Large aperture wide-angle zoom lens

Abstract

To provide a zoom lens that has a large aperture ratio, a wide angle of view, and is compact despite having a small number of lenses, has little overall length movement during zooming, and has good optical performance over the entire zoom range.SOLUTION: A large aperture ratio wide-angle zoom lens is composed of, in order from an object side, a first lens group G1 comprising a negative single lens, and a rear group Gr having an aperture stop S and a focus lens group and having a positive refractive power as a whole consisting of a plurality groups. When changing the magnification from a wide-angle end to a telephoto end, the large aperture ratio wide-angle zoom lens reduces a distance between the first lens group G1 and a lens group Gr, and when focusing from an object at infinity to an object at a short distance, it moves a negative lens group in the rear group Gr toward an image plane to satisfy a specific conditional expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system suitable for a photographic lens used in imaging devices such as still cameras and video cameras, and more particularly to a large aperture wide-angle zoom lens employing an inner focus system suitable for autofocus cameras. [Background technology]

[0002] A small and lightweight zoom lens is a negative-group-first zoom lens. Patent Document 1 describes a zoom lens that has a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with negative refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive refractive power, and that, by satisfying certain conditions, can provide a wide-angle zoom lens with a maximum angle of view of 80° or more, a zoom ratio of approximately 2.7x, and an F-number of approximately 2.8.

[0003] Furthermore, Patent Document 2 describes a zoom lens that is composed of, in order from the object side, a first lens group G1 with negative refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, an aperture stop, a fourth lens group G4 with negative refractive power, a fifth lens group G5 with positive refractive power, and a sixth lens group G6 with negative refractive power, and that satisfies certain conditions, making it possible to provide a zoom lens that is bright with an F-number of approximately 2.8 over the entire zoom range and has a focal length of approximately 24 mm at the wide-angle end.

[0004] Furthermore, Patent Document 3 describes a zoom lens that is made up of a first lens group, a second lens group, a third lens group, and a final lens group that has negative refractive power and is positioned closest to the image, and in which the distance between adjacent lens groups changes during zooming, and that, by satisfying certain conditions, can achieve a small, lightweight zoom lens with a short overall lens length. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-93976 [Patent Document 2] Japanese Patent Application Publication No. 2018-4963 [Patent Document 3] Japanese Patent Publication No. 2021-156963 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional wide-angle zoom lenses for SLR cameras often use a retrofocus design with a negative lens group leading the lens to ensure sufficient back focus. Mirrorless cameras, which have become popular in recent years, do not require a quick-return mirror, so the flange focal distance of the body is short. This means that the back focus of the interchangeable lens can be short, creating a demand for a compact zoom format.

[0007] The zoom lens disclosed in Patent Document 1 is compatible with single-lens reflex cameras, and at the wide-angle end, the entire optical system is a retrofocus type with a negative lens group leading, ensuring sufficient back focus. As a result, the overall optical length is long and compactness has not been achieved. Furthermore, because it is a retrofocus type, the first lens group is configured with strong negative refractive power, and aberration correction in that sub-system increases the group thickness of the first lens group, hindering efforts to reduce size and weight.

[0008] The large-aperture wide-angle zoom lens disclosed in Patent Document 2 is a negative-group-first type zoom lens, and has the same problems as Patent Document 1. Furthermore, because the focus group is located on the image side of the first group, the group thickness including the first group and the focus group is large, which hinders the reduction of the overall length.

[0009] The zoom lens disclosed in Patent Document 3 has a negative-first group configuration, and although it is a compact, lightweight zoom lens with a short overall lens length, the amount of movement of the first lens group when changing magnification is large, and even though it is compact at the telephoto end, there is a position where the overall length is large across the entire lens, which places a burden on the mechanical structure and makes it difficult to prevent the center of gravity from shifting when changing magnification.

[0010] The present invention provides a zoom lens that has a large aperture ratio, a wide angle of view, is compact, has little overall length movement during zooming, and has good optical performance throughout the entire zoom range, despite having a small number of lens elements, by the means described below. [Means for solving the problem]

[0011] In order to solve the above problems, the optical system is configured with, in order from the object side, a first lens group G1 which is a negative single lens, an aperture stop S, and a rear lens group Gr which is made up of multiple groups and has a positive refractive power as a whole, The rear group Gr further comprises a second lens group G2 consisting of a positive single lens, a third lens group G3 having negative refractive power and including the aperture stop S, a fourth lens group G4 having a focus lens group and having positive refractive power as a whole, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power, When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the Second lens group G2 The distance between the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases, When focusing from an object at infinity to an object at a close distance, the negative lens group in the rear group Gr moves toward the image plane, and the large aperture ratio wide-angle zoom lens satisfies the following conditional expression: (1) -1.28 <f1 / ft<-0.56 (2) 0.63 <frw / frt<0.93 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end when the object distance of the rear lens group Gr is infinity frt: composite focal length at the telephoto end when the object distance of the rear group Gr is infinity

[0012] In order to solve the above problem, a rear lens group Gr is configured, in order from the object side, of a first lens group G1 having a negative single lens, an aperture stop S, and a focus lens group, and has a positive refractive power as a whole, and the rear lens group Gr is further configured of a second lens group G2 having a positive single lens, a third lens group G3 having a negative refractive power and an aperture stop S, a fourth lens group G4 having a focus lens group and has a positive refractive power as a whole, a fifth lens group G5 having a positive refractive power, and a sixth lens group G6 having a negative refractive power, and when changing magnification from the wide-angle end to the telephoto end, The distance between G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases, and when focusing from an object at infinity to an object at a close distance, the negative lens group G4IF in the fourth lens group G4 moves toward the image plane, and the following condition is satisfied: (1) -1.28 <f1 / ft<-0.56 (2) 0.63 <frw / frt<0.93 (3) -0.66 <Mrw<-0.38 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end when the object distance of the rear lens group Gr is infinity frt: composite focal length at the telephoto end when the object distance of the rear group Gr is infinity Mrw: Lateral magnification of the rear group Gr at the wide-angle end when the object distance is infinity [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a zoom lens that has a large aperture ratio, a wide angle of view, is compact, has little overall length movement during zooming, and has good optical performance throughout the entire zoom range, despite having a small number of lens elements. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a lens configuration diagram of a large-aperture wide-angle zoom lens according to a first embodiment of the present invention when focused on infinity at the wide-angle end. [Figure 2] 10A and 10B are longitudinal aberration diagrams for an object at infinity in Example 1 of the present invention, where a is the wide-angle end, b is the intermediate focal length (45.69 mm), and c is the telephoto end. [Figure 3] 10A and 10B are diagrams showing lateral aberrations at an object at infinity in Example 1 of the present invention, where a is the wide-angle end, b is the intermediate focal length (45.69 mm), and c is the telephoto end. [Figure 4] 10A and 10B are longitudinal aberration diagrams of Example 1 of the present invention at an object distance of 1 m, where a is at the wide-angle end, b is at the intermediate focal length (45.69 mm), and c is at the telephoto end. [Figure 5] 10A and 10B are lateral aberration diagrams for Example 1 of the present invention at an object distance of 1 m, where a is at the wide-angle end, b is at the intermediate focal length (45.69 mm), and c is at the telephoto end. [Figure 6] FIG. 10 is a lens configuration diagram of a large-aperture wide-angle zoom lens according to a second embodiment of the present invention when focused on infinity at the wide-angle end. [Figure 7] 10A and 10B are longitudinal aberration diagrams for an object at infinity in Example 2 of the present invention, where a is the wide-angle end, b is the intermediate focal length (40.64 mm), and c is the telephoto end. [Figure 8] 10A and 10B are diagrams showing lateral aberrations at an object at infinity in Example 2 of the present invention, where a is at the wide-angle end, b is at the intermediate focal length (40.64 mm), and c is at the telephoto end. [Figure 9] 10A and 10B are longitudinal aberration diagrams of Example 2 of the present invention at an object distance of 1 m, where a is at the wide-angle end, b is at an intermediate focal length (40.64 mm), and c is at the telephoto end. [Figure 10] 10A and 10B are diagrams showing lateral aberrations at an object distance of 1 m in Example 2 of the present invention, where a is at the wide-angle end, b is at the intermediate focal length (40.64 mm), and c is at the telephoto end. [Figure 11] FIG. 10 is a lens configuration diagram of a large-aperture wide-angle zoom lens according to a third embodiment of the present invention when focused on infinity at the wide-angle end. [Figure 12] 10A and 10B are longitudinal aberration diagrams for an object at infinity in Example 3 of the present invention, where a is the wide-angle end, b is the intermediate focal length (46.10 mm), and c is the telephoto end. [Figure 13]10A and 10B are diagrams showing lateral aberration at an object at infinity in Example 3 of the present invention, where a is the wide-angle end, b is the intermediate focal length (46.10 mm), and c is the telephoto end. [Figure 14] 10A and 10B are longitudinal aberration diagrams of Example 3 of the present invention at an object distance of 1 m, where a is the wide-angle end, b is the intermediate focal length (46.10 mm), and c is the telephoto end. [Figure 15] 10A and 10B are lateral aberration diagrams of Example 3 of the present invention at an object distance of 1 m, where a is the wide-angle end, b is the intermediate focal length (46.10 mm), and c is the telephoto end. [Figure 16] FIG. 10 is a lens configuration diagram of a large-aperture wide-angle zoom lens according to a fourth embodiment of the present invention when focused on infinity at the wide-angle end. [Figure 17] 10A and 10B are longitudinal aberration diagrams for an object at infinity in Example 4 of the present invention, where a is the wide-angle end, b is the intermediate focal length (42.49 mm), and c is the telephoto end. [Figure 18] 10A and 10B are diagrams showing lateral aberrations at an object at infinity in Example 4 of the present invention, where a is the wide-angle end, b is the intermediate focal length (42.49 mm), and c is the telephoto end. [Figure 19] 10A and 10B are longitudinal aberration diagrams of Example 4 of the present invention at an object distance of 1 m, where a is at the wide-angle end, b is at an intermediate focal length (42.49 mm), and c is at the telephoto end. [Figure 20] 10A and 10B are lateral aberration diagrams of Example 4 of the present invention at an object distance of 1 m, where a is at the wide-angle end, b is at the intermediate focal length (42.49 mm), and c is at the telephoto end. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a large aperture ratio wide-angle zoom lens according to the present invention will be described.

[0016] The zoom lens of each embodiment is used in imaging devices such as digital cameras, video cameras, broadcast cameras, surveillance cameras, etc. The zoom lens of each embodiment can also be used as a projection optical system in an image projection device (projector).

[0017] As shown in the lens construction diagrams of FIGS. 1, 6, 11 and 16, the large aperture ratio wide-angle zoom lens of the present invention has a refractive power arrangement in the lens optical system that is composed of, in order from the object side, a first lens group G1 which is a negative single lens, an aperture stop S, and a rear lens group Gr which is made up of multiple groups having a positive refractive power overall, the first lens group G1 being a negative single lens, an aperture stop S, and a focus lens group. The lens is composed of, in order from the object side, a first lens group G1 which is a negative single lens, a second lens group G2 which is a positive single lens, a third lens group G3 which has an aperture stop S and has negative refractive power, a fourth lens group G4 which has a focus lens group and has positive refractive power as a whole, a fifth lens group G5 which has positive refractive power, and a sixth lens group G6 which has negative refractive power.When varying magnification from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.When focusing from an object at infinity to an object at a close distance, a rear portion G4IF of the fourth lens group G4 moves toward the image plane.

[0018] The reason why the above configuration is necessary is as follows: In the wide-angle zoom lens with a large aperture ratio of the present invention, the refractive power arrangement in the lens optical system is configured to consist of, in order from the object side, a first lens group G1 which is a negative single lens, an aperture stop S, and a rear group Gr which is made up of multiple groups having a focus lens group and has a positive refractive power overall, thereby making the entire lens optical system retrofocus and achieving a wide angle of view at the wide-angle end.

[0019] Furthermore, by making the refractive power arrangement of each group approximately symmetrical, such as negative-positive-negative-positive-positive-negative, chromatic aberration of magnification and distortion can be easily corrected.

[0020] Furthermore, by constructing the negative refractive power first lens group G1 with a single lens and minimizing the group thickness of the first lens group G1, the overall length of the lens optical system is reduced. When the first lens group G1 is a negative single lens, its negative refractive power can be relatively weaker than that of a lens group consisting of two negative-positive lenses. This reduces the amount of residual aberration and enables the group thickness to be further reduced. Furthermore, when the first lens group G1 is constructed with two negative-positive lenses, the rear principal point is located closer to the object than the image-side surface of the positive lens, making it difficult to ensure the principal point distance between the negative first lens group G1 and the positive rear group Gr. Therefore, to ensure a sufficient zoom ratio, the refractive power of the rear group Gr must be reduced. With a negative-positive two-element configuration, not only is the group thickness of the first lens group increased, but the conjugate distance of the rear group Gr also increases, resulting in an increase in the overall length. Therefore, having the first lens group G1 be a negative single lens is advantageous in terms of reducing the overall length, aberration correction, and cost.

[0021] In addition, by making the first lens group G1 thinner, it is possible to increase the amount of movement of the rear group Gr, which is closer to the image than the first lens group G1, during zooming. This reduces the refractive power of the rear group Gr and reduces residual aberrations in the rear group Gr. Furthermore, by making the first lens group G1 thinner, it is possible to reduce the overall length at the telephoto end even if the amount of movement of the rear group Gr is relatively large.

[0022] Furthermore, in the present invention, the lateral magnification of the rear group Gr at the telephoto end is higher than that at the wide-angle end, so making the refractive power of the rear group Gr at the telephoto end weaker than that at the wide-angle end is advantageous in terms of aberration correction at the telephoto end. Furthermore, in a large-aperture zoom lens like the present invention, in which the rear group Gr moves during zooming and the F-number does not change from the wide-angle end to the telephoto end, the axial marginal ray height of the rear group Gr is relatively higher at the telephoto end than at the wide-angle end, so the rear group Gr requires greater aberration correction capabilities. In the present invention, this requirement is met by making the refractive power of the rear group Gr weaker at the telephoto end. Furthermore, reducing the number of lenses constituting the rear group Gr also enables cost reduction.

[0023] Furthermore, by limiting the lateral magnification of the rear lens unit Gr at the wide-angle end, the present invention suppresses the doubling of residual aberrations in the first lens unit by the rear lens unit Gr and suppresses an increase in the overall optical length. Furthermore, by suppressing the change in the overall optical length when changing magnification from the wide-angle end to the telephoto end, it is possible to simplify the mechanical structure.

[0024] Furthermore, by limiting the lateral magnification of the rear group Gr at the telephoto end, the present invention suppresses the doubling of residual aberrations in the first lens group by the rear group Gr and suppresses increases in the overall optical length. By using the magnification of the rear group Gr at close to 1x, the conjugate distance of the rear group Gr is kept close to its minimum, making it possible to shorten the overall length even with a small refractive power of the rear group Gr. This suppresses aberrations in the rear group Gr, making it possible to reduce the number of lens elements in the lens configuration.

[0025] Furthermore, the rear lens group Gr of the present invention has a multi-group structure of five or more groups, with each group moving independently during zooming. This suppresses fluctuations in spherical aberration, coma, astigmatism, and other aberrations during zooming, enabling excellent aberration correction.

[0026] Furthermore, the second lens group G2, which is the lens group closest to the object in the rear group Gr, converges the axial light beam diverged by the first lens group G1 and transfers it to the lens group closest to the image. Because the present invention has an aperture stop S in the third lens group G3, it is useful to give this second lens group G2 positive refractive power in order to reduce the aperture stop diameter.

[0027] Furthermore, by setting the sixth lens group G6, which has negative refractive power and is located closest to the image side in the rear group Gr, as a magnifying system throughout the entire zoom range, the overall lens length throughout the entire zoom range can be shortened.

[0028] Furthermore, by providing a lens in the fourth lens group G4, which has a positive refractive power and is located at the rear of the fourth lens group G4 and is closer to the object than the focus group G4IF, which is a negative lens group, with positive refractive power, the ray height of the focus group G4IF, which is a negative lens group in the fourth lens group G4, can be lowered, and a lightweight inner focus group can be obtained.

[0029] In addition, by arranging lens groups with positive refractive power on the object side and image side of the focus group G4IF at the rear of the fourth lens group G4, it becomes easier to suppress aberration fluctuations when the focus group G4IF at the rear of the fourth lens group, which has negative refractive power, focuses.

[0030] Furthermore, by reducing the movement of the first lens group G1 during zooming, the mechanical structure can be simplified, and the center of gravity can be moved less, resulting in a more reliable product.

[0031] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of this embodiment satisfies the following conditional expression. (1) -1.28 <f1 / ft<-0.56 (2) 0.63 <frw / frt<0.93 (3) -0.66 <Mrw<-0.38 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end when the object distance of the rear lens group Gr is infinity frt: composite focal length at the telephoto end when the object distance of the rear group Gr is infinity Mrw: Lateral magnification of the rear group Gr at the wide-angle end when the object distance is infinity

[0032] In conditional formula (1), by appropriately specifying the ratio between the focal length of the first lens group G1 and the focal length at the telephoto end, it is possible to reduce the overall length of the lens optical system and improve performance. It also prevents residual aberrations in the first lens group from being multiplied by the rear group Gr, and prevents an increase in the overall optical length. Furthermore, because the magnification of the rear group Gr is close to 1x, the conjugate distance of the rear group Gr is close to a minimum, making it possible to shorten the overall length at the telephoto end even with a small refractive power of the rear group Gr. Furthermore, because aberrations generated by the rear group Gr can be suppressed, it is possible to reduce the number of lens elements in the lens configuration.

[0033] If the lower limit of conditional expression (1) is exceeded and the negative refractive power of the first lens group G1 becomes relatively weak, it becomes impossible to suppress an increase in the filter diameter at the wide-angle end and an increase in the overall optical length at the wide-angle end due to an increase in the conjugate distance of the rear group Gr, which is undesirable.

[0034] On the other hand, if the upper limit of conditional formula (1) is exceeded and the negative refractive power of the first lens group G1 becomes relatively strong, the lateral magnification of the rear group Gr at the telephoto end becomes that of a magnifying system, so the conjugate distance of the rear group Gr at the telephoto end becomes long, and the total optical length at the telephoto end increases due to the increased relative movement of the rear group Gr. Furthermore, the increase in residual aberrations in the first lens group G1 and the further increase in residual aberrations due to the magnifying effect of the rear group Gr cannot be suppressed, making it difficult to suppress the deterioration of aberrations in the entire system, and therefore making it difficult to configure the first lens group G1 with a single lens. Furthermore, if the maximum aperture f-number is to be fixed during zooming, the aperture diaphragm diameter at the telephoto end will become large, which will increase the diameter of the mechanical diaphragm unit and make it difficult to reduce the outer diameter of the product.

[0035] It should be noted that, with regard to conditional expression (1), it is desirable to limit the lower limit to -1.12 and the upper limit to -0.64, thereby making it possible to ensure the above-mentioned effect.

[0036] By appropriately specifying the ratio of the focal length of the rear group Gr at the wide-angle end to the focal length of the rear group Gr at the telephoto end in conditional expression (2), it is possible to make the refractive power of the rear group Gr at the telephoto end weaker than that at the wide-angle end, thereby favoring aberration correction at the telephoto end. Furthermore, in a large-aperture ratio zoom lens such as the present invention, in which the F-number does not change from the wide-angle end to the telephoto end, the height of the axial marginal ray of the rear group Gr becomes high at the telephoto end, which tends to worsen aberrations related to aperture. By making the refractive power of the rear group Gr weaker at the telephoto end, the worsening of aberrations related to aperture is suppressed. Furthermore, the number of lenses constituting the rear group Gr can be reduced, thereby reducing costs.

[0037] If the upper limit of conditional expression (2) is exceeded and the refractive power of the rear group Gr at the telephoto end becomes relatively strong, it becomes difficult to ensure the desired focal length at the telephoto end. Furthermore, because aberrations related to the aperture diameter worsen, the number of lenses in the rear group Gr must be increased and aspherical lenses must be used to correct aberrations, resulting in increased costs. Furthermore, if the refractive power of the rear group Gr at the wide-angle end becomes relatively weak, the overall length at the wide-angle end increases, which increases the filter diameter at the wide-angle end. Furthermore, the amount of movement of the first lens group G1 during magnification changes increases, making it difficult to suppress changes in the center of gravity during magnification changes.

[0038] On the other hand, if the lower limit of conditional expression (2) is exceeded and the refractive power of the rear group Gr at the telephoto end becomes relatively weak, the conjugate distance of the rear group Gr at the telephoto end becomes long, the overall length at the telephoto end becomes long, and the amount of movement of the first lens group G1 during magnification changes becomes large, making it difficult to suppress changes in movement of the center of gravity during magnification changes. Also, if the refractive power of the rear group Gr at the wide-angle end becomes relatively strong, the conjugate distance of the rear group Gr at the wide-angle end becomes short, making it difficult to ensure a sufficient back focus.

[0039] It is to be noted that, with regard to conditional expression (2), it is desirable to set the lower limit to 0.75 and the upper limit to 0.89, thereby making it possible to ensure the above-mentioned effect.

[0040] By appropriately defining the lateral magnification of the rear group Gr at the wide-angle end in conditional expression (3), it is possible to prevent the rear group Gr from doubling the residual aberration of the first lens group G1 and to prevent an increase in the overall optical length at the wide-angle end.

[0041] If the lower limit of conditional expression (3) is exceeded and the lateral magnification of the rear group Gr shifts in the magnifying direction, the refractive power of the first lens group G1 must be strengthened in order to maintain the focal length at the wide-angle end, and it becomes impossible to suppress the deterioration of the aberrations of the entire system due to the increase in the residual aberrations of the first lens group G1, making it difficult to configure the first lens group G1 from a single lens.

[0042] If the upper limit of conditional expression (3) is exceeded and the lateral magnification of the rear group Gr shifts in the reduction direction, the refractive power of the first lens group G1 must be weakened to maintain the focal length of the entire system at the wide-angle end, which is undesirable as it increases the filter diameter at the wide-angle end and makes it impossible to suppress the overall optical length at the wide-angle end due to the longer conjugate distance of the rear group Gr.

[0043] It should be noted that, preferably, the lower limit of conditional expression (3) should be set to -0.62 and the upper limit to -0.40, thereby making it possible to ensure the above-mentioned effect.

[0044] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of the present invention satisfies the following conditional expression. (4) 60 <G1abbe however G1abbe: Abbe number of the first lens group G1, which is a negative single lens

[0045] In conditional expression (4), by appropriately defining the Abbe number of the first lens group G1, which is a negative single lens, it is possible to suppress residual chromatic aberration in the first lens group G1, and by making the first lens group G1 a single lens, it is possible to make the entire optical system compact and suppress fluctuations in chromatic aberration during magnification change.

[0046] If the lower limit of conditional expression (4) is exceeded and the Abbe number of the negative single lens element first lens group G1 becomes smaller, the residual chromatic aberration of the first lens group G1 increases further. To correct chromatic aberration throughout the entire optical system, the residual chromatic aberration of the rear group Gr must also be increased, otherwise it becomes difficult to cancel out the residual chromatic aberration of the first lens group G1. Increasing the residual chromatic aberration of the rear group Gr is undesirable because it makes it impossible to suppress fluctuations in chromatic aberration during magnification changes.

[0047] It should be noted that, preferably, the lower limit of conditional expression (4) should be set to 62, thereby making it possible to ensure the above-mentioned effect.

[0048] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of the present invention satisfies the following conditional expression. (5) 1.04 <M6w however M6w: lateral magnification of the sixth lens group G6 at the wide-angle end

[0049] In conditional expression (5), by appropriately defining the lateral magnification of the sixth lens group G6 at the wide-angle end, an increase in the overall optical length at the wide-angle end is suppressed.

[0050] If the lower limit of conditional expression (5) is exceeded and the magnification of the sixth lens group G6 at the wide-angle end shifts in the direction of reduction, the refractive power of the lens group closer to the object than the sixth lens group G6 must be weakened in order to maintain the focal length at the wide-angle end. This increases the overall optical length at the wide-angle end and the outer diameter of the first lens group G1, making it difficult to achieve compactness.

[0051] It should be noted that, preferably, by setting the lower limit of conditional expression (5) to 1.10, the above-mentioned effect can be more reliably achieved.

[0052] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of the present invention satisfies the following conditions: (6) -1.39 <M2t<-0.73 however M2t: lateral magnification of the second lens group G2 at the telephoto end when the object distance is infinity

[0053] In the present invention, when the first lens group G1 has a negative focal length, the second lens group G2 has a positive focal length, and the lateral magnification of the second lens group G2 is close to 1:1 at the telephoto end, the conjugate distance of the second lens group G2 is close to its minimum. This reduces the contribution to the overall optical length of the group closer to the image than the second lens group G2, making it possible to further increase the aberration correction contribution of the group closer to the image than the second lens group G2. Conditional formula (6) defines the lateral magnification contribution of the second lens group G2 at the telephoto end for this purpose.

[0054] If the lower limit of conditional expression (6) is exceeded and the lateral magnification of the second lens group G2 at the telephoto end shifts in the enlarging direction, the focal length of the second lens group G2 must be increased in order to ensure a sufficient distance between the first lens group G1 and the second lens group G2 at the telephoto end, which is undesirable because it increases the burden of shortening the overall length of the group closer to the image than the second lens group G2.

[0055] On the other hand, if the upper limit of conditional expression (6) is exceeded and the lateral magnification of the second lens group G2 at the telephoto end shifts in the reduction direction, the magnification of the second lens group G2 at the wide-angle end must be shifted even more in the reduction direction in order to obtain the desired zoom ratio, which undesirably increases the overall length at the wide-angle end and the diameter of the front lens element.

[0056] It should be noted that, with regard to conditional expression (6), it is desirable to limit the lower limit to -1.32 and the upper limit to -0.83, thereby making it possible to ensure the above-mentioned effect.

[0057] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of the present invention satisfies the following conditions: (7) -2.25 <f1 / f2<-1.28 however f1: focal length of the first lens group G1 f2: the focal length of the second lens group G2

[0058] In conditional expression (7), by appropriately defining the ratio of the focal length of the first lens group G1 to the focal length of the second lens group G2, it becomes possible to reduce the overall length of the lens optical system and achieve high performance.

[0059] If the lower limit of conditional expression (7) is exceeded and the negative refractive power of the first lens group G1 becomes relatively weak, the filter diameter at the wide-angle end becomes large, which is undesirable. Also, in order to ensure a sufficient distance between the first lens group G1 and the second lens group G2 at the telephoto end, it becomes difficult to obtain a predetermined zoom ratio unless the lateral magnification of the second lens group G2 at the telephoto end is reduced.

[0060] On the other hand, if the upper limit of conditional expression (7) is exceeded and the negative refractive power of the first lens group G1 becomes relatively strong, the lateral magnification of the second lens group G2 at the telephoto end must be shifted in the enlarging direction in order to maintain the focal length at the telephoto end, which increases the relative movement amount of the second lens group G2 and increases the overall optical length at the telephoto end.In addition, it is not possible to suppress the deterioration of the overall system aberrations due to the increase in residual aberrations of the first lens group G1 and the further increase in residual aberrations of the first lens group G1 caused by the magnifying effect of the second lens group G2.

[0061] It should be noted that, with regard to conditional expression (7), it is desirable to limit the lower limit to -2.00 and the upper limit to -1.44, thereby making it possible to ensure the above-mentioned effect.

[0062] Furthermore, it is preferable that the large aperture ratio wide-angle zoom lens of the present invention satisfies the following conditions: (8) |ft / f3r|<0.59 however ft: focal length at the telephoto end when the object distance is infinity f3r: composite focal length at the telephoto end from the third lens group G3 to the final lens group when the object distance is infinity

[0063] In conditional expression (8), by appropriately defining the ratio between the focal length at the telephoto end when the object distance is infinity and the composite focal length from the third lens group G3 to the final lens group, it becomes possible to dedicate the functions of the third lens group G3 and subsequent lens groups to aberration correction. In this invention, the magnification burden of the second lens group G2 is set to approximately 1x magnification at the telephoto end, thereby shortening the conjugate distance of the composite system consisting of the first lens group G1 and the second lens group G2 at the telephoto end. Furthermore, by constructing the negative first lens group G1 and the positive second lens group G2 with single lenses and shortening the magnification spacing between them at the telephoto end, the composite thickness of the first lens group G1 and the second lens group G2 is reduced. This shortens the overall length of the composite system consisting of the first lens group G1 and the second lens group G2, allowing the functions of the third lens group G3 and subsequent lens groups to be devoted to aberration correction. To further clarify this functional division, the refractive power of the composite system consisting of the third lens group G3 and subsequent lens groups is minimized to suppress the deterioration of aberrations with increasing aperture. Furthermore, the number of components can be reduced, thereby reducing costs.

[0064] If the upper limit of conditional expression (8) is exceeded and the combined refractive power from the third lens group G3 to the final lens group becomes too strong, it becomes difficult to correct aberrations related to the aperture. In addition, the number of lenses in the lens structure must be increased in order to correct aberrations.

[0065] It is to be noted that, preferably, the upper limit of conditional expression (8) should be set to 0.51, thereby making it possible to ensure the above-mentioned effect.

[0066] Furthermore, in the present invention, some of the lenses are aspherical, but it is also possible to add a diffractive optical surface or a metalens structure surface to improve the ability to correct spherical aberration, astigmatism, chromatic aberration, etc.

[0067] Furthermore, by moving the focus lens group in the direction of the optical axis when varying the magnification, it is possible to provide a degree of freedom in correcting aberrations, thereby achieving higher performance and a more compact design.

[0068] Next, lens configurations and specific numerical data of examples of the large aperture ratio wide-angle zoom lens of the present invention will be described. Note that in the following description, the lens configurations will be described in order from the object side to the image side.

[0069] In [Surface Data], the surface number is the number of the lens surface or aperture stop S counted from the object side, r is the radius of curvature of each surface, d is the spacing between surfaces, nd is the refractive index for the d-line (wavelength 587.56 nm), and vd is the Abbe number for the d-line.

[0070] An asterisk (*) next to a surface number indicates that the lens surface is aspherical, and BF represents the back focal length.

[0071] The (stop) attached to the surface number indicates that the aperture stop S is located at that position. The radius of curvature for the plane or aperture stop S is marked as ∞ (infinity).

[0072] [Aspherical Surface Data] shows the coefficient values ​​that determine the aspherical shape of lens surfaces marked with an * in [Surface Data]. The aspherical shape is determined by the following equation, where y is the displacement from the optical axis in a direction perpendicular to the optical axis, z is the displacement (sag) from the intersection of the aspherical surface and the optical axis in the direction of the optical axis, r is the radius of curvature of the reference sphere, K is the Conic coefficient, and A4, A6, A8, A10, A12, and A14 are the aspherical coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th orders, respectively.

[0073] TIFF0007814741000001.tif26123

[0074] [Various Data] shows values ​​such as zoom ratio and focal length for each focal length state.

[0075] [Variable Distance Data] shows the variable distance and BF values ​​at infinity and an object distance of 1 m for each focal length state.

[0076] [Lens Group Data] shows the surface number of each lens group closest to the object and the composite focal length of the entire group.

[0077] In the aberration diagrams corresponding to the respective examples, d, g, and C represent the d-line, g-line, and C-line, respectively, and ΔS and ΔM represent the sagittal image surface and meridional image surface, respectively.

[0078] In the following specification values, the focal length f, radius of curvature r, lens surface spacing d, and other length units are all in millimeters (mm) unless otherwise specified; however, this is not a limitation, as optical systems can achieve equivalent optical performance with proportional magnification and proportional reduction. [Example]

[0079] 1 is a lens configuration diagram of a large-aperture wide-angle zoom lens according to Example 1 of the present invention, when focusing on infinity at the wide-angle end. From the object side, the lens configuration includes a first lens group G1 which is a negative single lens, a second lens group G2 which is a positive single lens, a third lens group G3 which has negative refractive power and an aperture stop S, a fourth lens group G4 which has a focus lens group G4IF and has positive refractive power as a whole, a fifth lens group G5 which has positive refractive power, and a sixth lens group G6 which has negative refractive power.

[0080] The first lens group G1 is composed of a negative meniscus lens whose object-side surface is aspherical and whose convex surface faces the object side.

[0081] The second lens group G2 is made up of a positive meniscus lens with its convex surface facing the object side.

[0082] The third lens group G3 is composed of a negative meniscus lens whose object-side surface is aspherical and whose convex surface faces the object-side, a biconvex lens, an aperture stop S, and a biconcave lens whose object-side surface is aspherical.

[0083] The fourth lens group G4 is composed of a positive meniscus lens with a concave surface facing the object side, and a focus group G4IF which is a cemented negative lens consisting of a positive meniscus lens with a convex surface facing the object side and a negative meniscus lens with a convex surface facing the object side, and when focusing from an object at infinity to an object at a close distance, the focus group G4IF which is a cemented negative lens moves towards the image plane.

[0084] The fifth lens group G5 is made up of a biconvex lens.

[0085] The sixth lens group G6 is composed of a negative meniscus lens whose object-side surface is aspherical and whose concave surface faces the object side.

[0086] When changing magnification from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.

[0087] The specifications of the large aperture ratio wide-angle zoom lens according to Example 1 are shown below. Numerical Example 1 Unit: mm [Face Data] Surface number rd nd vd Object surface ∞ (d0) 1* 395.0478 1.5000 1.55032 75.49 2 30.3243 (d2) 3 30.9408 4.9510 2.00100 29.13 4 247.1861 (d4) 5* 90.6752 1.5000 2.00069 25.46 6 35.7621 2.0252 7 78.2460 3.5949 1.43700 95.10 8 -36.1961 1.5000 9 (Aperture) ∞ 3.4162 10* -40.4325 0.8000 1.95906 17.47 11 133.0729 (d11) 12 -986.0801 5.5865 1.87071 40.73 13 -26.7067 (d13) 14 128.8485 1.6617 1.95906 17.47 15 185.7796 0.8000 1.43700 95.10 16 29.5295 (d16) 17 102.9615 6.6046 1.49700 81.60 18 -36.2114 (d18) 19* -20.3642 0.8000 1.45860 90.19 20 -78.0000 13.0000 Image plane ∞ [Aspherical data] 1st page 5th page K 0.00000 0.00000 A4 1.90533E-06 -9.20299E-06 A6 2.13641E-09 -9.02662E-09 A8 -1.26216E-11 5.66328E-11 A10 2.34545E-14 -1.28492E-13 A12 -1.87845E-17 0.00000E+00 A14 5.31133E-21 0.00000E+00 10th page 19th page K 0.00000 0.00000 A4 -1.12082E-05 1.97608E-05 A6 -2.76338E-08 2.66668E-08 A8 3.75594E-10 -4.52780E-11 A10 -5.23832E-12 2.37844E-13 A12 1.91851E-14 0.00000E+00 A14 0.00000E+00 0.00000E+00 [Various data] Wide-angle Mid-range Telephoto Focal length 28.80 45.69 67.00 F-number 2.89 2.89 2.89 Full angle of view 2ω 76.24 52.35 37.54 Image height Y 21.63 21.63 21.63 Lens length 117.50 107.07 114.90 [Variable Interval Data] Wide-angle Mid-range Telephoto d0 ∞ ∞ ∞ d2 44.7403 19.4526 5.1490 d4 3.0000 4.1546 6.5152 d11 3.7819 6.3605 8.7091 d13 1.5000 1.5000 1.5000 d16 5.3472 7.3815 18.7379 d18 11.3907 8.6682 6.5479 BF 13.0000 24.8137 32.9999 Wide-angle Mid-range Telephoto d0 882.5000 892.9289 885.1009 d2 44.7403 19.4526 5.1490 d4 3.0000 4.1546 6.5152 d11 3.7819 6.3605 8.7091 d13 3.0499 4.2143 5.6041 d16 3.7973 4.6671 14.6338 d18 11.3907 8.6682 6.5479 BF 13.0000 24.8138 32.9999 [Lens group data] Group starting plane focal length G1 1 -59.77 G2 3 34.93 G3 5 -32.63 G4 12 43.52 G5 17 54.77 G6 19 -60.36 G4IF 14 -99.84 [Example]

[0088] 6 is a lens configuration diagram of the large aperture ratio wide-angle zoom lens of Example 2 of the present invention when focusing at infinity at the wide-angle end. From the object side, the lens configuration is composed of a first lens group G1 which is a negative single lens, a second lens group G2 which is a positive single lens, a third lens group G3 which has negative refractive power and an aperture stop S, a fourth lens group G4 which has a focus lens group G4IF and has positive refractive power as a whole, a fifth lens group G5 which has positive refractive power, and a sixth lens group G6 which has negative refractive power.

[0089] The first lens group G1 is composed of a negative meniscus lens whose object-side surface is aspherical and whose convex surface faces the object side.

[0090] The second lens group G2 is made up of a biconvex lens.

[0091] The third lens group G3 is composed of a negative meniscus lens whose object-side surface is aspherical and whose convex surface faces the object side, a biconvex lens, an aperture stop S, and a cemented negative lens composed of a biconvex lens and a biconcave lens.

[0092] The fourth lens group G4 is composed of a biconvex lens and a focus group G4IF which is a cemented negative lens consisting of a positive meniscus lens with its convex surface facing the object side and a negative meniscus lens with its convex surface facing the object side, and when focusing from an object at infinity to an object at a close distance, the cemented negative lens focus group G4IF moves toward the image plane.

[0093] The fifth lens group G5 is made up of a biconvex lens.

[0094] The sixth lens group G6 is composed of a negative meniscus lens whose object-side surface is aspherical and whose concave surface faces the object side.

[0095] When changing magnification from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.

[0096] The specifications of the large aperture ratio wide-angle zoom lens according to Example 2 are shown below. Numerical Example 2 Unit: mm [Face Data] Surface number rd nd vd Object surface ∞ (d0) 1* 679.2858 1.5000 1.61997 63.88 2 35.0494 (d2) 3 37.5310 4.9782 2.00100 29.13 4 -10284.8890 (d4) 5* 413.2319 1.5000 2.00100 29.13 6 81.0540 1.3980 7 159.7793 3.7226 1.43700 95.10 8 -36.0860 1.5000 9 (Aperture) ∞ 1.0991 10 182.1106 4.0851 1.43700 95.10 11 -24.4206 0.8000 1.89286 20.36 12 48.7917 (d12) 13 481.2347 4.4450 2.00100 29.13 14 -30.6389 (d14) 15 234.5366 1.7248 1.95906 17.47 16 1296.8170 0.8000 1.51823 58.96 17 27.7659 (d17) 18 55.0817 6.7499 1.49700 81.60 19 -35.2661 (d19) 20* -17.8763 0.8000 1.49700 81.60 21 -78.2002 12.9920 Image plane ∞ [Aspherical data] 1 page 5 pages 20 pages K 0.00000 0.00000 0.00000 A4 1.17010E-06 -1.02216E-05 2.84890E-05 A6 -1.96483E-09 -8.69843E-09 6.95283E-08 A8 1.02328E-11 7.02836E-11 -2.45901E-10 A10 -2.48545E-14 -2.27976E-13 1.11008E-12 A12 2.77498E-17 0.00000E+00 0.00000E+00 A14 -1.16686E-20 0.00000E+00 0.00000E+00 [Various data] Wide-angle Mid-range Telephoto Focal length 28.79 40.64 67.01 F-number 2.89 2.89 2.89 Full angle of view 2ω 78.16 58.88 38.09 Image height Y 21.63 21.63 21.63 Lens length 119.84 111.72 114.87 [Variable Interval Data] Wide-angle Mid-range Telephoto d0 ∞ ∞ ∞ d2 47.1782 28.8910 7.6345 d4 4.2452 5.4220 8.9474 d12 4.3006 5.9548 8.2288 d14 1.5000 1.5000 1.5000 d17 4.3011 5.2918 13.6086 d19 10.2222 8.2170 7.7080 BF 12.9920 21.3378 32.1423 Wide-angle Mid-range Telephoto d0 880.1580 888.2830 885.1278 d2 47.1782 28.8910 7.6345 d4 4.2452 5.4220 8.9474 d12 4.3006 5.9548 8.2288 d14 2.5600 3.0724 4.3573 d17 3.2410 3.7193 10.7513 d19 10.2222 8.2170 7.7080 BF 12.9920 21.3379 32.1422 [Lens group data] Group starting plane focal length G1 1 -59.66 G2 3 37.37 G3 5 -34.41 G4 13 46.41 G5 18 44.36 G6 20 -46.83 G4IF 15 -67.52 [Example]

[0097] 11 is a lens configuration diagram of a large aperture ratio wide-angle zoom lens according to Example 3 of the present invention when focusing at infinity at the wide-angle end. From the object side, the lens configuration is composed of, in order, a first lens group G1 which is a negative single lens, a second lens group G2 which is a positive single lens, a third lens group G3 which has a negative refractive power and an aperture stop, a fourth lens group G4 which has a focus lens group G4IF and has a positive refractive power as a whole, a fifth lens group G5 which has positive refractive power, and a sixth lens group G6 which has negative refractive power.

[0098] The first lens group G1 is composed of a negative meniscus lens element with aspherical surfaces on both sides and a convex surface facing the object side.

[0099] The second lens group G2 is made up of a positive meniscus lens with its convex surface facing the object side.

[0100] The third lens group G3 is composed of a positive meniscus lens with a concave surface facing the object side, a positive meniscus lens with an aspherical surface on the image side and a concave surface facing the object side, an aperture stop S, and a cemented negative lens consisting of a positive meniscus lens with a concave surface facing the object side and a biconcave lens.

[0101] The fourth lens group G4 is composed of a positive meniscus lens with its concave surface facing the object side, and a focus group G4IF which is a cemented negative lens consisting of a biconvex lens and a biconcave lens.When focusing from an object at infinity to an object at a close distance, the focus group G4IF which is a cemented negative lens moves toward the image plane.

[0102] The fifth lens group G5 is made up of a biconvex lens.

[0103] The sixth lens group G6 is composed of a negative meniscus lens whose object-side surface is aspherical and whose concave surface faces the object side.

[0104] When changing magnification from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.

[0105] A large aperture ratio wide-angle zoom lens according to a third embodiment will be described below. Numerical Example 3 Unit: mm [Face Data] Surface number rd nd vd Object surface ∞ (d0) 1* 153.2184 1.5000 1.61997 63.88 2* 30.0168 (d2) 3 32.7003 5.2930 2.00100 29.13 4 236.4670 (d4) 5 -135.3086 2.3747 1.43700 95.10 6 -48.4242 0.2000 7 -164.0638 1.5246 2.00330 28.27 8* -125.3595 1.5000 9 (Aperture) ∞ 1.2948 10 -1150.4612 2.7728 1.55032 75.49 11 -28.6061 0.8000 2.00272 19.32 12 48.0876 4.9522 13 -4468.0969 (d13) 1.91082 35.25 14 -28.9975 1.5000 15 554.7312 (d15) 1.95906 17.47 16 -228.4114 0.8000 1.51742 52.15 17 32.6337 (d17) 18 48.6024 7.5836 1.49700 81.60 19 -38.8119 (d19) 20* -20.0549 0.8000 1.55332 71.68 21 -78.0000 13.0000 Image plane ∞ [Aspherical data] 1 screen 2 screen 8 screen 20 screen K 0.00000 0.00000 0.00000 0.00000 A4 8.48613E-08 -1.45345E-06 1.25874E-05 2.21825E-05 A6 -7.31997E-10 -2.69463E-09 1.77852E-08 1.32575E-08 A8 4.36530E-12 -3.89258E-12 -1.30870E-10 2.40202E-11 A10 -1.71694E-14 1.18602E-14 7.38852E-13 1.40451E-13 A12 3.21351E-17 0.00000E+00 0.00000E+00 0.00000E+00 A14 -1.95666E-20 0.00000E+00 0.00000E+00 0.00000E+00 [Various data] Wide-angle Mid-range Telephoto Focal length 28.80 46.10 67.50 F-number 2.90 2.88 2.92 Full angle of view 2ω 78.15 52.91 38.41 Image height Y 21.63 21.63 21.63 Lens length 118.50 107.77 118.50 [Variable Interval Data] Wide-angle Mid-range Telephoto d0 ∞ ∞ ∞ d2 46.9041 20.8935 7.7245 d4 4.0783 5.9167 9.1858 d13 4.9522 8.0038 10.4616 d15 1.5000 1.5000 1.5000 d17 4.3775 5.7445 16.7571 d19 10.8653 9.0119 7.0484 BF 13.0000 23.8815 33.0000 Wide-angle Mid-range Telephoto d0 881.5000 892.2254 881.5000 d2 46.9041 20.8935 7.7245 d4 4.0783 5.9167 9.1858 d13 4.9522 8.0038 10.4616 d15 2.8667 3.9925 5.2390 d17 3.0108 3.2520 13.0181 d19 10.8653 9.0119 7.0484 BF 13.0000 23.8816 33.0000 [Lens group data] Group starting plane focal length G1 1 -60.50 G2 3 37.42 G3 5 -35.27 G4 13 49.16 G5 18 44.71 G6 20 -49.03 G4IF 15 -82.38 [Example]

[0106] 16 is a lens configuration diagram of a large aperture ratio wide-angle zoom lens according to Example 4 of the present invention when focusing on infinity at the wide-angle end. From the object side, the lens configuration includes, in order, a first lens group G1 which is a negative single lens, a second lens group G2 which is a positive single lens, a third lens group G3 which has negative refractive power and an aperture stop S, a fourth lens group G4 which has a focus lens group G4IF and has positive refractive power as a whole, a fifth lens group G5 which has positive refractive power, and a sixth lens group G6 which has negative refractive power.

[0107] The first lens group G1 is made up of a biconcave lens with aspherical surfaces on both sides.

[0108] The second lens group G2 is made up of a biconvex lens whose image-side surface is aspherical.

[0109] The third lens group G3 is composed of a biconcave lens, an aperture stop, a biconvex lens, a biconcave lens, and a biconvex lens.

[0110] The fourth lens group G4 is composed of a positive meniscus lens whose object-side surface is aspherical and whose concave surface faces the object side, a biconvex lens, and a focus group G4IF which is a biconcave lens whose image-side surface is aspherical, and when focusing from an object at infinity to an object at a close distance, the focus group G4IF which is a biconcave lens whose image-side surface is aspherical moves towards the image plane.

[0111] The fifth lens group G5 is made up of a biconvex lens.

[0112] The sixth lens group G6 is composed of a negative meniscus lens whose object-side surface is aspherical and whose concave surface faces the object side.

[0113] When changing magnification from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, the distance between the third lens group G3 and the fourth lens group G4 increases, the distance between the fourth lens group G4 and the fifth lens group G5 increases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.

[0114] The specifications of the large aperture ratio wide-angle zoom lens according to Example 4 are shown below. Numerical Example 4 Unit: mm [Face Data] Surface number rd nd vd Object surface ∞ (d0) 1* -197.3343 1.5000 1.61997 63.88 2* 40.8039 (d2) 3 29.7549 5.3262 1.91082 35.25 4* -331.8441 (d4) 5 -202.9850 1.5000 1.49700 81.60 6 68.4471 4.9041 7 (Aperture) ∞ 0.9582 8 96.3005 3.9194 1.49700 81.60 9 -25.4450 0.5000 10 -23.3574 0.8000 1.96300 24.11 11 37.0511 0.8739 12 120.4120 3.3345 1.49700 81.60 13 -34.4852 (d13) 14* -56.0749 1.7359 2.00069 25.46 15 -45.0903 2.0602 16 85.3000 6.4121 1.59282 68.62 17 -24.0147 (d17) 18 -71.0151 0.8000 1.51823 58.96 19* 72.8299 (d19) 20 167.8995 4.0959 1.68430 26.81 21 -52.6242 (d21) 22* -18.6005 0.8000 1.59349 67.00 23 -78.8006 13.0000 Image plane ∞ [Aspherical data] 1st page 2nd page 4th page K 0.00000 0.00000 0.00000 A4 2.79295E-05 2.77380E-05 3.39479E-06 A6 -9.58387E-08 -7.55966E-08 -8.28259E-09 A8 2.05575E-10 1.03135E-10 3.08713E-11 A10 -2.70561E-13 -4.48036E-14 -4.34856E-14 A12 2.04224E-16 0.00000E+00 0.00000E+00 A14 -6.76067E-20 0.00000E+00 0.00000E+00 14th page 19th page 22nd page K 0.00000 0.00000 0.00000 A4 -1.06892E-05 -5.87719E-06 2.17770E-05 A6 -2.09507E-08 2.18953E-09 7.66426E-09 A8 -2.04915E-11 -1.59064E-10 2.88840E-11 A10 -4.80637E-13 9.30138E-13 2.88061E-13 A12 0.00000E+00 -1.87674E-15 0.00000E+00 A14 0.00000E+00 0.00000E+00 0.00000E+00 [Various data] Wide-angle Mid-range Telephoto Focal length 28.80 42.49 67.50 F-number 2.89 2.89 2.89 Full angle of view 2ω 78.46 57.02 36.93 Image height Y 21.63 21.63 21.63 Lens total length 118.49 111.15 118.49 [Variable Interval Data] Wide-angle Mid-range Telephoto d0 ∞ ∞ ∞ d2 44.3386 24.2432 6.3276 d4 3.0000 4.5300 8.7095 d13 1.2549 5.1920 11.6772 d17 1.5000 1.5000 1.5000 d19 4.2717 4.7571 11.8637 d21 11.6016 10.4121 8.3297 BF 13.0000 21.0000 30.5572 Wide-angle Mid-range Telephoto d0 881.5129 888.8453 881.5149 d2 44.3386 24.2432 6.3276 d4 3.0000 4.5300 8.7095 d13 1.2549 5.1920 11.6772 d17 2.3446 2.8100 3.5883 d19 3.4271 3.4471 9.7754 d21 11.6016 10.4121 8.3297 BF 13.0001 21.0000 30.5573 [Lens group data] Group starting plane focal length G1 1 -54.41 G2 3 30.19 G3 5 -30.64 G4 14 44.64 G5 20 59.00 G6 22 -41.23 G4IF 18 -69.25

[0115] Below is a list of values ​​corresponding to the conditional expressions in the above-mentioned embodiments. [Conditional expression corresponding value] Conditional Expression Example 1 Example 2 Example 3 Example 4 (1) -1.28 <f1 / ft<-0.56 -0.89 -0.89 -0.90 -0.81 (2) 0.63 <frw / frt<0.93 0.81 0.85 0.79 0.82 (3) -0.66 <Mrw<-0.38 -0.48 -0.48 -0.48 -0.53 (4) 60 <G1abbe 75.50 63.88 63.88 63.88 (5) 1.04 <M6w 1.23 1.29 1.28 1.33 (6) -1.39 <M2t<-0.73 -1.18 -1.25 -1.24 -0.98 (7) -2.25 <f1 / f2<-1.28 -1.71 -1.60 -1.62 -1.80 (8) |ft / f3r|<0.59 0.41 0.29 0.37 0.12

[0116] <Other embodiments> The technology disclosed in the present embodiment is not limited to the above-described embodiments and examples, and various modifications are possible. The shapes and numerical values ​​of each part shown in the above-described numerical examples are examples for implementing the present technology, and the technical scope of the present technology should not be interpreted as being limited by these.

[0117] Furthermore, in the above-described embodiment and example, the configuration is described as being substantially made up of six lens groups, but the configuration may also include a lens that has substantially no refractive power.

[0118] This technology can be configured as follows. [1] Starting from the object side, a first lens group G1 consisting of a negative single lens; The rear lens group Gr has an aperture stop S and a focus lens group, and is made up of multiple groups, and has a positive refractive power as a whole. When zooming from the wide-angle end to the telephoto end, the distance between the first lens group G1 and the rear lens group Gr decreases, When focusing from an object at infinity to an object at a close distance, the negative lens group in the rear lens group Gr moves toward the image plane, A large aperture ratio wide-angle zoom lens characterized by satisfying the following conditional expression: (1) -1.28 <f1 / ft<-0.56 (2) 0.63 <frw / frt<0.93 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end when the object distance of the rear lens group Gr is infinity frt: composite focal length at the telephoto end when the object distance of the rear group Gr is infinity [2] Starting from the object side, a first lens group G1 consisting of a negative single lens; It is composed of an aperture stop S and a rear group Gr, which has a focus lens group and has a positive refractive power as a whole. The rear group Gr further a second lens group G2 consisting of a positive single lens; a third lens group G3 having a negative refractive power and including the aperture stop S; a fourth lens group G4 having a focus lens group and having a positive refractive power as a whole; a fifth lens group G5 having a positive refractive power; and a sixth lens group G6 with negative refractive power, When changing magnification from the wide-angle end to the telephoto end, The distance between the first lens group G1 and the second lens group G2 is reduced, The distance between the second lens group G2 and the third lens group G3 increases, The distance between the third lens group G3 and the fourth lens group G4 increases, The distance between the fourth lens group G4 and the fifth lens group G5 increases, The distance between the fifth lens group G5 and the sixth lens group G6 is reduced, When focusing from an object at infinity to a close object, The negative lens group G4IF in the fourth lens group G4 moves toward the image plane, A large aperture ratio wide-angle zoom lens characterized by satisfying the following conditional expression: (1) -1.28 <f1 / ft<-0.56 (2) 0.63 <frw / frt<0.93 (3) -0.66 <Mrw<-0.38 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end when the object distance of the rear lens group Gr is infinity frt: composite focal length at the telephoto end when the object distance of the rear group Gr is infinity Mrw: Lateral magnification of the rear group Gr at the wide-angle end when the object distance is infinity [3] The large aperture ratio wide-angle zoom lens according to [1] or [2], characterized in that the following conditional expression is satisfied: (4) 60 <G1abbe however G1abbe: Abbe number of the first lens group G1, which is a negative single lens [4] The large aperture ratio wide-angle zoom lens according to [2] or [3], characterized in that the following conditional expression is satisfied: (5) 1.04 <M6w however M6w: lateral magnification of the sixth lens group G6 at the wide-angle end [5] The large aperture ratio wide-angle zoom lens according to any one of [2] to [4], characterized in that the following conditional expressions are satisfied: (6) -1.39 <M2t<-0.73 however M2t: lateral magnification of the second lens group G2 at the telephoto end when the object distance is infinity [6] The large aperture ratio wide-angle zoom lens according to any one of [2] to [5], characterized in that the following conditional expressions are satisfied: (7) -2.25 <f1 / f2<-1.28 however f1: focal length of the first lens group G1 f2: the focal length of the second lens group G2 [7] The large aperture ratio wide-angle zoom lens according to any one of [2] to [6], characterized in that the following conditional expressions are satisfied: (8) |ft / f3r|<0.59 however ft: focal length at the telephoto end when the object distance is infinity f3r: composite focal length at the telephoto end from the third lens group G3 to the final lens group when the object distance is infinity

[0119] Those skilled in the art will recognize various modifications, combinations, subcombinations, and variations depending on design requirements and other factors, and it goes without saying that these are within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0120] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G4IF focus lens group G5 5th lens group G6 6th lens group Gr rear group S aperture stop I image plane

Claims

1. Starting from the object side, a first lens group G1 consisting of a negative single lens; the rear lens group Gr having an aperture stop S and a focus lens group, and having a positive refractive power as a whole, and being made up of a plurality of lens groups; The rear group Gr further a second lens group G2 consisting of a positive single lens; a third lens group G3 having a negative refractive power and including the aperture stop S; a fourth lens group G4 having a focus lens group and having a positive refractive power as a whole; a fifth lens group G5 having a positive refractive power; and and a sixth lens group G6 having a negative refractive power, When changing magnification from the wide-angle end to the telephoto end, The distance between the first lens group G1 and the second lens group G2 is reduced, The distance between the second lens group G2 and the third lens group G3 increases, The distance between the third lens group G3 and the fourth lens group G4 increases, The distance between the fourth lens group G4 and the fifth lens group G5 increases, The distance between the fifth lens group G5 and the sixth lens group G6 is reduced, When focusing from an object at infinity to an object at a close distance, the negative lens group in the rear group Gr moves toward the image plane, A large aperture ratio wide-angle zoom lens characterized by satisfying the following conditional expression: (1) -1.28<f1 / ft<-0.56 (2) 0.63<frw / frt<0.93 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end of the rear group Gr when the object distance is infinity frt: composite focal length at the telephoto end of the rear group Gr when the object distance is infinity

2. Starting from the object side, a first lens group G1 consisting of a negative single lens; The lens is composed of an aperture stop S and a rear lens group Gr having a focus lens group and having a positive refractive power as a whole. The rear group Gr further a second lens group G2 consisting of a positive single lens; a third lens group G3 having a negative refractive power and including the aperture stop S; a fourth lens group G4 having a focus lens group and having a positive refractive power as a whole; a fifth lens group G5 having a positive refractive power; and and a sixth lens group G6 having a negative refractive power, When changing magnification from the wide-angle end to the telephoto end, The distance between the first lens group G1 and the second lens group G2 is reduced, The distance between the second lens group G2 and the third lens group G3 increases, The distance between the third lens group G3 and the fourth lens group G4 increases, The distance between the fourth lens group G4 and the fifth lens group G5 increases, The distance between the fifth lens group G5 and the sixth lens group G6 is reduced, When focusing from an object at infinity to a close object, The negative lens group G4IF in the fourth lens group G4 moves toward the image plane, A large aperture ratio wide-angle zoom lens characterized by satisfying the following conditional expression: (1) -1.28<f1 / ft<-0.56 (2) 0.63<frw / frt<0.93 (3) -0.66<Mrw<-0.38 however, f1: focal length of the first lens group G1 ft: focal length at the telephoto end when the object distance is infinity frw: composite focal length at the wide-angle end of the rear group Gr when the object distance is infinity frt: composite focal length at the telephoto end of the rear group Gr when the object distance is infinity Mrw: lateral magnification of the rear group Gr at the wide-angle end when the object distance is infinity

3. 3. A large aperture ratio wide-angle zoom lens according to claim 1, wherein the following condition is satisfied: (4) 60<G1abbe however G1abbe: Abbe number of the first lens group G1, which is a negative single lens

4. 3. The large aperture wide-angle zoom lens according to claim 2, wherein the following condition is satisfied: (5) 1.04<M6w however M6w: lateral magnification of the sixth lens group G6 at the wide-angle end

5. 3. The large aperture wide-angle zoom lens according to claim 2, wherein the following condition is satisfied: (6) -1.39<M2t<-0.73 however M2t: lateral magnification of the second lens group G2 at the telephoto end when the object distance is infinity

6. 3. The large aperture wide-angle zoom lens according to claim 2, wherein the following condition is satisfied: (7) -2.25<f1 / f2<-1.28 however f1: focal length of the first lens group G1 f2: focal length of the second lens group G2

7. 3. The large aperture wide-angle zoom lens according to claim 2, wherein the following condition is satisfied: (8) |ft / f3r|<0.59 however ft: focal length at the telephoto end when the object distance is infinity f3r: composite focal length at the telephoto end from the third lens group G3 to the final lens group when the object distance is infinity

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