the d-line, and the dashed line shows the meridional image plane (dM) of the d-line. In the distortion diagram, the vertical axis shows half angle of view (ω) and the horizontal axis shows distortion. These matters are the same in each aberration diagram shown in other examples, so explanations will be omitted below.

[0077] [Face data] Surface number rd nd vd 1 40.511 1.500 1.61997 63.88 2 21.676 14.640 3 -1653.720 1.100 1.49700 81.61 4 36.543 2.800 1.82115 24.06 5* 47.383 (d5) 6 42.628 3.700 1.78880 28.43 7 -433.932 2.640 8 -45.205 1.000 1.78472 25.68 9 -779.660 (d9) 10S∞1.600 11* 42.515 5.400 1.49710 81.56 12* -48.214 0.600 13 32.619 1.000 1.76182 26.52 14 19.703 9.800 1.49700 81.61 15 -30.994 (d15) 16 162.690 0.800 1.62299 58.16 17 18.688 (d17) 18 62.621 6.400 1.78590 44.20 19 -25.103 0.200 20 -33.110 1.000 1.51680 64.20 21 43.245 5.150 22* -47.465 1.800 1.80610 40.73 23* -308.703 (d23) 24 ∞ 2.500 1.51680 64.17 25∞1.000

[0078] [Aspheric data] Surface number k A4 A6 A8 A10 A12 5 0 -3.99470E-06 -2.28741E-09 -3.62738E-11 1.36932E-13 -2.19282E-16 11 0 -1.74483E-05 2.09696E-09 -2.82624E-10 1.62458E-12 -5.93895E-15 12 0 7.74171E-06 7.46727E-09 -2.21089E-10 1.31945E-12 -4.87961E-15 22 0 -9.85489E-05 3.41633E-07 -1.55834E-09 4.72082E-12 -5.47210E-15 23 0 -8.19989E-05 3.80646E-07 -1.53795E-09 4.39500E-12 -5.30103E-15

[0079] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 28.838 39.200 53.342 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d5 14.746 7.808 2.377 d9 14.584 8.359 1.500 d15 2.668 2.200 3.060 d17 9.930 10.398 9.537 d23 13.000 20.877 28.159

[0080] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 330.0 330.0 330.0 d15 3.940 3.969 5.771 d17 8.657 8.629 6.826

[0081] [Focal length data for each lens group] Group Range Focal length G1 1-5 -42.850 G2 6-9 185.268 G3 10-15 23.397 G4 16-17 -33.962 G5 18-23 224.153 CG 24-25∞ EXAMPLES

[0082] (1) Optical configuration of zoom lens 5 is a lens cross-sectional view showing the lens configuration of a zoom lens of Example 2 according to the present invention. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this example, the third lens group G3 is the positive lens group Pa according to the present invention, the fourth lens group G4 is the negative lens group N according to the present invention, and the fifth lens group G5 is the positive lens group Pb according to the present invention.

[0083] The configuration of each lens group will be described below: The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave toward the image side, a biconcave lens, and a positive meniscus lens concave toward the image side.

[0084] The second lens group G2 is composed of a cemented lens in which, from the object side, a negative meniscus lens having a concave shape facing the image side and a positive meniscus lens having a concave shape facing the image side are cemented together.

[0085] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a positive meniscus lens having a concave shape facing the image side, and a cemented lens formed by cementing a negative meniscus lens having a concave shape facing the image side and a biconvex lens.

[0086] The fourth lens group G4 is composed of a negative meniscus lens having a concave shape facing the image side, that is, the fourth lens group G4 is composed of one single lens element.

[0087] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0088] In the zoom lens of Example 2, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 and the fifth lens group G5 move toward the object side along the same locus, and the fourth lens group G4 moves toward the object side with respect to the image surface. Also, when focusing from infinity to a close object, the fourth lens group G4 moves toward the image side.

[0089] (2) Numerical examples Next, a numerical example in which specific numerical values ​​of the zoom lens are applied will be described. The following shows the "surface data", "aspheric data", "variable magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens. Also, Figs. 6 to 8 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object at infinity.

[0090] [Face data] Surface number rd nd vd 1 46.855 1.600 1.72916 54.67 2 22.331 9.300 3 -305.021 1.200 1.49700 81.61 4 33.148 4.540 5 28.960 3.000 1.84666 23.78 6 38.886 (d6) 7 29.665 1.000 1.83481 42.72 8 17.416 5.600 1.61800 63.39 9 264.044 (d9) 10S∞1.000 11* 35.221 3.900 1.59349 67.00 12 3482.550 0.590 13 32.402 1.000 1.64769 33.84 14 16.844 7.400 1.49700 81.61 15 -49.342 (d15) 16 188.619 0.800 1.69680 55.46 17 18.246 (d17) 18 44.715 6.895 1.77250 49.62 19 -22.886 0.480 20 -29.688 1.000 1.54814 45.82 21 43.522 5.400 22* -62.525 1.800 1.80604 40.74 23* -203.845 (d23) 24 ∞ 2.500 1.51680 64.17 25∞1.000

[0091] [Aspheric data] Surface number k A4 A6 A8 A10 A12 11 0 -1.27379E-05 -1.06984E-08 -8.12515E-11 6.82657E-13 -2.30405E-15 22 0 -1.22699E-04 1.55487E-07 3.44562E-10 -1.12741E-12 1.66430E-14 23 0 -1.00224E-04 2.67618E-07 -8.68046E-11 1.90506E-14 3.72873E-15

[0092] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 24.719 33.901 43.645 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d6 23.636 11.183 3.853 d9 12.600 6.233 1.737 d15 2.435 2.238 2.553 d17 6.108 6.305 5.990 d23 13.000 20.573 26.992

[0093] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 300.0 300.0 300.0 d15 3.661 4.016 5.051 d17 4.882 4.527 3.492

[0094] [Focal length data for each lens group] Group Range Focal length G1 1-6 -38.660 G2 7-9 72.953 G3 10-15 28.299 G4 16-17 -29.045 G5 18-23 72.482 CG 24-25∞ EXAMPLES

[0095] (1) Optical configuration of zoom lens 9 is a lens cross-sectional view showing the lens configuration of a zoom lens of Example 3 according to the present invention. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this example, the second lens group G2 is the positive lens group Pa according to the present invention, the third lens group G3 is the negative lens group N according to the present invention, and the fourth lens group G4 is the positive lens group Pb according to the present invention.

[0096] The configuration of each lens group will be described below. The first lens group G1 is composed of, from the object side, a negative meniscus lens concave toward the image side, a negative meniscus lens concave toward the image side, and a positive meniscus lens concave toward the image side.

[0097] The second lens group G2 is composed of, in order from the object side, an aperture stop S, a biconvex lens, a negative meniscus lens convex on the image side, a biconvex lens, and a cemented lens formed by cementing a negative meniscus lens concave on the image side and a biconvex lens.

[0098] The third lens group G3 is composed of a negative meniscus lens having a concave shape facing the image side, that is, the third lens group G3 is composed of one single lens element.

[0099] The fourth lens group G4 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0100] In the zoom lens of Example 3, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 and the fourth lens group G4 move toward the object side along the same trajectory, and the third lens group G3 moves toward the object side with respect to the image surface. Also, when focusing from infinity to a close object, the third lens group G3 moves toward the image side.

[0101] (2) Numerical examples Next, a numerical example in which specific numerical values ​​of the zoom lens are applied will be described. The following shows the "surface data", "aspheric data", "variable magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens. Also, Figs. 10 to 12 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object at infinity.

[0102] [Face data] Surface number rd nd vd 1 45.952 1.500 1.72916 54.67 2 21.265 10.900 3 237.042 1.200 1.49700 81.61 4 37.966 6.400 5 47.328 3.100 1.80000 29.84 6* 97.297 (d6) 7S∞1.000 8* 47.289 4.400 1.61875 63.73 9* -50.951 1.450 10 -29.943 1.000 1.51823 58.90 11 -309.633 0.260 12 91.408 5.400 1.49700 81.61 13 -29.493 0.200 14 131.839 1.000 1.65412 39.68 15 19.682 8.400 1.49700 81.61 16 -29.677 (d16) 17 181.727 0.800 1.51680 64.20 18 17.550 (d18) 19 30.729 7.800 1.59282 68.62 20 -23.631 0.200 21 -38.214 1.000 1.51680 64.20 22 34.923 5.260 23* -45.120 1.800 1.76802 49.24 24* -339.370 (d24) 25∞2.500 1.51680 64.17 26∞1.000

[0103] [Aspheric data] Surface number k A4 A6 A8 A10 A12 6 0 -2.42337E-06 -4.13743E-09 -1.00930E-11 6.08312E-14 -1.34618E-16 8 0 -7.53617E-06 2.23917E-08 2.23406E-11 1.62568E-12 -5.76875E-15 9 0 1.48132E-05 3.88226E-08 1.21260E-10 1.24904E-12 -4.43535E-15 23 0 -9.92712E-05 1.96620E-07 3.12240E-10 -7.57955E-12 3.29600E-14 24 0 -7.60952E-05 3.13986E-07 -6.31332E-10 4.37504E-14 4.95619E-15

[0104] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 24.722 33.903 43.649 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d6 31.322 13.540 2.429 d16 2.907 2.640 2.600 d18 6.044 6.312 6.352 d24 13.000 19.158 25.322

[0105] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 300.0 300.0 300.0 d16 4.265 4.605 5.274 d18 4.686 4.346 3.678

[0106] [Focal length data for each lens group] Group Range Focal length G1 1-6 -52.309 G2 7-16 25.718 G3 17-18 -37.652 G4 19-24 190.665 CG 25-26∞ EXAMPLES

[0107] (1) Optical configuration of zoom lens Fig. 13 is a lens cross-sectional view showing the lens configuration of a zoom lens of Example 4 according to the present invention. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this example, the third lens group G3 is the positive lens group Pa according to the present invention, the fourth lens group G4 is the negative lens group N according to the present invention, and the fifth lens group G5 is the positive lens group Pb according to the present invention.

[0108] The configuration of each lens group will be described below. The first lens group G1 is composed of, from the object side, a negative meniscus lens concave toward the image side, a negative meniscus lens concave toward the image side, a biconcave lens, and a positive meniscus lens concave toward the image side.

[0109] The second lens group G2 is composed of, in order from the object side, a biconvex lens and a biconcave lens.

[0110] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens formed by cementing a negative meniscus lens having a concave shape on the image side and a biconvex lens.

[0111] The fourth lens group G4 is composed of a negative meniscus lens having a concave shape facing the image side, that is, the fourth lens group G4 is composed of one single lens element.

[0112] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0113] In the zoom lens of Example 4, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 and the fifth lens group G5 move toward the object side along the same locus, and the fourth lens group G4 moves toward the object side with respect to the image surface. Also, when focusing from infinity to a close object, the fourth lens group G4 moves toward the image side.

[0114] (2) Numerical examples Next, a numerical example to which specific numerical values ​​of the zoom lens are applied will be described. The "surface data", "aspheric data", "variable magnification data (when focusing on an object at infinity)", "variable magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens are shown below. Also, Figs. 14 to 16 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object at infinity.

[0115] [Face data] Surface number rd nd vd 1 52.537 1.500 1.83481 42.72 2 19.564 6.700 3* 248.211 2.000 1.53116 56.04 4* 69.396 6.500 5 -77.130 1.000 1.49700 81.61 6 36.985 0.200 7 32.778 4.800 1.69895 30.05 8 354.900 (d8) 9 39.796 4.000 1.80420 46.50 10 -102.483 3.000 11 -45.840 1.000 1.80610 33.27 12 387.849 (d12) 13S∞1.000 14* 110.503 3.600 1.49710 81.56 15* -52.666 0.200 16 28.820 1.000 1.80000 29.84 17 18.687 9.100 1.49700 81.61 18 -26.236 (d18) 19 -307.118 0.800 1.51680 64.20 20 19.117 (d20) 21 32.733 8.500 1.49700 81.61 22 -20.706 0.200 23 -44.608 1.000 1.48749 70.44 24 48.669 5.150 25* -50.417 1.500 1.69350 53.20 26* -326.071 (d26) 27 ∞ 2.500 1.51680 64.17 28∞1.000

[0116] [Aspheric data] Surface number k A4 A6 A8 A10 A12 3 104.338 5.87363E-05 -1.68656E-07 3.92096E-10 -3.88660E-13 -4.35876E-16 4 13.765 5.19123E-05 -1.79933E-07 2.67402E-10 -4.97263E-14 -1.78065E-15 14 0 -2.43348E-05 2.46966E-09 3.49774E-10 -5.56209E-14 1.72160E-15 15 0 4.73268E-06 3.11665E-08 4.83439E-10 -8.48951E-13 4.25586E-15 25 0 -1.69820E-04 6.54018E-07 -2.52374E-09 1.04924E-11 -2.16956E-14 26 0 -1.36399E-04 7.60055E-07 -2.54843E-09 7.67085E-12 -1.15934E-14

[0117] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 20.600 28.299 38.798 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d8 18.150 8.523 1.167 d12 9.826 5.577 1.656 d18 2.485 2.201 3.055 d20 5.891 6.176 5.322 d26 13.000 20.613 28.330

[0118] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 300.0 300.0 300.0 d18 3.410 3.535 5.111 d20 4.966 4.842 3.265

[0119] [Focal length data for each lens group] Group Range Focal length G1 1-8 -29.955 G2 9-12 94.610 G3 13-18 24.451 G4 19-20 -34.795 G5 21-26 110.230 CG 27-28∞ EXAMPLES

[0120] (1) Optical configuration of zoom lens Fig. 17 is a lens cross-sectional view showing the lens configuration of a zoom lens of Example 5 according to the present invention. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this example, the third lens group G3 is the positive lens group Pa according to the present invention, the fourth lens group G4 is the negative lens group N according to the present invention, and the fifth lens group G5 is the positive lens group Pb according to the present invention.

[0121] The configuration of each lens group will be described below. The first lens group G1 is composed of, from the object side, a negative meniscus lens concave toward the image side, a negative meniscus lens concave toward the image side, and a positive meniscus lens concave toward the image side.

[0122] The second lens group G2 is composed of, in order from the object side, a positive meniscus lens having a concave shape facing the image side, and a negative meniscus lens having a convex shape facing the image side.

[0123] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens formed by cementing a negative meniscus lens having a concave shape on the image side and a biconvex lens.

[0124] The fourth lens group G4 is composed of a biconcave lens, that is, the fourth lens group G4 is composed of one single lens element.

[0125] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0126] In the zoom lens of Example 5, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 and the fifth lens group G5 move toward the object side along the same locus, and the fourth lens group G4 moves toward the object side with respect to the image surface. Also, when focusing from infinity to a close object, the fourth lens group G4 moves toward the image side.

[0127] (2) Numerical examples Next, a numerical example to which specific numerical values ​​of the zoom lens are applied will be described. The "surface data", "aspheric data", "variable magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens are shown below. Also, Figs. 18 to 20 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object at infinity.

[0128] [Face data] Surface number rd nd vd 1 40.431 1.500 1.72916 54.67 2 18.851 8.300 3 206.724 1.200 1.49700 81.61 4 23.053 4.750 5* 63.842 3.600 1.58144 40.75 6 473.989 (d6) 7 44.365 2.600 1.85025 30.05 8 205.807 2.300 9 -26.627 1.000 1.65160 58.55 10 -57.608 (d10) 11S∞1.000 12* 30.005 5.500 1.49710 81.56 13* -42.901 0.200 14 67.771 1.000 1.69895 30.05 15 21.567 8.300 1.49700 81.61 16 -28.302 (d16) 17 -225.290 0.800 1.48749 70.44 18 20.336 (d18) 19 28.053 9.000 1.49700 81.61 20 -25.778 0.360 21 -199.876 1.000 1.48749 70.44 22 36.384 5.600 23* -46.528 1.500 1.69350 53.20 24* -322.828 (d24) 25∞2.500 1.51680 64.17 26∞1.000

[0129] [Aspheric data] Surface number k A4 A6 A8 A10 A12 5 0 1.50123E-05 1.01378E-08 1.54171E-10 -5.82881E-13 1.29706E-15 12 0 -1.35562E-05 1.42835E-08 2.01889E-10 -8.41463E-13 5.67008E-15 13 0 2.03313E-05 2.56042E-08 7.97875E-12 6.50224E-13 2.72603E-15 23 0 -1.04390E-04 3.52369E-07 8.34182E-12 -5.65180E-12 4.03488E-15 24 0 -7.41185E-05 4.30076E-07 -4.27344E-10 -3.46987E-12 8.46178E-15

[0130] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 20.603 28.305 38.803 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d6 12.353 6.131 1.113 d10 12.197 6.641 1.500 d16 2.959 2.195 3.438 d18 6.456 7.219 5.977 d24 13.001 20.882 27.959

[0131] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 300.0 300.0 300.0 d16 4.050 3.814 6.063 d18 5.365 5.600 3.351

[0132] [Focal length data for each lens group] Group Range Focal length G1 1-6 -31.546 G2 7-10 350.820 G3 11-16 23.939 G4 17-18 -38.221 G5 19-24 84.521 CG 25-26∞ EXAMPLES

[0133] (1) Optical configuration of zoom lens 21 is a lens cross-sectional view showing the lens configuration of a zoom lens of Example 6 according to the present invention. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having positive refractive power, and the magnification is changed by changing the distance on the optical axis between adjacent lens groups. In this example, the third lens group G3 is the positive lens group Pa according to the present invention, the fourth lens group G4 is the negative lens group N according to the present invention, and the fifth lens group G5 is the positive lens group Pb according to the present invention.

[0134] The configuration of each lens group will be described below: The first lens group G1 is composed of, in order from the object side, a negative meniscus lens concave toward the image side, a biconcave lens, and a positive meniscus lens concave toward the image side.

[0135] The second lens group G2 is composed of, in order from the object side, a negative meniscus lens having a concave shape facing the image side, and a positive meniscus lens having a convex shape facing the image side.

[0136] The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconvex lens, and a cemented lens formed by cementing a negative meniscus lens having a concave shape on the image side and a biconvex lens.

[0137] The fourth lens group G4 is composed of a negative meniscus lens having a concave shape facing the image side, that is, the fourth lens group G4 is composed of one single lens element.

[0138] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens, a biconcave lens, and a negative meniscus lens having a convex shape facing the image side.

[0139] The sixth lens group G6 is composed of a biconvex lens.

[0140] In the zoom lens of Example 6, when zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 and the fifth lens group G5 move toward the object side along the same locus, the fourth lens group G4 moves toward the object side, and the sixth lens group is fixed with respect to the image surface. Also, when focusing from infinity to a close object, the fourth lens group G4 moves toward the image side.

[0141] (2) Numerical examples Next, a numerical example to which specific numerical values ​​of the zoom lens are applied will be described. The "surface data", "aspheric data", "variable magnification data (when focusing on an object at a finite distance)", and "focal length data of each lens group" of the zoom lens are shown below. Also, Figs. 22 to 24 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, intermediate focal length, and telephoto end when focusing on an object at infinity.

[0142] [Face data] Surface number rd nd vd 1 51.558 1.600 1.69680 55.46 2 23.562 8.700 3 -824.263 1.200 1.49700 81.61 4 31.222 5.300 5 29.335 3.000 1.84666 23.78 6 40.544 (d6) 7 30.587 1.000 1.83481 42.72 8 17.282 5.500 1.61997 63.88 9 180.487 (d9) 10S∞1.000 11* 36.477 2.550 1.59349 67.00 12* 188.340 0.260 13 33.044 1.000 1.60342 38.03 14 17.124 8.100 1.49700 81.61 15 -32.265 (d15) 16 189.357 0.800 1.56883 56.04 17 16.386 (d17) 18 40.517 6.700 1.75500 52.32 19 -21.706 0.280 20 -24.479 1.000 1.54072 47.23 21 25.518 4.900 22* -73.790 1.800 1.80604 40.74 23* -219.998 (d23) 24 26891.800 3.200 1.72916 54.67 25 -92.223 12.500 26 ∞ 2.500 1.51680 64.17 27∞1.000

[0143] [Aspheric data] Surface number k A4 A6 A8 A10 A12 11 0 -3.95079E-06 -2.56387E-08 -2.83126E-10 -6.21002E-14 -2.18663E-15 12 0 1.57750E-05 -1.78106E-08 -1.54441E-10 -9.95994E-13 9.02354E-16 22 0 -8.68425E-05 2.00621E-08 2.83431E-10 -7.06240E-12 6.08187E-14 23 0 -7.10563E-05 1.10831E-07 -3.10811E-10 1.52486E-12 6.68018E-15

[0144] [Magnification data (focused at infinity)] Wide Angle Mid-Telephoto Focal length 24.719 33.901 43.650 Fno 2.91 2.91 2.91 Image height 21.633 21.633 21.633 d6 23.476 11.524 4.479 d9 10.685 5.546 1.845 d15 2.206 2.063 2.156 d17 6.022 6.164 6.072 d23 1.000 9.013 16.557

[0145] [Magnification data (when focusing at a finite distance)] Wide Angle Mid-Telephoto Shooting distance 300.0 300.0 300.0 d15 3.417 3.773 4.452 d17 4.811 4.454 3.776

[0146] [Focal length data for each lens group] Group Range Focal length G1 1-6 -42.010 G2 7-9 84.473 G3 10-15 26.610 G4 16-17 -31.5891 G5 18-23 175.536 G6 24-25 126.052 CG 26-27∞

[0147] [Conditional expression corresponding value] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 (1)(Rnf+Rnr) / (Rnf-Rnr) 1.26 1.21 1.21 0.88 0.83 1.19 (2)fn / ft -0.64 -0.67 -0.86 -0.90 -0.99 -0.72 (3)(1-βnt2)×βrt2 -4.53 -3.67 -3.43 -3.54 -2.76 -4.03 (4)vdn 58.16 55.46 64.20 64.20 70.44 56.04 (5)XF / XR -0.68 -1.19 -1.34 -0.64 -0.47 -0.79 (6)Ymax / BFw 1.38 1.38 1.38 1.38 1.38 1.43 (7)βprt / βprw 0.91 0.65 0.91 0.79 0.68 0.88 [Industrial Applicability]

[0148] According to the present invention, it is possible to provide a wide-angle to standard zoom lens and an imaging device that are large in diameter, small in size, and have high optical performance. [Explanation of symbols]

[0149] G1: First lens group G2: Second lens group G3: Third lens group G4: Fourth lens group G5: Fifth lens group G6: 6th lens group S Aperture CG...Cover glass IP...Image plane

Claims

1. a first lens group having negative refractive power and disposed closest to the object; a positive lens group Pa having a positive refractive power, a negative lens group N having a negative refractive power, and a positive lens group Pb having a positive refractive power, in this order from the object side, on the image side of the first lens group; When changing magnification from the wide-angle end to the telephoto end, the first lens group moves toward the image side, and the positive lens group Pa and the positive lens group Pb move toward the object side along the same locus, and the magnification is changed by changing the interval on the optical axis between adjacent lens groups, By moving the negative lens group N toward the image side, focusing is performed from infinity to a finite distance object, The negative lens group N is composed of one lens element, A zoom lens characterized by satisfying the following conditions: 0.80<(Rnf+Rnr) / (Rnf-Rnr)<1.40...(1) -1.20< fn / ft <-0.50...(2) vdn > 50...(4) however, Rnf: radius of curvature of the surface closest to the object in the negative lens group N Rnr: radius of curvature of the surface closest to the image side in the negative lens group N fn: focal length of the negative lens group N ft: focal length of the zoom lens at the telephoto end vdn: Abbe number of the lens element constituting the negative lens group N

2. 2. The zoom lens according to claim 1, which satisfies the following conditions: -5.40 <(1-βnt ２ )×βrt ２ < -2.40 ・・・(3) however, βnt: lateral magnification of the negative lens unit N at the telephoto end βrt: composite lateral magnification at the telephoto end of all lens units located on the image side of the negative lens unit N

3. 3. The zoom lens according to claim 1, further comprising a stop between the first lens group and the positive lens group Pa.

4. 4. The zoom lens according to claim 1, which satisfies the following condition: -1.60 ≦ XF / XR ≦ -0.30 ... (5) however, XF: the movement distance on the optical axis of the first lens group when changing magnification from the wide-angle end to the telephoto end XR: the moving distance on the optical axis of the positive lens group Pa when changing magnification from the wide-angle end to the telephoto end

5. 5. The zoom lens according to claim 1, which satisfies the following condition: 0.70 < Ymax / BFw < 1.60 (6) however, Ymax: Maximum image height of the zoom lens BFw: Back focus of the zoom lens at the wide-angle end when focused on infinity

6. 6. The zoom lens according to claim 1, wherein the positive lens group Pb has at least one lens surface having an aspheric shape, and the following condition is satisfied: 0.50 < βprt / βprw < 1.70 (7) however, βprw: lateral magnification of the positive lens group Pb at the wide-angle end βprt: lateral magnification of the positive lens group Pb at the telephoto end

7. 7. An imaging apparatus comprising: the zoom lens according to claim 1; and an image sensor on an image side of the zoom lens for converting an optical image formed by the zoom lens into an electrical signal.

Images