JP5359558B2 - Lens system, optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens system that reduces the size of the entire lens system and simplifies a focusing mechanism by properly setting the arrangement of focusing groups, and to provide optical equipment and a manufacturing method for a lens system. <P>SOLUTION: The lens system includes, in order from an object side along an optical axis, at least a first lens group G1 having positive refractive power, and second to fourth lens groups G2 to G4. The first lens group G1 has a front lens group G1a and a rear lens group G1b disposed on the image side of the front lens group G1a, with an air spacing, and moves the rear lens group G1b in the direction of the optical axis to adjust a focal point. The fourth lens group G4 includes, in order from the object side, a negative lens and positive lens (joined negative lens L41), a negative lens L42, and an aperture stop S. In zooming from a wide-angle end to a telephoto end, the fourth lens group G4 is fixed with respect to an image surface I in the direction of the optical axis. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a lens system used in an optical apparatus such as a digital still camera.

  Conventionally, as a focusing method for an optical system with a high zoom ratio, a so-called front lens feeding method (see, for example, Patent Document 1) for feeding out a lens group disposed closest to the object side, or an internal focusing method (for example, Patent Document) 2).

JP-A-11-258504 JP 2004-212612 A

  However, when trying to focus, the conventional front-lens pay-out method generally moves the lens group arranged closest to the object side, which is large and heavy, and there is a risk that the holding mechanism and the drive mechanism for the focusing group will increase in size. there were. Further, when focusing on an object at a short distance, there is a possibility that the entire length of the lens system becomes large.

  Further, in the conventional internal focusing method, since the second lens group or a group subsequent thereto, which is lighter than the first lens group disposed closest to the object side, can be set as the focusing group, the focusing group is maintained. There is an advantage that the mechanism and the drive mechanism can be reduced in size. However, with the in-focus method, it is generally impossible to focus on an object at the same shooting distance with the same extension amount over the entire zoom range from the wide-angle end state to the telephoto end state. There was a risk of becoming.

The present invention has been made in view of such a problem, and by appropriately setting the arrangement of the focusing group, a lens system that simultaneously achieves downsizing of the entire lens system and simplification of the focusing mechanism , An object is to provide an optical instrument .

In order to achieve the above object, the lens system of the present invention is substantially composed of a first lens group having a positive refractive power and second to sixth lens groups arranged in order from the object side along the optical axis. It consists of six lens groups, and zooming is performed by changing the distance between the lens groups, and the first lens group is arranged with an air space on the image side of the front lens group and the front lens group. The rear partial lens group, the focus is adjusted by moving the rear partial lens group in the optical axis direction, and the fourth lens group is arranged in order from the object side, a negative lens, a positive lens, The zoom lens has a negative lens and an aperture stop, and is fixed in the optical axis direction with respect to the image plane when zooming from the wide-angle end state to the telephoto end state.

  The fourth lens group preferably includes a cemented lens of a negative lens and a positive lens, a negative lens, and an aperture stop arranged in order from the object side.

  In addition, the fourth lens group includes, in order from the object side, a cemented lens of a negative lens having a concave surface facing the object side and a positive lens having a concave surface facing the image side, and a negative lens having a concave surface facing the object side And an aperture stop.

  The fourth lens group preferably has a negative refractive power.

  Further, when the focal length in the telephoto end state in the entire lens system is ft and the focal length of the rear lens group in the first lens group is f1b, the following formula 1.30 <ft / f1b < It is preferable that the condition of 3.10 is satisfied.

  The second lens group preferably has a negative refractive power.

  Further, when the focal length of the second lens group is f2 and the focal length of the fourth lens group is f4, the following condition of 0.23 <| f2 / f4 | <0.88 is satisfied. preferable.

Further, the focal length of the second lens group and f2, the focal length of the fifth lens group has a f5, the following formula 0.40 <| to satisfy the condition of <1.00 | f2 / f5 preferable.

  In addition, it is preferable that at least one of the front lens group and the rear lens group in the first lens group has a positive refractive power.

  Further, when the total length of the entire lens system in the telephoto end state is TL, and the focal length of the rear lens group in the first lens group is f1b, the following expression 0.90 <TL / f1b <2. It is preferable that the condition of 48 is satisfied.

  The first lens group is preferably fixed in the optical axis direction with respect to the image plane in the infinite focus state when zooming from the wide-angle end state to the telephoto end state.

The first lens group has a positive refractive power, the second lens group has a negative refractive power, the third lens group has a positive refractive power, the fourth lens group Preferably, the fifth lens group has a negative refractive power, the fifth lens group has a positive refractive power, and the sixth lens group has a negative refractive power.

  Further, it is preferable that the whole or a part of the fourth lens group is moved so as to have a component in a direction perpendicular to the optical axis.

  Further, the present invention is an optical apparatus including any one of the lens systems that forms an image of an object on a predetermined image plane.

According to the present invention, since the arrangement of the focusing group is appropriately set, a lens system capable of obtaining high imaging performance while simultaneously achieving downsizing of the entire lens system and simplification of the focusing mechanism , Optical equipment can be provided.

It is a figure which shows the mode of the movement of each lens group in the refractive power distribution of the lens system which concerns on each Example of this invention, and the change of the focal distance state from a wide-angle end state to a telephoto end state. It is a figure which shows the structure of the lens system which concerns on 1st Example. FIG. 4 is a diagram illustrating various aberrations of the lens system according to Example 1 when focusing on infinity, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. FIG. 4 is a coma aberration diagram of the lens system according to Example 1 in a lens shift state (0.4 mm) in an infinitely focused state, where (a) is a wide-angle end state, (b) is an intermediate focal length state, and (c). Indicates the telephoto end state. FIG. 4 is a diagram illustrating various aberrations of the lens system according to Example 1 when focusing at close distance, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. It is a figure which shows the structure of the lens system which concerns on 2nd Example. FIG. 5A is a diagram illustrating various aberrations of the lens system according to Example 2 during focusing at infinity, where FIG. 5A illustrates a wide-angle end state, FIG. 5B illustrates an intermediate focal length state, and FIG. FIG. 6 is a coma aberration diagram of a lens shift state (0.4 mm) in an infinitely focused state of a lens system according to Example 2, where (a) is a wide angle end state, (b) is an intermediate focal length state, and (c). Indicates the telephoto end state. FIG. 5A is a diagram illustrating various aberrations of the lens system according to Example 2 during focusing at a short distance, where FIG. It is a figure which shows the structure of the lens system which concerns on 3rd Example. FIG. 6A is a diagram illustrating various aberrations of the lens system according to Example 3 when focusing on infinity, where (a) shows a wide angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. FIG. 10 is a diagram illustrating various aberrations of the lens system according to Example 3 when focusing at short distance, where (a) shows a wide-angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. It is a figure which shows the structure of the lens system which concerns on 4th Example. FIG. 6A is a diagram illustrating various aberrations of the lens system according to Example 4 during focusing at infinity, where FIG. 5A illustrates a wide-angle end state, FIG. 5B illustrates an intermediate focal length state, and FIG. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 4 during focusing at short distance, where (a) shows a wide angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. It is a figure which shows the structure of the lens system which concerns on 5th Example. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 5 during focusing at infinity, where (a) shows a wide angle end state, (b) shows an intermediate focal length state, and (c) shows a telephoto end state. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 5 during focusing at short distance, where FIG. 10A illustrates a wide-angle end state, FIG. 9B illustrates an intermediate focal length state, and FIG. It is a schematic sectional view of a digital single-lens reflex camera CAM provided with the lens system configured as described above as a photographing lens. It is a flowchart for demonstrating the manufacturing method of the lens system of the said structure.

  Hereinafter, the lens system according to the present embodiment will be described with reference to the drawings. The lens system of the present embodiment is a lens system having at least a first lens group having positive refractive power and second to fourth lens groups arranged in order from the object side along the optical axis. The one lens group includes a front partial lens group and a rear partial lens group disposed on the image side of the front partial lens group at an air interval, and is focused by moving the rear partial lens group in the optical axis direction. The fourth lens group includes a negative lens, a positive lens, a negative lens, and an aperture stop arranged in order from the object side. When zooming from the wide-angle end state to the telephoto end state, It is fixed in the optical axis direction with respect to the surface.

  The lens system of the present embodiment has a plurality of lens groups, so that an optical system with a high zoom ratio can be easily configured. Further, the first lens group has a positive refractive power, so that it is possible to balance the reduction of the total length and the correction of distortion. The first lens group is divided into at least two groups, a front partial lens group and a rear partial lens group disposed on the image side of the front partial lens group at an air interval, of which the rear partial lens group By adjusting the focus at, the focusing mechanism can be simplified, and as a result, the focusing speed can be increased. At the same time, it is possible to minimize the short-distance variation in spherical aberration and field curvature due to focus adjustment. Furthermore, it is possible to focus on an object at the same shooting distance with the same feeding amount over the entire zooming range from the wide-angle end state to the telephoto end state. The fourth lens group includes a negative lens, a positive lens, a negative lens, and an aperture stop arranged in order from the object side. When zooming from the wide-angle end state to the telephoto end state, the fourth lens group emits light to the image plane. With the configuration fixed in the axial direction, spherical aberration and field curvature can be corrected well. Further, as in the present embodiment, the distortion is easily corrected by positioning the aperture stop on the image side of the fourth lens group. Further, by arranging the stop position closer to the lens mount than the image blur correction mechanism, the stop mechanism can be simplified.

  In the lens system according to the present embodiment, in order to satisfactorily correct spherical aberration and curvature of field, the fourth lens group includes a negative lens and a positive lens, which are arranged in order from the object side, a negative lens, It is preferable to have an aperture stop.

  In the lens system according to the present embodiment, in order to satisfactorily correct spherical aberration and curvature of field, the fourth lens group is arranged in order from the object side, the negative lens having the concave surface facing the object side, and the image side. It is preferable to have a cemented lens with a positive lens with a concave surface facing the lens, a negative lens with a concave surface facing the object side, and an aperture stop.

  In the lens system according to the present embodiment, it is preferable that the fourth lens group has a negative refractive power in order to satisfactorily correct spherical aberration.

  In the lens system according to the present embodiment, when the focal length in the telephoto end state in the entire lens system is ft and the focal length of the rear lens group in the first lens group is f1b, the following conditional expression It is preferable to satisfy (1).

  1.30 <ft / f1b <3.10 (1)

  Conditional expression (1) is a condition for defining an appropriate range for the focal length of the entire lens system in the telephoto end state and the focal length ratio of the rear lens group in the first lens unit located closest to the image side. It is a formula. When the upper limit of conditional expression (1) is exceeded, the refractive power of the rear lens group becomes relatively strong. As a result, coma aberration during focusing and aberration fluctuations of field curvature become large, which is not preferable. If the lower limit of conditional expression (1) is not reached, the refractive power of the rear lens group will be relatively weak. Although it is advantageous in terms of aberration correction, the amount of movement of the focusing group becomes large, and the balance between miniaturization and high performance cannot be achieved. As a result, the total length of the lens becomes large, which is contrary to the intention of the present invention.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 2.95. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 2.80. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 2.65.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.50. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.70. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.90.

  In the lens system according to the present embodiment, it is preferable that the second lens group has a negative refractive power in order to satisfactorily correct coma and curvature of field.

  In the lens system according to this embodiment, it is preferable that the following conditional expression (2) is satisfied when the focal length of the second lens group is f2 and the focal length of the fourth lens group is f4.

  0.23 <| f2 / f4 | <0.88 (2)

  Conditional expression (2) is a conditional expression for defining an appropriate range for the focal length ratio between the second lens group and the fourth lens group. If the upper limit of conditional expression (2) is exceeded, the refractive power of the second lens group becomes relatively weak, and the fluctuation of coma aberration generated in the second lens group during zooming becomes large. . In addition, the refractive power of the fourth lens group becomes relatively strong, the amount of movement increases during zooming, and the variation in field curvature that occurs in the fourth lens group increases. As a result, it becomes difficult to suppress degradation of performance in the entire zoom range from the wide-angle end state to the telephoto end state.

  If the lower limit value of conditional expression (2) is not reached, the refractive power of the second lens group becomes relatively strong, resulting in insufficient correction of coma aberration. In addition, it becomes difficult for the second lens group to efficiently contribute to zooming, and it becomes impossible to secure a high zooming ratio of about 4 times or more. Further, since the refractive power of the fourth lens group becomes relatively weak, spherical aberration and field curvature generated in the fourth lens group become excessively large, and the object of the present invention is to obtain excellent optical performance. It can no longer be achieved.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.80. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.75. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.70.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.30. In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (2) to 0.35. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.40.

  In the lens system according to the present embodiment, when the fifth lens group is provided on the image side of the fourth lens group, the focal length of the second lens group is f2, and the focal length of the fifth lens group is f5. It is preferable that the following conditional expression (3) is satisfied.

  0.40 <| f2 / f5 | <1.00 (3)

  Conditional expression (3) is a conditional expression for defining an appropriate range for the focal length ratio between the second lens group and the fifth lens group. If the upper limit value of conditional expression (3) is exceeded, the refractive power of the second lens group becomes relatively weak, and the fluctuation of coma aberration generated in the second lens group during zooming becomes large. . In addition, the refractive power of the fifth lens group becomes relatively strong, the amount of movement increases during zooming, and the variation in spherical aberration that occurs in the fifth lens group increases. As a result, it becomes difficult to suppress degradation of performance in the entire zoom range from the wide-angle end state to the telephoto end state.

  If the lower limit of conditional expression (3) is not reached, the refractive power of the second lens group becomes relatively strong, making it difficult for the second lens group to efficiently contribute to zooming. Therefore, it becomes impossible to secure a high zoom ratio of about 4 or more. Furthermore, since the refractive power of the fifth lens group becomes relatively weak, the spherical aberration and coma aberration generated in the fifth lens group become excessively large, thereby achieving the object of the present invention to obtain excellent optical performance. It becomes impossible.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.95. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.90. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.85.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.50. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.55. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.60.

In the lens system according to the present embodiment, it is preferable that at least one of the front lens group and the rear lens group in the first lens group has a positive refractive power. In order to minimize the overall length and minimize the occurrence of distortion, the front lens group in the first lens group preferably has a positive refractive power. In order to minimize the short-distance variation in spherical aberration and field curvature due to focus adjustment, it is preferable that the rear lens group in the first lens group has a positive refractive power.

  In the lens system according to the present embodiment, when the total length of the entire lens system in the telephoto end state is TL and the focal length of the rear lens group in the first lens group is f1b, the following conditional expression (4 ) Is preferably satisfied.

  0.90 <TL / f1b <2.48 (4)

  Conditional expression (4) is a conditional expression for defining an appropriate range for the overall length of the entire lens system and the focal length ratio of the rear lens group in the first lens group located closest to the object side. When the upper limit value of conditional expression (4) is exceeded, the refractive power of the rear lens group becomes relatively strong. As a result, coma aberration during focusing and aberration fluctuations of field curvature become large, which is not preferable. If the lower limit of conditional expression (4) is not reached, the refractive power of the rear lens group will be relatively weak. Although it is advantageous in terms of aberration correction, the amount of movement of the focusing group becomes large, and the balance between miniaturization and high performance cannot be achieved. As a result, the total length of the lens becomes large, which is contrary to the intention of the present invention.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 2.20. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 1.90. Furthermore, in order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 1.75.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.00. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.10. Furthermore, in order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.20.

  In the lens system according to the present embodiment, in order to reduce performance deterioration due to decentration, particularly to minimize deterioration of field curvature, and to realize good optical performance, the first lens group has a wide-angle end. When zooming from the state to the telephoto end state, it is preferably fixed in the optical axis direction with respect to the image plane in the infinitely focused state.

  In the lens system according to the present embodiment, in order to correct spherical aberration, coma aberration, and field curvature, and to achieve excellent optical performance with a high zoom ratio, the image side of the fourth lens group And a fifth lens group and a sixth lens group, the first lens group has a positive refractive power, the second lens group has a negative refractive power, and the third lens group has a positive refractive power. Preferably, the fourth lens group has a negative refractive power, the fifth lens group has a positive refractive power, and the sixth lens group has a negative refractive power.

  Further, in the lens system according to the present embodiment, in order to obtain a state in which the spherical aberration, the sine condition, and the Petzval sum are well corrected so that the image is good at the time of lens shift, the whole or one of the fourth lens group. It is preferable to correct the image blur on the image plane when the camera shake occurs by moving the part so as to have a component perpendicular to the optical axis. The spherical aberration and the sine condition are corrected in order to suppress decentration coma generated at the center of the screen when the shift lens group is shifted in a direction substantially orthogonal to the optical axis. The Petzval sum is corrected to suppress curvature of field that occurs at the periphery of the screen when the shift lens group is shifted in a direction substantially orthogonal to the optical axis.

  FIG. 19 is a schematic cross-sectional view of a digital single-lens reflex camera CAM (optical apparatus) provided with the lens system having the above configuration as a photographic lens 1. In the digital single-lens reflex camera CAM shown in FIG. 19, light from an object (subject) (not shown) is collected by the photographing lens 1 and imaged on the focusing screen 4 via the quick return mirror 3. The light imaged on the focusing screen 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 6.

  Further, when a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light of an object (subject) (not shown) condensed by the photographing lens 1 is captured on the image sensor 7. Form an image. Thereby, the light from the object (subject) is captured by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can photograph an object (subject) with the camera CAM. The camera CAM described in FIG. 19 may be one that holds the photographing lens 1 in a detachable manner or may be molded integrally with the photographing lens 1. The camera CAM may be a so-called single-lens reflex camera or a compact camera that does not have a quick return mirror or the like.

  Next, a manufacturing method of the lens system having the above configuration will be described with reference to FIG. First, each lens (for example, the lenses L11 to L61 in FIG. 2) is assembled in a cylindrical barrel (step S1). When assembling the lenses into the lens barrel, the lenses may be incorporated into the lens barrel one by one in the order along the optical axis, or a part or all of the lenses may be integrally held by the holding member and then assembled with the lens barrel member. Good. Next, after each lens is incorporated in the lens barrel, it is confirmed whether an object image is formed in a state where each lens is incorporated in the lens barrel, that is, whether the centers of the lenses are aligned (step) S2). Subsequently, various operations of the lens system are confirmed (step S3). As an example of various operations, a zooming operation for zooming from the wide-angle end state to the telephoto end state (for example, the second lens group G2, the third lens group G3, the fifth lens group G5, and the sixth lens in FIG. 2). Lens group G6 moves along the optical axis direction), and a lens for focusing from a long distance object point to a short distance object point (for example, rear lens group G1b in FIG. 2) moves along the optical axis direction. And a camera shake correction operation for moving at least a part of the lenses (for example, the fourth lens group G4 in FIG. 2) so as to have a component perpendicular to the optical axis. Note that the order of confirming the various operations is arbitrary.

  Hereinafter, each embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a state of movement of each lens unit in a refractive power distribution and a change in focal length state from the wide-angle end state (W) to the telephoto end state (T) according to each embodiment. As shown in FIG. 1, the lens system according to each example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive lens arrayed in order from the object side. A third lens group G3 having negative refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power It is composed of When the focal length state changes from the wide-angle end state to the telephoto end state (that is, zooming), the first lens group G1 and the fourth lens group G4 are fixed with respect to the image plane I, and the first lens group G1 and the first lens group G1 The distance between the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, the distance between the third lens group G3 and the fourth lens group G4 increases, and the fourth lens The distance between the group G4 and the fifth lens group G5 decreases, and the distance between the fifth lens group G5 and the sixth lens group G6 decreases.

In each embodiment, the aspherical surface has a height in the direction perpendicular to the optical axis as y, and the distance (sag) along the optical axis from the tangential plane of the apex of each aspherical surface to each aspherical surface at height y. When the quantity is S (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic coefficient is κ, and the n-th aspherical coefficient is Cn, the following equation (a) is given. . In each embodiment, the secondary aspheric coefficient C2 is 0, and the description thereof is omitted. “E-n” represents “× 10 ⁻ⁿ ”. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

S (y) = (y ² / r) / {1+ (1−κ · y ² / r ² ) ^1/2 }
+ C4 × y ⁴ + C6 × y ⁶ + C8 × y ⁸ + C10 × y ¹⁰ (a)

  Moreover, in each Example, the value of a specification is hung up on a table | surface (Table 1, 6, 11, 16, 21). In [Overall specifications] in the table, f is the focal length of the entire system, and F.F. NO indicates the F number and 2ω indicates the angle of view. The total lens length represents the distance on the optical axis from the first surface of the lens surface to the image plane I when focusing on infinity. In [Lens data], the surface number is the order of the lens surfaces from the object side along the direction in which the light beam travels, r is the radius of curvature of each lens surface, and d is the next optical surface (or image from each optical surface). The distance between the surfaces, which is the distance on the optical axis to the surface), nd represents the refractive index for the d-line (wavelength 587.6 nm), and νd represents the Abbe number for the d-line (wavelength 587.6 nm). When the lens surface is aspherical, an asterisk is attached to the surface number, and the paraxial radius of curvature is indicated in the column of the radius of curvature r. The curvature radius “0.0000” indicates a plane or an opening. Further, the description of the refractive index “1.00000” of air is omitted. In [Lens Group Focal Length Data], the starting surface and focal length of each group are shown.

In [Aspherical Data] (Tables 2, 7, 12, 17, and 22), R represents a vertex curvature radius, κ represents a conical constant, and C _{4 to} C ₁₀ represent values of each aspheric constant. In [Variable Interval Data] (Tables 3, 8, 13, 18, 23), the variable interval at the time of focusing at infinity at each of the focal lengths in the wide-angle end state, intermediate focal length state, and telephoto end state of the lens system is shown. Show. Further, in [focusing group movement amount] (Tables 4, 9, 14, 19, 24), f is the focal length, Δ1b is the focal length of the rear partial lens group G1b when focusing at a short distance (in a shooting distance of 1.8 m). Indicates the amount of movement (note that movement toward the object side is positive). In [Values for Conditional Expressions] (Tables 5, 10, 15, 20, and 25), values corresponding to the conditional expressions (1) to (4) are shown.

  Here, “mm” is generally used as a unit of focal length, radius of curvature, surface interval, and other lengths listed in all the following specification values. However, since the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced, the unit is not limited to “mm”, and other appropriate units can be used.

(First embodiment)
1st Example is described using FIGS. 2-5 and Table 1-Table 5. FIG. FIG. 2 is a diagram illustrating a configuration of a lens system according to the first example. As shown in FIG. 2, in the lens system according to the first example, the first lens group G1 includes a front partial lens group G1a and a rear partial lens group G1b, which are arranged in order from the object side. The front lens group G1a includes, in order from the object side, a cemented positive lens L11 formed by bonding a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens L12 having a convex surface facing the object side. Consists of The rear partial lens group G1b is composed of a cemented positive lens L13 that is formed by bonding a negative meniscus lens having a convex surface toward the object side and a positive meniscus lens having a convex surface toward the object side, which are arranged in order from the object side.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a cemented negative lens L22 formed by bonding a biconcave lens and a biconvex lens, and a biconcave lens L23 arranged in order from the object side. The

  The third lens group G3 is composed of a biconvex lens L31, a cemented negative lens L32 formed by bonding a biconvex lens and a biconcave lens, and a positive meniscus lens L33 with a convex surface facing the object side, which are arranged in order from the object side. The

  The fourth lens group G4 includes, in order from the object side, a cemented negative lens L41 including a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. It is composed of a negative meniscus lens L42 having a convex surface. In the present embodiment, the entire fourth lens group G4 or a part thereof moves as a shift lens group so as to have a component in a direction substantially orthogonal to the optical axis.

  The fifth lens group G5 is composed of a biconvex lens L51 arranged in order from the object side, and a cemented positive lens L52 formed by bonding a biconvex lens and a negative meniscus lens having a convex surface facing the image side.

  The sixth lens group G6 is composed of a cemented negative lens L61 that is formed by bonding a biconcave lens and a biconvex lens arranged in order from the object side.

  The image plane I is formed on an image sensor (not shown), and the image sensor is composed of a CCD, a CMOS, or the like. (The description of the image plane I is the same in the following embodiments.)

  The aperture stop S is disposed closest to the object side of the fourth lens group G4, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  Table 1 below lists values of specifications of the first embodiment.

(Table 1)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state f 81.59 to 199.36 to 392.00
FNO 4.59-5.61-5.87
2ω 29.77-12.13-6.20
Image height 21.60 to 21.60 to 21.60
Total lens length 258.89 to 258.89 to 258.89
[Lens data]
Surface number r d nd νd
1 131.4316 3.30 1.79952 42.24
2 79.5641 10.60 1.49782 82.52
3 -1117.1906 0.10
4 125.2669 3.70 1.49782 82.52
5 226.1411 (d5)
6 97.0031 3.00 1.84666 23.78
7 69.6269 10.00 1.58913 61.16
8 5170.1602 (d8)
9 281.7482 2.00 1.81600 46.62
10 55.1616 3.80
11 -253.2341 2.00 1.75500 52.32
12 33.0485 6.65 1.80810 22.76
13 -1843.9411 1.80
14 -121.8581 2.00 1.81600 46.62
15 81.1182 (d15)
16 44.5000 5.50 1.64000 60.08
17 -500.9830 0.20
18 47.5000 6.15 1.60300 65.44
19 -153.9169 2.00 1.80518 25.42
20 52.6835 0.50
* 21 44.6691 4.75 1.59201 67.02
22 351.2823 (d22)
23 229.8851 1.80 1.75700 47.82
24 19.3839 3.95 1.79504 28.54
25 41.9378 1.70
26 306.0080 2.00 1.75500 52.32
27 93.0447 3.30
28 0.0000 (d28) (Aperture stop S)
* 29 40.9184 4.75 1.59201 67.02
30 -1709.5554 1.00
31 118.3219 5.60 1.48749 70.23
32 -25.1824 2.00 1.72047 34.71
33 -46.7938 (d33)
34 -31.1643 1.50 1.80400 46.57
35 37.1717 4.90 1.72825 28.46
36 -115.4294 (Bf)
[Each group focal length data]
Group Start surface Focal length G1 1 110.8156
G2 9 -31.3101
G3 16 42.4527
G4 23 -52.0327
G5 29 41.9333
G6 34 -47.7618

  In the first embodiment, the 21st and 29th lens surfaces are formed in an aspherical shape. Table 2 below shows [Aspherical data].

(Table 2)
[Aspherical data]
21st surface R κ C ₄ C ₆ C ₈ C ₁₀
44.6691 +3.3063 -6.0735 × 10 ^-6 -5.8617 × 10 ^-9 + 6.7417 × 10 ^-13 -1.7957 × 10 ^-14
29th surface R κ C ₄ C ₆ C ₈ C ₁₀
40.9184 +5.2049 -6.7013 × 10 ^-6 -1.5290 × 10 ^-8 + 2.1354 × 10 ^-11 -2.4026 × 10 ^-13

  In the first example, the axial air distance d5 between the front lens group G1a and the rear lens group G1b, the axial air distance d8 between the first lens group G1 and the second lens group G2, and the second lens group G2. On-axis air gap d15 between the third lens group G3, on-axis air gap d22 between the third lens group G3 and the fourth lens group G4, and on-axis air gap d28 between the fourth lens group G4 and the fifth lens group G5 The axial air distance d33 between the fifth lens group G5 and the sixth lens group G6 and the back focus Bf change during zooming. Table 3 below shows [variable interval data].

(Table 3)
[Variable interval data]
Wide angle end Intermediate focal length Telephoto end
d5 12.7115 12.7115 12.7115
d8 2.0000 23.7622 28.4231
d15 53.3167 23.8139 2.0000
d22 2.9663 10.7068 27.8599
d28 23.1736 15.3971 2.0146
d33 9.1769 7.4489 3.0225
Bf 54.9998 64.5041 82.3125

  Table 4 below shows [focus group movement amount] in the first embodiment.

(Table 4)
[Focus group movement]
Wide angle end Intermediate focal length Telephoto end f 81.5935 199.3602 392.0025
Δ1b 10.7115 10.7115 10.7115

  Table 5 below shows [Conditional Expression Corresponding Values] in the first example.

(Table 5)
[Conditional expression values]
ft = 392.0025
f1b = 201.0773
f2 = -31.3101
f4 = -52.0327
f5 = 41.9333
TL = 258.8947
(1) ft / f1b = 1.9495
(2) | f2 / f4 | = 0.6017
(3) | f2 / f5 | = 0.7467
(4) TL / f1b = 1.2875

  3 to 5 are graphs showing various aberrations of the first example with respect to the d-line (wavelength 587.6 nm). 3A is a diagram showing various aberrations in the infinite focus state in the wide-angle end state (f = 81.59 mm), and FIG. 3B is infinite in the intermediate focal length state (f = 199.36 mm). FIG. 3C shows various aberrations in the infinite focus state in the telephoto end state (f = 392.00 mm). 4A is a coma aberration diagram in the lens shift state (0.4 mm) in the infinite focus state in the wide-angle end state (f = 81.59 mm), and FIG. 4B is the intermediate focal length state ( FIG. 4C is a coma aberration diagram in the lens shift state (0.4 mm) in the infinite focus state at f = 199.36 mm), and FIG. 4C is the infinite focus state in the telephoto end state (f = 392.00 mm). It is a coma aberration figure of a lens shift state (0.4mm). FIG. 5A is a diagram showing various aberrations in the short-distance focusing state (shooting distance 1.8 m) in the wide-angle end state (f = 81.59 mm), and FIG. 5B is the intermediate focal length state (f = 199.36mm) are various aberrations in the short distance focusing state (shooting distance 1.8m), and FIG. 5C is the short distance focusing state (shooting distance 1.8m) in the telephoto end state (f = 392.00mm). FIG.

  In each aberration diagram, FNO indicates an F number, A indicates a half angle of view with respect to the image height, and H0 indicates an object height with respect to each image height. In the figure showing spherical aberration, the F-number value corresponding to the maximum aperture is shown. In the figure showing astigmatism and distortion, the maximum image height is shown. In the figure showing coma aberration, the value of each image height is shown. Indicates. Moreover, in the figure which shows astigmatism, a continuous line shows a sagittal image surface and a broken line shows a meridional image surface. The explanation of the above aberration diagrams is the same in the other examples, and the explanation is omitted.

  As is apparent from the respective aberration diagrams, in the first example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Second embodiment)
The second embodiment will be described with reference to FIGS. 6 to 9 and Tables 6 to 10. FIG. 6 is a diagram illustrating a configuration of a lens system according to the second example. As shown in FIG. 6, in the lens system according to the second example, the first lens group G1 is composed of a front partial lens group G1a and a rear partial lens group G1b arranged in order from the object side. The front lens group G1a includes, in order from the object side, a cemented positive lens L11 formed by bonding a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens L12 having a convex surface facing the object side. Consists of The rear partial lens group G1b is composed of a cemented positive lens L13 that is formed by bonding a negative meniscus lens having a convex surface toward the object side and a positive meniscus lens having a convex surface toward the object side, which are arranged in order from the object side.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a cemented negative lens L22 formed by bonding a biconcave lens and a biconvex lens, and a biconcave lens L23 arranged in order from the object side. The

  The third lens group G3 includes a biconvex lens L31, a cemented positive lens L32 formed by bonding a biconvex lens and a biconcave lens, and a positive meniscus lens L33 with a convex surface facing the object side, which are arranged in order from the object side. The

  The fourth lens group G4 includes, in order from the object side, a cemented negative lens L41 including a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. It is composed of a negative meniscus lens L42 having a convex surface. In the present embodiment, the entire fourth lens group G4 or a part thereof moves as a shift lens group so as to have a component in a direction substantially orthogonal to the optical axis.

  The fifth lens group G5 is composed of a biconvex lens L51 arranged in order from the object side, and a cemented positive lens L52 formed by bonding a biconvex lens and a negative meniscus lens having a convex surface facing the image side.

  The sixth lens group G6 is composed of a cemented negative lens L61 that is formed by bonding a biconcave lens and a biconvex lens arranged in order from the object side.

  The aperture stop S is disposed closest to the object side of the fourth lens group G4, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  Table 6 below lists values of specifications of the second embodiment.

(Table 6)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state f 81.59 to 199.36 to 392.00
FNO 4.59 to 5.61 to 5.85
2ω 29.77-12.13-6.20
Image height 21.60 to 21.60 to 21.60
Total lens length 258.89 to 258.89 to 258.89
[Lens data]
Surface number r d nd νd
1 131.2682 3.30 1.79952 42.24
2 79.2077 10.60 1.49782 82.52
3 -1090.3032 0.10
4 123.2408 3.70 1.49782 82.52
5 220.9763 (d5)
6 96.1976 3.00 1.84666 23.78
7 69.0965 10.00 1.58913 61.16
8 4928.1656 (d8)
9 288.2296 2.00 1.81600 46.62
10 54.2542 3.80
11 -249.4274 2.00 1.75500 52.32
12 32.8351 6.65 1.80810 22.76
13 -1937.0128 1.80
14 -118.0849 2.00 1.81600 46.62
15 86.5424 (d15)
16 44.5000 5.50 1.64000 60.08
17 -500.0000 0.20
18 47.5000 6.15 1.60300 65.44
19 -154.7487 2.00 1.80518 25.42
20 51.9426 0.50
* 21 45.3806 4.75 1.59201 67.02
22 409.1975 (d22)
23 229.8851 1.80 1.75700 47.82
24 19.2035 3.95 1.79504 28.54
25 42.0732 1.70
26 553.9438 2.00 1.75500 52.32
27 103.9914 3.30
28 0.0000 (d28) (Aperture stop S)
* 29 41.2885 4.75 1.59201 67.02
30 -299.5240 1.00
31 142.3003 5.60 1.48749 70.23
32 -25.3123 2.00 1.72047 34.71
33 -47.5235 (d33)
34 -33.2184 1.50 1.80400 46.57
35 34.4337 4.90 1.72825 28.46
36 -160.1625 (Bf)
[Each group focal length data]
Group Start surface Focal length G1 1 110.1486
G2 9 -31.3559
G3 16 42.7470
G4 23 -51.5772
G5 29 40.9494
G6 34 -46.5805

  In the second example, the lens surfaces of the 21st surface and the 29th surface are formed in an aspherical shape. Table 7 below shows [Aspherical data].

(Table 7)
[Aspherical data]
21st surface R κ C ₄ C ₆ C ₈ C ₁₀
45.3806 +3.5082 -6.2708 × 10 ^-6 -6.0885 × 10 ^-9 + 8.5423 × 10 ^-13 -1.9843 × 10 ^-14
29th surface R κ C ₄ C ₆ C ₈ C ₁₀
41.2885 +5.3966 -7.1249 × 10 ^-6 -1.6306 × 10 ^-8 + 2.2822 × 10 ^-11 -2.6353 × 10 ^-13

  In the second example, the axial air distance d5 between the front lens group G1a and the rear lens group G1b, the axial air distance d8 between the first lens group G1 and the second lens group G2, and the second lens group G2 On-axis air gap d15 between the third lens group G3, on-axis air gap d22 between the third lens group G3 and the fourth lens group G4, and on-axis air gap d28 between the fourth lens group G4 and the fifth lens group G5 The axial air distance d33 between the fifth lens group G5 and the sixth lens group G6 and the back focus Bf change during zooming. Table 8 below shows [variable interval data].

(Table 8)
[Variable interval data]
Wide angle end Intermediate focal length Telephoto end
d5 12.5666 12.5666 12.5666
d8 2.0000 23.5395 28.6365
d15 52.7950 23.5222 2.0000
d22 3.3567 11.0899 27.5152
d28 23.7470 15.7538 2.7671
d33 8.8798 7.1223 2.4250
Bf 54.9997 64.7502 82.4337

  Table 9 below shows [focusing group movement amount] in the second embodiment.

(Table 9)
[Focus group movement]
Wide angle end Intermediate focal length Telephoto end f 81.5935 199.3601 392.0023
Δ1b 10.5666 10.5666 10.5666

  Table 10 below shows [conditional expression corresponding values] in the second embodiment.

(Table 10)
[Conditional expression values]
ft = 392.0023
f1b = 199.4630
f2 = -31.3559
f4 = -51.5772
f5 = 40.9494
TL = 258.8947
(1) ft / f1b = 1.9653
(2) | f2 / f4 | = 0.6079
(3) | f2 / f5 | = 0.7657
(4) TL / f1b = 1.2980

  7 to 9 are graphs showing various aberrations of the second example with respect to the d-line (wavelength 587.6 nm). That is, FIG. 7A is a diagram showing various aberrations in the infinitely focused state in the wide-angle end state (f = 81.59 mm), and FIG. 7B is an infinite point in the intermediate focal length state (f = 199.36 mm). FIG. 7C shows various aberrations in the infinite focus state in the telephoto end state (f = 392.00 mm). 8A is a coma aberration diagram in the lens shift state (0.4 mm) in the infinite focus state in the wide-angle end state (f = 81.59 mm), and FIG. 8B is the intermediate focal length state ( FIG. 8C is a coma aberration diagram in the lens shift state (0.4 mm) in the infinite focus state at f = 199.36 mm), and FIG. 8C is the infinite focus state in the telephoto end state (f = 392.00 mm). It is a coma aberration figure of a lens shift state (0.4mm). FIG. 9A is a diagram showing various aberrations in the near-in-focus state (shooting distance 1.8 m) in the wide-angle end state (f = 81.59 mm), and FIG. 9B is the intermediate focal length state (f = 199.36mm) are various aberrations in the short distance focusing state (shooting distance 1.8m), and FIG. 9C is the short distance focusing state (shooting distance 1.8m) in the telephoto end state (f = 392.00mm). FIG.

  As is apparent from the respective aberration diagrams, in the second example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Third embodiment)
A third embodiment will be described with reference to FIGS. 10 to 12 and Tables 11 to 15. FIG. FIG. 10 is a diagram illustrating a configuration of a lens system according to the third example. As shown in FIG. 10, in the lens system according to the third example, the first lens group G1 is composed of a front partial lens group G1a and a rear partial lens group G1b arranged in order from the object side. The front lens group G1a includes, in order from the object side, a cemented positive lens L11 formed by bonding a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens L12 having a convex surface facing the object side. Consists of The rear partial lens group G1b is composed of a cemented positive lens L13 that is formed by bonding a negative meniscus lens having a convex surface toward the object side and a positive meniscus lens having a convex surface toward the object side, which are arranged in order from the object side.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a cemented negative lens L22 formed by bonding a biconcave lens and a biconvex lens, and a biconcave lens L23 arranged in order from the object side. The

  The third lens group G3 includes, in order from the object side, a positive meniscus lens L31 having a convex surface facing the object side, a cemented positive lens L32 formed by bonding a biconvex lens and a biconcave lens, and a convex surface facing the object side. And a positive meniscus lens L33.

  The fourth lens group G4 includes, in order from the object side, a cemented negative lens L41 including a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. It is composed of a negative meniscus lens L42 having a convex surface.

  The fifth lens group G5 includes a cemented positive lens L51 formed by bonding a biconvex lens and a negative meniscus lens having a convex surface toward the image side, which are arranged in order from the object side, and a biconvex lens L52.

  The sixth lens group G6 is composed of a cemented negative lens L61 that is formed by bonding a biconcave lens and a biconvex lens arranged in order from the object side.

  The aperture stop S is disposed closest to the object side of the fourth lens group G4, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  Table 11 below provides values of specifications of the third example.

(Table 11)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state f 81.59 to 199.36 to 392.00
FNO 4.59-5.61-5.80
2ω 29.77-12.13-6.20
Image height 21.60 to 21.60 to 21.60
Total lens length 258.89 to 258.89 to 258.89
[Lens data]
Surface number r d nd νd
1 133.8083 3.30 1.79952 42.24
2 78.8175 10.60 1.49782 82.52
3 -1382.5946 0.10
4 123.9007 3.70 1.49782 82.52
5 225.7793 (d5)
6 96.4071 3.00 1.84666 23.78
7 69.2697 10.00 1.58913 61.16
8 4131410.10 (d8)
9 285.2072 2.00 1.81600 46.62
10 56.3264 3.69
11 -326.3135 2.00 1.75500 52.32
12 33.7548 6.48 1.80810 22.76
13 -2938.9650 1.80
14 -139.5484 2.00 1.81600 46.62
15 80.6087 (d15)
16 36.3892 6.50 1.63854 55.38
17 1172.1590 0.20
18 47.5000 6.00 1.60300 65.44
19 -193.2842 2.00 1.79504 28.69
20 34.9652 0.50
* 21 34.4094 4.75 1.59201 67.02
22 250.3789 (d22)
23 338.2642 1.80 1.75500 52.32
24 21.0000 3.84 1.85026 32.35
25 55.4412 1.25
26 257.4850 2.00 1.81600 46.62
27 55.5783 3.30
28 0.0000 (d28) (Aperture stop S)
29 34.7699 6.40 1.48749 70.23
30 -54.0693 1.50 1.78470 26.29
31 -118.0352 5.00
* 32 101.5391 3.44 1.59201 67.02
33 -103.4701 (d33)
34 -37.4152 1.50 1.81600 46.62
35 39.2241 4.35 1.76182 26.52
36 -273.3331 (Bf)
[Each group focal length data]
Group Start surface Focal length G1 1 111.2886
G2 9 -33.1811
G3 16 45.7397
G4 23 -50.3605
G5 29 40.4786
G6 34 -49.4603

  In the third embodiment, the lens surfaces of the 21st surface and the 32nd surface are formed in an aspherical shape. Table 12 below shows [Aspherical data].

(Table 12)
[Aspherical data]
21st surface R κ C ₄ C ₆ C ₈ C ₁₀
34.4094 +2.1394 -7.8728 × 10 ^-6 -1.0276 × 10 ^-8 + 5.7397 × 10 ^-13 -3.9681 × 10 ^-14
32nd surface R κ C ₄ C ₆ C ₈ C ₁₀
101.5391 +8.6994 -3.7200 × 10 ^-6 -5.5601 × 10 ^-9 + 2.6654 × 10 ^-11 -6.1182 × 10 ^-14

  In the third example, the axial air distance d5 between the front lens group G1a and the rear lens group G1b, the axial air distance d8 between the first lens group G1 and the second lens group G2, and the second lens group G2 On-axis air gap d15 between the third lens group G3, on-axis air gap d22 between the third lens group G3 and the fourth lens group G4, and on-axis air gap d28 between the fourth lens group G4 and the fifth lens group G5 The axial air distance d33 between the fifth lens group G5 and the sixth lens group G6 and the back focus Bf change during zooming. Table 13 below shows [variable interval data].

(Table 13)
[Variable interval data]
Wide angle end Intermediate focal length Telephoto end
d5 12.5694 12.5694 12.5694
d8 2.0000 24.6107 29.4259
d15 53.7638 23.9276 2.0000
d22 2.0000 9.2256 26.3380
d28 20.5472 13.9626 2.0000
d33 10.0198 7.9655 1.9516
Bf 54.9999 63.6389 81.6154

  Table 14 below shows [focus group movement amount] in the third embodiment.

(Table 14)
[Focus group movement]
Wide angle end Intermediate focal length Telephoto end f 81.5936 199.3606 392.0046
Δ1b 10.5694 10.5694 10.5694

  Table 15 below shows [Conditional Expression Corresponding Values] in the third example.

(Table 15)
[Conditional expression values]
ft = 392.0046
f1b = 195.4172
f2 = -33.1811
f4 = -50.3605
f5 = 40.4786
TL = 258.8949
(1) ft / f1b = 2.0060
(2) | f2 / f4 | = 0.6589
(3) | f2 / f5 | = 0.8197
(4) TL / f1b = 1.3248

  11 and 12 are graphs showing various aberrations of the third example with respect to the d-line (wavelength 587.6 nm). That is, FIG. 11A is a diagram showing various aberrations in the infinite focus state in the wide-angle end state (f = 81.59 mm), and FIG. 11B is infinite in the intermediate focal length state (f = 199.36 mm). FIG. 11C shows various aberrations in the infinite focus state in the telephoto end state (f = 392.00 mm). FIG. 12A is a diagram showing various aberrations in the short-distance focusing state (shooting distance 1.8 m) in the wide-angle end state (f = 81.59 mm), and FIG. 12B is the intermediate focal length state (f = 199.36mm) are various aberrations in the short distance focusing state (shooting distance 1.8m), and FIG. 12 (c) is the short distance focusing state (shooting distance 1.8m) in the telephoto end state (f = 392.00mm). FIG.

  As is apparent from the respective aberration diagrams, in the third example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(Fourth embodiment)
The fourth embodiment will be described with reference to FIGS. 13 to 15 and Tables 16 to 20. FIG. 13 is a diagram illustrating a configuration of a lens system according to the fourth example. As shown in FIG. 13, in the lens system according to the fourth example, the first lens group G1 is composed of a front partial lens group G1a and a rear partial lens group G1b arranged in order from the object side. The front lens group G1a includes, in order from the object side, a cemented positive lens L11 formed by bonding a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens L12 having a convex surface facing the object side. Consists of The rear partial lens group G1b is composed of a cemented positive lens L13 that is formed by bonding a negative meniscus lens having a convex surface toward the object side and a positive meniscus lens having a convex surface toward the object side, which are arranged in order from the object side.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a cemented negative lens L22 formed by bonding a biconcave lens and a biconvex lens, and a biconcave lens L23 arranged in order from the object side. The

  The third lens group G3 includes, in order from the object side, a positive meniscus lens L31 having a convex surface facing the object side, a cemented positive lens L32 formed by bonding a biconvex lens and a biconcave lens, and a convex surface facing the object side. And a positive meniscus lens L33.

  The fourth lens group G4 includes, in order from the object side, a cemented negative lens L41 including a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. It is composed of a negative meniscus lens L42 having a convex surface.

  The fifth lens group G5 includes a cemented positive lens L51 formed by bonding a biconvex lens and a negative meniscus lens having a convex surface toward the image side, which are arranged in order from the object side, and a biconvex lens L52.

  The sixth lens group G6 is composed of a cemented negative lens L61 that is formed by bonding a biconcave lens and a biconvex lens arranged in order from the object side.

  The aperture stop S is disposed closest to the object side of the fourth lens group G4, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  Table 16 below provides values of specifications of the fourth embodiment.

(Table 16)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state f 81.59 to 199.36 to 392.00
FNO 4.59-5.61-5.81
2ω 29.77-12.13-6.20
Image height 21.60 to 21.60 to 21.60
Total lens length 258.89 to 258.89 to 258.89
[Lens data]
Surface number r d nd νd
1 133.2189 3.30 1.79952 42.24
2 78.8413 10.60 1.49782 82.52
3 -1349.4584 0.10
4 122.6506 3.70 1.49782 82.52
5 220.7135 (d5)
6 97.4575 3.00 1.84666 23.78
7 69.9753 10.00 1.58913 61.16
8 24541.3080 (d8)
9 282.3894 2.00 1.81600 46.62
10 56.0314 3.60
11 -461.8664 2.00 1.75500 52.32
12 33.3947 6.76 1.80810 22.76
13 -738.5057 1.80
14 -126.0189 2.00 1.81600 46.62
15 74.9764 (d15)
16 37.2017 6.19 1.64000 60.08
17 576.2061 0.20
18 47.5000 6.00 1.60300 65.44
19 -7507.9456 2.00 1.80518 25.42
20 36.3965 0.50
* 21 34.8130 4.75 1.59201 67.02
22 233.2302 (d22)
23 229.8851 1.80 1.75500 52.32
24 21.0000 3.87 1.85026 32.35
25 56.8337 1.27
26 310.8842 2.00 1.81600 46.62
27 51.7027 3.30
28 0.0000 (d28) (Aperture stop S)
29 33.4670 6.20 1.48749 70.23
30 -59.9741 1.50 1.72342 37.95
31 -389.3003 4.00
* 32 92.5529 3.79 1.59201 67.02
33 -79.9013 (d33)
34 -36.8881 1.50 1.81600 46.62
35 44.4662 4.15 1.75520 27.51
36 -209.2278 (Bf)
[Each group focal length data]
Group Start surface Focal length G1 1 111.9505
G2 9 -33.2912
G3 16 45.4892
G4 23 -50.1305
G5 29 40.9529
G6 34 -50.9236

  In the fourth embodiment, the lens surfaces of the 21st surface and the 32nd surface are formed in an aspherical shape. Table 17 below shows [Aspherical data].

(Table 17)
[Aspherical data]
21st surface R κ C ₄ C ₆ C ₈ C ₁₀
34.8130 +2.1787 -7.5607 × 10 ^-6 -9.8093 × 10 ^-9 + 7.0798 × 10 ^-13 -3.7586 × 10 ^-14
32nd surface R κ C ₄ C ₆ C ₈ C ₁₀
92.5529 +10.9948 -5.1008 × 10 ^-6 -6.0990 × 10 ^-9 + 2.5694 × 10 ^-11 -6.0529 × 10 ^-14

  In the fourth example, the axial air gap d5 between the front lens group G1a and the rear lens group G1b, the axial air gap d8 between the first lens group G1 and the second lens group G2, and the second lens group G2. On-axis air gap d15 between the third lens group G3, on-axis air gap d22 between the third lens group G3 and the fourth lens group G4, and on-axis air gap d28 between the fourth lens group G4 and the fifth lens group G5 The axial air distance d33 between the fifth lens group G5 and the sixth lens group G6 and the back focus Bf change during zooming. Table 18 below shows [variable interval data].

(Table 18)
[Variable interval data]
Wide angle end Intermediate focal length Telephoto end
d5 12.7700 12.7700 12.7700
d8 2.0000 24.7297 29.0024
d15 54.4773 24.4138 2.0000
d22 2.0000 9.3337 27.4749
d28 20.1271 13.9837 2.0000
d33 10.6112 8.2089 1.8252
Bf 54.9997 63.5451 81.9118

  Table 19 below shows [focusing group movement amount] in the fourth example.

(Table 19)
[Focus group movement]
Wide angle end Intermediate focal length Telephoto end f 81.5936 199.3606 392.0046
Δ1b 10.7700 10.7700 10.7700

  Table 20 below shows [Conditional Expression Corresponding Values] in the fourth example.

(Table 20)
[Conditional expression values]
ft = 392.0023
f1b = 198.5617
f2 = -33.2912
f4 = -50.1305
f5 = 40.9529
TL = 258.8947
(1) ft / f1b = 1.9742
(2) | f2 / f4 | = 0.6641
(3) | f2 / f5 | = 0.8129
(4) TL / f1b = 1.039

  14 and 15 are graphs showing various aberrations of the fourth example with respect to the d-line (wavelength 587.6 nm). 14A is a diagram showing various aberrations in the infinite focus state in the wide-angle end state (f = 81.59 mm), and FIG. 14B is an infinite point in the intermediate focal length state (f = 199.36 mm). FIG. 14C shows various aberrations in the infinite focus state in the telephoto end state (f = 392.00 mm). FIG. 15A is a diagram showing various aberrations in the short-distance focusing state (shooting distance 1.8 m) in the wide-angle end state (f = 81.59 mm), and FIG. 15B is the intermediate focal length state (f = 199.36mm) are various aberrations in the short distance focusing state (shooting distance 1.8m), and FIG. 15 (c) is the short distance focusing state (shooting distance 1.8m) in the telephoto end state (f = 392.00mm). FIG.

  As is apparent from each aberration diagram, in the fourth example, it is understood that various aberrations are well corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

(5th Example)
The fifth embodiment will be described with reference to FIGS. 16 to 18 and Tables 21 to 25. FIG. FIG. 16 is a diagram illustrating a configuration of a lens system according to the fifth example. As shown in FIG. 16, in the lens system according to Example 5, the first lens group G1 includes a front partial lens group G1a and a rear partial lens group G1b, which are arranged in order from the object side. The front lens group G1a includes, in order from the object side, a cemented positive lens L11 formed by bonding a negative meniscus lens having a convex surface facing the object side and a biconvex lens, and a positive meniscus lens L12 having a convex surface facing the object side. Consists of The rear partial lens group G1b is composed of a cemented positive lens L13 that is formed by bonding a negative meniscus lens having a convex surface toward the object side and a positive meniscus lens having a convex surface toward the object side, which are arranged in order from the object side.

  The second lens group G2 includes a negative meniscus lens L21 having a convex surface directed toward the object side, a cemented negative lens L22 formed by bonding a biconcave lens and a biconvex lens, and a biconcave lens L23 arranged in order from the object side. The

  The third lens group G3 includes, in order from the object side, a positive meniscus lens L31 having a convex surface facing the object side, a cemented positive lens L32 formed by bonding a biconvex lens and a biconcave lens, and a convex surface facing the object side. And a positive meniscus lens L33.

  The fourth lens group G4 includes, in order from the object side, a cemented negative lens L41 including a negative meniscus lens having a convex surface facing the object side and a positive meniscus lens having a convex surface facing the object side. It is composed of a negative meniscus lens L42 having a convex surface.

  The fifth lens group G5 includes a cemented positive lens L51 that is formed by bonding a biconvex lens and a negative meniscus having a convex surface toward the image side, which are arranged in order from the object side, and a biconvex lens L52.

  The sixth lens group G6 is composed of a cemented negative lens L61 that is formed by bonding a biconcave lens and a biconvex lens arranged in order from the object side.

  The aperture stop S is disposed closest to the object side of the fourth lens group G4, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  Table 21 below provides values of specifications of the fifth example.

(Table 21)
[Overall specifications]
Wide-angle end state Intermediate focal length state Telephoto end state f 81.59 to 199.36 to 392.00
FNO 4.59-5.61-5.80
2ω 29.77-12.13-6.20
Image height 21.60 to 21.60 to 21.60
Total lens length 258.90-258.90-258.90
[Lens data]
Surface number r d nd νd
1 133.6762 3.30 1.79952 42.24
2 79.0071 10.60 1.49782 82.52
3 -1375.1125 0.10
4 123.6607 3.70 1.49782 82.52
5 225.7101 (d5)
6 97.7416 3.00 1.84666 23.78
7 70.2029 10.00 1.58913 61.16
8 44043.7160 (d8)
9 268.7227 2.00 1.81600 46.62
10 57.1628 3.64
11 -333.8661 2.00 1.75500 52.32
12 33.9852 6.40 1.80810 22.76
13 -10324.962 1.80
14 -146.8295 2.00 1.81600 46.62
15 77.5945 (d15)
16 35.9057 6.40 1.63854 55.38
17 568.1739 0.20
18 47.5000 6.00 1.60300 65.44
19 -247.4569 2.00 1.79504 28.69
20 34.2135 0.50
* 21 33.5894 4.88 1.59201 67.02
22 277.3494 (d22)
23 290.3258 1.80 1.75500 52.32
24 21.0000 3.83 1.85026 32.35
25 55.5062 1.27
26 272.4402 2.00 1.81600 46.62
27 54.3181 3.30
28 0.0000 (d28) (Aperture stop S)
29 34.7823 6.20 1.48749 70.23
30 -57.3362 1.50 1.78470 26.29
31 -145.0487 4.00
* 32 109.8688 3.49 1.59201 67.02
33 -90.1349 (d33)
34 -37.9388 1.50 1.81600 46.62
35 39.7626 4.36 1.76182 26.52
36 -237.8547 (Bf)
[Each group focal length data]
Group Start surface Focal length G1 1 112.0296
G2 9 -33.3823
G3 16 45.7985
G4 23 -50.1309
G5 29 40.9799
G6 34 -51.4035

  In the fifth embodiment, the lens surfaces of the 21st surface and the 32nd surface are formed in an aspherical shape. Table 22 below shows [Aspherical data].

(Table 22)
[Aspherical data]
21st surface R κ C ₄ C ₆ C ₈ C ₁₀
33.5894 +2.0354 -7.9225 × 10 ^-6 -1.0415 × 10 ^-8 + 5.4592 × 10 ^-13 -4.0884 × 10 ^-14
32nd surface R κ C ₄ C ₆ C ₈ C ₁₀
109.8688 -4.4025 -2.6052 × 10 ^-6 -4.9948 × 10 ^-9 + 2.5279 × 10 ^-11 -5.5767 × 10 ^-14

  In the fifth example, the axial air distance d5 between the front lens group G1a and the rear lens group G1b, the axial air distance d8 between the first lens group G1 and the second lens group G2, and the second lens group G2. On-axis air gap d15 between the third lens group G3, on-axis air gap d22 between the third lens group G3 and the fourth lens group G4, and on-axis air gap d28 between the fourth lens group G4 and the fifth lens group G5 The axial air distance d33 between the fifth lens group G5 and the sixth lens group G6 and the back focus Bf change during zooming. Table 23 below shows [variable interval data].

(Table 23)
[Variable interval data]
Wide angle end Intermediate focal length Telephoto end
d5 12.7840 12.7840 12.7840
d8 2.0000 24.8714 29.5496
d15 54.2502 24.2109 2.0000
d22 2.0000 9.1679 26.7006
d28 20.1680 13.8569 2.0000
d33 10.9315 8.6853 2.1288
Bf 55.0000 63.5573 81.9705

  Table 24 below shows [focusing group movement amount] in the fifth example. In the table, the movement toward the object side is positive.

(Table 24)
[Focus group movement]
Wide angle end Intermediate focal length Telephoto end f 81.5937 199.3609 392.0050
Δ1b 10.7840 10.7840 10.7840

  Table 25 below shows [Conditional Expression Corresponding Values] in the fifth example.

(Table 25)
[Conditional expression values]
ft = 392.0050
f1b = 198.6996
f2 = -33.3823
f4 = -50.1309
f5 = 40.9799
TL = 258.8950
(1) ft / f1b = 1.9729
(2) | f2 / f4 | = 0.6659
(3) | f2 / f5 | = 0.8146
(4) TL / f1b = 1.3029

17 and 18 are graphs showing various aberrations of the fifth example with respect to the d-line (wavelength 587.6 nm). 15A is a diagram showing various aberrations in the infinite focus state in the wide-angle end state (f = 81.59 mm ), and FIG. 15B is an infinite point in the intermediate focal length state (f = 199.36 mm ). FIG. 15C shows various aberrations in the infinite focus state in the telephoto end state (f = 392.00 mm). FIG. 16A is a diagram showing various aberrations in the short-distance focusing state (shooting distance 1.8 m) in the wide-angle end state (f = 81.59 mm), and FIG. 16B is the intermediate focal length state (f = 199.36 mm ) are various aberrations in the short distance focusing state (shooting distance 1.8 m). FIG. 16C is the short distance focusing state (shooting distance 1.8 m) in the telephoto end state (f = 392.00 mm). FIG.

  As is apparent from each aberration diagram, in the fifth example, it is understood that various aberrations are favorably corrected in each focal length state from the wide-angle end state to the telephoto end state, and excellent imaging performance is obtained.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  In the above embodiment, a 6-group configuration is shown, but the present invention can also be applied to other group configurations such as a 5-group and a 7-group. Further, a configuration in which a lens or a lens group is added closest to the object side, or a configuration in which a lens or a lens group is added closest to the image side may be used. The lens group refers to a portion having at least one lens separated by an air interval that changes during zooming.

  In addition, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. The focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor). In particular, the rear lens group G1b is preferably a focusing lens group.

  In addition, the lens group or the partial lens group is moved so as to have a component perpendicular to the optical axis, or rotated (swinged) in the in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the fourth lens group G4 is an anti-vibration lens group.

  Each lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. Note that it is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to processing and assembly adjustment errors can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. On the other hand, when the lens surface is aspherical, this aspherical surface is an aspherical surface by grinding, a glass mold aspherical surface made of glass with an aspherical shape, and a composite type in which resin is formed on the glass surface in an aspherical shape Any aspherical surface may be used. Each lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  The aperture stop S is preferably disposed in the vicinity of the fourth lens group G4 (in the present embodiment, on the image side of the fourth lens group G4), but the role of the aperture stop S in the lens frame without providing a member as an aperture stop. May be substituted.

  Further, each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength range in order to reduce flare and ghost and achieve high optical performance with high contrast.

  The lens system of the present embodiment has a zoom ratio of about 4 to 5, and a focal length in the telephoto end state is 300 mm or more.

  In the lens system of the present embodiment, it is preferable that the fourth lens group G4 has one positive lens component and two negative lens components. In addition, it is preferable that the lens components are arranged in the order of negative positive / negative in order from the object side with an air gap interposed therebetween.

  In addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

  As described above, according to the present invention, a lens system that can achieve high imaging performance while simultaneously achieving a reduction in the overall length of the lens system and simplification of the focusing mechanism, an optical apparatus including the lens system, and A manufacturing method can be provided.

G1 First lens group G1a Front partial lens group G1b Rear partial lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group S Aperture stop I Image surface CAM Digital SLR Camera (optical equipment)

Claims (14)

In order from an object along an optical axis, a first lens group having a positive refractive power, consisting essentially of six lens groups by the second to sixth lens group, a distance between the lens groups Change the magnification,
The first lens group includes a front partial lens group and a rear partial lens group disposed on the image side of the front partial lens group with an air gap therebetween, and the rear partial lens group is moved in the optical axis direction. To adjust the focus,
The fourth lens group includes a negative lens, a positive lens, a negative lens, and an aperture stop arranged in order from the object side. When zooming from the wide-angle end state to the telephoto end state, On the other hand, the lens system is fixed in the optical axis direction.   The lens system according to claim 1, wherein the fourth lens group includes a cemented lens of a negative lens and a positive lens, a negative lens, and an aperture stop, which are arranged in order from the object side.   The fourth lens group is arranged in order from the object side, a cemented lens of a negative lens having a concave surface facing the object side and a positive lens having a concave surface facing the image side, a negative lens having a concave surface facing the object side, The lens system according to claim 1, further comprising an aperture stop.   The lens system according to claim 1, wherein the fourth lens group has negative refractive power. When the focal length in the telephoto end state in the entire lens system is ft and the focal length of the rear lens group in the first lens group is f1b, the following expression 1.30 <ft / f1b <3. 10
The lens system according to claim 1, wherein the following condition is satisfied.   The lens system according to claim 1, wherein the second lens group has a negative refractive power. When the focal length of the second lens group is f2 and the focal length of the fourth lens group is f4, the following expression 0.23 <| f2 / f4 | <0.88
The lens system according to claim 1, wherein the following condition is satisfied. When the focal length of the second lens group is f2, and the focal length of the fifth lens group is f5, the following expression is given: 0.40 <| f2 / f5 | <1.00
The lens system according to claim 1, wherein the following condition is satisfied.   9. The lens system according to claim 1, wherein at least one of the front lens group and the rear lens group in the first lens group has a positive refractive power. . When the total length of the entire lens system in the telephoto end state is TL, and the focal length of the rear lens group in the first lens group is f1b, the following expression 0.90 <TL / f1b <2.48
The lens system according to claim 1, wherein the following condition is satisfied.   The first lens group is fixed in an optical axis direction with respect to an image plane in an infinite focus state when zooming from a wide-angle end state to a telephoto end state. The lens system according to any one of the above. The first lens group has a positive refractive power, the second lens group has a negative refractive power, the third lens group has a positive refractive power, the fourth lens group of negative It has refractive power, The said 5th lens group has positive refractive power, The said 6th lens group has negative refractive power, It is any one of Claims 1-11 characterized by the above-mentioned. Lens system.   The lens system according to any one of claims 1 to 12, wherein the whole or a part of the fourth lens group is moved so as to have a component in a direction orthogonal to the optical axis.   An optical apparatus comprising a lens system for forming an image of an object on a predetermined image plane, wherein the lens system is the lens system according to any one of claims 1 to 13. .

Images