Image formation optical system

Abstract

To provide an image formation optical system which is small and light by itself and has a small and light focusing unit, thereby being suitable for a small and light telephoto lens.SOLUTION: The image formation optical system includes: a first group G1 having a positive power as a whole; a second group G2 formed of a lens which moves on an optical axis at the time of focusing; and a third group G3 with a power, which are arranged in the direction from an object to an image. The imaging formation optical system satisfies a predetermined condition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an imaging optical system suitable for a photographing lens used in a still camera, a video camera, etc.

Background Art

[0002] Conventionally, as an imaging optical system suitable for a long-focus photographing lens (hereinafter referred to as a telephoto lens), a telephoto-type imaging optical system in which a lens group with positive power and a lens group with negative power are arranged in order from the object side to the image side is known. By adopting the telephoto-type power arrangement, it becomes possible to shorten the overall optical length of the telephoto lens, which tends to be long and heavy.

[0003] In addition, telephoto lenses are often used for photographing sports, animals, etc., and high-speed autofocus is required. When the telephoto lens adopts the overall extension method of moving the entire imaging optical system for focusing, the weight of the lens that moves during focusing becomes large, and it is difficult to realize high-speed autofocus. Therefore, the inner focus method is often adopted.

[0004] Furthermore, in recent years, the use of telephoto lenses in video shooting has increased. When used in video shooting, autofocus often uses the contrast detection method. In the contrast detection method, it is common to make the focusing unit perform an operation called wobbling to detect the contrast. Therefore, a telephoto lens equipped with a lighter focusing unit than before is desired.

[0005] In addition, in recent years, with the spread of mirrorless cameras designed to be small, miniaturization and light weight are also required for telephoto lenses. When miniaturizing and lightening the telephoto lens, in addition to miniaturizing its imaging optical system, it is important to miniaturize and lighten the movable parts. This is because the size and arrangement of the actuator affect the size and weight of the movable parts.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Although the imaging optical system described in Patent Document 1 realizes high performance while adopting inner focus, the miniaturization and weight reduction of the focusing unit are insufficient. Also, it cannot be said that the overall optical length with respect to the focal length is sufficiently small.

[0008] The present invention has been made in view of such a situation, and an object thereof is to provide an imaging optical system suitable for a compact and lightweight telephoto lens by making the imaging optical system itself compact and lightweight and having a compact and lightweight focusing unit.

Means for Solving the Problems

[0009] To achieve the above object, the imaging optical system of the present invention comprises, in order from the object side to the image side, a first group G1 having positive power as a whole, a second group G2 composed of lenses that move on the optical axis during focusing, and a third group G3 having power. The first group G1 is composed of, in order from the object side to the image side, a first a-group G1a, a plurality of lenses, and a first b-group G1b. The first a-group G1a has at least two positive lenses in order from the most object side, and a meniscus-shaped negative lens with a convex surface facing the object side on the most image side. The first b-group G1b has, on the most object side, a lens component including the most image-side positive lens or positive lenses of the first group G1. Between the first a-group G1a and the first b-group G1b, there is the longest air interval D_A11 in the first group G1, An imaging optical system characterized by satisfying the following conditional expressions. (1) 0.05 < D_A11 / D_G1 < 0.44 However, D_A11 is the longest air interval in the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens located closest to the object side in the first group G1 to the image-side lens surface of the lens located closest to the image side.

Advantages of the Invention

[0010] According to the imaging optical system for implementing the present invention, since the optical system itself is small and lightweight and has a small and lightweight focusing unit, it is possible to provide an imaging optical system suitable for a small and lightweight telephoto lens.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

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

[0013] With such a group configuration, the second group G2 and the third group G3, which are focusing units, can be reduced in diameter by the converging effect of the light beam by the first group G1 having a positive power as a whole. Since the weight can be easily reduced by reducing the diameter of the focusing unit, which is a movable part, the actuator can also be reduced in size and weight. Since the actuator can be reduced in size and weight while reducing the diameters of the second group G2 and the third group G3, it is possible to make the telephoto lens small and light.

[0014] Also, by arranging the first group G1 having a positive power on the object side, and the second group G2 and the third group G3 having a negative power on the image side, a telephoto-type power arrangement can be configured, and there is an effect of shortening the overall length of the imaging optical system. Also, in order to facilitate the provision of a dust and drip-proof mechanism, it is desirable that the first group G1 arranged on the most object side and the lens arranged on the most image side of the imaging optical system are always fixed with respect to the image plane. Also, since it is conceivable that the user touches the lens arranged on the most image side of the imaging optical system when attaching and detaching the interchangeable lens to and from the camera, it is desirable that a unit that is always fixed with respect to the image plane is arranged on the most image side of the imaging optical system.

[0015] Also, the first group G1 is composed of, in order from the object side to the image side, a first a group G1a, a plurality of lenses, and a first b group G1b. The first a group G1a has at least two positive lenses in order from the most object side, and a meniscus-shaped negative lens with a convex surface facing the object side on the most image side. The first b group G1b has, on the most object side, a positive lens or a lens component including a positive lens on the most image side of the first group G1. By having the longest air interval D_A11 in the first group G1 between the first a group G1a and the first b group G1b, it is possible to achieve both weight reduction and aberration correction of the first group G1.

[0016] The lens components of the present invention are a single lens and a cemented lens. The lens components including a positive lens are a single lens with one positive lens as well as a cemented lens having a positive lens.

[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 However, D_A11 is the longest air interval within the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens disposed most on the object side within the first group G1 to the image-side lens surface of the lens disposed most on the image side.

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

[0019] When the longest air interval within the first group G1 becomes longer exceeding the upper limit value of the conditional expression (1), it becomes difficult to arrange a lens with a strong power necessary for miniaturization and a lens necessary for correcting the aberration generated there. When the longest air interval within the first group G1 becomes shorter exceeding the lower limit value of the conditional expression (1), lenses with large diameters are arranged closely, making it difficult to reduce the weight.

[0020] By limiting the upper limit value of the conditional expression (1) to 0.40, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (1) to 0.10, the above-described effect can be made more certain, which is preferable.

[0021] More preferably, by limiting the upper limit value of the conditional expression (1) to 0.35, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (1) to 0.15, the above-described effect can be made more certain, which is preferable.

[0022] Furthermore, 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 However, D_A11 is the longest air gap within the first group G1, and D_A12 is the second longest air gap between the first subgroup G1a and the first subgroup 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 subgroup G1a and the first subgroup G1b to the length on the optical axis of the first group G1 when the imaging optical system is focused at infinity.

[0024] When the length on the optical axis of the first group G1 becomes shorter beyond the upper limit value of the conditional expression (2), it becomes more difficult to arrange the lens with a strong power required for miniaturization and the lens required to correct the aberration generated there. When the sum of the two air gaps becomes shorter beyond the lower limit value of the conditional expression (2), lenses with a large diameter are arranged densely, making it more difficult to reduce the weight.

[0025] By limiting the upper limit value of the conditional expression (2) to 0.60, the above-mentioned effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (2) to 0.20, the above-mentioned effect can be made more certain, which is preferable.

[0026] More preferably, by limiting the upper limit value of the conditional expression (2) to 0.52, the above-mentioned effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (2) to 0.30, the above-mentioned effect can be made more certain, which is preferable.

[0027] Furthermore, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (3) 0.05 < D_G1a / D_G1 < 0.45 However, D_G1a is the length on the optical axis of the first subgroup G1a, and D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged most on the object side of the first group G1 to the image-side lens surface of the lens arranged most on the image side.

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

[0029] When the length on the optical axis within the first subgroup G1a exceeds the upper limit value of conditional expression (3), the volume of the lens with a large diameter increases, making it difficult to reduce the weight. When the length on the optical axis of the first group G1 exceeds the lower limit value of conditional expression (3), 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-mentioned effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (3) to 0.10, the above-mentioned effect can be made more certain, which is preferable.

[0031] More preferably, by limiting the upper limit value of conditional expression (3) to 0.35, the above-mentioned effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (3) to 0.15, the above-mentioned effect can be made more certain, which is preferable.

[0032] Furthermore, 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 However, D_A1all is the sum of all the air spaces within the first group G1, D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side in the first group G1 to the image-side lens surface of the lens arranged on the most image side.

[0033] Conditional expression (4) defines the ratio of the sum of all the air spaces 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 length on the optical axis of the first group G1 becomes shorter than the upper limit value of conditional expression (4), it becomes more difficult to arrange the lens with high power required for miniaturization and the lens required to correct the aberration generated there. If the total of all air gaps in the first group G1 becomes smaller than the lower limit value of conditional expression (4), lenses with large diameters will be arranged closely, making weight reduction more difficult.

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

[0036] More preferably, by limiting the upper limit value of conditional expression (4) to 0.65, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (4) to 0.40, the above-described effect can be made more certain, which is preferable.

[0037] Furthermore, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (5) atan(H_Img / f)< 7.00° However, H_Img is the maximum image height, f is the focal length of the imaging optical system when focused at infinity.

[0038] Conditional expression (5) defines the approximate angle of view of the imaging optical system from the maximum image height of the imaging optical system and the focal length of the imaging optical system when focused at infinity.

[0039] If the angle of view becomes larger than the upper limit value of conditional expression (5), it is not preferable because it becomes difficult to arrange lenses suitable for correcting aberrations in the peripheral angle of view. If the value of conditional expression (5) becomes smaller and the angle of view becomes smaller, the number of lenses in the first group G1 is too large as the quantity required for aberration correction, resulting in an optical system that is not suitable for miniaturization and weight reduction, which is the object of the invention.

[0040] By limiting the upper limit value of conditional expression (5) to 5.00°, the above-described effect can be made more certain, which is preferable. By setting the lower limit value of conditional expression (5) to 0.40°, the above-described effect can be made more certain, which is preferable.

[0041] More preferably, by limiting the upper limit value of conditional expression (5) to 3.50°, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (5) to 1.00°, the above-described effect can be made more certain, which is preferable.

[0042] Furthermore, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (6) 0.10 < LT / f < 1.00 However, LT is the distance on the optical axis from the most object-side surface 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.

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

[0044] When the overall optical length becomes longer exceeding the upper limit of conditional expression (6), it becomes difficult to reduce the size and weight as a telephoto lens. When the overall optical length becomes shorter exceeding the lower limit of conditional expression (6), the movement amount of the focusing unit cannot be made large, and if an attempt is made to achieve a practical minimum shooting distance, the power of the focusing unit has to be increased, so the aberration generated in the focusing unit becomes large and it becomes difficult to obtain good performance in a wide shooting distance range.

[0045] By limiting the upper limit value of conditional expression (6) to 0.64, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (6) to 0.15, the above-described effect can be made more certain, which is preferable.

[0046] More preferably, by limiting the upper limit value of the conditional expression (6) to 0.56, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (6) to 0.30, the above-described effect can be made more certain, which is preferable.

[0047] Furthermore, in the imaging optical system of the present invention, the first group G1b is characterized by consisting of a negative lens and a positive lens, or a positive lens and a negative lens.

[0048] It is desirable to use one negative lens and one positive lens each for the first group G1b for chromatic aberration correction and weight reduction. It is more desirable that it is a cemented lens for simplification of the lens configuration.

[0049] Furthermore, the imaging optical system of the present invention is characterized by satisfying the following conditional expression. (7) -60.00 < Φ_G2G3 / Φ < -3.00 However, Φ is the power of the imaging optical system at infinity focus, Φ_G2G3 is the combined power of the second group G2 and the third group G3 at infinity focus.

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

[0051] When the negative combined power of the second group G2 and the third group G3 becomes small beyond the upper limit value of the conditional expression (7), the telephoto effect weakens and it becomes difficult to miniaturize the imaging optical system. When the negative combined power of the second group G2 and the third group G3 becomes large beyond the lower limit value of the conditional expression (7), the action of expanding aberration becomes large, making it difficult to obtain good performance.

[0052] By limiting the upper limit value of the conditional expression (7) to -5.00, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of the conditional expression (7) to -50.00, the above-described effect can be made more certain, which is preferable.

[0053] More preferably, the upper limit value of conditional expression (7) is limited to -8.30, so that the above-described effect can be made more certain, which is preferable. Limiting the lower limit value of conditional expression (7) to -25.00 can make the above-described effect more certain, which is preferable.

[0054] (8) 1.00 < D_EXP / H_Img < 11.00 However, 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] 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] When the exit pupil moves away from the image plane toward the object side beyond the upper limit value of conditional expression (8), the ray height near the image plane increases. However, there are parts for attaching to the camera near the image plane, and since the rays are scattered, it becomes difficult to secure the peripheral light quantity. When the exit pupil approaches the image plane beyond the lower limit value of conditional expression (8), the chief ray exit angle of the lens arranged closest to the image side increases. When using an image sensor used in a digital camera or the like, the image sensor generally has the characteristic that its sensitivity decreases with respect to light having a large incident angle to the image sensor. Therefore, when the incident angle of the rays is large, it becomes difficult to secure the peripheral light quantity.

[0057] Limiting the upper limit value of conditional expression (8) to 8.00 can make the above-described effect more certain, which is preferable. Limiting the lower limit value of conditional expression (8) to 2.00 can make the above-described effect more certain, which is preferable.

[0058] More preferably, the upper limit value of conditional expression (8) is limited to 4.30, so that the above-described effect can be made more certain, which is preferable. Limiting the lower limit value of conditional expression (8) to 2.70 can make the above-described effect more certain, which is preferable.

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

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

[0061] If the negative power of the third group G3 becomes smaller beyond the upper limit value of the conditional expression (9), in order to maintain the telephoto-type power arrangement while maintaining the focal length of the entire system, it is necessary to increase the negative power of the second group G2. If the negative 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 becomes difficult to obtain good performance within a wide shooting distance range. If the negative power of the third group G3 becomes larger beyond the lower limit value of the conditional expression (9), it becomes difficult to ensure sufficient back focus. Also, since the action of expanding the aberration becomes large, it becomes difficult to obtain good performance.

[0062] It is preferable to limit the upper limit value of the conditional expression (9) to -1.50 to make the above-mentioned effect more certain. It is preferable to limit the lower limit value of the conditional expression (9) to -26.00 to make the above-mentioned effect more certain.

[0063] More preferably, it is preferable to limit the upper limit value of the conditional expression (9) to -4.00 to make the above-mentioned effect more certain. It is preferable to limit the lower limit value of the conditional expression (9) to -11.00 to make the above-mentioned effect more certain.

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

[0065] By arranging the rear unit RU with a sign different from that of the power of the image blur correction unit IU, it is possible to increase the power of the image blur correction unit IU while maintaining the power of the third group G3, and it is possible to increase the amount of image blur correction with respect to the movement amount of the image blur correction unit IU (hereinafter referred to as the anti-shake coefficient). Increasing the anti-shake coefficient can reduce the movement amount of the image blur correction unit IU, so it is possible to reduce the size of the actuator, which is advantageous for reducing the size and weight of the telephoto lens.

[0066] In addition, since the image blur correction unit IU has at least one positive lens and at least one negative lens, it is possible to correct chromatic aberration within the image blur correction unit IU and obtain good performance during image blur correction.

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

[0068] When the power of the image blur correction unit IU becomes smaller than the lower limit value of the conditional expression (10), the anti-shake coefficient becomes smaller, so it becomes necessary to increase the driving amount of the image blur correction unit IU, making it difficult to miniaturize the actuator and, consequently, the telephoto lens. When the power of the image blur correction unit IU becomes larger than the upper limit value of the conditional expression (10), although the anti-shake coefficient can be utilized, the aberration generated in the image blur correction unit IU becomes larger, and the variation of coma aberration and astigmatism when driving in a direction perpendicular to the optical axis becomes larger, making it difficult to obtain good performance during image blur correction.

[0069] By limiting the upper limit value of conditional expression (10) to 26.00, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (10) to 5.00, the above-described effect can be made more certain, which is preferable.

[0070] More preferably, by limiting the upper limit value of conditional expression (10) to 22.00, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (10) to 7.00, the above-described effect can be made more certain, which is preferable.

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

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

[0073] When the negative power of the second group G2 becomes smaller beyond the upper limit value of conditional expression (11), the role of the negative power arranged on the telephoto-type image side is borne by the third group G3, and the negative power of the third group G3 increases. Since the action of expanding the aberration in the third group G3 becomes larger, it becomes difficult to obtain good performance. When the negative power of the second group G2 becomes larger beyond the lower limit value of conditional expression (11), aberrations, particularly astigmatism, are likely to occur in the second group G2 which is a focusing unit, so it becomes difficult to obtain good performance in a wide shooting distance range.

[0074] By limiting the upper limit value of conditional expression (11) to -0.20, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (11) to -12.00, the above-described effect can be made more certain, which is preferable.

[0075] More preferably, by limiting the lower limit value of the conditional expression (11) to -6.00, the above-described effect can be made more certain, which is preferable.

[0076] Furthermore, the imaging optical system of the present invention is characterized by having a negative lens that satisfies the following conditional expression on the image side of the aperture stop. (12) 10.00 < ν_d < 30.00 (13) 0.020 < P_gF + 0.0018*ν_d - 0.6483 < 0.080 However, ν_d is the Abbe number with respect to the d-line of the negative lens, P_gF is the partial dispersion ratio with respect to the g-line and F-line of the negative lens. The partial dispersion ratio is defined as P_gF = (ng - nF) / (nF - nC). ng: Refractive index with respect to the g-line (wavelength λ = 435.84 nm). nF: Refractive index with respect to the F-line (wavelength λ = 486.13 nm). nC: Refractive index with respect to the C-line (wavelength λ = 656.27 nm).

[0077] By having a negative lens that satisfies the conditional expressions (12) and (13) on the image side of the aperture stop S, good chromatic aberration correction can be obtained.

[0078] The conditional expression (12) defines a preferable range for the Abbe number with respect to the d-line of the negative lens.

[0079] When the Abbe number with respect to the d-line becomes larger beyond the upper limit value of the conditional expression (12), the action of canceling chromatic aberration becomes weaker, and it becomes difficult to correct chromatic aberration in the entire lens system. Also, it becomes difficult to select a material that satisfies the conditional expression (13). When the Abbe number with respect to the d-line becomes smaller beyond the lower limit value of the conditional expression (12), the action of expanding chromatic aberration becomes larger, and it becomes difficult to correct chromatic aberration in the entire lens system.

[0080] By limiting the upper limit value of conditional expression (12) to 24.00, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (12) to 15.00, the above-described effect can be made more certain, which is preferable.

[0081] More preferably, by limiting the upper limit value of conditional expression (12) to 21.00, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (12) to 16.00, the above-described effect can be made more certain, which is preferable.

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

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

[0084] By limiting the upper limit value of conditional expression (13) to 0.048, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (13) to 0.024, the above-described effect can be made more certain, which is preferable.

[0085] More preferably, by limiting the upper limit value of conditional expression (13) to 0.041, the above-described effect can be made more certain, which is preferable. By limiting the lower limit value of conditional expression (13) to 0.027, the above-described effect can be made more certain, which is preferable.

[0086] Furthermore, the imaging optical system of the present invention is characterized in that the object-side and image-side surfaces of all lenses are spherical or planar. Since spherical lenses can be equivalently processed even if rotation occurs around the center of the sphere during processing, they are easier to fabricate compared to non-spherical lenses. Since the lenses constituting the imaging optical system of a telephoto lens tend to have a large aperture, it is desirable to be able to obtain lenses with good processing accuracy at low processing costs.

[0087] Next, the lens configuration of an embodiment according to the imaging optical system of the present invention will be described. In the following description, the lens configuration will be 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 [surface data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each surface, d is the distance between each surface, nd is the refractive index with respect to the d-line (wavelength 587.56 nm), vd is the Abbe number with respect to the d-line, and P_gF indicates the partial dispersion ratio with respect to the g-line and F-line.

[0090] BF represents the back focus.

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

[0092] [Various data] shows values such as the focal length when the shooting distance is INF, 20 m, and 3.2 m.

[0093] [Variable interval data] shows the values of the variable interval and BF when the shooting distance is INF, 20 m, and 3.2 m.

[0094] [Lens group data] shows the surface number of the most object-side surface constituting each lens group and the combined focal length of the entire group.

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

[0096] Also, in the lens configuration diagrams of each embodiment, the arrow represents the locus of the lens group during zooming from the wide-angle end to the telephoto end, I represents the image plane, and the dashed-dotted line passing through the center is the optical axis.

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

Embodiment

[0098] Figure 1 is a lens configuration diagram of the imaging optical system according to 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 biconcave negative lens L5, a biconvex positive lens L6, a meniscus-shaped negative lens L7 with a convex surface facing the object side, and a meniscus-shaped positive lens L8 with a convex surface facing the object side, which form a cemented lens. As a whole, it has positive power. Also, 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.

[0099] The second group G2 is composed of a cemented lens consisting 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. As a whole, it has negative power. Also, the second group G2 moves from the object side to the image side on the optical axis during focusing from an infinite object to a near-distance object.

[0100] The third group G3 is composed of an image blur correction unit IU and a rear unit RU, and has a negative power as a whole. Also, the third group G3 is fixed with respect to the image plane during focusing.

[0101] The image blur 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 power as a whole. Also, the image blur correction unit IU moves in a direction substantially perpendicular to the optical axis so as to reduce image blur due to blur of the imaging optical system.

[0102] The rear unit RU is composed of a cemented lens consisting of a biconvex positive lens L14, a biconcave negative lens L15, and a meniscus positive lens L16 with its convex surface facing the object side, a three-cemented lens consisting 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 power as a whole. Also, 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. The lens component Ln disposed closest to the image side in the imaging optical system is the negative lens L20.

[0104] Subsequently, the specifications of the imaging optical system according to Example 1 are shown below. Numerical Example 1 Unit: mm [Surface Data] Surface number r d nd vd P_gF Object plane ∞ (d0) 1 128.6213 8.5472 1.49700 81.61 0.5389 2 1855.0184 0.2257 3 82.1712 9.8467 1.43700 95.10 0.5336 4 291.1918 3.7000 5 86.2308 2.5000 1.77250 49.63 0.5504 6 57.9504 3.3543 7 61.4411 9.6400 1.43700 95.10 0.5336 8 197.3978 18.5622 9 -333.8043 2.0000 1.77250 49.63 0.5504 10 93.3984 0.3617 11 73.6505 9.0058 1.43700 95.10 0.5336 12 -256.0975 29.8177 13 126.7983 1.5000 1.77250 49.63 0.5504 14 32.4202 6.7928 1.56732 42.84 0.5744 15 614.6770 (d15) 16 91.7650 2.6326 1.67270 32.17 0.5963 17 5455.7778 1.5000 1.77250 49.63 0.5504 18 49.7976 (d18) 19 (Diaphragm) ∞ 14.3265 20 115.6881 3.1058 1.67270 32.17 0.5963 21 -37.9788 1.0000 1.59282 68.62 0.5440 22 70.0614 2.1219 23 -243.6318 0.9000 1.88300 40.81 0.5656 24 47.2089 5.8618 25 28.0943 5.4009 1.68960 31.14 0.6031 26 -1449.5194 5.0141 27 -357.0678 1.0000 1.94594 17.98 0.6546 28 21.1709 5.9068 1.69895 30.05 0.6028 29 149.0456 2.9324 30 41.7292 10.1981 1.75520 27.53 0.6098 31 -22.5524 1.0000 1.88300 40.81 0.5656 32 31.9918 7.5209 1.77047 29.74 0.5951 33 -92.9755 3.7907 34 -34.1613 1.0000 1.90043 37.37 0.5767 35 -86.9114 (BF) Image plane ∞ [Various data] INF 20m 3.2m Focal length 485.00 429.90 258.32 F-number 5.80 5.80 5.95 Full field angle 2ω 5.06 4.88 3.95 Image height Y 21.63 21.63 21.63 Overall lens length 252.34 252.34 252.34 [Variable interval data] INF 20m 3.2m d0 ∞ 19410.1882 2898.0257 d15 5.1467 7.4232 21.9757 d18 28.9503 26.6738 12.1213 BF 37.1732 37.1732 37.1732 [Lens group data] Group Starting surface Focal length G1 1 171.54 G2 16 -126.77 G3 20 -78.05 IU 20 -44.51 RU 25 65.16 Ln 34 -63.07

Example

[0105] FIG. 7 is a lens configuration diagram of the imaging optical system according to Embodiment 2 of the present invention. The first group G1 is composed of a biconvex positive lens L1, a meniscus positive lens L2 with a convex surface facing the object side, a meniscus negative lens L3 with a convex surface facing the object side, a meniscus positive lens L4 with a convex surface facing the object side, a biconcave negative lens L5, a biconvex positive lens L6, a meniscus negative lens L7 with a convex surface facing the object side, and a meniscus positive lens L8 with a convex surface facing the object side, which form a cemented lens, and has positive power as a whole. Also, 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 including a meniscus positive lens L9 with a convex surface facing the object side and a meniscus negative lens L10 with a convex surface facing the object side, and has negative power as a whole. Also, the second group G2 moves from the object side to the image side on the optical axis when focusing from an infinite object to a near-distance object.

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

[0108] The image blur 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 negative power as a whole. Also, the image blur correction unit IU moves in a direction substantially perpendicular to the optical axis so as to reduce image blur due to blur of the imaging optical system.

[0109] The rear unit RU is composed of a cemented lens consisting of a biconvex positive lens L14, a biconcave negative lens L15, and a meniscus positive lens L16 with its convex surface facing the object side, a three-lens cemented lens consisting 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 power as a whole. Also, the rear unit RU is always fixed with respect to the image plane.

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

[0111] Subsequently, the specifications of the imaging optical system according to Example 2 are shown below. Numerical Example 2 Unit: mm [Surface Data] Surface number r d nd vd P_gF Object surface ∞ (d0) 1 140.7884 9.2799 1.49700 81.61 0.5389 2 -2983.6838 1.3052 3 80.6730 10.2729 1.43700 95.10 0.5336 4 267.2084 3.7000 5 88.2176 2.5000 1.77250 49.63 0.5504 6 58.6143 3.0731 7 61.1979 9.6400 1.43700 95.10 0.5336 8 174.3498 18.5785 9 -346.0581 2.0000 1.77250 49.63 0.5504 10 96.0936 3.5160 11 75.0504 9.2576 1.43700 95.10 0.5336 12 -256.0553 30.4691 13 179.2783 1.5000 1.77250 49.63 0.5504 14 33.6244 7.0233 1.56732 42.84 0.5744 15 1876.2500 (d15) 16 91.4634 2.6101 1.67270 32.17 0.5963 17 430.5662 1.5000 1.77250 49.63 0.5504 18 52.4328 (d18) 19 (Aperture) ∞ 8.9386 20 47.2400 3.5406 1.64769 33.84 0.5924 21 -53.3700 1.0000 1.59410 60.47 0.5552 22 36.8596 2.7076 23 -470.0733 0.9000 1.88300 40.81 0.5656 24 52.0060 5.5310 25 30.1323 4.7326 1.69895 30.05 0.6028 26 -167.2045 4.5845 27 -137.6655 1.0000 1.92286 20.88 0.6390 28 20.9954 4.5531 1.72047 34.71 0.5834 29 95.3035 5.3990 30 49.7673 7.9623 1.77047 29.74 0.5951 31 -24.7722 1.0000 1.88100 40.14 0.5700 32 33.7336 5.5745 1.77047 29.74 0.5951 33 -101.9666 2.4752 34 -41.3845 1.0000 1.91082 35.25 0.5822 35 -88.8866 (BF) Image plane ∞ [Various data] INF 20m 3.3m Focal length 504.99 455.35 287.93 F-number 5.80 5.81 5.81 Full picture angle 2ω 4.87 4.69 3.81 Image height Y 21.63 21.63 21.63 Overall lens length 261.95 261.95 261.95 [Variable interval data] INF 20m 3.3m d0 ∞ 20213.4581 3014.6257 d15 4.9136 7.6311 25.3377 d18 29.7949 27.0774 9.3709 BF 50.1169 50.1169 50.1170 [Lens group data] Group Starting surface Focal length G1 1 187.32 G2 16 -145.23 G3 20 -102.31 IU 20 -52.63 RU 25 79.76 Ln 34 -85.88

Example

[0112] FIG. 13 is a lens configuration diagram of the imaging optical system according to Embodiment 3 of the present invention. The first group G1 includes 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 biconcave negative lens L5, a biconvex positive lens L6, a meniscus-shaped negative lens L7 with a convex surface facing the object side, and a meniscus-shaped positive lens L8 with a convex surface facing the object side, which together form a cemented lens, and has a positive power as a whole. Also, 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.

[0113] The second group G2 is composed of a cemented lens including 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 power as a whole. Also, the second group G2 moves from the object side to the image side on the optical axis when focusing from an infinite object to a near-distance object.

[0114] The third group G3 is composed of an image blur correction unit IU and a rear unit RU, and has a negative power as a whole. Also, the third group G3 is fixed with respect to the image plane during focusing.

[0115] The image blur correction unit IU is composed of a cemented lens of a biconvex positive lens L11 and a biconcave negative lens L12, and a meniscus-shaped negative lens L13 with a convex surface facing the object side, and has a negative power as a whole. Also, the image blur correction unit IU moves in a direction substantially perpendicular to the optical axis so as to reduce image blur due to blur of the imaging optical system.

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

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

[0118] Subsequently, the specifications of the imaging optical system according to Example 3 are shown below. Numerical Example 3 Unit: mm [Surface Data] Surface number r d nd vd P_gF Object plane ∞ (d0) 1 129.1671 9.3042 1.49700 81.61 0.5389 2 1997.2381 1.6817 3 83.2780 10.1121 1.43700 95.10 0.5336 4 308.2174 3.7000 5 87.5533 2.5000 1.77250 49.63 0.5504 6 58.3974 2.9835 7 62.7900 9.6400 1.43700 95.10 0.5336 8 211.2563 18.5318 9 -251.1669 2.0000 1.77250 49.63 0.5504 10 102.3545 4.7635 11 80.9017 8.9888 1.43700 95.10 0.5336 12 -185.6506 30.0422 13 135.3400 1.5000 1.77250 49.63 0.5504 14 33.5732 6.7076 1.56732 42.84 0.5744 15 8516.1691 (d15) 16 85.4947 2.6556 1.68960 31.14 0.6031 17 2193.1449 1.5000 1.77250 49.63 0.5504 18 45.4644 (d18) 19 (Diaphragm) ∞ 18.0876 20 104.0250 3.4744 1.62004 36.26 0.5922 21 -31.6896 1.0000 1.61997 63.88 0.5426 22 47.0550 2.2173 23 964.2787 0.9000 1.88300 40.81 0.5656 24 46.1161 5.0266 25 25.6649 6.0771 1.67270 32.17 0.5963 26 -1312.8296 3.6458 27 -2120.5231 1.0000 1.94594 17.98 0.6546 28 18.2224 6.7476 1.69895 30.05 0.6028 29 88.4439 0.9216 30 34.2077 9.8217 1.75520 27.53 0.6098 31 -20.9612 1.0000 1.88300 40.81 0.5656 32 25.4542 8.3904 1.75520 27.53 0.6098 33 -106.2780 3.6661 34 -33.3334 1.0000 1.90043 37.37 0.5767 35 -89.4967 (BF) Image plane ∞ [Various data] INF 20m 3.1m Focal length 485.01 420.05 236.23 F-number 5.80 5.80 5.93 Full angle of view 2ω 5.05 4.86 3.91 Image height Y 21.63 21.63 21.63 Overall length of lens 253.59 253.59 253.59 [Variable interval data] INF 20m 3.1m d0 ∞ 19388.4694 2878.0087 d15 5.1495 7.2432 20.5336 d18 29.0361 26.9423 13.6519 BF 29.8213 29.8213 29.8213 [Lens group data] Group Starting surface Focal length G1 1 166.46 G2 16 -116.88 G3 20 -61.29 IU 20 -40.99 RU 25 62.41 Ln 34 -59.49

Example

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

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

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

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

[0123] The rear unit RU is composed of a biconvex positive lens L13, a cemented lens composed of a biconcave negative lens L14 and a biconvex positive lens L15 on the object side, a three-piece cemented lens composed of a biconvex positive lens L16, a biconcave negative lens L17, and a meniscus-shaped positive lens L18 with a convex surface facing the object side, and a meniscus-shaped negative lens L19 with a concave surface facing the object side, and has negative power as a whole. Also, 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. The lens component Ln disposed closest to the image side in the imaging optical system is the negative lens L19.

[0125] Subsequently, the specifications of the imaging optical system according to Example 4 are shown below. Numerical Example 4 Unit: mm [Surface Data] Surface number r d nd vd P_gF Object surface ∞ (d0) 1 152.6407 5.9639 1.49700 81.61 0.5389 2 479.5683 6.9529 3 80.8597 11.9755 1.43700 95.10 0.5336 4 585.1357 6.0275 5 72.6166 2.5000 1.69680 55.46 0.5426 6 58.8047 31.4706 7 68.7654 11.2371 1.43700 95.10 0.5336 8 -142.8542 2.0000 1.77250 49.63 0.5504 9 77.6483 5.8849 10 50.6036 7.7034 1.43700 95.10 0.5336 11 255.1568 23.4115 12 169.1233 1.4000 1.88300 40.81 0.5656 13 31.9189 7.9145 1.62004 36.30 0.5873 14 -406.6786 (d14) 15 131.6201 0.9000 1.49700 81.61 0.5389 16 45.7614 (d16) 17 (Aperture) ∞ 10.6662 18 77.1288 3.0224 1.77047 29.74 0.5951 19 -69.5028 0.9000 1.59282 68.62 0.5440 20 47.7243 4.0951 21 -266.3337 0.9000 1.88300 40.81 0.5656 22 50.7912 5.5666 23 28.3565 6.1268 1.67270 32.17 0.5963 24 -106.0047 5.8834 25 -62.5186 1.0000 1.94594 17.98 0.6546 26 21.1671 5.8948 1.67270 32.17 0.5963 27 -301.0473 0.2000 28 48.3691 8.6180 1.80809 22.76 0.6287 29 -22.9490 1.0000 1.88300 40.81 0.5656 30 43.1894 4.9693 1.75520 27.53 0.6098 31 674.8222 17.5497 32 -34.2110 1.0000 1.90043 37.37 0.5767 33 -54.5225 (BF) Image plane ∞ [Various data] INF 20m 3.2m Focal length 494.99 436.96 259.71 F-number 5.79 5.79 5.98 Full picture angle 2ω 4.95 4.80 4.00 Image height Y 21.63 21.63 21.63 Overall lens length 271.35 271.35 271.35 [Variable interval data] INF 20m 3.2m d0 ∞ 19802.1759 2952.4687 d14 5.1657 7.5881 22.9611 d16 26.7072 24.2849 8.9118 BF 36.7468 36.7468 36.7468 [Lens group data] Group Starting surface Focal length G1 1 178.94 G2 15 -141.64 G3 18 -76.68 IU 18 -50.47 RU 23 63.88 Ln 32 -104.42

Example

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

[0127] The second group G2 consists of a meniscus-shaped negative lens L9 with a convex surface facing the object side and a meniscus-shaped positive lens L10 with a convex surface facing the object side, and has negative power as a whole. Also, L9 within the second group G2 moves from the object side to the image side along the optical axis when focusing from an infinite object to a near-distance object, and L10 moves from the image side to the object side along the optical axis when focusing from an infinite object to a near-distance object.

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

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

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

[0131] The rear unit RU consists of a biconvex positive lens L15, a biconcave negative lens L16, a cemented lens consisting of a biconvex positive lens L17 on the object side, a three-cemented lens consisting of a biconvex positive lens L18, a biconcave negative lens L19, and a biconvex positive lens L20, and a meniscus-shaped negative lens L21 with a concave surface facing the object side, and has a negative power as a whole. Also, 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. The lens component Ln disposed closest to the image side in the imaging optical system is the negative lens L21.

[0133] Subsequently, the specifications of the imaging optical system according to Example 5 will be shown. Numerical Example 5 Unit: mm [Surface Data] Surface number r d nd vd P_gF Object plane ∞ (d0) 1 165.9553 7.2259 1.49700 81.61 0.5389 2 1118.6991 5.9139 3 78.0278 12.7478 1.43700 95.10 0.5336 4 454.9471 5.7283 5 82.0549 2.5000 1.69680 55.46 0.5426 6 61.6396 30.2069 7 65.9390 11.8209 1.43700 95.10 0.5336 8 -166.5051 2.0000 1.77250 49.63 0.5504 9 82.4791 4.8154 10 45.3814 5.1733 1.43700 95.10 0.5336 11 73.3250 20.4403 12 93.6788 1.4000 1.87070 40.73 0.5682 13 31.0049 9.1421 1.62004 36.30 0.5873 14 429.8293 (d14) 15 175.7816 0.9000 1.49700 81.61 0.5389 16 47.6860 (d16) 17 46.7191 3.4927 1.43700 95.10 0.5336 18 128.7495 (d18) 19 (Aperture) ∞ 6.1727 20 -479.9920 6.4679 1.43700 95.10 0.5336 21 -115.9436 1.1220 22 67.7872 2.8066 1.72825 28.32 0.6075 23 -60.9571 0.9000 1.59282 68.62 0.5440 24 28.4378 4.3934 25 -107.6193 0.9000 1.87070 40.73 0.5682 26 42.1364 2.2000 27 24.7730 6.4089 1.73037 32.23 0.5899 28 -60.2057 1.6700 29 -56.4289 1.0000 1.94594 17.98 0.6546 30 18.0984 6.2978 1.67270 32.17 0.5963 31 -213.9943 0.2000 32 40.9517 8.1326 1.80809 22.76 0.6287 33 -18.5101 1.0000 1.88300 40.81 0.5656 34 66.1994 4.4519 1.75211 25.05 0.6192 35 -346.0767 3.0030 36 -37.3060 1.0000 1.90043 37.37 0.5767 37 -123.7684 (BF) Image plane ∞ [Various data] INF 20m 3.3m Focal length 499.98 442.50 265.66 F-number 5.79 5.79 5.93 Full angle of view 2ω 4.91 4.73 3.77 Image height Y 21.63 21.63 21.63 Overall lens length 274.28 274.28 274.28 [Variable interval data] INF 20m 3.3m d0 ∞ 19999.9799 3016.4353 d14 17.0185 18.9756 27.2466 d16 25.2166 21.9800 1.8334 d18 2.7269 4.0065 15.8821 BF 47.6862 47.6863 47.6863 [Lens group data] Group Starting surface Focal length G1 11 199.97 G2 15 -2175.01 G3 20 -51.85 IU 22 -27.37 RU 27 46.46 Ln 36 -59.63

[0134] The conditional expression corresponding values corresponding to each of the above embodiments are shown below. Conditional expression corresponding value Conditional expression ex1 ex2 ex3 ex4 ex5 1 D_A11 / D_G1 0.28 0.27 0.27 0.25 0.25 2 (D_A11+D_A12) / D_G1 0.46 0.44 0.43 0.44 0.43 3 D_G1a / D_G1 0.23 0.24 0.24 0.27 0.29 4 D_A1all / D_G1 0.53 0.54 0.55 0.59 0.56 5 atan(H_Img / f) 2.55 2.45 2.55 2.50 2.48 6 LT / f 0.52 0.52 0.52 0.55 0.55 7 Φ_G2G3 / Φ -13.30 -10.53 -16.83 -13.59 -11.77 8 D_EXP / h_img 3.41 4.02 2.93 3.48 3.47 9 Φ_G3 / Φ -6.21 -4.94 -7.91 -6.46 -9.64 10 |Φ_OS / Φ| 10.90 9.59 11.83 9.81 18.27 11 Φ_G2 / Φ -3.83 -3.48 -4.15 -3.49 -0.23 12 ν_d 17.98 20.88 17.98 17.98 17.98 13 P_g,F+0.0018*ν_d-0.6483 0.039 0.028 0.039 0.039 0.039

[0135] <Other Embodiments> The technology disclosed by this embodiment is not limited to the descriptions of the above embodiments and examples, and various modified implementations are possible. The shapes and numerical values of each part shown in the above numerical examples are all examples for implementing this technology, and the technical scope of this technology is not construed as being limited thereby.

[0136] This technology can also be configured as follows. [Item 1] It consists of, in order from the object side toward the image side, a first group G1 having a positive power as a whole, a second group consisting of lenses that move on the optical axis during focusing, and a third group having a power. The first group G1 consists of, in order from the object side toward the image side, a first a-group G1a, a plurality of lenses, and a first b-group G1b. The first a-group G1a has at least two positive lenses in order from the most object side, and a meniscus-shaped negative lens with its convex surface facing the object side on the most image side. The first b-group G1b has, on the most object side, a lens component including the most image-side positive lens or positive lenses of the first group G1. Between the first a-group G1a and the first b-group G1b, it has the longest air interval D_A11 within the first group G1. An imaging optical system characterized by satisfying the following conditional expressions. (1) 0.05 < D_A11 / D_G1 < 0.44 However, D_A11 is the longest air interval within the first group G1. D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side. [Item 2] The imaging optical system according to [Item 1], characterized by satisfying the following conditional expressions. (2) 0.10 < (D_A11 + D_A12) / D_G1 < 0.70 However, D_A11 is the longest air interval within the first group G1. D_A12 is the second longest air gap between the first group G1a and the first group G1b. [Item 3] The imaging optical system according to [Item 1] or [Item 2], characterized by satisfying the following conditional expression. (3) 0.05 < D_G1a / D_G1 < 0.45 However, D_G1a is the length on the optical axis of the first group G1a, D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side. [Item 4] The imaging optical system according to any one of [Item 1] to [Item 3], characterized by satisfying the following conditional expression. (4) 0.15 < D_A1all / D_G1 < 0.75 However, 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 arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side. [Item 5] The imaging optical system according to any one of [Item 1] to [Item 4], characterized by satisfying the following conditional expression. (5) atan(H_Img / f)< 7.00° However, 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 by satisfying the following conditional expression. (6) 0.10 < LT / f < 1.00 However, LT is the distance on the optical axis from the most object-side surface 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 [Claims 1] to [Claims 6], wherein the first group G1b is composed of a negative lens and a positive lens, or a positive lens and a negative lens. [Claim 8] The imaging optical system according to any one of [Claims 1] to [Claims 7], characterized by satisfying the following conditional expression. (7) -60.00 < Φ_G2G3 / Φ < -3.00 However, Φ is the power of the imaging optical system at infinite focus, Φ_G2G3 is the combined power of the second group G2 and the third group G3 at infinite focus. [Claim 9] The imaging optical system according to any one of [Claims 1] to [Claims 8], characterized by satisfying the following conditional expression. (8) 1.00 < D_EXP / H_Img < 11.00 However, D_EXP is the distance on the optical axis from the exit pupil of the imaging optical system to the image plane at infinite focus, H_Img is the maximum image height. [Claim 10] The imaging optical system according to any one of [Claims 1] to [Claims 9], characterized by satisfying the following conditional expression. (9) -35.00 < Φ_G3 / Φ < -1.00 However, Φ is the power of the imaging optical system at infinite focus, Φ_G3 is the power of the third group G3. [Claim 11] The third group G3 has an image blur correction unit IU, a rear unit RU is provided on the image side of the image blur correction unit IU, the signs of the powers of the image blur correction unit IU and the rear unit RU are different, the image blur correction unit IU has at least one positive lens and at least one negative lens, The imaging optical system according to any one of [Claims 1] to [Claims 10], characterized by satisfying the following conditional expression. (10) 3.00 < |Φ_OS / Φ| < 35.00 However, Φ_OS is the power of the image blur correction unit IU, Φ is the power at infinity focus of the imaging optical system. [Item 12] The imaging optical system according to any one of [Item 1] to [Item 11], characterized by satisfying the following conditional expression. (11) -20.00 < Φ_G2 / Φ < -0.13 However, Φ_G2 is the power of the second group G2, Φ is the power at infinity focus of the imaging optical system. [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 has a negative lens satisfying the following conditional expression on the image side of the aperture stop S. (12) 10.00 < ν_d < 30.00 (13) 0.020 < P_gF + 0.0018*ν_d - 0.6483 < 0.080 However, ν_d is the Abbe number with respect to the d-line of the negative lens arranged on the image side of the aperture stop S, P_gF is the partial dispersion ratio with respect to the g-line and F-line of the negative lens arranged on the image side of the aperture stop S. The partial dispersion ratio is defined as P_gF = (ng - nF) / (nF - nC). ng: Refractive index with respect to the g-line (wavelength λ = 435.84 nm). nF: Refractive index with respect to the F-line (wavelength λ = 486.13 nm). nC: Refractive index with respect to the C-line (wavelength 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 surface and the image side surface of all lenses are spherical or flat.

[0137] Those skilled in the art can conceive various modifications, combinations, sub - combinations, and changes according to design factors and other factors, but it goes without saying that they are included in the scope of the appended claims and their equivalents.

Description of Symbols

[0138] G1 Group 1 G2 Group 2 G3 Group 3 G1a Group 1a G1b Group 1b IU Image blur correction unit RU Rear unit Ln Lens component arranged closest to the image side S Aperture stop I Image plane

Claims

1. It consists of a first group G1 having a positive power as a whole, a second group G2 consisting of a lens that moves on the optical axis during focusing, and a third group G3 having a power, in order from the object side toward the image side. The first group G1 consists of a first a-group G1a, a plurality of lenses, and a first b-group G1b, in order from the object side toward the image side. The first a-group G1a has at least two positive lenses in order from the most object side, and a meniscus-shaped negative lens with a convex surface facing the object side on the most image side. The first b-group G1b has, on the most object side, a lens component including the most image-side positive lens or positive lenses of the first group G1. Between the first a-group G1a and the first b-group G1b, there is the longest air interval D_A11 within the first group G1. An imaging optical system characterized by satisfying the following conditional expression. (1) 0.05 < D_A11 / D_G1 < 0.44 However, D_A11 is the longest air interval within the first group G1. D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side.

2. The imaging optical system according to Claim 1, characterized by satisfying the following conditional expression. (2) 0.10 < (D_A11 + D_A12) / D_G1 < 0.70 However, D_A11 is the longest air interval within the first group G1. D_A12 is the second-longest air interval between the first a-group G1a and the first b-group G1b.

3. The imaging optical system according to Claim 1, characterized by satisfying the following conditional expression. (3) 0.05 < D_G1a / D_G1 < 0.45 However, D_G1a is the length on the optical axis of the first a-group G1a. D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side.

4. The imaging optical system according to Claim 1, characterized by satisfying the following conditional expression. (4) 0.15 < D_A1all / D_G1 < 0.75 However, D_A1all is the sum of all air intervals within the first group G1. D_G1 is the distance on the optical axis from the object-side lens surface of the lens arranged on the most object side of the first group G1 to the image-side lens surface of the lens arranged on the most image side.

5. The imaging optical system according to Claim 1, characterized by satisfying the following conditional expression. (5) atan(H_Img / f) < 7.00° However, H_Img is the maximum image height. f is the focal length of the imaging optical system at infinity focus.

6. The imaging optical system according to claim 1, characterized by satisfying the following conditional expression. (6) 0.10 < LT / f < 1.00 However, LT is the distance on the optical axis from the most object-side surface 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.

7. The imaging optical system according to claim 1, characterized in that the first group 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 by satisfying the following conditional expression. (7) -60.00 < Φ_G2G3 / Φ < -3.00 However, _G2G3 is the combined power of the second group G2 and the third group G3 at infinity focus, Φ is the power Φ of the imaging optical system at infinity focus.

9. The imaging optical system according to claim 1, characterized by satisfying the following conditional expression. (8) 1.00 < D_EXP / H_Img < 11.00 However, D_EXP is the distance on the optical axis from the exit pupil of the imaging optical system at infinity focus to the image plane, H_Img is the maximum image height.

10. The imaging optical system according to claim 1, characterized by satisfying the following conditional expression. (9) -35.00 < Φ_G3 / Φ < -1.00 However, Φ_G3 is the power of the third group G3, Φ is the power of the imaging optical system at infinity focus.

11. The third group G3 has an image blur correction unit IU, has a rear unit RU on the image side of the image blur correction unit IU, the signs of the powers of the image blur correction unit IU and the rear unit RU are different, the image blur correction unit IU has at least one positive lens and at least one negative lens, The imaging optical system according to claim 1, characterized by satisfying the following conditional expression. (10) 3.00 < |Φ_OS / Φ| < 35.00 However, Φ_OS is the power of the image blur correction unit, Φ is the power of the imaging optical system at infinity focus.

12. The imaging optical system according to claim 1, characterized by satisfying the following conditional expression. (11) -20.00 < Φ_G2 / Φ < -0.13 However, Φ_G2 is the power of the second group G2, Φ is the power of the imaging optical system at infinity focus.

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

14. The imaging optical system according to claim 1, characterized in that the object-side surface and the image-side surface of all lenses are spherical or planar.

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