JP6314471B2 - Zoom lens system - Google Patents

Description

  The present invention relates to a zoom lens system including a wide angle region suitable for use in an interchangeable lens camera.

  2. Description of the Related Art An interchangeable lens camera is known in which a photographing lens attached to a camera body can be exchanged according to a photographing scene or a user's photographing preference. In an interchangeable lens camera, a lens mount and a camera mount are provided so that both the photographic lens and the camera body can be attached and detached. Therefore, the zoom lens system mounted on the photographic lens has an image plane from the last lens surface. It is required to ensure a long back focus, which is the distance to the distance.

  On the other hand, it is desirable that the zoom lens system be as compact as possible. However, if the zoom lens system is forcibly made compact, distortion aberration around the screen increases at the short focal length end. In order to correct this distortion, a technique of performing software image processing inside the camera on the image taken by the image sensor is used, but correction of distortion by image processing is performed by complementing each pixel. Therefore, the resolving power of the captured image after image processing is reduced.

  Patent Documents 1 to 3 disclose a zoom lens system having a negative, positive, and negative four-group configuration as a zoom lens system aiming at widening, compactness, and high zoom ratio. Such a negative lens advance type (negative lead type) zoom lens system generally has the advantage of being able to secure the back focus because it can enhance the retrofocus property, while the lens configuration is asymmetrical, so the peripheral performance Is insufficient, and large distortion is likely to occur. Furthermore, the zoom lens systems of Patent Documents 1 to 3 cannot satisfactorily correct not only distortion aberration but also various aberrations such as spherical aberration, coma aberration, field curvature, and lateral chromatic aberration, and have sufficient optical performance. Has not been achieved.

JP 2012-226307 A JP 2012-173298 A JP 2012-133230 A

  The present invention has been made on the basis of the above awareness of problems, has a zoom ratio of up to about 4 times while covering a wide angle region, and is excellent in correcting various aberrations including distortion aberration well. An object of the present invention is to obtain a zoom lens system capable of achieving the optical performance.

The zoom lens system of the present invention includes, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive refractive power. In the zoom lens system composed of the fourth lens group, the distance between the first lens group and the second lens group decreases during zooming from the short focal length end to the long focal length end, and the second lens group and the third lens group At least the first lens group, the second lens group, and the third lens group move in the optical axis direction so that the distance between the lens groups is increased and the distance between the third lens group and the fourth lens group is increased; The second lens group or the third lens group is characterized by having an aperture stop for adjusting the amount of light and satisfying the following conditional expressions (1 ′) , (2), and (3).
(1 ′) −2.00 <ENw / f1 < −1.00
(2) d1G / AST <0.33
(3) −0.40 <ΔD4 / ΔD3 <0.35
However,
ENw: distance in the optical axis direction from the lens surface closest to the object side at the short focal length end (lens surface closest to the object side of the first lens group) to the entrance pupil position,
f1: the focal length of the first lens group,
d1G: thickness in the optical axis direction of the first lens group (distance in the optical axis direction from the most object side lens surface to the most image side lens surface of the first lens group),
AST: distance in the optical axis direction from the lens surface closest to the object side at the short focal length end (lens surface closest to the object side of the first lens group) to the aperture stop
ΔD4: A movement amount in the optical axis direction of the fourth lens group upon zooming from the short focal length end to the long focal length end (a movement amount toward the object side is indicated by a positive value, and a movement amount toward the image side is indicated) Negative value),
ΔD3: Amount of movement of the third lens unit in the optical axis direction during zooming from the short focal length end to the long focal length end (the amount of movement to the object side is indicated by a positive value, and the amount of movement to the image side is Negative value),
It is.

Among the condition ranges defined by the conditional expression (1 ′), it is preferable that the following conditional expression (1 ″) is satisfied.
(1 ″) − 2.00 <ENw / f1 ≦ −1.22

Among the condition ranges defined by the conditional expression (2), it is preferable that the following conditional expression (2 ′) is satisfied.
(2 ′) d1G / AST <0.30

The zoom lens system according to the present invention preferably satisfies the following conditional expression (4).
(4) -2.20 <f1 / fw <−1.40
However,
f1: the focal length of the first lens group,
fw: focal length of the entire lens system at the short focal length end,
It is.

The zoom lens system according to the present invention preferably satisfies the following conditional expression (5).
(5) 1.50 <(β2t / β2w) / (β3t / β3w) <2.70
However,
β2t: lateral magnification of the second lens group at the time of focusing at infinity at the long focal length end,
β2w: lateral magnification of the second lens unit at the time of focusing on infinity at the short focal length end,
β3t: lateral magnification of the third lens group at the time of focusing on infinity at the long focal length end,
β3w: lateral magnification of the third lens group at the time of focusing at infinity at the short focal length end,
It is.

The zoom lens system according to the present invention preferably satisfies the following conditional expression (6).
(6) 1.70 <fbw / f12w <3.00
However,
fbw: Back focus of the entire lens system at the short focal length end (distance in the optical axis direction from the lens surface closest to the image side of the fourth lens group to the image surface),
f12w: the combined focal length of the first lens group and the second lens group at the short focal length end,
It is.

In the zoom lens system according to the present invention, it is preferable that the fourth lens group includes a positive single lens and satisfies the following conditional expression (7).
(7) 0.40 <f123t / f4 <2.00
However,
f123t: the combined focal length of the first lens group, the second lens group, and the third lens group at the long focal length end,
f4: focal length of the positive single lens of the fourth lens group,
It is.

The zoom lens system according to the present invention preferably satisfies the following conditional expression (8).
(8) 0.80 <d2G / f2 <1.40
However,
d2G: thickness in the optical axis direction of the second lens group (distance in the optical axis direction from the most object side lens surface to the most image side lens surface of the second lens group),
f2: focal length of the second lens group,
It is.

The zoom lens system according to the present invention preferably satisfies the following conditional expression (9).
(9) -1.80 <f2 / f1 <-1.00
However,
f2: focal length of the second lens group,
f1: the focal length of the first lens group,
It is.

In the zoom lens system of the present invention, the third lens group is a negative single lens, and this negative single lens is a focus lens that moves to the image side during focusing from an object at infinity to a short distance object. It is preferable that Formula (10) is satisfied.
(10) -1.30 <f3 / f4 <−0.40
However,
f3: focal length of the negative single lens of the third lens group,
f4: focal length of the fourth lens group,
It is.

  The zoom lens system of the present invention can fix the fourth lens group with respect to the image plane during zooming from the short focal length end to the long focal length end.

  Alternatively, the zoom lens system of the present invention can move the fourth lens group to the object side or the image side with respect to the image plane when zooming from the short focal length end to the long focal length end.

  According to the present invention, a zoom lens that has a zoom ratio of up to about 4 times while covering a wide angle range, and that can satisfactorily correct various aberrations including distortion and achieve excellent optical performance. A system is obtained.

It is a lens block diagram at the time of infinity focusing in the short focal distance end of Numerical Example 1 of the zoom lens system according to the present invention. FIG. 2 is a diagram illustrating various aberrations in the configuration of FIG. 1. FIG. 3 is a lens configuration diagram at the time of focusing on infinity at an intermediate focal length in Example 1 of the same numerical value. FIG. 4 is a diagram illustrating various aberrations in the configuration of FIG. 3. 6 is a lens configuration diagram at the time of infinity focusing at the long focal length end of the numerical example 1. FIG. FIG. 6 is a diagram illustrating various aberrations in the configuration of FIG. 5. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Numerical Example 2 of the zoom lens system by the present invention. FIG. 8 is a diagram illustrating various aberrations in the configuration of FIG. 7. It is a lens block diagram at the time of infinity focusing in the intermediate focal distance of the numerical example 2; FIG. 10 is a diagram of various aberrations in the configuration of FIG. 9. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the numerical example 2; FIG. 12 is a diagram illustrating various aberrations in the configuration of FIG. 11. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Numerical Example 3 of the zoom lens system by the present invention. FIG. 14 is a diagram illustrating various aberrations in the configuration of FIG. 13. FIG. 12 is a lens configuration diagram at the time of focusing on infinity at an intermediate focal length in Example 3 of the same numerical value. FIG. 16 is a diagram illustrating various aberrations in the configuration of FIG. 15. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the numerical example 3; FIG. 18 is a diagram illustrating various aberrations in the configuration of FIG. 17. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Numerical Example 4 of the zoom lens system by the present invention. FIG. 20 is a diagram illustrating various aberrations in the configuration in FIG. 19. FIG. 12 is a lens configuration diagram at the time of focusing on infinity at an intermediate focal length in Example 4 of the same numerical value. FIG. 22 is a diagram illustrating various aberrations in the configuration in FIG. 21. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the numerical example 4; FIG. 24 is a diagram of various aberrations in the configuration in FIG. 23. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Numerical Example 5 of the zoom lens system by the present invention. FIG. 26 is a diagram illustrating various aberrations in the configuration in FIG. 25. FIG. 11 is a lens configuration diagram at the time of focusing on infinity at an intermediate focal length in the numerical example 5. FIG. 28 is a diagram of various aberrations in the configuration of FIG. 27. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the same numerical example 5. FIG. 30 is a diagram of various aberrations in the configuration of FIG. 29. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Reference Example 1 of the zoom lens system according to the present invention. FIG. 32 is a diagram of various aberrations in the configuration of FIG. 31. It is a lens block diagram at the time of an infinite focus in the intermediate focal length of the reference example 1 . FIG. 34 is a diagram of various aberrations in the configuration of FIG. 33. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the reference example 1 . FIG. 36 is a diagram showing various aberrations in the configuration of FIG. It is a lens block diagram at the time of infinity focusing in the short focal distance end of Example 2 of the zoom lens system according to the present invention. FIG. 38 is a diagram of various aberrations in the configuration of FIG. 37. It is a lens block diagram at the time of infinity focusing in the intermediate focal distance of the reference example 2 . FIG. 40 is a diagram of various aberrations in the configuration of FIG. 39. It is a lens block diagram at the time of infinity focusing in the long focal distance end of the reference example 2 . FIG. 42 is a diagram of various aberrations in the configuration of FIG. 41. It is a simple movement figure which shows the 1st zoom locus | trajectory of the zoom lens system by this invention. It is a simple movement figure which shows the 2nd zoom locus | trajectory of the zoom lens system by this invention. It is a simple movement figure which shows the 3rd zoom locus | trajectory of the zoom lens system by this invention. It is a simple movement figure which shows the 4th zoom locus | trajectory of the zoom lens system by this invention.

The zoom lens system of the present embodiment has first negative refractive powers in order from the object side as shown in the simplified movement diagrams of FIGS. 43 to 46 through Numerical Example 1-5 and Reference Example 1-2 . The lens group G1 includes a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power. I is the image plane.

The zoom lens system of the present embodiment is configured so that the short focal length end (Wide) to the long focal length end as shown in the simplified movement diagrams of FIGS. 43 to 46 through Numerical Example 1-5 and Reference Example 1-2 . When zooming to (Tele), the distance between the first lens group G1 and the second lens group G2 decreases, the distance between the second lens group G2 and the third lens group G3 increases, and the third lens group G3 and the second lens group G3 increase. The interval between the four lens groups G4 increases.

  In the numerical examples 1, 4, and 5, the zoom lens system according to the present embodiment has the first lens group G1 when zooming from the short focal length end to the long focal length end as shown in the simplified movement diagram of FIG. Once moved to the image side and then returned to the object side (to make a U-turn), as a result, it returned to a position almost the same as the position at the short focal length end, and the second lens group G2 monotonously moved to the object side. The third lens group G3 monotonously moves to the object side, and the fourth lens group G4 is fixed with respect to the image plane I (imaging element) (does not move in the optical axis direction). An aperture stop S for adjusting the amount of light is located between the second lens group G2 and the third lens group G3 (immediately before the third lens group G3). The aperture stop S is long from the short focal length end. At the time of zooming to the focal length end, it moves in the optical axis direction integrally with the third lens group G3 (the third lens group G3 has an aperture stop S).

  In Numerical Example 2, in the zoom lens system of the present embodiment, as shown in the simplified movement diagram of FIG. 44, the first lens group G1 is temporarily moved to the image side upon zooming from the short focal length end to the long focal length end. And then return to the object side (to make a U-turn). As a result, the position returns to almost the same position as the short focal length end, and the second lens group G2 monotonously moves to the object side, and the third lens group G3 Monotonously moves to the object side, and the fourth lens group G4 monotonously moves to the object side. An aperture stop S for adjusting the amount of light is located between the second lens group G2 and the third lens group G3 (immediately before the third lens group G3). The aperture stop S is long from the short focal length end. At the time of zooming to the focal length end, it moves in the optical axis direction integrally with the third lens group G3 (the third lens group G3 has an aperture stop S).

  In Numerical Example 3, in the zoom lens system of the present embodiment, as shown in the simplified movement diagram of FIG. 45, the first lens group G1 is temporarily moved to the image side upon zooming from the short focal length end to the long focal length end. And then return to the object side (to make a U-turn). As a result, the position returns to almost the same position as the short focal length end, and the second lens group G2 monotonously moves to the object side, and the third lens group G3 Monotonously moves to the object side, and the fourth lens group G4 monotonously moves to the image side. An aperture stop S for adjusting the amount of light is located between the second lens group G2 and the third lens group G3 (immediately before the third lens group G3). The aperture stop S is long from the short focal length end. At the time of zooming to the focal length end, it moves in the optical axis direction integrally with the third lens group G3 (the third lens group G3 has an aperture stop S).

The zoom lens system according to this embodiment, in Reference Example 1-2, as shown in path of FIG. 46, upon zooming from the short focal end to the long focal length end, the first lens group G1 is temporarily After moving to the image side, returning to the object side (turning to the U side) results in returning to the same position as the position at the short focal length end, and the second lens group G2 monotonously moves to the object side, and the third lens The group G3 monotonously moves toward the object side, and the fourth lens group G4 is fixed with respect to the image plane I (does not move in the optical axis direction). An aperture stop S for adjusting the amount of light is located in the second lens group G2, and this aperture stop S is integrated with the second lens group G2 upon zooming from the short focal length end to the long focal length end. (The second lens group G2 has an aperture stop S). In FIG. 46, for convenience of illustration, the aperture stop S, although depicted as being located between the second lens group G2 and the third lens group G3 (immediately after the second lens group G2), Reference In Example 1-2 , the aperture stop S is positioned so as to be sandwiched between the lenses constituting the second lens group G2 from both sides in the optical axis direction.

In the zoom lens system according to the present embodiment, the third lens group G3 moves closer to an object at infinity as shown in the simplified movement diagrams of FIGS. 43 to 46 through Numerical Example 1-5 and Reference Example 1-2 . A focusing lens group is configured to move to the image side during focusing on a distance object.

In Numerical Example 1-4, the first lens group G1 includes a negative lens 11, a negative lens 12, a negative lens 13, and a positive lens 14 in order from the object side. The negative lens 12 has both spherical surfaces in Numerical Example 1-3, and both surfaces are aspheric (not spherical) in Numerical Example 4. The negative lens 13 is aspheric on both surfaces throughout Numerical Example 1-4.
In Numerical Example 5 and Reference Example 1 , the first lens group G1 includes a negative lens 11 ′, a negative lens 12 ′, and a positive lens 13 ′ in order from the object side. The negative lens 12 ′ has two aspheric surfaces.
In the reference example 2 , the first lens group G1 includes a negative lens 11 ″ and a positive lens 12 ″ in order from the object side. The negative lens 11 ″ has an aspheric image side surface.

In Numerical Example 1-5, the second lens group G2 includes a positive lens 21, a positive lens 22, a negative lens 23, a positive lens 24, and a positive lens 25 in order from the object side. The positive lens 21 has two aspheric surfaces.
In the reference example 1 , the second lens group G2 includes, in order from the object side, a positive lens 21 ′, a negative lens 22 ′, a positive lens 23 ′, and a positive lens 24 ′. The positive lens 21 'has two aspheric surfaces. The negative lens 22 ′ and the positive lens 23 ′ are cemented. An aperture stop S for adjusting the amount of light is located between the positive lens 21 ′ and the negative lens 22 ′, and this aperture stop S is the second lens during zooming from the short focal length end to the long focal length end. It moves in the optical axis direction integrally with the lens group G2 (the second lens group G2 has an aperture stop S).
In the second embodiment , the second lens group G2 includes, in order from the object side, a positive lens 21 ″, a negative lens 22 ″, a negative lens 23 ″, a positive lens 24 ″, and a positive lens 25 ″. The positive lens 21 ″ has two aspheric surfaces. The negative lens 23 "and the positive lens 24" are cemented. An aperture stop S for adjusting the amount of light is located between the positive lens 24 ″ and the positive lens 25 ″. The aperture stop S is a second lens for zooming from the short focal length end to the long focal length end. It moves in the optical axis direction integrally with the lens group G2 (the second lens group G2 has an aperture stop S).

The third lens group G3 includes a negative single lens 31 through Numerical Example 1-5 and Reference Example 1-2 . In Numerical Example 1-5, an aperture stop S for adjusting the amount of light is positioned immediately before the third lens group G3 (negative single lens 31). The aperture stop S extends from the short focal length end to the long focal length. When zooming to the end, the lens moves integrally with the third lens group G3 in the optical axis direction (the third lens group G3 has an aperture stop S).

The fourth lens group G4 includes a positive single lens 41 through Numerical Example 1-5 and Reference Example 1-2 . The positive single lens 41 has two aspheric surfaces.

  The zoom lens system of the present embodiment is a negative / positive / negative four-group type (negative lead type), and has the advantage that it is easy to ensure the back focus because the retrofocus property can be enhanced, and the back focus is ensured to be long. It is suitable for mounting on the taking lens of an interchangeable lens camera that is required.

  On the other hand, a negative, positive, and negative four-group type zoom lens system generally has an asymmetric lens configuration, so that peripheral performance is insufficient and large distortion is likely to occur. Furthermore, the zoom lens systems of Patent Documents 1 to 3 cannot satisfactorily correct not only distortion aberration but also various aberrations such as spherical aberration, coma aberration, field curvature, and lateral chromatic aberration, and have sufficient optical performance. Has not been achieved.

  In view of this, the zoom lens system of the present embodiment has the first lens group G1 to G1 in order to solve the above-described problems of the negative, positive and negative four-group type zoom lens systems including Patent Documents 1 to 3, and to improve the performance thereof. Various parameters such as the power and thickness of the fourth lens group G4, the zooming movement amount, the position of the aperture stop S, and the entrance pupil position are optimally set.

Conditional expressions (1) , (1 ′), and (1 ″) are the optical axes from the most object side lens surface (the most object side lens surface of the first lens group G1) to the entrance pupil position at the short focal length end. The ratio between the direction distance and the focal length of the first lens group G1 is defined, and the entrance pupil position at the short focal length end is normalized by the focal length of the first lens group G1. By satisfying 1), the entire lens system can be made compact by suppressing an increase in the front lens diameter, and excellent optical performance can be achieved by correcting distortion, coma and lateral chromatic aberration at the short focal length end. This effect can be obtained more significantly by satisfying conditional expressions (1 ′) and (1 ″) .
In order to cover the wide-angle range, it is necessary to increase the negative power of the first lens group G1, but the peripheral portion of the first lens group G1 has a stronger negative power and is barrel-shaped on the image plane. Distortion increases. In order to prevent this, the first lens group G1 covers the wide-angle region while keeping the entrance pupil position as close as possible to the image plane within a range satisfying the conditional expression (1) or the conditional expression (1 ′). It is possible to effectively suppress the negative distortion that occurs in.
If the upper limit of conditional expression (1) is exceeded, the entrance pupil position will be too close to the object side and distortion at the short focal length end will increase.
When the lower limit of conditional expressions (1) , (1 ′) and (1 ″) is exceeded, the entrance pupil position moves away from the first lens group G1, and the off-axis light beam at the front lens becomes high, so the front lens diameter increases. As a result, it is difficult to correct off-axis aberrations such as coma and lateral chromatic aberration mainly at the short focal length end.

Conditional expressions (2) and (2 ′) indicate the thickness in the optical axis direction of the first lens group G1 (the distance in the optical axis direction from the lens surface closest to the object side to the lens surface closest to the image side of the first lens group G1). ) And the distance in the optical axis direction from the lens surface closest to the object side (the lens surface closest to the object side of the first lens group G1) to the aperture stop S at the short focal length end. The position of the aperture stop S at the distance end is normalized by the thickness of the first lens group G1. By satisfying conditional expression (2), the increase of the front lens diameter is suppressed and the entire lens system is made compact. In addition, coma and lateral chromatic aberration at the short focal length end are corrected well and excellent optical performance is achieved. Can be achieved. This effect can be obtained more significantly by satisfying conditional expression (2 ′).
In order to effectively suppress the negative distortion generated in the first lens group G1 while covering the wide angle region, if the entrance pupil position is too close to the image plane, the position where the incident light to the first lens group G1 is high Thus, both the total length and the front lens diameter of the first lens group G1 are increased. Therefore, by controlling the thickness of the first lens group G1 within a range that satisfies the conditional expression (2) or (2 ′), both the total length and the front lens diameter of the first lens group G1 can be suppressed to be small. .
If the upper limit of conditional expression (2) is exceeded, the thickness of the first lens group G1 will become too large and the front lens diameter will increase. As a result, it becomes difficult to correct coma and lateral chromatic aberration mainly at the short focal length end.

Conditional expression (3) defines the ratio of the zooming movement amount of the third lens group G3 and the fourth lens group G4. By satisfying conditional expression (3), the incident angle of off-axis rays on the imaging surface is kept small, and distortion, coma, and lateral chromatic aberration are corrected well, mainly at the long focal length end. Optical performance can be achieved.
If negative distortion is suppressed excessively on the wide angle side (short focal length end side), positive distortion occurs on the telephoto side (long focal length end side). In order to improve this, the zooming amount of the third lens group G3 and the fourth lens group G4 close to the image plane side is appropriately set within the range satisfying the conditional expression (3), so that the telephoto side Positive distortion can be effectively suppressed at the (long focal length end side).
If the upper limit of conditional expression (3) is exceeded, the amount of zoom movement to the object side of the fourth lens group G4 becomes too large, and the fourth lens group G4 is too close to the third lens group G3 during zooming. The incident angle of off-axis rays on the imaging surface mainly at the long focal length end is increased. Further, when the third lens group G3 and the fourth lens group G4 are close to each other, the combined power of these lens groups approaches negative, and it becomes difficult to correct distortion at the long focal length end.
If the lower limit of conditional expression (3) is exceeded, the fourth lens group G4 will be too close to the image plane I during zooming, making it difficult to ensure back focus. Further, the lens diameter of the fourth lens group G4 increases too much, and it becomes difficult to correct coma aberration and lateral chromatic aberration mainly at the long focal length end.
Note that the value of conditional expression (3) becomes zero when the fourth lens group G4 is fixed to the image plane I at the time of zooming, as in Numerical Examples 1 , 4 , 5 and Reference Examples 1 and 2. (Does not move in the optical axis direction). Fixing the fourth lens group G4 to the image plane I at the time of zooming is advantageous in that the zoom mechanism can be simplified and reduced in weight.

  Here, the conditional expressions (1), (2), and (3) are not necessarily satisfied at the same time (these conditional expressions are not integral), and the conditional expressions (1), (2), and (3) Even a zoom lens system satisfying a part (one or two) can obtain a certain effect and can be included in the technical scope of the zoom lens system according to the present invention.

Conditional expression (4) defines the ratio between the focal length of the first lens group G1 and the focal length of the entire lens system at the short focal length end, and the focal length of the first lens group G1 is defined as the short focal length end. Is normalized by the focal length of the entire lens system. By satisfying conditional expression (4), the first lens group G1 and thus the entire lens system can be made compact while covering the wide angle range, and distortion, coma, and lateral chromatic aberration at the short focal length end side (wide angle side) are achieved. Can be corrected well to achieve excellent optical performance.
When the upper limit of conditional expression (4) is exceeded, the power of the first lens group G1 becomes too strong, and it becomes difficult to correct negative distortion at the short focal length end side (wide angle side).
When the lower limit of conditional expression (4) is exceeded, the power of the first lens group G1 becomes too weak, and the thickness and front lens diameter of the first lens group G1 must be increased to cover the wide-angle range. . When the front lens diameter of the first lens group G1 increases, it becomes difficult to correct off-axis aberrations such as coma and lateral chromatic aberration mainly on the short focal length end side (wide angle side).

Conditional expression (5) defines the variable magnification burden ratio (variable magnification contribution ratio) of the second lens group G2 and the third lens group G3. By satisfying conditional expression (5), it is possible to achieve excellent optical performance while suppressing variations in spherical aberration, coma aberration, and field curvature during zooming.
If the upper limit of conditional expression (5) is exceeded, the power of the second lens group G2 becomes too strong in order to increase the zooming efficiency in the second lens group G2 (the zooming burden of the second lens group G2 becomes too large). ), The variation in spherical aberration and coma during zooming becomes large.
When the lower limit of conditional expression (5) is exceeded, the power of the third lens group G3 becomes too strong to increase the zooming efficiency in the third lens group G3 (the zooming burden of the third lens group G3 becomes too large). Therefore, the variation in field curvature during zooming becomes large.

Conditional expression (6) shows the back focus of the entire lens system at the short focal length end (the distance in the optical axis direction from the lens surface closest to the image side of the fourth lens group G4 to the image plane I) and the short focal length end. The ratio of the combined focal length of the first lens group G1 and the second lens group G2 is defined, and the back focus of the entire lens system at the short focal length end is changed to the first lens group G1 and the second lens at the short focal length end. This is normalized by the combined focal length of group G2. By satisfying conditional expression (6), it is possible to achieve excellent optical performance by properly correcting the curvature of field over the entire zoom range, while ensuring a long back focus and providing an interchangeable lens camera. A zoom lens system suitable for mounting on a photographing lens can be obtained.
When the upper limit of conditional expression (6) is exceeded, the combined power of the first lens group G1 and the second lens group G2 becomes too strong, and the field curvature is overcorrected over the entire zoom range.
If the lower limit of conditional expression (6) is exceeded, the back focus becomes too short, and a zoom lens system that is inappropriate for mounting on a photographing lens of a lens interchangeable camera that requires a long back focus is required. turn into.

As described above, the fourth lens group G4 includes the positive single lens 41 through Numerical Example 1-5 and Reference Example 1-2 .
Conditional expression (7) indicates that, in this configuration, the combined focal length of the first lens group G1, the second lens group G2, and the third lens group G3 at the long focal length end, and the positive single lens 41 of the fourth lens group G4. Specifies the ratio to the focal length. By satisfying conditional expression (7), mainly at the long focal length end, the incident angle of off-axis rays on the imaging surface is kept small, and coma is corrected well to achieve excellent optical performance. Can do.
When the upper limit of conditional expression (7) is exceeded, the power of the positive single lens 41 of the fourth lens group G4 becomes too strong, and it becomes difficult to correct coma aberration mainly at the long focal length end.
When the lower limit of conditional expression (7) is exceeded, the power of the positive single lens 41 of the fourth lens group G4 becomes too weak, and the incident angle on the imaging surface mainly at the long focal length end becomes large.

Conditional expression (8) indicates that the thickness in the optical axis direction of the second lens group G2 (the distance in the optical axis direction from the most object-side lens surface to the most image-side lens surface of the second lens group G2), and the second The ratio is defined with respect to the focal length of the lens group G2, and the thickness of the second lens group G2 in the optical axis direction is normalized by the focal length of the second lens group G2. By satisfying conditional expression (8), the thickness of the second lens group G2 is suppressed to shorten the overall length of the lens, and excellent optical performance is achieved by properly correcting spherical aberration, coma and astigmatism. Can be achieved.
If the upper limit of conditional expression (8) is exceeded, the power of the second lens group G2 becomes too strong, making it difficult to correct spherical aberration, coma aberration, and astigmatism. Also, the thickness of the second lens group G2 becomes too large, and the total lens length increases.
If the lower limit of conditional expression (8) is exceeded, the power of the second lens group G2 becomes too weak and the spherical aberration becomes over.

Conditional expression (9) defines the ratio between the focal length of the first lens group G1 and the focal length of the second lens group G2. Satisfying conditional expression (9) can correct field curvature, spherical aberration, coma, and astigmatism, and achieve excellent optical performance, while ensuring a long back focus. It is possible to obtain a zoom lens system suitable for being mounted on a photographing lens of an interchangeable lens camera.
If the upper limit of conditional expression (9) is exceeded, the power of the second lens group G2 becomes too strong, making it difficult to correct spherical aberration, coma aberration, and astigmatism. In addition, since the power of the first lens group G1 is weakened, it is difficult to ensure the back focus.
If the lower limit of conditional expression (9) is exceeded, the power of the first lens group G1 becomes too strong, and the field curvature is overcorrected over the entire zoom range.

As described above, through the numerical value example 1-5 and the reference example 1-2 , the third lens group G3 includes the negative single lens 31, and the negative single lens 31 moves from an infinite object to a short distance object. A focusing lens that moves to the image side during focusing is constructed.
Conditional expression (10) defines the ratio between the focal length of the negative single lens 31 of the third lens group G3 and the focal length of the fourth lens group G4 in this configuration. By satisfying conditional expression (10), it is possible to satisfactorily correct field curvature and coma and achieve excellent optical performance.
When the upper limit of conditional expression (10) is exceeded, the power of the negative single lens 31 of the third lens group G3 becomes too strong, and the field curvature is over in the entire zoom range.
When the lower limit of conditional expression (10) is exceeded, the power of the fourth lens group G4 becomes too strong, and it becomes difficult to correct coma mainly at the long focal length end. In addition, since the power of the negative single lens 31 of the third lens group G3 is weakened, the amount of focus movement of the negative single lens 31 of the third lens group G3 increases, and the variation in field curvature during focusing increases.

Next, specific numerical value examples 1-5 and reference example 1-2 will be described. In the aberration diagrams and tables, d-line, g-line, C-line, F-line, and e-line are aberrations for each wavelength, S is sagittal, M is meridional, FNO. Is F-number, and f is the focal length of the entire system. , W is the half angle of view (°), Y is the image height, fB is the back focus (distance in the optical axis direction from the lens surface closest to the image side of the fourth lens group G4 to the image plane I), L is the total lens length, R is the radius of curvature, d is the lens thickness or lens interval, N (d) is the refractive index for the d-line, and ν (d) is the Abbe number for the d-line. In the table, “entrance pupil position” indicates “distance in the optical axis direction from the most object-side lens surface of the first lens group G1 to the entrance pupil position”. The f-number, focal length, half angle of view, image height, back focus, total lens length, entrance pupil position, and lens interval d that varies with zooming are short focal length end-intermediate focal length-long focal length end. It shows in order. The unit of length is [mm].
A rotationally symmetric aspheric surface is defined by the following equation.
x = cy ² / [1+ [1- (1 + K) c ² y ² ] ^1/2 ] + A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰ + A12y ¹² ...
(Where c is the curvature (1 / r), y is the height from the optical axis, K is the conic coefficient, A4, A6, A8
, ... is the aspheric coefficient of each order, x is the sag amount)

[Numerical Example 1]
1 to 6 and Tables 1 to 4 show Numerical Example 1 of the zoom lens system according to the present invention. 1 is a lens configuration diagram at the time of focusing on infinity at the short focal length end, FIG. 2 is a diagram of various aberrations thereof, FIG. 3 is a lens configuration diagram of focusing at infinity at an intermediate focal length, and FIG. FIG. 5 is a lens configuration diagram at the time of focusing at infinity at the long focal length end, and FIG. 6 is a diagram showing various aberrations thereof. Table 1 shows surface data, Table 2 shows various data, Table 3 shows aspherical data, and Table 4 shows lens group data.

  The zoom lens system according to Numerical Example 1 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. And a fourth lens group G4 having a positive refractive power. An aperture stop S for adjusting the amount of light is located between the second lens group G2 and the third lens group G3 (immediately before the third lens group G3). The aperture stop S is long from the short focal length end. At the time of zooming to the focal length end, it moves in the optical axis direction integrally with the third lens group G3 (the third lens group G3 has an aperture stop S).

  The first lens group G1, in order from the object side, is a negative meniscus lens 11 convex toward the object side, a negative meniscus lens 12 convex toward the object side, a negative meniscus lens 13 convex toward the object side, and a convex toward the object side. And a positive meniscus lens 14. The negative meniscus lens 13 has two aspheric surfaces.

  The second lens group G2, in order from the object side, includes a positive meniscus lens 21 convex to the object side, a biconvex positive lens 22, a negative meniscus lens 23 convex to the object side, a biconvex positive lens 24, and a biconvex lens. And a positive lens 25. The positive meniscus lens 21 has two aspheric surfaces.

  The third lens group G3 includes a negative meniscus single lens 31 convex toward the object side.

  The fourth lens group G4 includes a biconvex positive single lens 41. The biconvex positive single lens 41 has two aspheric surfaces.

(Table 1)
Surface data surface number R d N (d) ν (d)
1 21.964 0.800 1.80139 45.5
2 14.223 1.518
3 17.291 0.800 1.80139 45.5
4 10.622 5.001
5 * 83.987 0.800 1.75501 51.2
6 * 9.555 0.800
7 12.289 2.019 1.95906 17.5
8 16.187 d8
9 * 7.518 1.952 1.51633 64.1
10 * 9.887 1.489
11 48.055 3.859 1.61340 44.3
12 -48.243 3.958
13 33.918 0.615 1.80518 25.4
14 11.438 0.516
15 13.610 2.150 1.61800 63.4
16 -566.961 0.200
17 17.139 1.973 1.72916 54.7
18 -31.054 d18
19 stops ∞ 1.000
20 15.650 0.800 1.80000 29.9
21 6.881 d21
22 * 15.901 2.082 1.61881 63.8
23 * -48.748-
(Table 2)
Various data zoom ratio (magnification ratio) 3.06
Short focal length end Intermediate focal length Long focal length end
FNO. 2.7 3.1 3.5
f 4.50 8.30 13.78
W 49.7 31.7 19.6
Y 5.00 5.00 5.00
fB 8.93 8.93 8.93
L 63.14 57.92 59.55
Entrance pupil position 12.901 13.386 15.678
d8 19.659 7.515 1.229
d18 0.800 4.026 8.711
d21 1.416 5.113 8.343
(Table 3)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8 A10
5 0.000 -0.2110E-03 0.4032E-05 -0.3230E-07 0.1078E-09
6 0.000 -0.4399E-03 0.3108E-05 -0.8983E-08 -0.2667E-09
9 0.000 0.9445E-04 0.2246E-05 -0.7455E-07
10 0.000 0.5094E-03 0.6648E-05 -0.4392E-07
22 0.000 0.1306E-03 -0.8553E-05
23 0.000 0.1889E-03 -0.1000E-04
(Table 4)
Lens group data group Start surface Focal length
1 1 -8.96
2 9 13.05
3 20 -16.00
4 22 19.62

[Numerical Example 2]
7 to 12 and Tables 5 to 8 show Numerical Example 2 of the zoom lens system according to the present invention. FIG. 7 is a lens configuration diagram when focusing on infinity at the short focal length end, FIG. 8 is a diagram showing various aberrations thereof, FIG. 9 is a lens configuration diagram when focusing on infinity at an intermediate focal length, and FIG. FIG. 11 is a lens configuration diagram at the time of focusing at infinity at the long focal length end, and FIG. 12 is a diagram showing various aberrations thereof. Table 5 shows surface data, Table 6 shows various data, Table 7 shows aspherical data, and Table 8 shows lens group data.

  The lens configuration of Numerical Example 2 is the same as the lens configuration of Numerical Example 1.

(Table 5)
Surface data surface number R d N (d) ν (d)
1 21.731 0.800 1.80139 45.5
2 12.879 2.370
3 18.749 0.800 1.80139 45.5
4 12.034 4.208
5 * 118.418 0.800 1.75501 51.2
6 * 9.692 0.800
7 12.804 2.019 1.95906 17.5
8 17.769 d8
9 * 7.304 1.952 1.51633 64.1
10 * 9.110 1.111
11 40.790 3.190 1.61340 44.3
12 -38.665 3.103
13 34.434 0.615 1.80518 25.4
14 11.532 0.542
15 14.014 3.278 1.60 300 65.5
16 -637.559 0.751
17 16.704 1.912 1.72916 54.7
18 -34.245 d18
19 stops ∞ 1.000
20 13.672 0.800 1.80000 29.9
21 6.469 d21
22 * 28.491 2.015 1.56908 71.3
23 * -17.891-
(Table 6)
Various data zoom ratio (magnification ratio) 3.10
Short focal length end Intermediate focal length Long focal length end
FNO. 2.7 3.2 3.8
f 4.50 8.29 13.95
W 49.6 31.3 19.4
Y 5.00 5.00 5.00
fB 8.99 10.46 11.91
L 63.14 56.63 60.16
Entrance pupil position 12.869 13.279 15.276
d8 20.104 7.321 1.152
d18 0.800 3.697 8.018
d21 1.183 3.088 7.013
(Table 7)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8 A10
5 0.000 -0.2352E-03 0.4168E-05 -0.3117E-07 0.1008E-09
6 0.000 -0.4724E-03 0.3953E-05 -0.1959E-07 -0.1501E-09
9 0.000 -0.7385E-05 0.1260E-05 -0.1159E-06
10 0.000 0.3949E-03 0.4418E-05 -0.7892E-07
22 0.000 0.1045E-04 -0.1123E-04
23 0.000 0.3825E-04 -0.1254E-04
(Table 8)
Lens group data group Start surface Focal length
1 1 -8.94
2 9 13.01
3 20 -16.15
4 22 19.62

[Numerical Example 3]
13 to 18 and Tables 9 to 12 show Numerical Example 3 of the zoom lens system according to the present invention. 13 is a lens configuration diagram at the time of focusing at infinity at the short focal length end, FIG. 14 is a diagram of various aberrations thereof, FIG. 15 is a lens configuration diagram at the time of focusing at infinity at an intermediate focal length, and FIG. FIG. 17 is a lens configuration diagram at the time of focusing at infinity at the long focal length end, and FIG. 18 is a diagram showing various aberrations thereof. Table 9 shows surface data, Table 10 shows various data, Table 11 shows aspherical data, and Table 12 shows lens group data.

The lens configuration of Numerical Example 3 is different from that of Numerical Examples 1 and 2 in the following points.
(1) The positive lens 22 of the second lens group G2 is a positive meniscus lens convex on the image side.

(Table 9)
Surface data surface number R d N (d) ν (d)
1 18.757 0.800 1.83481 42.7
2 10.533 2.939
3 15.899 0.800 1.75501 51.2
4 10.526 3.577
5 * 52.309 0.800 1.80139 45.5
6 * 8.920 0.800
7 12.399 2.028 1.95906 17.5
8 18.818 d8
9 * 8.675 1.952 1.51633 64.1
10 * 9.608 1.336
11 -191.886 4.206 1.63930 44.9
12 -16.135 5.863
13 72.070 0.615 1.80000 29.9
14 11.276 0.478
15 12.852 2.209 1.61800 63.4
16 -68.796 0.200
17 31.821 2.292 1.61800 63.4
18 -14.960 d18
19 stops ∞ 1.000
20 59.027 0.800 1.80 100 35.0
21 10.815 d21
22 * 14.178 1.922 1.61800 63.4
23 * -80.678-
(Table 10)
Various data zoom ratio (magnification ratio) 2.51
Short focal length end Intermediate focal length Long focal length end
FNO. 3.7 4.0 4.2
f 4.52 8.53 11.33
W 49.8 30.8 23.5
Y 5.00 5.00 5.00
fB 11.37 10.42 9.34
L 65.14 61.46 63.04
Entrance pupil position 11.939 12.703 13.849
d8 17.237 4.986 1.731
d18 0.800 5.800 8.846
d21 1.118 5.641 8.507
(Table 11)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8 A10
5 0.000 -0.1352E-03 0.3677E-05 -0.4067E-07 0.1720E-09
6 0.000 -0.3897E-03 0.1981E-05 -0.1677E-07 -0.4083E-09
9 0.000 0.7720E-04 -0.5617E-05 -0.1283E-06
10 0.000 0.4659E-03 -0.5817E-05 -0.2049E-06
22 0.000 0.1911E-03 0.3980E-05
23 0.000 0.3046E-03 0.5327E-05
(Table 12)
Lens group data group Start surface Focal length
1 1 -8.29
2 9 13.94
3 20 -16.65
4 22 19.66

[Numerical Example 4]
19 to 24 and Tables 13 to 16 show Numerical Example 4 of the zoom lens system according to the present invention. 19 is a lens configuration diagram at the time of focusing at infinity at the short focal length end, FIG. 20 is a diagram of various aberrations thereof, FIG. 21 is a lens configuration diagram at the time of focusing at infinity at an intermediate focal length, and FIG. FIG. 23 is a lens configuration diagram at the time of focusing on infinity at the long focal length end, and FIG. 24 is a diagram showing various aberrations thereof. Table 13 shows surface data, Table 14 shows various data, Table 15 shows aspheric data, and Table 16 shows lens group data.

The lens configuration of Numerical Example 4 is different from the lens configuration of Numerical Examples 1 and 2 in the following points.
(1) Both surfaces of the negative meniscus lens 12 of the first lens group G1 are aspheric surfaces (not spherical surfaces).
(2) The negative lens 13 of the first lens group G1 is a biconcave negative lens.
(3) The positive lens 22 of the second lens group G2 is a positive meniscus lens convex on the image side.
(4) The negative lens 23 of the second lens group G2 is a biconcave negative lens.

(Table 13)
Surface data surface number R d N (d) ν (d)
1 16.938 1.145 1.81600 46.6
2 12.508 2.912
3 * 21.381 0.900 1.51633 64.1
4 * 10.283 6.401
5 * -83.083 0.800 1.72903 54.0
6 * 9.594 0.100
7 11.817 1.945 1.95906 17.5
8 15.317 d8
9 * 9.526 1.952 1.51633 64.1
10 * 81.982 1.499
11 -90.072 3.678 1.54072 47.2
12 -21.809 2.966
13 -132.166 0.615 1.85026 32.3
14 10.117 0.504
15 11.773 2.419 1.57135 53.0
16 -29.117 0.234
17 15.786 1.782 1.72916 54.7
18 -43.340 d18
19 stops ∞ 1.000
20 21.088 0.800 1.80000 29.9
21 7.623 d21
22 * 13.934 2.324 1.61800 63.4
23 * -46.984-
(Table 14)
Various data zoom ratio (magnification ratio) 2.49
Short focal length end Intermediate focal length Long focal length end
FNO. 2.7 2.9 3.3
f 4.55 6.76 11.34
W 49.2 37.4 23.6
Y 5.00 5.00 5.00
fB 8.89 8.89 8.89
L 63.74 60.89 63.76
Entrance pupil position 14.850 15.227 16.824
d8 18.326 10.936 4.878
d18 0.800 3.322 7.700
d21 1.746 3.763 8.316
(Table 15)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8 A10
3 0.000 0.1022E-03 -0.5974E-06 -0.1160E-08 0.3657E-10
4 0.000 0.8584E-04 -0.1074E-05 -0.1759E-07 -0.1043E-09
5 0.000 -0.4356E-03 0.5437E-05 -0.2887E-07 0.8282E-10
6 0.000 -0.6774E-03 0.7600E-05 -0.4271E-07 0.3085E-09
9 0.000 -0.2055E-05 -0.1555E-05 0.6187E-07
10 0.000 0.2708E-03 -0.6092E-06 0.6430E-07
22 0.000 -0.4510E-04 -0.3051E-05 -0.2185E-07
23 0.000 0.4888E-04 -0.5316E-05
(Table 16)
Lens group data group Start surface Focal length
1 1 -7.73
2 9 13.05
3 20 -15.33
4 22 17.65

[Numerical Example 5]
25 to 30 and Tables 17 to 20 show Numerical Example 5 of the zoom lens system according to the present invention. 25 is a lens configuration diagram at the time of focusing on infinity at the short focal length end, FIG. 26 is a diagram of various aberrations thereof, FIG. 27 is a lens configuration diagram of focusing at infinity at an intermediate focal length, and FIG. 29 is a lens configuration diagram at the time of focusing on infinity at the long focal length end, and FIG. 30 is a diagram showing various aberrations thereof. Table 17 shows surface data, Table 18 shows various data, Table 19 shows aspherical data, and Table 20 shows lens group data.

The lens configuration of Numerical Example 5 is different from the lens configuration of Numerical Examples 1 and 2 in the following points.
(1) The first lens group G1 includes, in order from the object side, a negative meniscus lens 11 ′ convex toward the object side, a biconcave negative lens 12 ′, and a positive meniscus lens 13 ′ convex toward the object side. The biconcave negative lens 12 'has two aspheric surfaces.

(Table 17)
Surface data surface number R d N (d) ν (d)
1 23.680 0.700 1.88300 40.8
2 12.845 4.974
3 * -139.212 0.800 1.69350 53.2
4 * 9.609 0.800
5 12.310 2.121 1.95906 17.5
6 16.702 d6
7 * 8.344 1.952 1.51633 64.1
8 * 13.365 1.600
9 39.149 1.623 1.54072 47.2
10 -38.748 3.442
11 167.961 0.615 1.80518 25.4
12 10.014 0.613
13 14.216 1.836 1.59551 39.2
14 -57.365 0.200
15 12.869 2.144 1.72916 54.7
16 -39.878 d16
17 stops ∞ 1.000
18 12.871 0.800 1.85026 32.3
19 6.505 d19
20 * 19.017 2.159 1.61800 63.4
21 * -51.464-
(Table 18)
Various data zoom ratio (magnification ratio) 4.00
Short focal length end Intermediate focal length Long focal length end
FNO. 2.7 3.2 4.2
f 5.00 10.04 20.00
W 46.5 26.8 14.0
Y 5.00 5.00 5.00
fB 9.14 9.14 9.14
L 61.34 54.00 59.80
Entrance pupil position 12.804 13.316 16.528
d6 22.750 8.233 1.181
d16 0.800 4.155 8.965
d19 1.267 5.089 13.130
(Table 19)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8 A10
3 0.000 -0.1495E-03 0.4080E-05 -0.3565E-07 0.1126E-09
4 0.000 -0.3451E-03 0.3816E-05 -0.1144E-07 -0.3008E-09
7 0.000 -0.1789E-03 -0.2920E-05 -0.2117E-06
8 0.000 0.8151E-04 -0.2576E-05 -0.2511E-06
20 0.000 0.9373E-04 -0.8015E-06
21 0.000 0.1057E-03 -0.1605E-05
(Table 20)
Lens group data group Start surface Focal length
1 1 -10.50
2 7 12.72
3 18 -16.41
4 20 22.73

[Reference Example 1]
31 to 36 and Tables 21 to 24 show Reference Example 1 of the zoom lens system according to the present invention. 31 is a lens configuration diagram at the time of focusing on infinity at the short focal length end, FIG. 32 is a diagram of various aberrations thereof, FIG. 33 is a lens configuration diagram of focusing at infinity at an intermediate focal length, and FIG. FIG. 35 is a lens configuration diagram at the time of focusing at infinity at the long focal length end, and FIG. 36 is a diagram showing various aberrations thereof. Table 21 shows surface data, Table 22 shows various data, Table 23 shows aspherical data, and Table 24 shows lens group data.

The lens configuration of the reference example 1 is different from the lens configuration of the numerical examples 1 and 2 in the following points.
(1) The first lens group G1 includes, in order from the object side, a negative meniscus lens 11 ′ convex toward the object side, a biconcave negative lens 12 ′, and a positive meniscus lens 13 ′ convex toward the object side. The biconcave negative lens 12 'has two aspheric surfaces.
(2) The second lens group G2 includes, in order from the object side, a biconvex positive lens 21 ′, a biconcave negative lens 22 ′, a biconvex positive lens 23 ′, and a biconvex positive lens 24 ′. The biconvex positive lens 21 ′ has two aspheric surfaces. The biconcave negative lens 22 ′ and the biconvex positive lens 23 ′ are cemented.
(3) Between the biconvex positive lens 21 ′ and the biconcave negative lens 22 ′ of the second lens group G2, an aperture stop S for adjusting the amount of light is located, and this aperture stop S is at the short focal length end. When zooming from 1 to the long focal length end, it moves in the optical axis direction integrally with the second lens group G2 (the second lens group G2 has an aperture stop S).

(Table 21)
Surface data surface number R d N (d) ν (d)
1 14.683 0.800 1.77250 49.6
2 5.378 2.704
3 * -169.193 0.800 1.58636 60.9
4 * 10.308 0.100
5 10.485 0.800 1.80810 22.8
6 23.915 d6
7 * 6.286 2.289 1.58636 60.9
8 * -84.612 1.427
9 stop ∞ 1.268
10 -8.337 0.800 1.80610 40.7
11 5.926 1.986 1.49700 81.6
12 -7.050 0.750
13 10.169 0.856 1.72916 54.7
14 -107.271 d14
15 10.378 0.800 1.80610 40.7
16 5.867 d16
17 * 19.949 1.681 1.77377 47.2
18 * -142.776-
(Table 22)
Various data zoom ratio (magnification ratio) 2.88
Short focal length end Intermediate focal length Long focal length end
FNO. 3.5 4.3 5.8
f 6.18 10.42 17.78
W 40.3 25.5 15.3
Y 5.00 5.00 5.00
fB 9.20 9.20 9.20
L 42.60 38.95 42.62
Entrance pupil position 7.504 6.419 5.373
d6 12.842 5.052 0.716
d14 0.800 5.207 11.563
d16 2.699 2.429 4.083
(Table 23)
Aspheric data surface number K A4 A6 A8
3 0.000 -0.2323E-03 0.1472E-04 -0.4793E-06
4 0.000 -0.7375E-03 0.1172E-04 -0.6976E-06
7 0.000 -0.1539E-03 0.6526E-05 -0.4318E-06
8 0.000 0.1826E-03 0.5131E-05 -0.5228E-06
17 0.000 0.2845E-03 0.1122E-05 -0.3397E-06
18 0.000 0.2330E-03 -0.1674E-06 -0.3879E-06
(Table 24)
Lens group data group Start surface Focal length
1 1 -9.16
2 7 10.86
3 15 -18.18
4 17 22.72

[Reference Example 2]
37 to 42 and Tables 25 to 28 show Reference Example 2 of the zoom lens system according to the present invention. 37 is a lens configuration diagram at the time of focusing at infinity at the short focal length end, FIG. 38 is a diagram of various aberrations thereof, FIG. 39 is a lens configuration diagram at the time of focusing on infinity at an intermediate focal length, and FIG. 41 is a lens configuration diagram at the time of focusing on infinity at the long focal length end, and FIG. 42 is a diagram showing various aberrations thereof. Table 25 shows surface data, Table 26 shows various data, Table 27 shows aspherical data, and Table 28 shows lens group data.

The lens configuration of the reference example 2 is different from the lens configuration of the numerical examples 1 and 2 in the following points.
(1) The first lens group G1 includes, in order from the object side, a biconcave negative lens 11 ″ and a positive meniscus lens 12 ″ convex toward the object side. The biconcave negative lens 11 ″ has an aspheric image side surface.
(2) The second lens group G2 includes, in order from the object side, a biconvex positive lens 21 ″, a negative meniscus lens 22 ″ convex to the object side, a biconcave negative lens 23 ″, and a biconvex positive lens 24 ″. The biconvex positive lens 21 "has two aspheric surfaces. The biconcave negative lens 23 "and the biconvex positive lens 24" are cemented.
(3) Between the biconvex positive lens 24 ″ and the biconvex positive lens 25 ″ of the second lens group G2, an aperture stop S for adjusting the amount of light is located, and this aperture stop S is at the short focal length end. When zooming from 1 to the long focal length end, it moves in the optical axis direction integrally with the second lens group G2 (the second lens group G2 has an aperture stop S).

(Table 25)
Surface data surface number R d N (d) ν (d)
1 -43.619 0.700 1.85400 40.4
2 * 8.255 0.699
3 12.898 1.194 1.95906 17.5
4 21.669 d4
5 * 8.415 2.820 1.58313 59.5
6 * -20.124 0.100
7 35.191 0.692 1.80420 46.5
8 10.569 4.955
9 -13.064 0.800 1.65844 50.9
10 6.222 1.623 1.61800 63.4
11 -10.962 1.164
12 stops ∞ 0.800
13 12.234 1.023 1.72916 54.7
14 -40.762 d14
15 24.483 0.800 1.80000 29.9
16 7.081 d16
17 * 24.815 1.681 1.61881 63.8
18 * -51.350-
(Table 26)
Various data zoom ratio (magnification ratio) 2.85
Short focal length end Intermediate focal length Long focal length end
FNO. 2.9 4.0 5.7
f 7.46 13.02 21.24
W 35.8 21.3 13.2
Y 5.00 5.00 5.00
fB 12.19 12.19 12.19
L 49.40 46.60 53.19
Entrance pupil position 8.911 8.359 8.000
d4 16.367 6.425 1.796
d14 0.800 3.221 5.380
d16 0.996 5.718 14.772
(Table 27)
Aspheric data (Aspherical coefficient not shown is 0.00)
Surface number K A4 A6 A8
2 0.000 -0.3015E-03 -0.9221E-06 -0.3524E-07
5 0.000 -0.1125E-03 -0.4229E-06 0.2486E-06
6 0.000 0.4013E-03 -0.1434E-05 0.3173E-06
17 0.000 0.1893E-03 -0.3581E-05
18 0.000 0.2226E-03 -0.4309E-05
(Table 28)
Lens group data group Start surface Focal length
1 1 -10.87
2 5 12.05
3 15 -12.71
4 17 27.27

Table 29 shows values for the conditional expressions of Numerical Example 1-5 and Reference Example 1-2 .
(Table 29)
Example 1 Example 2 Example 3 Example 4
Conditional expression (1) -1.44 -1.44 -1.44 -1.92
Conditional expression (2) 0.24 0.24 0.24 0.29
Conditional expression (3) 0.00 0.33 -0.38 0.00
Conditional expression (4) -1.99 -1.99 -1.83 -1.70
Conditional expression (5) 2.18 1.73 2.33 1.84
Conditional expression (6) 2.30 2.31 2.87 2.22
Conditional expression (7) 1.42 1.94 1.22 1.49
Conditional expression (8) 1.28 1.27 1.37 1.20
Conditional expression (9) -1.46 -1.46 -1.68 -1.69
Conditional expression (10) -0.82 -0.82 -0.85 -0.87
Example 5 Reference Example 1 Reference Example 2
Conditional expression (1) -1.22 -0.82 -0.82
Conditional expression (2) 0.20 0.24 0.08
Conditional expression (3) 0.00 0.00 0.00
Conditional expression (4) -2.10 -1.48 -1.46
Conditional expression (5) 2.26 2.68 1.54
Conditional expression (6) 2.21 1.75 2.60
Conditional expression (7) 1.59 1.40 1.48
Conditional expression (8) 1.10 0.86 1.16
Conditional expression (9) -1.21 -1.19 -1.11
Conditional expression (10) -0.72 -0.80 -0.47

As apparent from Table 29, Numerical Example 1-5 and Reference Example 1-2 satisfy the conditional expressions (1) to (10), and the various aberrations are compared as apparent from the various aberration diagrams. Correctly corrected.

  Even if a lens or a lens group having no substantial power is added to the zoom lens system included in the scope of claims of the present invention, it is included in the technical scope of the present invention. It ’s not avoided.)

G1 first lens group 11 having negative refractive power 11 negative lens 12 negative lens 13 negative lens 14 positive lens 11 ′ negative lens 12 ′ negative lens 13 ′ positive lens 11 ″ negative lens 12 ″ positive lens G2 second lens having positive refractive power Lens group 21 Positive lens 22 Positive lens 23 Negative lens 24 Positive lens 25 Positive lens 21 'Positive lens 22' Negative lens 23 'Positive lens 24' Positive lens 21 "Positive lens 22" Negative lens 23 "Negative lens 24" Positive lens 25 ”Positive lens G3 Third lens group 31 with negative refractive power Negative single lens G4 Fourth lens group 41 with positive refractive power Positive single lens S Aperture stop I Image plane

Claims (11)

In order from the object side, the lens unit includes a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power. In zoom lens system,
Upon zooming from the short focal length end to the long focal length end, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group increases, and the third lens group At least the first lens group, the second lens group, and the third lens group move in the optical axis direction so that the interval between the fourth lens groups is increased;
The second lens group or the third lens group has an aperture stop for adjusting the amount of light, and satisfies the following conditional expressions (1 ′) , (2), and (3): Lens system.
(1 ′) −2.00 <ENw / f1 < −1.00
(2) d1G / AST <0.33
(3) −0.40 <ΔD4 / ΔD3 <0.35
However,
ENw: Distance in the optical axis direction from the lens surface closest to the object side to the entrance pupil position at the short focal length end,
f1: the focal length of the first lens group,
d1G: the thickness of the first lens group in the optical axis direction,
AST: distance in the optical axis direction from the lens surface closest to the object side to the aperture stop at the short focal length end,
ΔD4: A movement amount in the optical axis direction of the fourth lens group upon zooming from the short focal length end to the long focal length end (a movement amount toward the object side is indicated by a positive value, and a movement amount toward the image side is indicated) Negative value),
ΔD3: Amount of movement of the third lens unit in the optical axis direction during zooming from the short focal length end to the long focal length end (the amount of movement to the object side is indicated by a positive value, and the amount of movement to the image side is (Shown as negative). The zoom lens system according to claim 1, wherein the zoom lens system satisfies the following conditional expression (1 ″).
(1 ″) − 2.00 <ENw / f1 ≦ −1.22 The zoom lens system according to claim 1 or 2, wherein the zoom lens system satisfies the following conditional expression (4).
(4) -2.20 <f1 / fw <−1.40
However,
f1: the focal length of the first lens group,
fw: focal length of the entire lens system at the short focal length end. 4. The zoom lens system according to claim 1, wherein the zoom lens system satisfies the following conditional expression (5).
(5) 1.50 <(β2t / β2w) / (β3t / β3w) <2.70
However,
β2t: lateral magnification of the second lens group at the time of focusing at infinity at the long focal length end,
β2w: lateral magnification of the second lens unit at the time of focusing on infinity at the short focal length end,
β3t: lateral magnification of the third lens group at the time of focusing on infinity at the long focal length end,
β3w: lateral magnification of the third lens unit at the time of focusing at infinity at the short focal length end. The zoom lens system according to any one of claims 1 to 4, wherein the zoom lens system satisfies the following conditional expression (6).
(6) 1.70 <fbw / f12w <3.00
However,
fbw: Back focus of the entire lens system at the short focal length end,
f12w: the combined focal length of the first lens group and the second lens group at the short focal length end. The zoom lens system according to any one of claims 1 to 5 , wherein the fourth lens group includes a positive single lens, and satisfies the following conditional expression (7).
(7) 0.40 <f123t / f4 <2.00
However,
f123t: the combined focal length of the first lens group, the second lens group, and the third lens group at the long focal length end,
f4: focal length of the positive single lens in the fourth lens group. The zoom lens system according to any one of claims 1 to 6, wherein the zoom lens system satisfies the following conditional expression (8).
(8) 0.80 <d2G / f2 <1.40
However,
d2G: the thickness of the second lens group in the optical axis direction,
f2: Focal length of the second lens group. 8. The zoom lens system according to claim 1, wherein the zoom lens system satisfies the following conditional expression (9).
(9) -1.80 <f2 / f1 <-1.00
However,
f2: focal length of the second lens group,
f1: Focal length of the first lens group. 9. The zoom lens system according to claim 1 , wherein the third lens group includes a negative single lens, and the negative single lens moves to the image side during focusing from an object at infinity to a short-distance object. A zoom lens system that satisfies the following conditional expression (10):
(10) -1.30 <f3 / f4 <−0.40
However,
f3: focal length of the negative single lens of the third lens group,
f4: Focal length of the fourth lens group. 10. The zoom lens system according to claim 1 , wherein the fourth lens group is fixed with respect to the image plane when zooming from the short focal length end to the long focal length end. . 10. The zoom lens system according to claim 1 , wherein the fourth lens unit moves toward the object side or the image side with respect to the image plane upon zooming from the short focal length end to the long focal length end. Zoom lens system.

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