Imaging optical system

Abstract

The purpose of the present invention is to provide an imaging optical system which is suitable for a compact and lightweight telephoto lens by having a compact and lightweight focusing unit itself. The imaging optical system is characterized in that the lens group of the imaging optical system is composed of a first group (G1) having positive refractive power as a whole, a second group (G2) composed of lenses moving on the optical axis during focusing, and a third group (G3) having refractive power, which are arranged in order from the object side to the image side, and the imaging optical system satisfies a predetermined conditional expression.

Description

Technical Field

[0001] The present invention relates to an imaging optical system suitable for photographic lenses used in still cameras, video cameras, etc. Background Art

[0002] Conventionally, as an imaging optical system suitable for a long-focus photographic lens (hereinafter, a telephoto lens), a telephoto-type imaging optical system in which a lens group with a positive refractive power and a lens group with a negative refractive power are arranged in order from the object side toward the image side is known. By adopting the telephoto-type refractive power configuration, the overall optical length of the telephoto lens, which tends to be long and heavy, can be shortened.

[0003] Moreover, telephoto lenses are often used in photographing sports, animals, etc., and high-speed autofocus is required. If the overall retraction method in which the entire imaging optical system is moved for focusing is adopted for a telephoto lens, the weight of the lens that moves during focusing becomes large, and it is difficult to achieve high-speed autofocus. Therefore, the internal focusing method is often adopted.

[0004] In addition, in recent years, the use of telephoto lenses in video shooting has been increasing. When used in video shooting, contrast detection method is often used for autofocus. In the contrast detection method, in order to detect the contrast, generally the focusing unit performs a swinging motion. Therefore, a telephoto lens equipped with a lighter focusing unit than before is expected.

[0005] In addition, in recent years, with the popularization of mirrorless cameras designed to be small, miniaturization and light weight are also required for telephoto lenses. When miniaturizing and lightening a telephoto lens, in addition to miniaturizing the imaging optical system, it is also important to miniaturize and lighten the movable part. This is because the size or configuration of the actuator depends on the size or weight of the movable part.

[0006] Patent Document 1: Japanese Patent No. 6627313

[0007] The imaging optical system described in Patent Document 1 achieves high performance while adopting internal focusing, but the miniaturization and lightening of the focusing unit are insufficient. Also, it cannot be said that the overall optical length is small enough with respect to the focal length. Summary of the Invention

[0008] The present invention has been made in view of such circumstances, and an object thereof is to provide an imaging optical system that is small and light in weight itself and has a small and light focusing unit, and thus is suitable for a small and light telephoto lens.

[0009] In order to achieve the above object, the imaging optical system of the present invention is characterized in that the lens group of the imaging optical system is composed of a first group G1 having a positive optical power as a whole, arranged in order from the object side toward the image side, a second group G2 composed of lenses that move on the optical axis during focusing, and a third group G3 having an optical power. The first group G1 is composed of a first sub-group G1a, a plurality of lenses, and a first sub-group G1b, arranged in order from the object side toward the image side. The first sub-group G1a has at least two positive lenses arranged in order from the position closest to the object side, and a meniscus-shaped negative lens with a convex surface facing the object side arranged at the position closest to the image side. The first sub-group G1b has the positive lens closest to the image side of the first group G1 or a lens component including a positive lens at the position closest to the object side, and has the longest air gap D_A11 within the first group G1 between the first sub-group G1a and the first sub-group G1b. The imaging optical system satisfies the following conditional expressions. (1) 0.05 < D_A11 / D_G1 < 0.44 Wherein, D_A11 is the longest air gap within the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged at the position closest to the object side of the first group G1 to the image-side lens surface of the lens arranged at the position closest to the image side of the first group G1. Advantages of the Invention

[0010] According to the imaging optical system of the present invention, an imaging optical system can be provided. The optical system itself is small and lightweight, and has a small and lightweight focusing unit, thus being suitable for a small and lightweight telephoto lens. Brief Description of the Drawings

[0011] Figure 1 is the lens structure diagram at infinity of Embodiment 1 of the present invention. Figure 2 is the longitudinal aberration diagram at infinity of Embodiment 1 of the present invention. Figure 3 is the longitudinal aberration diagram at a shooting distance of 3.2 m of Embodiment 1 of the present invention. Figure 4 is the lateral aberration diagram at infinity of Embodiment 1 of the present invention. Figure 5 is the lateral aberration diagram at a shooting distance of 3.2 m of Embodiment 1 of the present invention. Figure 6 is the lateral aberration diagram at 0.3° anti-vibration at infinity of Embodiment 1 of the present invention. Figure 7 is the lens structure diagram at infinity of Embodiment 2 of the present invention. Figure 8It is the longitudinal aberration diagram at infinity in Embodiment 2 of the present invention. Figure 9 It is the longitudinal aberration diagram at a shooting distance of 3.3 m in Embodiment 2 of the present invention. Figure 10 It is the lateral aberration diagram at infinity in Embodiment 2 of the present invention. Figure 11 It is the lateral aberration diagram at a shooting distance of 3.3 m in Embodiment 2 of the present invention. Figure 12 It is the lateral aberration diagram at 0.3° anti-vibration at infinity in Embodiment 2 of the present invention. Figure 13 It is the lens structure diagram at infinity in Embodiment 3 of the present invention. Figure 14 It is the longitudinal aberration diagram at infinity in Embodiment 3 of the present invention. Figure 15 It is the longitudinal aberration diagram at a shooting distance of 3.1 m in Embodiment 3 of the present invention. Figure 16 It is the lateral aberration diagram at infinity in Embodiment 3 of the present invention. Figure 17 It is the lateral aberration diagram at a shooting distance of 3.1 m in Embodiment 3 of the present invention. Figure 18 It is the lateral aberration diagram at 0.3° anti-vibration at infinity in Embodiment 3 of the present invention. Figure 19 It is the lens structure diagram at infinity in Embodiment 4 of the present invention. Figure 20 It is the longitudinal aberration diagram at infinity in Embodiment 4 of the present invention. Figure 21 It is the longitudinal aberration diagram at a shooting distance of 3.2 m in Embodiment 4 of the present invention. Figure 22 It is the lateral aberration diagram at infinity in Embodiment 4 of the present invention. Figure 23 It is the lateral aberration diagram at a shooting distance of 3.2 m in Embodiment 4 of the present invention. Figure 24 It is the lateral aberration diagram at 0.3° anti-vibration at infinity in Embodiment 4 of the present invention. Figure 25 It is the lens structure diagram at infinity in Embodiment 5 of the present invention. Figure 26 It is the longitudinal aberration diagram at infinity in Embodiment 5 of the present invention. Figure 27 It is the longitudinal aberration diagram at a shooting distance of 3.3 m in Embodiment 5 of the present invention. Figure 28It is the lateral aberration diagram at infinity in Embodiment 5 of the present invention. Figure 29 It is the lateral aberration diagram at a shooting distance of 3.3 m in Embodiment 5 of the present invention. Figure 30 It is the lateral aberration diagram at 0.3° anti-shake at infinity in Embodiment 5 of the present invention. Detailed implementation manners

[0012] The imaging optical system of the present invention will be described. As can be seen from the lens structure diagrams shown in Figure 1 , Figure 7 , Figure 13 , Figure 19 , Figure 25 , the lens group of the imaging optical system of the present invention is characterized in that the lens group of the imaging optical system is composed of a first group G1 having a positive optical power arranged in order from the object side toward the image side, a second group G2 composed of lenses that move on the optical axis during focusing, and a third group G3 having an optical power.

[0013] By adopting such a group structure, due to the converging effect of the first group G1 having a positive optical power on the whole on the light beam, the second group G2 and the third group G3 as the focusing units can be made smaller in diameter. By making the focusing unit as the movable part smaller in diameter, it is easy to make it lighter, so the actuator can also be made smaller and lighter. Since the second group G2 and the third group G3 are made smaller in diameter while the actuator can be made smaller and lighter, as a telephoto lens, it can be made smaller and lighter.

[0014] Moreover, by arranging the first group G1 having a positive optical power on the object side and arranging the second group G2 and the third group G3 having a negative optical power on the image side, a telephoto-type optical power configuration can be formed, so there is an effect of shortening the total length of the imaging optical system. And, since it is easy to endow a dust and drip-proof mechanism, it is expected that the first group G1 arranged at the position closest to the object side of the imaging optical system and the lens arranged at the position closest to the image side are always fixed with respect to the image plane. And, it can be considered that when the user attaches and detaches the interchangeable lens to the camera, the lens arranged at the position closest to the image side of the imaging optical system may be touched, so it is expected to arrange a unit that is always fixed with respect to the image plane at the position closest to the image side of the imaging optical system.

[0015] Further, the first lens group G1 is composed of a first sub-group G1a, a plurality of lenses, and a second sub-group G1b, which are arranged in sequence from the object side toward the image side. The first sub-group G1a has at least two positive lenses arranged in sequence starting from the position closest to the object side, and a meniscus negative lens with its convex surface facing the object side arranged at the position closest to the image side. The second sub-group G1b has, at the position closest to the object side, the positive lens closest to the image side of the first lens group G1 or a lens component including a positive lens, and has the longest air gap D_A11 within the first lens group G1 between the first sub-group G1a and the second sub-group G1b. Thus, both the weight reduction and aberration correction of the first lens group G1 can be achieved simultaneously.

[0016] In addition, the lens components of the present invention are single lenses or cemented lenses. The lens components including positive lenses are single lenses with one positive lens or cemented lenses with positive lenses.

[0017] Furthermore, the imaging optical system of the present invention is characterized by satisfying the following conditional expressions. (1) 0.05 < D_A11 / D_G1 < 0.44 Wherein, D_A11 is the longest air gap within the first lens group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged at the position closest to the object side of the first lens group G1 to the image-side lens surface of the lens arranged at the position closest to the image side of the first lens group G1.

[0018] The conditional expression (1) defines the ratio of the longest air gap within the first lens group G1 to the length on the optical axis of the first lens group G1 when the imaging optical system is focused at infinity.

[0019] If the upper limit value of the conditional expression (1) is exceeded and the longest air gap within the first lens group G1 becomes longer, it becomes difficult to arrange the high-power lenses required for miniaturization and the lenses required for correcting the aberration generated therein. If the lower limit value of the conditional expression (1) is exceeded and the longest air gap within the first lens group G1 becomes shorter, the lenses with large diameters are arranged closely, and thus it becomes difficult to achieve weight reduction.

[0020] By limiting the upper limit value of the conditional expression (1) to 0.40, the above-described effects can be made more reliable, and thus it is preferred. By limiting the lower limit value of the conditional expression (1) to 0.10, the above-described effects can be made more reliable, and thus it is preferred.

[0021] Furthermore, it is further expected that by limiting the upper limit value of the conditional expression (1) to 0.35, the above-described effects can be made more reliable, and thus it is preferred. By limiting the lower limit value of the conditional expression (1) to 0.15, the above-described effects can be made more reliable, and thus it is preferred.

[0022] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expressions. (2) 0.10 < (D_A11 + D_A12) / D_G1 < 0.70 Wherein, D_A11 is the longest air gap within the first group G1, D_A12 is the second longest air gap between the first sub-group G1a and the first sub-group G1b.

[0023] The conditional expression (2) defines the ratio of the sum of the longest air gap within the first group G1 and the second longest air gap between the first sub-group G1a and the first sub-group G1b to the on-axis length of the first group G1 when the imaging optical system is focused at infinity.

[0024] If the upper limit value of the conditional expression (2) is exceeded and the on-axis length of the first group G1 becomes shorter, it becomes more difficult to arrange the high-power lenses required for miniaturization and the lenses required for correcting the aberration generated therein. If the lower limit value of the conditional expression (2) is exceeded and the sum of the two air gaps becomes shorter, the large-diameter lenses are arranged closely, making it more difficult to achieve weight reduction.

[0025] By limiting the upper limit value of the conditional expression (2) to 0.60, the above-mentioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (2) to 0.20, the above-mentioned effects can be made more reliable, so it is preferred.

[0026] Furthermore, it is expected that by limiting the upper limit value of the conditional expression (2) to 0.52, the above-mentioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (2) to 0.30, the above-mentioned effects can be made more reliable, so it is preferred.

[0027] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expressions. (3) 0.05 < D_G1a / D_G1 < 0.45 Wherein, D_G1a is the on-axis length of the first sub-group G1a, D_G1 is the on-axis distance from the object-side lens surface of the lens arranged at the position closest to the object side of the first group G1 to the image-side lens surface of the lens arranged at the position closest to the image side of the first group G1.

[0028] The conditional expression (3) defines the ratio of the on-axis length within the first sub-group G1a of the imaging optical system to the on-axis length of the first group G1.

[0029] If the upper limit value of conditional expression (3) is exceeded and the length on the optical axis within the first group G1a increases, the volume of the lens with a large diameter increases, making it difficult to achieve weight reduction. If the lower limit value of conditional expression (3) is exceeded and the length on the optical axis of the first group G1 increases, it becomes difficult to miniaturize the entire lens system.

[0030] By limiting the upper limit value of conditional expression (3) to 0.40, the above-described effects can be made more reliable, which is therefore preferable. By limiting the lower limit value of conditional expression (3) to 0.10, the above-described effects can be made more reliable, which is therefore preferable.

[0031] Furthermore, it is further expected that by limiting the upper limit value of conditional expression (3) to 0.35, the above-described effects can be made more reliable, which is therefore preferable. By limiting the lower limit value of conditional expression (3) to 0.15, the above-described effects can be made more reliable, which is therefore preferable.

[0032] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (4) 0.15 < D_A1all / D_G1 < 0.75 Wherein, D_A1all is the sum of all air gaps within the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens disposed at the position closest to the object side of the first group G1 to the image-side lens surface of the lens disposed at the position closest to the image side of the first group G1.

[0033] Conditional expression (4) defines the ratio of the sum of all air gaps within the first group G1 of the imaging optical system to the length on the optical axis of the first group G1.

[0034] If the upper limit value of conditional expression (4) is exceeded and the length on the optical axis of the first group G1 decreases, it becomes more difficult to arrange the high-power lenses required for miniaturization and the lenses required for correcting the aberration generated therein. If the lower limit value of conditional expression (4) is exceeded and the sum of all air gaps within the first group G1 decreases, the lenses with a large diameter are arranged closely, making it more difficult to achieve weight reduction.

[0035] By limiting the upper limit value of conditional expression (4) to 0.70, the above-described effects can be made more reliable, which is therefore preferable. By limiting the lower limit value of conditional expression (4) to 0.25, the above-described effects can be made more reliable, which is therefore preferable.

[0036] Furthermore, it is further expected that by limiting the upper limit value of conditional expression (4) to 0.65, the above-described effects can be made more reliable, which is therefore preferable. By limiting the lower limit value of conditional expression (4) to 0.40, the above-described effects can be made more reliable, which is therefore preferable.

[0037] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expressions. (5) atan(H_Img / f) < 7.00° Wherein, H_Img is the maximum image height, f is the focal length of the imaging optical system at infinity focus.

[0038] Conditional expression (5) defines the approximate field angle of the imaging optical system based on the maximum image height of the imaging optical system and the focal length of the imaging optical system at infinity focus.

[0039] If the upper limit value of conditional expression (5) is exceeded and the field angle becomes larger, it is difficult to arrange lenses suitable for aberration correction for the peripheral field angle, so it is not preferred. If the value of conditional expression (5) becomes smaller and the field angle becomes smaller, the number of lens elements in the first group G1 is excessive as the number required for aberration correction, so it becomes unsuitable for a small and lightweight optical system for the purpose of the invention.

[0040] By limiting the upper limit value of conditional expression (5) to 5.00°, the foregoing effects can be made more reliable, so it is preferred. By setting a lower limit value of 0.40° in conditional expression (5), the foregoing effects can be made more reliable, so it is preferred.

[0041] Furthermore, it is expected that by limiting the upper limit value of conditional expression (5) to 3.50°, the foregoing effects can be made more reliable, so it is preferred. By limiting the lower limit value of conditional expression (5) to 1.00°, the foregoing effects can be made more reliable, so it is preferred.

[0042] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expressions. (6) 0.10 < LT / f < 1.00 Wherein, LT is the distance on the optical axis from the surface closest to the object side to the image plane of the imaging optical system at infinity focus, f is the focal length of the imaging optical system at infinity focus.

[0043] Conditional expression (6) defines the ratio of the overall optical length to the focal length of the imaging optical system at infinity focus.

[0044] If the upper limit of conditional expression (6) is exceeded and the overall optical length becomes longer, it is difficult to achieve miniaturization and light weight as a telephoto lens. If the lower limit of conditional expression (6) is exceeded and the overall optical length becomes shorter, a large movement amount of the focusing unit cannot be obtained. If a practical shortest shooting distance is to be achieved, the optical power of the focusing unit must be increased, so the aberration generated in the focusing unit becomes larger, and it is difficult to obtain good performance within a wide shooting distance range.

[0045] By limiting the upper limit value of conditional expression (6) to 0.64, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of conditional expression (6) to 0.15, the aforementioned effect can be made more reliable, so it is preferred.

[0046] Furthermore, it is expected that by limiting the upper limit value of conditional expression (6) to 0.56, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of conditional expression (6) to 0.30, the aforementioned effect can be made more reliable, so it is preferred.

[0047] In addition, the imaging optical system of the present invention is characterized in that the first group G1b is composed of a negative lens and a positive lens, or composed of a positive lens and a negative lens.

[0048] It is expected that the first group G1b uses one negative lens and one positive lens each to achieve chromatic aberration correction and weight reduction. And further, it is expected to be a cemented lens to simplify the lens structure.

[0049] In addition, the imaging optical system of the present invention is characterized in that the following conditional expression is satisfied. (7) -60.00 < Φ_G2G3 / Φ < -3.00 Wherein, Φ is the optical power of the imaging optical system at infinity focus, Φ_G2G3 is the combined optical power of the second group G2 and the third group G3 at infinity focus.

[0050] Conditional expression (7) stipulates the ratio of the combined optical power of the second group G2 and the third group G3 to the optical power of the entire system at infinity focus of the imaging optical system.

[0051] If it exceeds the upper limit value of conditional expression (7) and the negative combined optical power of the second group G2 and the third group G3 becomes smaller, the telephoto effect becomes weaker, and it is difficult to miniaturize the imaging optical system. If it exceeds the lower limit value of conditional expression (7) and the negative combined optical power of the second group G2 and the third group G3 becomes larger, the effect of aberration expansion becomes larger, so it is difficult to obtain good performance.

[0052] By limiting the upper limit value of conditional expression (7) to -5.00, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of conditional expression (7) to -50.00, the aforementioned effect can be made more reliable, so it is preferred.

[0053] Furthermore, it is expected that by limiting the upper limit value of conditional expression (7) to -8.30, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of conditional expression (7) to -25.00, the aforementioned effect can be made more reliable, so it is preferred.

[0054] (8) 1.00 < D_EXP / H_Img < 11.00 Wherein, D_EXP is the distance from the exit pupil to the image plane when the imaging optical system is focused at infinity, H_Img is the maximum image height.

[0055] The conditional expression (8) defines the ratio of the distance from the exit pupil to the image plane to the maximum image height when the imaging optical system is focused at infinity.

[0056] If the upper limit value of the conditional expression (8) is exceeded and the exit pupil moves away from the object side with respect to the image plane, the ray height near the image plane becomes higher. However, there is a part for mounting on a camera near the image plane, so the light becomes dim and it is difficult to ensure the peripheral light quantity. If the lower limit value of the conditional expression (8) is exceeded and the exit pupil approaches the image plane, the chief ray exit angle of the lens arranged at the position closest to the image side becomes larger. In the case of using an imaging element used in a digital camera or the like, this imaging element generally has the characteristic that the sensitivity to light with a large incident angle to the imaging element decreases. Therefore, if the incident angle of the light is large, it is difficult to ensure the peripheral light quantity.

[0057] By limiting the upper limit value of the conditional expression (8) to 8.00, the aforementioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (8) to 2.00, the aforementioned effects can be made more reliable, so it is preferred.

[0058] Furthermore, it is further expected that by limiting the upper limit value of the conditional expression (8) to 4.30, the aforementioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (8) to 2.70, the aforementioned effects can be made more reliable, so it is preferred.

[0059] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (9) -35.00 < Φ_G3 / Φ < -1.00 Wherein, Φ_G3 is the optical power of the third group G3, Φ is the optical power of the imaging optical system when focused at infinity.

[0060] The conditional expression (9) defines the ratio of the optical power of the third group G3 to the optical power of the entire system.

[0061] If the upper limit value of conditional expression (9) is exceeded and the negative optical power of the third group G3 decreases, in order to maintain the focal length of the entire system while maintaining the telephoto optical power configuration, it is necessary to increase the negative optical power of the second group G2. If the negative optical power of the second group G2, which is the focusing unit, becomes too large, the variation of the spherical aberration during focusing becomes large, and it is difficult to obtain good performance within a wide photographic distance range. If the lower limit value of conditional expression (9) is exceeded and the negative optical power of the third group G3 increases, it is difficult to ensure sufficient back focal length. Also, since the effect of aberration expansion becomes large, it is difficult to obtain good performance.

[0062] By limiting the upper limit value of conditional expression (9) to -1.50, the aforementioned effect can be made more reliable, so it is preferable. By limiting the lower limit value of conditional expression (9) to -26.00, the aforementioned effect can be made more reliable, so it is preferable.

[0063] Furthermore, it is expected that by limiting the upper limit value of conditional expression (9) to -4.00, the aforementioned effect can be made more reliable, so it is preferable. By limiting the lower limit value of conditional expression (9) to -11.00, the aforementioned effect can be made more reliable, so it is preferable.

[0064] In addition, the imaging optical system of the present invention is characterized in that the third group G3 has an image stabilization unit IU, the image stabilization unit IU has a rear unit RU on the image side, the signs of the optical powers of the image stabilization unit IU and the rear unit RU are different, the image stabilization unit IU has at least one positive lens and at least one negative lens, and the imaging optical system satisfies the following conditional expression. (10) 3.00 < |Φ_OS / Φ| < 35.00 Wherein, Φ_OS is the optical power of the image stabilization unit IU, Φ is the optical power of the imaging optical system at infinity focus.

[0065] By disposing the rear unit RU having a sign of optical power different from that of the image stabilization unit IU, it is possible to increase the optical power of the image stabilization unit IU while maintaining the optical power of the third group G3, and the image stabilization amount (hereinafter referred to as the anti-vibration coefficient) with respect to the movement amount of the image stabilization unit IU can be increased. If the anti-vibration coefficient is increased, the movement amount of the image stabilization unit IU can be reduced, so the size of the actuator can be reduced, which is beneficial to the miniaturization and light weight of the telephoto lens.

[0066] Also, since the image stabilization unit IU has at least one positive lens and at least one negative lens, chromatic aberration can be corrected within the image stabilization unit IU, and good performance can be obtained during image stabilization.

[0067] The conditional expression (10) defines the ratio of the optical power of the image stabilization unit IU to the optical power of the imaging optical system.

[0068] If the lower limit value of the conditional expression (10) is exceeded and the optical power of the image stabilization unit IU becomes smaller, the anti-vibration coefficient becomes smaller, resulting in the need to increase the driving amount of the image stabilization unit IU, making it difficult to miniaturize the actuator and, in turn, the telephoto lens. If the upper limit value of the conditional expression (10) is exceeded and the optical power of the image stabilization unit IU becomes larger, an anti-vibration coefficient can be obtained, but the aberration generated in the image stabilization unit IU becomes larger, and the variation of coma aberration or astigmatism aberration during driving in the direction perpendicular to the optical axis becomes larger. Therefore, it is difficult to obtain good performance during image stabilization.

[0069] By limiting the upper limit value of the conditional expression (10) to 26.00, the aforementioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (10) to 5.00, the aforementioned effects can be made more reliable, so it is preferred.

[0070] Furthermore, it is further expected that by limiting the upper limit value of the conditional expression (10) to 22.00, the aforementioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (10) to 7.00, the aforementioned effects can be made more reliable, so it is preferred.

[0071] In addition, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (11) -20.00 < Φ_G2 / Φ < -0.13 Wherein, Φ_G2 is the optical power of the second group G2, Φ is the optical power of the imaging optical system when focused at infinity.

[0072] The conditional expression (11) defines a preferred range for the ratio of the optical power of the second group G2 to the optical power of the imaging optical system.

[0073] If the upper limit value of the conditional expression (11) is exceeded and the negative optical power of the second group G2 becomes smaller, then by making the third group G3 assume the role of the negative optical power disposed on the telephoto image side, the negative optical power of the third group G3 becomes larger. Since the effect of aberration expansion in the third group G3 becomes larger, it is difficult to obtain good performance. If the lower limit value of the conditional expression (11) is exceeded and the negative optical power of the second group G2 becomes larger, it is easy to generate aberration, especially astigmatism aberration, in the second group G2 as the focusing unit. Therefore, it is difficult to obtain good performance within a wide range of shooting distances.

[0074] By limiting the upper limit value of the conditional expression (11) to -0.20, the aforementioned effects can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (11) to -12.00, the aforementioned effects can be made more reliable, so it is preferred.

[0075] Furthermore, it is further expected that by limiting the lower limit value of conditional expression (11) to -6.00, the aforementioned effect can be made more reliable, and thus it is preferable.

[0076] In addition, the imaging optical system of the present invention is characterized in that it has a negative lens satisfying the following conditional expressions at a position closer to the image side than the aperture stop. (12) 10.00 < ν_d < 30.00 (13) 0.020 < P_gF + 0.0018 * ν_d - 0.6483 < 0.080 Wherein, ν_d is the Abbe number of the negative lens for the d line, P_gF is the partial dispersion ratio of the negative lens for the g line and the F line, The partial dispersion ratio is defined as P_gF = (n_g - n_F) / (n_F - n_C), n_g is the refractive index for the g line, and the wavelength of the g line λ = 435.84 nm, n_F is the refractive index for the F line, and the wavelength of the F line λ = 486.13 nm, n_C is the refractive index for the C line, and the wavelength of the C line λ = 656.27 nm.

[0077] By having a negative lens satisfying conditional expressions (12) and (13) at a position closer to the image side than the aperture stop S, good chromatic aberration correction can be obtained.

[0078] Conditional expression (12) specifies a preferred range for the Abbe number of the negative lens for the d line.

[0079] If the upper limit value of conditional expression (12) is exceeded and the Abbe number for the d line becomes larger, the effect of eliminating chromatic aberration becomes weaker, and it is difficult to correct the chromatic aberration in the entire lens system. Also, it is difficult to select a material that satisfies conditional expression (13). If the lower limit value of conditional expression (12) is exceeded and the Abbe number for the d line becomes smaller, the effect of expanding chromatic aberration becomes larger, and it is difficult to correct the chromatic aberration in the entire lens system.

[0080] By limiting the upper limit value of conditional expression (12) to 24.00, the aforementioned effect can be made more reliable, and thus it is preferable. By limiting the lower limit value of conditional expression (12) to 15.00, the aforementioned effect can be made more reliable, and thus it is preferable.

[0081] Furthermore, it is further expected that by limiting the upper limit value of conditional expression (12) to 21.00, the aforementioned effect can be made more reliable, and thus it is preferable. By limiting the lower limit value of conditional expression (12) to 16.00, the aforementioned effect can be made more reliable, and thus it is preferable.

[0082] The conditional expression (13) defines a preferred range for the partial dispersion ratio of the negative lens with respect to the g-line and the F-line.

[0083] If the upper limit value of the conditional expression (13) is exceeded and the partial dispersion ratio with respect to the g-line and the F-line increases, then in particular, the chromatic aberration of the g-line increases in the positive direction, making it difficult to correct the chromatic aberration in the entire lens system. If the lower limit value of the conditional expression (13) is exceeded and the partial dispersion ratio with respect to the g-line and the F-line decreases, then in particular, the chromatic aberration of the g-line increases in the negative direction, making it difficult to correct the chromatic aberration in the entire lens system.

[0084] By limiting the upper limit value of the conditional expression (13) to 0.048, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (13) to 0.024, the aforementioned effect can be made more reliable, so it is preferred.

[0085] Furthermore, it is expected that by limiting the upper limit value of the conditional expression (13) to 0.041, the aforementioned effect can be made more reliable, so it is preferred. By limiting the lower limit value of the conditional expression (13) to 0.027, the aforementioned effect can be made more reliable, so it is preferred.

[0086] In addition, the imaging optical system of the present invention is characterized in that the object side and the image side of all lenses are composed of spherical surfaces or flat surfaces. Even if a spherical lens rotates around the center of the sphere during processing, equivalent processing can be performed. Therefore, compared with an aspherical lens, it is easier to manufacture. Since the lenses constituting the imaging optical system of a telephoto lens are likely to have a large aperture, it is possible to expect to obtain lenses with good processing accuracy at a low processing cost.

[0087] Next, the lens structure of the embodiment related to the imaging optical system of the present invention will be described. In the following description, the lens structure is described in the order from the object side to the image side.

[0088] Specific numerical data of each embodiment of the imaging optical system of the present invention are shown.

[0089] In the [surface data], the surface number is the number of the lens surface or the aperture stop counted from the object side, r represents the curvature radius of each surface, d represents the interval between each surface, nd represents the refractive index with respect to the d-line (wavelength 587.56 nm), vd represents the Abbe number with respect to the d-line, and P_gF represents the partial dispersion ratio with respect to the g-line and the F-line.

[0090] BF represents the back focal length.

[0091] (Stop) attached to the surface number indicates that the aperture stop S is at this position. ∞ (infinity) is entered for the curvature radius with respect to the plane or the aperture stop S.

[0092] Among [various data], the equivalent focal lengths at a shooting distance of INF, 20 m, and 3.2 m are shown.

[0093] Among [variable interval data], the variable interval and BF value at a shooting distance of INF, 20 m, and 3.2 m are shown.

[0094] Among [lens group data], the surface number closest to the object side that constitutes each lens group and the combined focal length of the entire group are shown.

[0095] In addition, in all the following specification values, unless otherwise specified, the units of the recorded focal length f, radius of curvature r, lens surface interval d, and other lengths are in millimeters (mm). However, in an optical system, equal optical performance can be obtained even with scale magnification and reduction, so it is not limited to this.

[0096] Moreover, in the lens structure diagrams of each embodiment, the arrow indicates the trajectory of the lens group when zooming from the wide-angle end to the telephoto end, I represents the image plane, and the single dotted line passing through the center represents the optical axis.

[0097] In the aberration diagrams corresponding to each embodiment, d, g, and C respectively represent the d-line, g-line, and C-line, and ΔS and ΔM respectively represent the sagittal image plane and the meridional image plane. [Embodiment 1]

[0098] Figure 1 It is the lens structure diagram of the imaging optical system of Embodiment 1 of the present invention. The first group G1 is composed of a meniscus-shaped positive lens L1 with a convex surface facing the object side, a meniscus-shaped positive lens L2 with a convex surface facing the object side, a meniscus-shaped negative lens L3 with a convex surface facing the object side, a meniscus-shaped positive lens L4 with a convex surface facing the object side, a double concave-shaped negative lens L5, a double convex-shaped positive lens L6, and a cemented lens composed of a meniscus-shaped negative lens L7 with a convex surface facing the object side and a meniscus-shaped lens L8 with a convex surface facing the object side, and has a positive optical power as a whole. And the first group G1 is always fixed relative to the image plane. Here, the first sub-group G1a is composed of L1, L2, and L3, and the first sub-group G1b is composed of L7 and L8.

[0099] The second group G2 is composed of a cemented lens composed of a meniscus-shaped positive lens L9 with a convex surface facing the object side and a meniscus-shaped negative lens L10 with a convex surface facing the object side, and has a negative optical power as a whole. And the second group G2 moves from the object side toward the image side on the optical axis when focusing from an infinitely distant object to a nearby object.

[0100] The third group G3 is composed of an image stabilization unit IU and a rear unit RU, and has a negative optical power as a whole. And the third group G3 is fixed relative to the image plane during focusing.

[0101] The image shake correction unit IU is composed of a cemented lens of a biconvex positive lens L11 and a biconcave negative lens L12 and a biconcave negative lens L13, and has a negative optical power as a whole. Further, the image shake correction unit IU moves in a direction substantially perpendicular to the optical axis to reduce the shake of the image caused by the shake of the imaging optical system.

[0102] The rear unit RU is composed of a biconvex positive lens L14, a cemented lens composed of a biconcave negative lens L15 and a meniscus positive lens L16 with the convex surface facing the object side, a three-piece cemented lens composed of a biconvex positive lens L17, a biconcave negative lens L18 and a biconvex positive lens L19, and a meniscus negative lens L20 with the concave surface facing the object side, and has a negative optical power as a whole. Further, the rear unit RU is always fixed with respect to the image plane.

[0103] The aperture stop S is disposed between the second group G2 and the third group G3. In the imaging optical system, the lens component Ln disposed at the position closest to the image side is the negative lens L20.

[0104] Next, the specification values of the imaging optical system according to the first embodiment are shown below. Numerical Example 1 Unit: mm [Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] [Example 2]

[0105] Figure 7 FIG. is a lens configuration diagram of the imaging optical system according to the second embodiment of the present invention. The first group G1 is composed of a biconvex positive lens L1, a meniscus positive lens L2 with the convex surface facing the object side, a meniscus negative lens L3 with the convex surface facing the object side, a meniscus positive lens L4 with the convex surface facing the object side, a biconcave negative lens L5, a biconvex positive lens L6, and a cemented lens composed of a meniscus negative lens L7 with the convex surface facing the object side and a lens L8 with the convex surface facing the object side, and has a positive optical power as a whole. Further, the first group G1 is always fixed with respect to the image plane. Here, the first a-group G1a is composed of L1, L2, and L3, and the first b-group G1b is composed of L7 and L8.

[0106] The second group G2 is composed of a cemented lens formed by a meniscus positive lens L9 with its convex surface facing the object side and a meniscus negative lens L10 with its convex surface facing the object side, and has a negative optical power as a whole. Also, when focusing from an infinitely distant object to a close object, the second group G2 moves from the object side toward the image side on the optical axis.

[0107] The third group G3 is composed of an image shake correction unit IU and a rear unit RU, and has a negative optical power as a whole. Also, the third group G3 is fixed relative to the image plane during focusing.

[0108] The image shake correction unit IU is composed of a cemented lens of a biconvex positive lens L11 and a biconcave negative lens L12 and a biconcave negative lens L13, and has a negative optical power as a whole. Also, the image shake correction unit IU moves in a direction substantially perpendicular to the optical axis to reduce the shake of the image caused by the shake of the imaging optical system.

[0109] The rear unit RU is composed of a biconvex positive lens L14, a cemented lens formed by a biconcave negative lens L15 and a meniscus positive lens L16 with its convex surface facing the object side, a three-lens cemented lens composed of a biconvex positive lens L17, a biconcave negative lens L18, and a biconvex positive lens L19, and a meniscus negative lens L20 with its concave surface facing the object side, and has a negative optical power as a whole. Also, the rear unit RU is always fixed relative to the image plane.

[0110] The aperture stop S is disposed between the second group G2 and the third group G3. In the imaging optical system, the lens component Ln disposed at the position closest to the image side is the negative lens L20.

[0111] Next, the specification values of the imaging optical system according to the second embodiment are shown below. Numerical Example 2 Unit: mm [Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] [Embodiment 3]

[0112] Figure 13It is the lens structure diagram of the imaging optical system according to Embodiment 3 of the present invention. The first group G1 is composed of a positive meniscus lens L1 with its convex surface facing the object side, a positive meniscus lens L2 with its convex surface facing the object side, a negative meniscus lens L3 with its convex surface facing the object side, a positive meniscus lens L4 with its convex surface facing the object side, a biconcave negative lens L5, a biconvex positive lens L6, and a cemented lens composed of a negative meniscus lens L7 with its convex surface facing the object side and a lens L8 with its convex surface facing the object side, and has a positive optical power as a whole. And, the first group G1 is always fixed relative to the image plane. Here, the first sub-group G1a is composed of L1, L2, and L3, and the first sub-group G1b is composed of L7 and L8.

[0113] The second group G2 is composed of a cemented lens composed of a positive meniscus lens L9 with its convex surface facing the object side and a negative meniscus lens L10 with its convex surface facing the object side, and has a negative optical power as a whole. And, when focusing from an infinitely distant object to a near object, the second group G2 moves from the object side toward the image side on the optical axis.

[0114] The third group G3 is composed of an image stabilization unit IU and a rear unit RU, and has a negative optical power as a whole. And, the third group G3 is fixed relative to the image plane during focusing.

[0115] The image stabilization unit IU is composed of a cemented lens of a biconvex positive lens L11 and a biconcave negative lens L12 and a negative meniscus lens L13 with its convex surface facing the object side, and has a negative optical power as a whole. And, the image stabilization unit IU moves in a direction substantially perpendicular to the optical axis to reduce the jitter of the image caused by the jitter of the imaging optical system.

[0116] The rear unit RU is composed of a biconvex positive lens L14, a cemented lens composed of a biconcave negative lens L15 and a positive meniscus lens L16 with its convex surface facing the object side, a three-piece cemented lens composed of a biconvex positive lens L17, a biconcave negative lens L18 and a biconvex positive lens L19, and a negative meniscus lens L20 with its concave surface facing the object side, and has a negative optical power as a whole. And, the rear unit RU is always fixed relative to the image plane.

[0117] The aperture stop S is disposed between the second group G2 and the third group G3. In the imaging optical system, the lens component Ln disposed at the position closest to the image side is the negative lens L20.

[0118] Next, the specification values of the imaging optical system according to Embodiment 3 are shown below. Numerical Example 3 Unit: mm [Surface Data] [Various data] [Variable interval data] [Lens group data] [Example 4]

[0119] Figure 19 is a lens structure diagram of the imaging optical system according to Example 4 of the present invention. The first group G1 is composed of a positive meniscus lens L1 with a convex surface facing the object side, a positive meniscus lens L2 with a convex surface facing the object side, a negative meniscus lens L3 with a convex surface facing the object side, a cemented lens composed of a positive biconvex lens L4 and a negative biconcave lens L5, a positive meniscus lens L6 with a convex surface facing the object side, and a cemented lens composed of a negative meniscus lens L7 with a convex surface facing the object side and a positive biconvex lens L8, and has a positive optical power as a whole. And the first group G1 is always fixed with respect to the image plane. Here, the first sub-group G1a is composed of L1, L2, and L3, and the first sub-group G1b is composed of L7 and L8.

[0120] The second group G2 is composed of a negative meniscus lens L9 with a convex surface facing the object side, and has a negative optical power as a whole. And the second group G2 moves on the optical axis from the object side toward the image side when focusing from an infinite object to a near object.

[0121] The third group G3 is composed of an image shake correction unit IU and a rear unit RU, and has a negative optical power as a whole. And the third group G3 is fixed with respect to the image plane during focusing.

[0122] The image shake correction unit IU is composed of a cemented lens of a positive biconvex lens L10 and a negative biconcave lens L11 and a negative biconcave lens L12, and has a negative optical power as a whole. And the image shake correction unit IU moves in a direction substantially perpendicular to the optical axis to reduce the shake of the image caused by the shake of the imaging optical system.

[0123] The rear unit RU is composed of a positive biconvex lens L13, a cemented lens composed of a negative biconcave lens L14 and a positive biconvex lens L15 facing the object side, a three-piece cemented lens composed of a positive biconvex lens L16, a negative biconcave lens L17 and a positive meniscus lens L18 with a convex surface facing the object side, and a negative meniscus lens L19 with a concave surface facing the object side, and has a negative optical power as a whole. And the rear unit RU is always fixed with respect to the image plane.

[0124] The aperture stop S is disposed between the second group G2 and the third group G3. In the imaging optical system, the lens component Ln disposed at the position closest to the image side is the negative lens L19.

[0125] Next, the specification values of the imaging optical system according to Embodiment 4 are shown below. Numerical Example 4 Unit: mm [Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data] [Embodiment 5]

[0126] Figure 25 is a lens configuration diagram of the imaging optical system according to Embodiment 5 of the present invention. The first group G1 is composed of a meniscus-shaped positive lens L1 with the convex surface facing the object side, a meniscus-shaped positive lens L2 with the convex surface facing the object side, a meniscus-shaped negative lens L3 with the convex surface facing the object side, a cemented lens composed of a biconvex positive lens L4 and a biconcave negative lens L5, a meniscus-shaped positive lens L6 with the convex surface facing the object side, and a cemented lens composed of a meniscus-shaped negative lens L7 with the convex surface facing the object side and a meniscus-shaped positive lens L8 with the convex surface facing the object side, and has a positive optical power as a whole. And the first group G1 is always fixed with respect to the image plane. Here, the first a-group G1a is composed of L1, L2, and L3, and the first b-group G1b is composed of L7 and L8.

[0127] The second group G2 is composed of a meniscus-shaped negative lens L9 with the convex surface facing the object side and a meniscus-shaped positive lens L10 with the convex surface facing the object side, and has a negative optical power as a whole. And L9 in the second group G2 moves from the object side toward the image side on the optical axis when focusing from an infinite object to a close object, and L10 moves from the image side toward the object side on the optical axis when focusing from an infinite object to a close object.

[0128] The third group G3 is composed of a lens component, an image shake correction unit IU, and a rear unit RU, and has a negative optical power as a whole. And the third group G3 is fixed with respect to the image plane during focusing.

[0129] The lens component is composed of a meniscus-shaped positive lens L11 with the concave surface facing the object side.

[0130] The image shake correction unit IU is composed of a cemented lens of a positive lens L12 with a biconvex shape and a negative lens L13 with a biconcave shape, and a negative lens L14 with a biconcave shape, and has a negative optical power as a whole. Further, the image shake correction unit IU moves in a direction substantially perpendicular to the optical axis to reduce the image shake caused by the shake of the imaging optical system.

[0131] The rear unit RU is composed of a positive lens L15 with a biconvex shape, a cemented lens composed of a negative lens L16 with a biconcave shape and a positive lens L17 with a biconvex shape facing the object side, a three-piece cemented lens composed of a positive lens L18 with a biconvex shape, a negative lens L19 with a biconcave shape, and a positive lens L20 with a biconvex shape, and a meniscus-shaped negative lens L21 with a concave surface facing the object side, and has a negative optical power as a whole. Further, the rear unit RU is always fixed with respect to the image plane.

[0132] The aperture stop S is disposed between the second group G2 and the third group G3. In the imaging optical system, the lens component Ln disposed at the position closest to the image side is the negative lens L21.

[0133] Next, the specification values of the imaging optical system according to Embodiment 5 are shown below. Numerical Example 5 Unit: mm [Surface Data] [Various Data] [Variable Interval Data] [Lens Group Data]

[0134] Next, the conditional corresponding values corresponding to the above-described respective embodiments are shown. Conditional Corresponding Values

[0135] <Other Embodiments> The technology disclosed by the present embodiment is not limited to the above-described embodiments and the description of the embodiments, and various modifications can be made. The shapes and numerical values of the respective parts shown in the above numerical examples are merely examples for implementing the present technology, and the technical scope of the present technology will not be construed as being limited by these shapes and numerical values.

[0136] The present technology can also adopt the following structure. [Item 1] An imaging optical system, characterized in that the lens group of the imaging optical system consists of a first group G1 having a positive optical power as a whole, arranged in order from the object side to the image side, a second group G2 composed of lenses that move on the optical axis during focusing, and a third group G3 having an optical power. The first group G1 is composed of a first sub-group G1a, a plurality of lenses, and a first sub-group G1b, arranged in order from the object side to the image side. The first sub-group G1a has at least two positive lenses arranged in order from the position closest to the object side, and a meniscus-shaped negative lens with its convex surface facing the object side, arranged at the position closest to the image side. The first sub-group G1b has, at the position closest to the object side, the positive lens closest to the image side of the first group G1 or a lens component including a positive lens. There is an air gap D_A11, which is the longest within the first group G1, between the first sub-group G1a and the first sub-group G1b. The imaging optical system satisfies the following conditional expressions. (1) 0.05 < D_A11 / D_G1 < 0.44 Wherein, D_A11 is the longest air gap within the first group G1. D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged at the position closest to the object side of the first group G1 to the image-side lens surface of the lens arranged at the position closest to the image side of the first group G1. [Item 2] The imaging optical system according to [Item 1], characterized in that it satisfies the following conditional expressions. (2) 0.10 < (D_A11 + D_A12) / D_G1 < 0.70 Wherein, D_A11 is the longest air gap within the first group G1. D_A12 is the second-longest air gap between the first sub-group G1a and the first sub-group G1b. [Item 3] The imaging optical system according to [Item 1] or [Item 2], characterized in that it satisfies the following conditional expressions. (3) 0.05 < D_G1a / D_G1 < 0.45 Wherein, D_G1a is the length on the optical axis of the first sub-group G1a. D_G1 is the distance on the optical axis from the object-side lens surface of the lens disposed at the position closest to the object side in the first group G1 to the image-side lens surface of the lens disposed at the position closest to the image side in the first group G1. [Item 4] The imaging optical system according to any one of [Item 1] to [Item 3], characterized in that the following conditional expression is satisfied. (4) 0.15 < D_A1all / D_G1 < 0.75 Wherein, D_A1all is the sum of all air gaps in the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens disposed at the position closest to the object side in the first group G1 to the image-side lens surface of the lens disposed at the position closest to the image side in the first group G1. [Item 5] The imaging optical system according to any one of [Item 1] to [Item 4], characterized in that the following conditional expression is satisfied. (5) atan(H_Img / f) < 7.00° Wherein, H_Img is the maximum image height, f is the focal length of the imaging optical system at infinity focus. [Item 6] The imaging optical system according to any one of [Item 1] to [Item 5], characterized in that the following conditional expression is satisfied. (6) 0.10 < LT / f < 1.00 Wherein, LT is the distance on the optical axis from the surface closest to the object side to the image plane of the imaging optical system at infinity focus, f is the focal length of the imaging optical system at infinity focus. [Item 7] The imaging optical system according to any one of [Item 1] to [Item 6], characterized in that the first sub-group G1b is composed of a negative lens and a positive lens, or composed of a positive lens and a negative lens. [Item 8] The imaging optical system according to any one of [Item 1] to [Item 7], characterized in that the following conditional expression is satisfied. (7) -60.00 < Φ_G2G3 / Φ < -3.00 Wherein, Φ is the optical power of the imaging optical system at infinity focus, Φ_G2G3 is the combined optical power when the second group G2 and the third group G3 are focused at infinity. [Item 9] The imaging optical system according to any one of [Item 1] to [Item 8], characterized in that The following conditional expression is satisfied. (8) 1.00 < D_EXP / H_Img < 11.00 Wherein, D_EXP is the distance on the optical axis from the exit pupil to the image plane when the imaging optical system is focused at infinity, and H_Img is the maximum image height. [Item 10] The imaging optical system according to any one of [Item 1] to [Item 9], characterized in that The following conditional expression is satisfied. (9) -35.00 < Φ_G3 / Φ < -1.00 Wherein, Φ is the optical power when the imaging optical system is focused at infinity, Φ_G3 is the optical power of the third group G3. [Item 11] The imaging optical system according to any one of [Item 1] to [Item 10], characterized in that The third group G3 has an image shake correction unit IU, There is a rear unit RU on the image side of the image shake correction unit IU, The signs of the optical powers of the image shake correction unit IU and the rear unit RU are different, The image shake correction unit IU has at least one positive lens and at least one negative lens, The imaging optical system satisfies the following conditional expression. (10) 3.00 < |Φ_OS / Φ| < 35.00 Wherein, Φ_OS is the optical power of the image shake correction unit IU, Φ is the optical power when the imaging optical system is focused at infinity. [Item 12] The imaging optical system according to any one of [Item 1] to [Item 11], characterized in that the following conditional expression is satisfied. (11) -20.00 < Φ_G2 / Φ < -0.13 Wherein, Φ_G2 is the optical power of the second group G2, Φ is the optical power when the imaging optical system is focused at infinity. [Item 13] The imaging optical system according to any one of [Item 1] to [Item 12], characterized in that the imaging optical system has an aperture stop S, and a negative lens satisfying the following conditional expression is provided at a position closer to the image side than the aperture stop S. (12) 10.00 < ν_d < 30.00 (13) 0.020 < P_gF + 0.0018 * ν_d - 0.6483 < 0.080 wherein ν_d is the Abbe number for the d-line of the negative lens arranged at a position closer to the image side than the aperture stop S, P_gF is the partial dispersion ratio for the g-line and F-line of the negative lens arranged at a position closer to the image side than the aperture stop S, The partial dispersion ratio is defined as P_gF = (n_g - n_F) / (n_F - n_C), n_g is the refractive index for the g-line, and the wavelength of the g-line λ = 435.84 nm, n_F is the refractive index for the F-line, and the wavelength of the F-line λ = 486.13 nm, n_C is the refractive index for the C-line, and the wavelength of the C-line λ = 656.27 nm. [Item 14] The imaging optical system according to any one of [Item 1] to [Item 13], characterized in that the object side and the image side of all lenses are composed of spherical surfaces or flat surfaces.

[0137] Those skilled in the art can conceive of various modifications, combinations, sub-combinations, and changes based on the main factors in the design or other factors, but these are included within the scope of the appended claims or their equivalents, which is natural. Symbol Explanation

[0138] G1 - the first group, G2 - the second group, G3 - the third group, G1a - the first a group, G1b - the first b group, IU - image shake correction unit, RU - rear unit, Ln - lens component arranged at the position closest to the image side, S - aperture stop, I - image plane.

Claims

1. An imaging optical system, characterized in that: The imaging optical system comprises a lens group which is arranged in order from the object side toward the image side and has a first group (G1) having positive refractive power as a whole, a second group (G2) consisting of lenses which move on the optical axis during focusing, and a third group (G3) having refractive power. The first group (G1) is composed of a group 1a (G1a), a plurality of lenses, and a group 1b (G1b) arranged in order from the object side to the image side. The group 1a (G1a) comprises at least two positive lenses arranged in order from the position closest to the object side, and a meniscus-shaped negative lens arranged at the position closest to the image side with its convex surface facing the object side. The group 1b (G1b) includes a positive lens closest to the image side of the group 1 (G1) or a lens component including a positive lens at a position closest to the object side. There is a longest air gap (D_A11) in the first group (G1) between the first group (G1a) and the first group (G1b), The imaging optical system satisfies the following conditional formula: (1)0.05 < D_A11 / D_G1 < 0.44 in, D_A11 is the longest air gap in group 1 (G1), D_G1 is the distance on the optical axis from the object side lens surface of the lens arranged closest to the object side in the first group (G1) to the image side lens surface of the lens arranged closest to the image side in the first group (G1).

2. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (2)0.10 < (D_A11+D_A12) / D_G1 < 0.70 in, D_A11 is the longest air gap in group 1 (G1), D_A12 is the second longest air gap between group 1a (G1a) and group 1b (G1b).

3. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (3)0.05 < D_G1a / D_G1 < 0.45 in, D_G1a is the length of group 1a (G1a) on the optical axis, D_G1 is the distance on the optical axis from the object side lens surface of the lens arranged closest to the object side in the first group (G1) to the image side lens surface of the lens arranged closest to the image side in the first group (G1).

4. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (4)0.15 < D_A1all / D_G1 < 0.75 in, D_A1all is the total of all air gaps in group 1 (G1), D_G1 is the distance on the optical axis from the object side lens surface of the lens arranged closest to the object side in the first group (G1) to the image side lens surface of the lens arranged closest to the image side in the first group (G1).

5. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (5) atan(H_Img / f)< 7.00° in, H_Img is the maximum image height, f is the focal length of the imaging optical system when focused at infinity.

6. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (6)0.10 < LT / f < 1.00 in, LT is the distance on the optical axis from the surface closest to the object to the image plane when the imaging optical system is focused at infinity. f is the focal length of the imaging optical system when focused at infinity.

7. The imaging optical system according to claim 1, characterized in that: The group 1b (G1b) consists of a negative lens and a positive lens, or a positive lens and a negative lens.

8. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (7)-60.00 < Φ_G2G3 / Φ < -3.00 in, Φ_G2G3 is the combined optical power of the second group (G2) and the third group (G3) when focusing at infinity, and Φ is the optical power of the imaging optical system when focusing at infinity.

9. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (8)1.00 < D_EXP / H_Img < 11.00 in, D_EXP is the distance from the exit pupil to the image plane on the optical axis when the imaging optical system is focused at infinity, and H_Img is the maximum image height.

10. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (9)-35.00 < Φ_G3 / Φ < -1.00 in, Φ_G3 is the focal power of the third group (G3), Φ is the optical power of the imaging optical system when it is focused at infinity.

11. The imaging optical system according to claim 1, characterized in that: The third group (G3) has an image shake correction unit (IU), A rear unit (RU) is provided on the image side of the image shake correction unit (IU), The image shake correction unit (IU) and the rear unit (RU) have different signs of optical power, The image shake correction unit (IU) has at least one positive lens and at least one negative lens, The imaging optical system satisfies the following conditional formula: (10)3.00 < |Φ_OS / Φ| < 35.00 in, Φ_OS is the optical power of the image jitter correction unit, Φ is the optical power of the imaging optical system when it is focused at infinity.

12. The imaging optical system according to claim 1, characterized in that: Satisfy the following conditions: (11)-20.00 < Φ_G2 / Φ < -0.13 in, Φ_G2 is the focal power of the second group (G2), Φ is the optical power of the imaging optical system when it is focused at infinity.

13. The imaging optical system according to claim 1, characterized in that: The imaging optical system has an aperture stop (S), and has a negative lens satisfying the following conditional expression at a position closer to the image side than the aperture stop (S), (12) 10.00 < ν_d < 30.00 (13)0.020 < P_gF+0.0018*ν_d-0.6483 < 0.080 in, ν_d is the Abbe number of the negative lens arranged closer to the image side than the aperture stop (S) for the d-line, P_gF is the partial dispersion ratio of the negative lens arranged closer to the image side than the aperture stop (S) for the g-line and F-line, The partial dispersion ratio is defined as P_gF = (ng-nF) / (nF-nC), ng is the refractive index for the g-line, the wavelength of the g-line is λ = 435.84nm, nF is the refractive index for F line, the wavelength of F line is λ=486.13nm, nC is the refractive index for the C line, and the wavelength of the C line λ=656.27 nm.

14. The imaging optical system according to claim 1, characterized in that: The object and image sides of all lenses consist of either spherical or flat surfaces.

Images