Optical system

Abstract

To provide an optical system that puts a focus group and an aspherical surface in a proper location, and thereby achieves miniaturization and lightweighting while excellently correcting various aberrations including focus breathing and distortion regardless of a large aperture ratio.SOLUTION: An optical system is composed of: a first lens group G1; a second lens group G2 and third lens roup G3 that have positive refractive power; a fourth lens group G4 that has the positive refractive power; and a fifth lens group G5 that has negative refractive power. In focusing from a point at infinity to a point at a close distance, the second lens group G2 and fourth lens group G4 move to an object side with respective different trajectories along an optical axis, the second lens group G2 has an aspherical surface lens G2asp shaped so as to weaken convex power from a center of the optical axis over a peripheral part thereof, and the fourth lens group G4 has one or more pieces of lenses with at least the positive and negative refractive power respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system suitable for lenses used in imaging devices such as still cameras and video cameras, and projection devices, and has a large aperture ratio, while being appropriately positioned to effectively correct various aberrations and contribute to weight reduction. [Background technology]

[0002] 2. Description of the Related Art In recent years, as imaging devices such as digital still cameras and video cameras have become increasingly high-resolution, there has been a growing demand for high optical performance with strong correction of various aberrations from infinity to close range.

[0003] Furthermore, with the dramatic improvement in autofocus (AF) accuracy in recent digital cameras, it is now possible to accurately focus even in bright optical systems with extremely narrow depth of field. As a result, it has become possible to shoot video with accurate focus even at maximum aperture, greatly expanding the range of visual expression. For this reason, there is a demand for optical systems that suppress changes in the field of view during focusing (hereinafter referred to as focus breathing) even in bright optical systems.

[0004] On the other hand, a method has been proposed in which two lens groups move on separate trajectories during focus drive to achieve high imaging performance from infinity to close range. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-140076 [Patent Document 2] International Publication No. 2021 / 241230 Summary of the Invention [Problem to be solved by the invention]

[0006] The optical system described in Patent Document 1 places the focus group before and after the lens group including the aperture stop, and drives them facing each other to suppress changes in the center of gravity during focusing and changes in AF speed due to attitude differences. It also effectively corrects various aberrations, including distortion, from infinity to close-up focus. However, when focusing from infinity to close-up focus, the lens group with negative refractive power, which is located closer to the object than the aperture stop, is moved toward the image, which creates the problem of significant focus breathing.

[0007] The optical system described in Patent Document 2 effectively corrects various aberrations, including distortion, from infinity to close range, while also appropriately correcting focus breathing. However, the optical system has the problem of being large and heavy.

[0008] The present invention has been made in light of these circumstances, and its object is to provide an optical system that is compact and lightweight, while providing excellent correction for various aberrations including focus breathing and distortion, despite having a large aperture ratio, by appropriately arranging the focus group and aspherical surfaces. [Means for solving the problem]

[0009] In order to achieve the above object, an optical system embodying the present invention is characterized in that it is composed of, in order from the object side, a first lens group G1, a second lens group G2 having positive refractive power, a third lens group G3, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power, and that during focusing from infinity to a close distance, the second lens group G2 and the fourth lens group G4 move toward the object side along different trajectories along the optical axis, the second lens group G2 has an aspherical lens G2asp whose shape weakens its convex power from the center of the optical axis to the periphery, and the fourth lens group G4 has at least one lens each having positive and one lens having negative refractive power.

[0010] Moreover, an optical system embodying the present invention is characterized in that the fifth lens group G5 satisfies the following conditional formula (1), and the third lens group G3 has a lens Lp with positive refractive power that simultaneously satisfies the following conditional formulas (2) and (3): (1) 1.10 < βG5 < 1.60 (2) 0.021 < Lp_ΔPgF < 0.055 (3) 1 / (Lp_f × Lp_νd) < 0.0020 βG5: Lateral magnification of the fifth lens group G5 when focusing at infinity Lp_ΔPgF: Anomalous partial dispersion ΔPgF of the lens Lp with positive refractive power that constitutes the third lens group G3 Lp_vd: Abbe number vd of the lens Lp having positive refractive power that constitutes the third lens group G3 Lp_f: focal length (mm) of the lens Lp with positive refractive power that constitutes the third lens group G3 when not cemented

[0011] The optical system embodying the present invention is characterized in that it satisfies the following conditional expressions: (4) 1.0 < f2 / f4 < 6.0 (5) (f4 / vd_G4ave) / f < 0.050 f: focal length at infinity (mm) f2: Focal length of the second lens group G2 when focused at infinity (mm) f4: Focal length of the fourth lens group G4 when focused at infinity (mm) vd_G4ave: average value of Abbe number νd of the positive lenses constituting the fourth lens group G4

[0012] In addition, the optical system embodying the present invention is characterized in that the fifth lens group G5 has an air lens AL that satisfies the following conditional expression by two adjacent lenses: (6) -1.00 < (R2air + R1air) / (R2air - R1air) < 1.00 R1air: Radius of curvature of the object side of the air lens AL in the fifth lens group G5 (mm) R2air: Radius of curvature on the image side of the air lens AL in the fifth lens group G5 (mm)

[0013] The optical system embodying the present invention is characterized in that it satisfies the following conditional expressions: (7) 0.005 < |(G2aspHnr - G2aspHinf) / f_G2| < 0.050 G2aspHinf: The height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp when focused at infinity G2aspHnr: Height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp at the closest focusing point The off-axis chief ray is defined as the ray that passes through the intersection of the aperture stop and the optical axis at the maximum angle of view. f2: Focal length of the second lens group G2 when focused at infinity (mm)

[0014] The optical system embodying the present invention is characterized in that it has an aperture stop S in the third lens group G3.

[0015] The optical system embodying the present invention is characterized in that the fourth lens group G4 includes an aspherical lens having a positive refractive power.

[0016] The optical system embodying the present invention is characterized in that the fifth lens group G5 has an aspherical lens having negative refractive power located closest to the image side. [Effects of the Invention]

[0017] According to the present invention, by appropriately arranging the focus group and aspherical surfaces, it is possible to provide an optical system that achieves small size and light weight while providing good correction for various aberrations, including focus breathing and distortion, despite having a large aperture ratio. [Brief explanation of the drawings]

[0018] [Figure 1] Lens cross-sectional view of the optical system of Example 1 at infinity [Figure 2] Longitudinal aberration diagram at infinity for the optical system of Example 1 [Figure 3] Longitudinal aberration diagram of the optical system of Example 1 at a shooting distance of 395 mm [Figure 4] Transverse aberration diagram at infinity of the optical system of Example 1 [Figure 5] Transverse aberration diagram of the optical system of Example 1 at a shooting distance of 395 mm [Figure 6] Lens cross-sectional view of the optical system of Example 2 at infinity [Figure 7] Longitudinal aberration diagram at infinity for the optical system of Example 2 [Figure 8] Longitudinal aberration diagram of the optical system of Example 2 at a shooting distance of 832 mm [Figure 9] Transverse aberration diagram at infinity for the optical system of Example 2 [Figure 10] Transverse aberration diagram of the optical system of Example 2 at a shooting distance of 832 mm [Figure 11] Lens cross-sectional view of the optical system of Example 3 at infinity [Figure 12] Longitudinal aberration diagram at infinity for the optical system of Example 3 [Figure 13] Longitudinal aberration diagram of the optical system of Example 3 at a shooting distance of 250 mm [Figure 14] Transverse aberration diagram at infinity for the optical system of Example 3 [Figure 15] Lateral aberration diagram of the optical system of Example 3 at a shooting distance of 250 mm [Figure 16] Lens cross-sectional view of the optical system of Example 4 at infinity [Figure 17] Longitudinal aberration diagram at infinity for the optical system of Example 4 [Figure 18] Longitudinal aberration diagram of the optical system of Example 4 at a shooting distance of 394 mm [Figure 19] Transverse aberration diagram at infinity for the optical system of Example 4 [Figure 20] Transverse aberration diagram of the optical system of Example 4 at a shooting distance of 394 mm [Figure 21] Lens cross section at infinity of the optical system of Example 5 [Figure 22] Longitudinal aberration diagram at infinity for the optical system of Example 5 [Figure 23]Longitudinal aberration diagram of the optical system of Example 5 at a shooting distance of 250 mm [Figure 24] Transverse aberration diagram at infinity for the optical system of Example 5 [Figure 25] Lateral aberration diagram of the optical system of Example 5 at a shooting distance of 250 mm [Figure 26] Lens cross section at infinity of the optical system of Example 6 [Figure 27] Longitudinal aberration diagram at infinity for the optical system of Example 6 [Figure 28] Longitudinal aberration diagram of the optical system of Example 6 at a shooting distance of 815 mm [Figure 29] Transverse aberration diagram at infinity for the optical system of Example 6 [Figure 30] Transverse aberration diagram of the optical system of Example 6 at a shooting distance of 815 mm DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, in the optical system of the present invention, the refractive indices of materials for the g-line (wavelength 435.8 nm), F-line (486.1 nm), d-line (587.6 nm), and C-line (656.3 nm) will be represented as Ng, NF, Nd, and NC, respectively. Unless otherwise specified, refractive indices refer to the refractive index at the d-line.

[0020] Furthermore, the Abbe number νd, the partial dispersion ratio PgF, and the anomalous partial dispersion ΔPgF are derived from the following equations. νd=(Nd-1) / (NF-NC) PgF = (Ng-NF) / (NF-NC) ΔPgF=PgF-0.64833+0.00180×νd

[0021] Examples of the optical system of the present invention will be described in detail below. Note that the following description of the examples is an example of the optical system of the present invention, and the present invention is not limited to these examples within the scope of the gist of the present invention.

[0022] As can be seen from the lens construction diagrams shown in Figures 1, 6, 11, 16, 21, and 26, the optical system of the present invention is composed of, in order from the object side, a first lens group G1, a second lens group G2 having positive refractive power, a third lens group G3, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power.When focusing from infinity to a close distance, the second lens group G2 and the fourth lens group G4 move toward the object side along different trajectories along the optical axis, the second lens group G2 has an aspherical lens G2asp that has a shape that weakens its convex power from the center of the optical axis to the periphery, and the fourth lens group G4 has at least one lens each having positive and one lens having negative refractive power.

[0023] By moving the two lens groups along different paths during focusing, it becomes easier to correct various aberrations, particularly spherical aberration, astigmatism, and coma, from infinity to close focus. Furthermore, by incorporating an aspherical lens G2asp with a shape that weakens its convex power from the optical axis center to the periphery in the second lens group G2, which extends toward the object side from infinity to close focus, this cancels out the narrowing of the angle of view at close focus compared to infinity, thereby suppressing the occurrence of so-called focus breathing. Furthermore, because this shape also generates negative distortion, it is possible to suppress positive distortion even when the telephoto ratio of the optical system is increased for compactness. Furthermore, by incorporating at least one lens element with positive and one lens element with negative refractive power in the fourth lens group G4, it becomes possible to suppress chromatic aberration fluctuations that occur during focusing, contributing to higher image quality. In addition, by giving the fifth lens group G5 negative refractive power, the exit pupil can be moved closer to the image side, which makes it possible to suppress vignetting in the peripheral angle of view due to restrictions on the camera mount diameter and to suppress light reduction that affects image quality.

[0024] Furthermore, in the optical system of the present invention, the fifth lens group G5 satisfies the following conditional expression (1), and the third lens group G3 includes a lens Lp with positive refractive power that simultaneously satisfies the following conditional expressions (2) and (3): (1) 1.10 <βG5< 1.60 (2) 0.021 < Lp_ΔPgF < 0.055 (3) 1 / (Lp_f × Lp_νd) < 0.0020 βG5: Lateral magnification of the fifth lens group G5 when focusing at infinity Lp_ΔPgF: Anomalous partial dispersion ΔPgF of the lens Lp with positive refractive power that constitutes the third lens group G3 Lp_vd: Abbe number vd of the lens Lp having positive refractive power that constitutes the third lens group G3 Lp_f: focal length (mm) of the lens Lp with positive refractive power that constitutes the third lens group G3 when not cemented

[0025] Conditional formula (1) defines the lateral magnification of the fifth lens group G5. Because the fifth lens group G5 has negative refractive power, it acts to magnify aberrations occurring in the optical systems in front of it. In particular, axial chromatic aberration is multiplied by the square of the lateral magnification, and its impact cannot be ignored in a lens with a large aperture ratio like that of the present invention. On the other hand, increasing the lateral magnification of the fifth lens group G5 is advantageous for shortening the overall length of the optical system, so the lateral magnification must be kept within an appropriate range. If the lateral magnification increases beyond the upper limit of conditional formula (1), it becomes possible to shorten the overall length of the optical system, but it becomes difficult to adequately correct axial chromatic aberration. If the lateral magnification decreases beyond the lower limit of conditional formula (1), axial chromatic aberration can be adequately corrected, but the optical system becomes bulky, which is undesirable.

[0026] In order to ensure the effect of the above-mentioned conditional expression (1), it is preferable to set the lower limit to 1.15 and the upper limit to 1.55. Furthermore, it is more preferable to set the lower limit to 1.20 and the upper limit to 1.50 in conditional expression (1), since this will further enhance the effect of the present invention.

[0027] Conditions (2) and (3) define the relationship between the anomalous partial dispersion ΔPgF of the positive refractive power lens Lp used in the third lens group G3, the Abbe number vd, and the focal length f. In an optical system with a large aperture ratio, such as the present invention, strong correction of axial chromatic aberration, which affects coloring throughout the entire image, is necessary. In the optical system of the present invention, since the fifth lens group G5 is a magnifying system, it is important to provide sufficient aberration correction in front of the fifth lens group G5. In particular, the third lens group G3 is located near the center of the optical system, which is advantageous for strong correction of axial chromatic aberration while minimizing the impact on lateral chromatic aberration. Therefore, the lenses used in the third lens group G3 must be appropriately selected. An effective means of correcting axial chromatic aberration is generally to select a material with positive anomalous partial dispersion and very low dispersion (e.g., FCD1 from HOYA Corporation) for the positive lens. However, the low refractive index of these materials makes them disadvantageous for product miniaturization. On the other hand, glass materials such as those used in the positive refractive power lens Lp of the present invention have the characteristic of having an extremely high refractive index, so by using them so that conditional expressions (2) and (3) are simultaneously satisfied, it becomes possible to achieve a compact product while correcting chromatic aberration. Note that conditional expression (2) specifies the range required for the second-order achromatic condition, and conditional expression (3) specifies the range required for the first-order achromatic condition, and deviations from the ranges of the conditions make it difficult to achieve sufficient achromatic effect.

[0028] If the anomalous partial dispersion of the lens Lp increases beyond the upper limit of conditional expression (2), the second-order achromatic effect becomes excessive, which is undesirable. If the anomalous partial dispersion decreases beyond the lower limit of conditional expression (2), the second-order achromatic effect becomes insufficient, making it difficult to sufficiently correct chromatic aberration. If the Abbe number or focal length of the lens Lp decreases beyond the upper limit of conditional expression (3), the first-order achromatic effect becomes insufficient, making it difficult to correct chromatic aberration.

[0029] Regarding the above-mentioned conditional expression (2), in order to ensure the effect, it is preferable to set the lower limit to 0.023 and the upper limit to 0.053. Furthermore, it is more preferable to set the lower limit to 0.026 and the upper limit to 0.050 in conditional expression (2), since this will further achieve the effect of the present invention. Similarly, regarding the above-mentioned conditional expression (3), in order to ensure the effect, it is preferable to set the upper limit to 0.0017. Furthermore, it is more preferable to set the upper limit to 0.0013 in conditional expression (3), since this will further achieve the effect of the present invention.

[0030] Furthermore, the optical system of the present invention is characterized by satisfying the following conditional expressions: (4) 1.0 < f2 / f4 < 6.0 (5) (f4 / vd_G4ave) / f < 0.050 f: focal length at infinity (mm) f2: Focal length of the second lens group G2 when focused at infinity (mm) f4: Focal length of the fourth lens group G4 when focused at infinity (mm) vd_G4ave: average value of Abbe number νd of the positive lenses constituting the fourth lens group G4

[0031] Conditional formula (4) defines the ratio of the focal lengths of the second lens group G2 and the fourth lens group G4, which are focus groups. The optical system of the present invention employs floating during focusing, and is configured to cancel out the spherical aberration, field curvature, and coma that occur in each focus group. Furthermore, by keeping the focal length ratio within an appropriate range, the focusing action can be dispersed, which makes it possible to reduce the total amount of focus movement of the second lens group G2 and the fourth lens group G4.

[0032] If the upper limit of conditional expression (4) is exceeded and the focal length of the fourth lens group G4 becomes relatively short, it becomes possible to suppress the amount of focus movement, but the various aberrations cannot be sufficiently canceled out, making it difficult to sufficiently suppress aberration fluctuations during focusing.On the other hand, if the lower limit of conditional expression (4) is exceeded and the focal length of the fourth lens group G4 becomes relatively long, it becomes possible to cancel out the various aberrations, but this is undesirable because the amount of focus movement increases and the overall optical length becomes long.

[0033] Regarding the above-mentioned conditional expression (4), in order to ensure the effect, it is preferable to set the lower limit to 1.2 and the upper limit to 5.8. Furthermore, it is more preferable to set the lower limit to 1.4 and the upper limit to 5.6 in conditional expression (4), since this will further enhance the effect of the present invention.

[0034] Conditional formula (5) defines the ratio of the focal length of the fourth lens group G4, which is the focusing group, to the average Abbe number of the positive lenses, as well as the relationship with the focal length of the entire system. Because the amount of chromatic aberration increases as the focal length of a lens increases or the Abbe number decreases, conditional formula (5) defines the amount of chromatic aberration generated in the fourth lens group G4. Because the fourth lens group G4 has positive refractive power, the Abbe number of the positive lens that constitutes the group is particularly important. Furthermore, to achieve good chromatic aberration correction from infinity to close range, it is preferable that the chromatic aberration generated in the fourth lens group G4, which is the focusing group, be small. However, if the focal length of the fourth lens group G4 becomes relatively long or the average Abbe number becomes small, exceeding the upper limit of conditional formula (5), it becomes difficult to adequately suppress chromatic aberration fluctuations during focusing.

[0035] Regarding the above-mentioned conditional expression (5), in order to ensure the effect, it is preferable to set the upper limit to 0.045. Furthermore, by setting the upper limit to 0.040, the effect of the present invention can be further achieved, which is more preferable.

[0036] Furthermore, in the optical system of the present invention, the fifth lens group G5 is characterized in that it has an air lens AL that satisfies the following conditional expression by two adjacent lenses: (6) -1.00 < (R2air + R1air) / (R2air - R1air) < 1.00 R1air: Radius of curvature of the object side of the air lens AL in the fifth lens group G5 (mm) R2air: Radius of curvature on the image side of the air lens AL in the fifth lens group G5 (mm)

[0037] Conditional formula (6) defines the shape of the air lens AL formed in the fifth lens group G5, known as the shape factor. Conditional formula (6) specifies the range within which the air lens AL can be biconvex. By forming it in the fifth lens group G5, where the axial light beam diameter tends to decrease near the image plane, the negative refraction on both sides enables correction of Petzval sum and field curvature. Furthermore, it is desirable for the radius of curvature of R2air to be negative, with the concave surface facing the object side. If the radius of curvature of R2air is positive or approaching it, the angle of incidence of off-axial light rays on this surface increases, resulting in significant coma and astigmatism, making it difficult to achieve high performance. Furthermore, it is desirable for the radius of curvature of R1air to be positive, with the convex surface facing the object side. If the radius of curvature of R1air is negative or approaching it, it becomes difficult to sufficiently stop down the light beam on the object side of the air lens AL, which leads to an increase in the size of the fourth focus group and inhibits high-speed autofocusing, which is undesirable. Therefore, R1air must be a positive value and R2air must be a negative value.

[0038] Furthermore, if the radius of curvature of R1air becomes smaller beyond the upper limit of conditional expression (6), the negative refractive power of the air lens AL on the object side becomes too strong, which undesirably causes large positive distortion.If the radius of curvature of R2air becomes larger beyond the lower limit of conditional expression (6), the angle of incidence of off-axial rays on that surface becomes too small, which undesirably makes it impossible to sufficiently correct coma.

[0039] Regarding the above-mentioned conditional expression (6), in order to ensure the effect, it is preferable to set the lower limit to -0.50 and the upper limit to 0.95. Furthermore, it is more preferable to set the lower limit to 0.00 and the upper limit to 0.90 in conditional expression (6), since this will further achieve the effect of the present invention.

[0040] Furthermore, the optical system of the present invention is characterized by satisfying the following conditional expressions: (7) 0.005 < |(G2aspHnr - G2aspHinf) / f_G2| < 0.050 G2aspHinf: The height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp when focused at infinity G2aspHnr: Height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp at the closest focusing point The off-axis chief ray is defined as the ray that passes through the intersection of the aperture stop and the optical axis at the maximum angle of view. f2: Focal length of the second lens group G2 when focused at infinity (mm)

[0041] Conditional expression (7) defines the ratio of the focal lengths of the second lens group G2 to the amount of focus variation in the height of off-axial chief rays passing through the object-side surface of the aspherical lens G2asp in the second lens group G2. Using an aspherical lens G2asp in the second lens group G2 is an effective way to suppress focus breathing, but to fully utilize this effect, it is important to significantly change the height of the off-axial chief rays passing through the aspherical lens G2asp during focusing. To significantly change the position where the light rays pass, it is sufficient to increase the focal length of the second lens group G2 to ensure sufficient focusing movement, but this also reduces the focusing effect and increases the thrust dimension, so it is necessary to keep this within an appropriate range.

[0042] If the absolute value of the focal length of the second lens group G2 becomes shorter by exceeding the upper limit of conditional expression (7), aberration fluctuations during focusing become larger, making it difficult to suppress focus breathing while satisfactorily correcting various aberrations.If the absolute value of the focal length of the second lens group G2 becomes longer by exceeding the lower limit of conditional expression (7), it becomes possible to suppress aberration fluctuations during focusing and focus breathing, but this is undesirable because it leads to an increase in the thrust direction of the optical system.

[0043] Regarding the above-mentioned conditional expression (7), in order to ensure the effect, it is preferable to set the lower limit to 0.007 and the upper limit to 0.045. Furthermore, it is more preferable to set the lower limit to 0.009 and the upper limit to 0.040 in conditional expression (7), since this will further enhance the effect of the present invention.

[0044] Furthermore, the optical system of the present invention is characterized in that an aperture stop S is provided in the third lens group G3.

[0045] Because the third lens group G3 is located near the center of the optical system of the present invention, providing an aperture diaphragm S there allows the center of the optical system to be closer to the center of the pupil. As a result, it becomes easier to achieve a symmetrical power distribution in the optical system, which facilitates correction of various aberrations, including distortion, and enables improved optical performance. Furthermore, because the focus group can be separated into front and rear groups sandwiching the aperture diaphragm S, it becomes possible to independently locate the actuator that drives the focus and the aperture diaphragm S unit, thereby suppressing bulkiness in the direction perpendicular to the optical axis. Furthermore, because it becomes easier to make the upper and lower marginal rays symmetrical with respect to the chief ray, it becomes easier to recover peripheral illumination when the aperture is stopped down, making it possible to reduce the likelihood of unnatural images even when electronic correction is performed.

[0046] Furthermore, the optical system of the present invention is characterized in that an aspherical lens having positive refractive power is disposed in the fourth lens group G4.

[0047] The fourth lens group G4 is the image-side focus group, and not only performs focusing, but also cancels aberrations generated by the second lens group G2, the object-side focus group. In particular, spherical aberration and coma generated by the second lens group G2 must be strongly corrected. However, using multiple lenses to correct these aberrations would make the fourth lens group G4 large and heavy, which would not only result in a bulky actuator but also hinder high-speed AF operation, making this undesirable. However, because spherical aberration and coma are monochromatic aberrations, it is possible to correct these aberrations by incorporating an aspherical lens within the fourth lens group G4. Furthermore, because the fourth lens group G4 has positive refractive power, it is desirable for the aspherical lens used for correction to also have positive refractive power. This allows for a reduction in the number of elements in the lens while still effectively correcting various aberrations, thereby reducing the weight of the focus moving parts and achieving both high-speed AF and high performance.

[0048] Furthermore, the optical system of the present invention is characterized in that an aspherical lens having negative refractive power is disposed closest to the image side of the fifth lens group G5.

[0049] The fifth lens group G5 is positioned so that the height of off-axial rays is higher than the height of on-axial rays, and a group with such a ray path can provide particularly strong correction of off-axial aberrations. Therefore, by arranging an aspherical lens in the fifth lens group G5 whose negative refractive power increases from the optical axis center toward the periphery, it is possible to effectively correct field curvature and distortion without increasing the number of lenses, thereby achieving both compactness and high performance. Since an aspherical lens can function more effectively when it is positioned where the difference between the height of on-axial rays and the height of off-axial rays is large, it is preferable to position it closest to the image.

[0050] Next, the lens configuration of an example of the optical system of the present invention will be described. In the following description, the lens configuration will be described in order from the object side to the image side. [Example]

[0051] 1 is a lens configuration diagram of an optical system according to a first embodiment of the present invention. The optical system is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving toward the object along different trajectories.

[0052] The first lens group G1 is composed of a biconcave negative lens and a biconvex positive lens.

[0053] The second lens group G2 is composed of a cemented lens that includes a biconvex positive lens G2asp whose object-side surface is aspherical and a biconcave negative lens.

[0054] The third lens group G3 is composed of a positive meniscus lens element with a concave surface facing the object side, a biconcave negative lens element, an aperture stop S, a cemented lens element consisting of a biconcave negative lens element and a biconvex positive lens element, a biconvex positive lens element with aspherical surfaces on both sides, and a cemented lens element consisting of a positive meniscus lens element Lp with a concave surface facing the object side and a biconcave negative lens element.

[0055] The fourth lens group G4 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconvex positive lens whose object-side surface is aspherical.

[0056] The fifth lens group G5 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconcave negative lens with aspherical surfaces on both sides, and an air lens AL is formed between the cemented lens and the negative lens. [Example]

[0057] 6 is a lens configuration diagram of an optical system according to Example 2 of the present invention. The optical system is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving toward the object along different trajectories.

[0058] The first lens group G1 is composed of a positive meniscus lens having a convex surface facing the object side, a positive meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side.

[0059] The second lens group G2 is composed of a positive meniscus lens G2asp having a convex surface facing the object side and an aspherical surface on the object side.

[0060] The third lens group G3 is composed of a cemented lens consisting of a biconvex positive lens Lp and a biconcave negative lens, an aperture stop S, a cemented lens consisting of a biconcave negative lens and a positive meniscus lens with its convex surface facing toward the object side, a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a cemented lens consisting of a biconvex positive lens and a negative meniscus lens with its concave surface facing toward the object side.

[0061] The fourth lens group G4 is composed of a negative meniscus lens with a convex surface facing the object side, and a positive biconvex lens with an aspherical surface on the object side.

[0062] The fifth lens group G5 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconcave negative lens with aspherical surfaces on both sides, and an air lens AL is formed between the cemented lens and the negative lens. [Example]

[0063] 11 is a lens configuration diagram of an optical system according to a third embodiment of the present invention. The optical system is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving toward the object along different trajectories.

[0064] The first lens group G1 is composed of a positive meniscus lens with its convex surface facing the object side.

[0065] The second lens group G2 is composed of a biconcave negative lens and a biconvex positive lens G2asp, both surfaces of which are aspherical.

[0066] The third lens group G3 is composed of a biconcave negative lens element, a cemented lens element consisting of a positive meniscus lens element Lp with its concave surface facing the object side and a negative meniscus lens element with its concave surface facing the object side, an aperture stop S, a biconvex positive lens element with aspherical surfaces on both sides, and a cemented lens element consisting of a negative meniscus lens element with its convex surface facing the object side and a biconvex positive lens element.

[0067] The fourth lens group G4 is composed of a biconcave negative lens and a biconvex positive lens with aspherical surfaces on both sides.

[0068] The fifth lens group G5 is composed of a biconvex positive lens, a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconcave negative lens with aspherical surfaces on both sides, and an air lens AL is formed between the cemented lens and the negative lens. [Example]

[0069] 16 is a lens configuration diagram of an optical system according to Example 4 of the present invention. The optical system is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with positive refractive power, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving toward the object along different trajectories.

[0070] The first lens group G1 is composed of a biconcave negative lens and a biconvex positive lens.

[0071] The second lens group G2 is composed of a cemented lens that includes a biconvex positive lens G2asp whose object-side surface is aspherical and a biconcave negative lens.

[0072] The third lens group G3 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, an aperture stop S, a cemented lens consisting of a biconcave negative lens and a biconvex positive lens, and a positive meniscus lens Lp with its concave surface facing the object side.

[0073] The fourth lens group G4 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconvex positive lens whose object-side surface is aspherical.

[0074] The fifth lens group G5 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a biconcave negative lens with aspherical surfaces on both sides, and an air lens AL is formed between the cemented lens and the negative lens. [Example]

[0075] 21 is a lens configuration diagram of an optical system according to a fifth embodiment of the present invention. The optical system is composed of 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, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving toward the object along different trajectories.

[0076] The first lens group G1 is composed of a biconcave negative lens, a negative meniscus lens with its convex surface facing the object side, and a biconvex positive lens.

[0077] The second lens group G2 is composed of a positive lens G2asp having a biconvex shape and aspherical surfaces on both sides.

[0078] The third lens group G3 is composed of a cemented lens consisting of a positive meniscus lens Lp with its concave surface facing the object side and a biconcave negative lens, an aperture stop S, a cemented lens consisting of a biconcave negative lens and a positive meniscus lens with its convex surface facing the object side, and a biconvex positive lens.

[0079] The fourth lens group G4 is composed of a cemented lens consisting of a biconcave negative lens and a biconvex positive lens, and a biconvex positive lens having aspherical surfaces on both sides.

[0080] The fifth lens group G5 is composed of a positive meniscus lens with its concave surface facing the object side, a cemented lens consisting of a negative meniscus lens with its convex surface facing the object side and a positive meniscus lens with its convex surface facing the object side, and a negative lens with a biconcave shape and aspherical surfaces on both sides, and an air lens AL is formed between the cemented lens and the negative lens. [Example]

[0081] 26 is a lens configuration diagram of an optical system according to Example 6 of the present invention. The optical system is composed of a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, a fourth lens group G4 with positive refractive power, and a fifth lens group G5 with negative refractive power, and focusing from infinity to close range is achieved by the second lens group G2 and the fourth lens group G4 moving from the image side to the object side along different trajectories.

[0082] The first lens group G1 is composed of a positive meniscus lens with a convex surface facing the object side, a positive meniscus lens with a convex surface facing the object side, and a cemented 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.

[0083] The second lens group G2 is composed of a positive meniscus lens G2asp having a convex surface facing the object side and an aspherical surface on the object side.

[0084] The third lens group G3 is composed of a negative meniscus lens with its convex surface facing the object side, an aperture stop S, a cemented lens consisting of a biconcave negative lens and a biconvex positive lens, and a biconvex positive lens Lp.

[0085] The fourth lens group G4 is composed of a negative meniscus lens element with a convex surface facing the object side, and a positive lens element with a biconvex shape and aspherical surfaces on both sides.

[0086] The fifth lens group G5 is composed of a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, and a negative meniscus lens whose concave surface faces the object side and whose object-side surface is aspherical, and an air lens AL is formed between the cemented lens and the negative meniscus lens.

[0087] Specific numerical data for each of the embodiments of the imaging optical system of the present invention described above will be shown below.

[0088] In the [Surface Data] section, the surface number is the lens surface or aperture stop number 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 (587.6 nm), vd is the Abbe number for the d-line, and PgF is the partial dispersion ratio for the g-line (wavelength 435.8 nm) and F-line (486.1 nm).

[0089] An asterisk (*) next to a surface number indicates that the lens surface is aspherical, and BF represents the back focal length.

[0090] The (diaphragm) next to the surface number indicates that an aperture diaphragm is located at that position. The radius of curvature for the plane or aperture diaphragm is marked as ∞ (infinity).

[0091] [Aspherical Data] shows the coefficient values ​​that give the aspherical shape of lens surfaces marked with an * in [Surface Data]. The aspherical shape is defined as follows: 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, ... are the aspherical coefficients of each order, respectively. The coordinates of the aspherical shape are expressed by the following equation:

[0092] TIFF2025124346000002.tif19123

[0093] [Various Data] shows values ​​such as focal length at each shooting distance and in focus state.

[0094] [Variable Distance Data] shows the variable distance and BF values ​​for each shooting distance and focus state.

[0095] [Lens Group Data] shows the surface number of each lens group closest to the object and the composite focal length of the entire group.

[0096] In addition, for all of the values ​​of the following specifications, the focal length f, radius of curvature r, lens surface spacing d, and other length units are given 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.

[0097] Also shown is a list of values ​​corresponding to the conditional expressions in each of these embodiments.

[0098] 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.

[0099] Numerical Example 1 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 -107.5100 1.0000 1.51742 52.15 2 61.9300 2.4700 3 78.3300 6.0500 2.00100 29.13 4 -489.3000 (d4) 5* 88.2600 5.0000 1.76450 49.09 6 -167.8500 1.0000 1.59270 35.45 7 215.0500 (d7) 8 -287.4900 2.9700 2.00100 29.13 9 -87.3400 0.9700 10 -125.8800 1.0000 1.59270 35.45 11 40.8900 6.6600 12 (Aperture) ∞ 3.3000 13 -97.6000 1.0100 1.85451 25.15 14 39.1700 10.5800 1.75500 52.32 15 -68.5200 0.2000 16* 61.7100 7.4700 1.76450 49.09 17* -151.3000 0.4000 18 -487.9700 5.0400 1.98612 16.48 0.6656 19 -52.2000 1.0000 1.85451 25.15 20 80.8100 (d20) 21 63.1000 7.9400 1.75500 52.32 22 -49.9400 1.0000 1.85451 25.15 23 463.3100 0.1500 24* 96.7600 5.3100 1.80610 40.73 25 -76.0700 (d25) 26 128.5400 4.6900 2.00069 25.46 27 -91.4600 1.0000 1.61396 44.29 28 25.9500 6.2600 29* -300.0000 1.0000 1.85135 40.10 30* 267.1100 (BF) Image plane ∞ [Aspherical data] 5th floor 16th floor 17th floor 24th floor 29th floor K 0.00000 0.00000 0.00000 0.00000 0.00000 A4 -2.17740E-06 -6.48260E-07 -4.35970E-07 -2.75230E-06 4.09140E-06 A6 -8.59080E-10 7.12940E-10 3.04410E-10 -8.33840E-10 -2.83210E-08 A8 -3.99910E-13 -6.61370E-13 -7.50130E-13 3.37100E-13 1.79340E-10 A10 4.24190E-16 4.59670E-16 5.39280E-16 0.00000E+00 -7.13360E-13 A12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 1.30860E-15 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 -8.76200E-19 30 sides K 0.00000 A4 1.05910E-05 A6 -2.73950E-08 A8 2.21150E-10 A10 -8.81720E-13 A12 1.85370E-15 A14 -1.57580E-18 [Various data] INF 395mm Focal length 48.27 44.69 F-number 1.24 1.38 Full angle of view 2ω 47.90 45.39 Image height Y 21.63 21.63 Lens length 123.38 123.38 [Variable Interval Data] INF 395mm d0 ∞ 271.3770 d4 9.3500 2.7500 d7 4.3100 10.9100 d20 6.6900 2.5600 d25 2.1500 6.2800 BF 17.4116 17.4116 [Lens group data] Group Starting plane Focal length G1 1 462.79 G2 5 143.09 G3 8 103398.14 G4 21 39.03 G5 26 -57.37

[0100] Numerical Example 2 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 81.1400 4.7000 1.75500 52.32 2 129.4400 0.1500 3 46.0800 10.4000 1.55032 75.50 4 115.6000 7.6000 5 109.6500 1.5000 1.60342 38.01 6 42.2600 (d6) 7* 61.1100 4.9500 1.76450 49.09 8 169.6900 (d8) 9 1369.2000 4.9200 1.94594 17.98 0.6546 10 -90.0600 1.0000 1.77047 29.74 11 52.9500 6.5900 12 (Aperture) ∞ 1.9300 13 -597.3400 1.0000 1.77047 29.74 14 35.9500 7.3100 1.59282 68.62 15 261.6500 0.1500 16 96.4000 7.3600 1.85033 42.70 17 -73.6500 1.0000 1.77047 29.74 18 100.9000 0.6800 19 74.8000 6.8000 2.00100 29.13 20 -98.0000 1.0000 1.77047 29.74 21 -263.8100 (d21) 22 841.3100 1.0000 1.84666 23.78 23 64.9200 0.2700 24* 48.1000 7.8800 1.76450 49.09 25 -86.0400 (d25) 26 102.1700 5.0000 2.00069 25.46 27 -191.1300 1.0000 1.61396 44.29 28 32.6400 5.6100 29* -149.4900 1.0000 1.68948 31.02 30* 300.0000 (BF) Image plane ∞ [Aspherical data] 7 screens 24 screens 29 screens 30 screens K 0.00000 0.00000 0.00000 0.00000 A4 -1.34170E-06 -2.10140E-06 -5.97450E-06 -4.17290E-06 A6 -7.37970E-10 -7.28010E-11 7.78050E-08 7.69700E-08 A8 -2.08620E-13 2.69240E-13 -1.89690E-10 -1.63300E-10 A10 4.08000E-16 -5.85700E-16 1.46960E-13 1.30570E-13 A12 -9.63930E-19 0.00000E+00 0.00000E+00 0.00000E+00 A14 7.18370E-22 0.00000E+00 0.00000E+00 0.00000E+00 [Various data] INF 832mm Focal length 82.63 74.71 F-number 1.24 1.31 Full angle of view 2ω 28.98 26.91 Image height Y 21.63 21.63 Lens length 136.91 136.91 [Variable Interval Data] INF 832mm d0 ∞ 694.8314 d6 13.9300 7.7100 d8 4.1900 10.4100 d21 8.6500 2.2500 d25 2.1500 8.5500 BF 17.1880 17.1880 [Lens group data] Group Starting plane Focal length G1 1 227.44 G2 7 122.50 G3 9 226.40 G4 22 78.97 G5 26 -74.63

[0101] Numerical Example 3 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 89.4300 4.0500 2.00069 25.46 2 179.0700 (d2) 3 -311.2700 1.0000 1.51742 52.15 4 24.6300 9.3000 5* 70.1600 5.4500 1.85135 40.10 6* -92.0300 (d6) 7 -282.0700 1.0000 1.61340 44.27 8 39.2900 7.3200 9 -43.7600 2.9000 1.98612 16.48 0.6656 10 -32.3500 1.0000 1.84666 23.78 11 -217.3900 1.0000 12 (Aperture) ∞ 1.0000 13* 188.1100 8.0800 1.85135 40.10 14* -54.2300 0.1500 15 68.3400 1.0000 1.85451 25.15 16 30.6000 14.5200 1.59282 68.62 17 -71.7300 (d17) 18 -102.4800 1.0000 1.85451 25.15 19 881.3700 0.1500 20* 49.8300 8.5700 1.76450 49.09 21* -58.1700 (d21) 22 104.8300 4.1100 1.59282 68.62 23 -141.4700 0.1500 24 130.1600 3.6900 1.98612 16.48 25 -100.9300 1.0000 1.78880 28.43 26 26.4400 5.7300 27* -300.0000 1.0000 1.85135 40.10 28* 300.0000 (BF) Image plane ∞ [Aspherical data] 5th floor 6th floor 13th floor 14th floor 20th floor K 0.00000 0.00000 0.00000 0.00000 0.00000 A4 -2.93360E-06 7.96680E-07 1.42910E-06 5.39790E-07 -2.54100E-06 A6 1.69060E-09 -5.74980E-10 -3.62850E-09 -1.47780E-09 -1.74430E-09 A8 -3.10320E-11 -2.25210E-11 2.61720E-12 -1.40150E-12 2.42580E-12 A10 8.02390E-14 6.85040E-14 -7.09200E-16 7.08140E-16 -6.82190E-15 A12 -5.52680E-17 -5.97010E-17 9.82190E-20 -7.89460E-19 6.27660E-18 A14 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 21st page 27th page 28th page K 0.00000 0.00000 0.00000 A4 3.57670E-06 1.33640E-06 1.28620E-05 A6 -4.37050E-09 -6.01760E-08 -5.29790E-08 A8 4.30360E-12 6.01450E-10 7.02630E-10 A10 -5.36930E-15 -2.73060E-12 -3.09550E-12 A12 3.46920E-18 5.34740E-15 6.34260E-15 A14 0.00000E+00 -3.78960E-18 -5.03830E-18 [Various data] INF 250mm Focal length 35.06 30.96 F-number 1.24 1.39 Full angle of view 2ω 62.68 62.95 Image height Y 21.63 21.63 Lens length 125.79 125.79 [Variable Interval Data] INF 250mm d0 ∞ 124.3576 d2 11.3600 6.7300 d6 3.5500 8.1800 d17 7.8400 2.2500 d21 2.1500 7.7400 BF 17.7164 17.7164 [Lens group data] Group Starting plane Focal length G1 1 174.58 G2 3 290.17 G3 7 86.53 G4 18 52.77 G5 22 -68.34

[0102] Numerical Example 4 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 -136.1200 1.0000 1.72825 28.32 2 82.1700 0.5000 3 61.5800 5.4300 2.00069 25.46 4 -455.3600 (d4) 5* 92.3900 4.2300 1.85135 40.10 6 -116.3600 1.0000 1.67270 32.17 7 99.8700 (d7) 8 225.6600 5.6200 1.85033 42.70 9 -43.3700 1.0000 1.77047 29.74 10 49.5000 4.9100 11 (Aperture) ∞ 2.9700 12 -85.3300 1.0000 1.77047 29.74 13 36.1300 7.6000 1.85033 42.70 14 -88.5500 0.4000 15 -401.3400 2.8200 1.98612 16.48 0.6656 16 -83.9100 (d16) 17 84.3800 3.9900 1.80420 46.50 18 -145.7300 1.0000 1.85451 25.15 19 52.0200 0.4700 20* 40.6000 7.6400 1.76450 49.09 21 -70.2000 (d21) 22 97.4000 4.5200 2.00069 25.46 23 -69.0200 1.0000 1.67270 32.17 24 26.0800 6.1800 25* -145.8300 1.0000 1.68948 31.02 26* 300.0000 (BF) Image plane ∞ [Aspherical data] 5th page 20th page 25th page 26th page K 0.00000 0.00000 0.00000 0.00000 A4 -3.75770E-06 -3.63450E-06 -1.43450E-06 5.66650E-06 A6 -2.66230E-09 3.05540E-10 1.12700E-08 9.37980E-09 A8 1.05900E-12 -3.88710E-12 -7.16250E-11 -3.86770E-11 A10 -9.22860E-16 4.23290E-15 1.47960E-13 1.05560E-13 A12 0.00000E+00 0.00000E+00 -1.02230E-16 -1.16590E-16 [Various data] INF 394mm Focal length 48.89 43.77 F-number 1.43 1.49 Full angle of view 2ω 48.85 46.89 Image height Y 22.50 22.50 Lens length 102.43 102.43 [Variable Interval Data] INF 394mm d0 ∞ 291.8469 d4 8.3600 2.9200 d7 3.5500 8.9900 d16 6.9000 2.2500 d21 2.1500 6.8000 BF 17.1875 17.1875 [Lens group data] Group Starting plane Focal length G1 1 228.15 G2 5 239.99 G3 8 208.41 G4 17 46.11 G5 22 -57.78

[0103] Numerical Example 5 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 -559.8900 1.0000 1.48749 70.44 2 30.1500 6.6700 3 1228.8800 1.0000 1.71736 29.50 4 47.7900 1.1700 5 43.3200 5.3200 2.00100 29.13 6 -364.9900 (d6) 7* 63.0000 3.1900 1.85135 40.10 8* -341.0200 (d8) 9 -463.3900 2.3700 1.98612 16.48 0.6656 10 -88.5600 1.0000 1.77047 29.74 11 33.5100 4.3800 12 (Aperture) ∞ 1.6000 13 -54831.5600 1.0000 1.85451 25.15 14 42.1100 4.1800 1.59282 68.62 15 837.3100 0.1500 16 80.2100 7.3100 1.75500 52.32 17 -36.5300 (d17) 18 -45.6400 1.0000 1.78880 28.43 19 46.9600 6.7700 1.59282 68.62 20 -55.8900 0.1500 21* 50.9800 6.8600 1.85135 40.10 22* -56.7500 (d22) 23 -2702.9800 2.7400 2.00100 29.13 24 -93.4800 0.1500 25 475.7700 1.0000 1.77047 29.74 26 20.0200 3.3900 1.98612 16.48 27 24.4600 5.8400 28* -261.2200 1.5500 1.68948 31.02 29* 800.0000 (BF) Image plane ∞ [Aspherical data] 7th floor 8th floor 21st floor 22nd floor 28th floor K 0.00000 0.00000 0.00000 0.00000 0.00000 A4 -5.30160E-06 5.22490E-07 -4.54930E-06 -2.34450E-08 8.03450E-06 A6 -1.20460E-08 -8.63240E-09 -1.05650E-09 -1.32830E-09 -6.61270E-08 A8 3.20280E-11 4.33450E-11 8.46400E-13 1.63680E-12 -1.14770E-10 A10 -1.96390E-14 -3.92610E-14 -1.28810E-15 -1.62660E-15 5.35840E-13 A12 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 -4.61670E-16 29 sides K 0.00000 A4 2.48730E-05 A6 -5.34120E-08 A8 -1.13960E-10 A10 7.84630E-13 A12 -9.55320E-16 [Various data] INF 250mm Focal length 33.61 30.84 F-number 1.44 1.52 Full angle of view 2ω 65.06 62.48 Image height Y 21.63 21.63 Lens length 105.02 105.02 [Variable Interval Data] INF 250mm d0 ∞ 145.3819 d6 5.9400 2.7500 d8 3.5500 6.7400 d17 6.2800 2.2500 d22 2.1500 6.1800 BF 17.3099 17.3099 [Lens group data] Group Starting plane Focal length G1 1 -316.04 G2 7 62.69 G3 9 125.19 G4 18 40.56 G5 23 -51.36

[0104] Numerical Example 6 Unit: mm [Face Data] Surface number rd nd vd PgF Object surface ∞ (d0) 1 65.4200 3.8800 1.94594 17.98 2 95.0400 0.1500 3 43.4800 9.9700 1.48749 70.44 4 175.6800 0.1500 5 37.3400 8.3900 1.43700 95.10 6 120.1300 1.0000 1.84666 23.78 7 31.9900 (d7) 8* 42.0300 3.6700 1.76450 49.09 9 94.1400 (d9) 10 98.4700 1.0000 1.77047 29.74 11 29.9000 6.5200 12 (Aperture) ∞ 3.7800 13 -70.8000 1.0000 1.85451 25.15 14 43.6900 5.9900 2.00100 29.13 15 -208.7300 0.4000 16 768.8700 3.2400 1.92286 20.88 0.6390 17 -91.0700 (d17) 18 336.8500 1.0000 1.84666 23.78 19 91.9600 0.3500 20* 46.5900 7.6100 1.59271 66.97 21* -51.2200 (d21) 22 73.3100 3.2300 2.00069 25.46 23 -890.4900 1.0000 1.56732 42.84 24 28.0500 9.4600 25* -28.9200 1.0000 1.51633 64.06 26 -57.8200 (BF) Image plane ∞ [Aspherical data] 8th floor 20th floor 21st floor 25th floor K 0.00000 0.00000 0.00000 0.00000 A4 -2.51040E-06 -4.15030E-06 -1.27420E-06 5.24720E-06 A6 -2.30330E-09 2.12170E-10 -6.64270E-11 5.86390E-09 A8 -2.87000E-12 -3.18600E-12 -4.55090E-12 -3.61960E-11 A10 -8.50190E-16 5.21900E-15 6.58400E-15 7.50780E-14 A12 0.00000E+00 0.00000E+00 0.00000E+00 -1.03400E-16 [Various data] INF 815mm Focal length 83.29 73.64 F-number 1.46 1.51 Full angle of view 2ω 28.78 26.35 Image height Y 21.63 21.63 Lens length 110.01 110.01 [Variable Interval Data] INF 815mm d0 ∞ 705.3250 d7 9.1100 5.5400 d9 2.7400 6.3100 d17 7.2100 2.2500 d21 2.1500 7.1100 BF 16.0126 16.0126 [Lens group data] Group Starting plane Focal length G1 1 143.11 G2 8 96.38 G3 10 -143.89 G4 18 57.80 G5 22 -69.25

[0105] [Conditional expression corresponding value] Conditional formula / Example EX1 EX2 EX3 EX4 EX5 EX6 (1) 1.36 1.24 1.26 1.34 1.40 1.27 (2) 0.047 0.039 0.047 0.047 0.047 0.028 (3) 0.0010 0.0006 0.0005 0.0006 0.0005 0.0005 (4) 3.7 1.6 5.5 5.2 1.5 1.7 (5) 0.017 0.019 0.031 0.020 0.022 0.010 (6) 0.84 0.64 0.84 0.70 0.83 0.02 (7) 0.023 0.025 0.010 0.011 0.035 0.018 [Explanation of symbols]

[0106] G1 First lens group G2 Second lens group G3 3rd lens group G4 4th lens group G5 5th lens group G2asp: An aspherical lens located in the second lens group G2 that weakens its convex power from the center of the optical axis to the periphery. Lp: A lens having positive refractive power that satisfies both conditional expressions (2) and (3) and is disposed in the third lens group G3 AL: An air lens formed by the fifth lens group G5 that satisfies conditional formula (6) S aperture stop I image plane

Claims

1. The lens is composed of, in order from the object side, a first lens group G1, a second lens group G2 having positive refractive power, a third lens group G3, a fourth lens group G4 having positive refractive power, and a fifth lens group G5 having negative refractive power, During focusing from infinity to a close distance, the second lens group G2 and the fourth lens group G4 move toward the object side along different loci along the optical axis, The second lens group G2 has an aspherical lens G2asp having a shape that weakens its convex power from the optical axis center to the periphery, The optical system is characterized in that the fourth lens group G4 has at least one lens having a positive refractive power and one lens having a negative refractive power.

2. 2. The optical system according to claim 1, wherein the fifth lens group G5 satisfies the following conditional expression (1), and the third lens group G3 includes a lens Lp having a positive refractive power that simultaneously satisfies the following conditional expressions (2) and (3): (1) 1.10 < βG5 < 1.60 (2) 0.021 < Lp_ΔPgF < 0.055 (3) 1 / (Lp_f × Lp_νd) < 0.0020 βG5: lateral magnification of the fifth lens group G5 when focusing at infinity Lp_ΔPgF: Anomalous partial dispersion ΔPgF of the lens Lp having a positive refractive power that constitutes the third lens group G3 Lp_vd: Abbe number vd of the lens Lp having positive refractive power that constitutes the third lens group G3 Lp_f: focal length (mm) of the lens Lp having positive refractive power that constitutes the third lens group G3 when not cemented

3. 2. The optical system according to claim 1, wherein the following condition is satisfied: (4) 1.0 < f2 / f4 < 6.0 (5) (f4 / vd_G4ave) / f < 0.050 f: focal length when focused at infinity (mm) f2: focal length (mm) of the second lens group G2 when focused at infinity f4: focal length (mm) of the fourth lens group G4 when focused at infinity vd_G4ave: average value of Abbe numbers νd of the positive lenses constituting the fourth lens group G4

4. 4. The optical system according to claim 1, wherein the fifth lens group G5 includes an air lens AL that satisfies the following conditional expression by two adjacent lenses: 1<g / (f<1)<g / (f<1). (6) -1.00 < (R2air + R1air) / (R2air - R1air) < 1.00 R1air: object-side radius of curvature of the air lens AL configured in the fifth lens group G5 (mm) R2air: image-side radius of curvature of the air lens AL configured in the fifth lens group G5 (mm)

5. 4. The optical system according to claim 1, wherein the following condition is satisfied: (7) 0.005 < | (G2aspHnr - G2aspHinf) / f_G2 | < 0.050 G2aspHinf: the height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp when focused at infinity G2aspHnr: Height (mm) of the off-axis chief ray on the object side of the aspherical lens G2asp at the closest focusing point The off-axis chief ray is defined as a ray passing through the intersection of the aperture stop and the optical axis at the maximum angle of view. f2: focal length (mm) of the second lens group G2 when focused at infinity

6. 4. The optical system according to claim 1, wherein the third lens group G3 includes an aperture stop S.

7. 4. The optical system according to claim 1, wherein the fourth lens group G4 includes an aspherical lens having a positive refractive power.

8. 4. The optical system according to claim 1, further comprising an aspherical lens having negative refractive power located closest to the image side of the fifth lens group G5.

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