JP7611652B2 - Zoom lens and imaging device - Google Patents

Description

This invention relates to a zoom lens and an imaging device.

In imaging devices using solid-state imaging elements, such as digital still cameras and digital video cameras, the number of pixels in solid-state imaging elements has been increasing in recent years, and as a result, there is a demand for optical systems with even higher performance than before. In addition, as imaging devices become more compact, there is a demand for optical systems with smaller zoom lenses.

Patent Document 1 discloses a variable magnification optical system consisting of, from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, and a fifth lens group having negative refractive power, as well as a variable magnification optical system consisting of, from the object side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having negative refractive power.

JP 2019-008031 A

In the zoom lenses described in Examples 1, 4, and 6 of Patent Document 1, the refractive power of the lens group having positive refractive power is weak, so the overall length cannot be shortened, and there is a problem in that the size is insufficient.

Therefore, the objective of this invention is to provide a compact zoom lens.

In order to achieve the above object, a zoom lens according to the present invention comprises, in order from the object side, a first lens group having negative refractive power, a middle group consisting of one or more lens groups and having positive refractive power as a whole, a lens group LN having negative refractive power, and a final lens group having negative refractive power,
When changing magnification or focusing, the spacing between adjacent lens groups changes,
It is characterized in that the following conditional expression is satisfied.
-1.20 ≦ f1 / fpt ≦ -0.05 (1)
0.05 ≦ fpMax / fw ≦ 1.25 (2)
however,
f1: focal length of the first lens group fpt: focal length of the intermediate group when focusing on infinity at the telephoto end fpMax: focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group fw: focal length of the zoom lens when focusing on infinity at the wide-angle end

In order to solve the above problem, the imaging device according to the present invention is characterized by having the zoom lens and an imaging element that converts the optical image formed by the zoom lens into an electrical signal.

The present invention makes it possible to provide a compact zoom lens and imaging device.

FIG. 2 is a cross-sectional view of a zoom lens according to a first embodiment of the present invention. 5A to 5C are aberration diagrams at the wide-angle end of the zoom lens of Reference Example 1. 5A to 5C are aberration diagrams at an intermediate focal length position of the zoom lens of Reference Example 1. 5A to 5C are aberration diagrams at the telephoto end of the zoom lens of Reference Example 1. FIG. 11 is a cross-sectional view of a zoom lens according to a second embodiment. 11A to 11C are aberration diagrams at the wide-angle end of the zoom lens of Example 2. 11A to 11C are aberration diagrams of the zoom lens of Example 2 at a middle focal length position. 11A to 11C are aberration diagrams at the telephoto end of the zoom lens of Example 2. FIG. 11 is a cross-sectional view of a zoom lens according to a third embodiment. 11A to 11C are aberration diagrams at the wide-angle end of the zoom lens of Example 3. 11A to 11C are aberration diagrams of the zoom lens of Example 3 at a middle focal length position. 11A to 11C are aberration diagrams at the telephoto end of the zoom lens of Example 3. FIG. 11 is a cross-sectional view of a zoom lens according to a fourth embodiment. 13A to 13C are aberration diagrams at the wide-angle end of the zoom lens of Example 4. 13A to 13C are aberration diagrams of the zoom lens of Example 4 at a middle focal length position. 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 4. FIG. 13 is a cross-sectional view of a zoom lens according to a fifth embodiment. 13A to 13C are aberration diagrams at the wide-angle end of the zoom lens of Example 5. 13A to 13C are aberration diagrams of the zoom lens of Example 5 at a middle focal length position. 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 5. FIG. 13 is a cross-sectional view of a zoom lens according to a sixth embodiment. 13A to 13C are aberration diagrams at the wide-angle end of the zoom lens of Example 6. 13A to 13C are aberration diagrams of the zoom lens of Example 6 at a middle focal length position. 13A to 13C are aberration diagrams at the telephoto end of the zoom lens of Example 6. 1 is a diagram illustrating an example of a configuration of an imaging device according to an embodiment of the present invention.

The following describes an embodiment of the zoom lens and imaging device according to the present invention. However, the zoom lens and imaging device described below are one aspect of the zoom lens and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following aspects.

1. Zoom lens 1-1. Optical configuration The zoom lens is configured, in order from the object side, of a first lens group having negative refractive power, an intermediate group consisting of one or more lens groups having positive refractive power overall, a lens group LN having negative refractive power, and a final lens group having negative refractive power. By adopting such an optical configuration of a telephoto type refractive power arrangement, it is possible to make the image side of the first lens group a power arrangement with a strong telephoto tendency, and it is possible to shorten the length on the optical axis from the intermediate group to the final lens group compared to the composite focal length from the intermediate group to the final lens group.

(1) First Lens Group The first lens group is a lens group having negative refractive power, and its specific configuration is not particularly limited as long as it has at least one lens having negative refractive power. It is preferable that the first lens group has at least one lens L1p having positive refractive power. It is preferable to have at least one lens having negative refractive power together with at least one positive lens L1p, since it is easy to suppress chromatic aberration and achieve good optical performance. It is also more preferable to configure the first lens group with a lens having negative refractive power, a lens having negative refractive power, and a lens having positive refractive power, in order from the object side, since it is easy to suppress chromatic aberration and to achieve a small size.

Here, a lens group is composed of one lens or multiple adjacent lenses, and moves the same amount along the optical axis on the same trajectory when changing magnification or focusing. When a lens group is composed of multiple lenses, the distance on the optical axis between each lens included in that lens group does not change when changing magnification or focusing. Also, the distance on the optical axis between adjacent lens groups changes when changing magnification or focusing.

(2) Intermediate group The intermediate group is a group having positive refractive power as a whole, and as long as it has one or more lens groups having positive refractive power, its specific configuration is not particularly limited. The intermediate group may have two or more lens groups having positive refractive power, or may have one or more lens groups having positive refractive power and one or more lens groups having negative refractive power. In addition, it is preferable that the intermediate group has a cemented lens of a lens having positive refractive power and a lens having negative refractive power, since it is easy to suppress chromatic aberration and to suppress the sensitivity of each lens. In addition, it is preferable that the lens group having the strongest refractive power among the lens groups in the intermediate group has at least one lens LpMp having positive refractive power. In addition, it is more preferable that the lens closest to the image side in the intermediate group has a convex shape toward the image side. By having this configuration, it is possible to satisfactorily correct the curvature of field, and it is easy to achieve miniaturization.

(3) Aperture Stop In the zoom lens, the arrangement of the aperture stop is not particularly limited. However, the aperture stop here refers to an aperture stop that determines the light beam diameter of the zoom lens, that is, an aperture stop that determines the Fno of the zoom lens. However, it is preferable to arrange the aperture stop closer to the image side than the first lens group, particularly in the intermediate group, in order to miniaturize the aperture unit. Furthermore, when the intermediate group includes a lens group having a negative refractive power, it is preferable to arrange the aperture stop closer to the object side than the lens group having the negative refractive power. In order to cancel the negative distortion and negative curvature of field that occur in the first lens group, it is sufficient to generate aberrations in the same direction before and after the aperture stop. Therefore, by arranging the aperture stop closer to the image side than the first lens group and closer to the object side than the lens group having a negative refractive power in the intermediate group, aberrations before and after the aperture stop can be efficiently canceled out, which is preferable in obtaining a zoom lens with high optical performance.

(4) Lens group LN
The lens group LN is a lens group having a negative refractive power, and the specific configuration is not particularly limited as long as it has at least one lens having a negative refractive power. In addition, it is preferable that the lens group LN has at least one lens having a positive refractive power, since it is easy to suppress chromatic aberration and achieve good optical performance. In addition, it is more preferable that the shape of the lens having a negative refractive power in the lens group LN is a concave shape on the image side, which makes it easy to correct the curvature of field and achieve miniaturization. It is even more preferable that it is a biconcave shape, which makes it easy to achieve miniaturization.

(5) Final lens group The final lens group is a lens group having negative refractive power, and its specific configuration is not particularly limited as long as it has at least one lens having negative refractive power. In addition, it is preferable that the final lens group has at least one lens having positive refractive power, since it is easy to suppress chromatic aberration and achieve good optical performance. In addition, it is preferable that the final lens group has a lens LnL having negative refractive power on the most image side, since it is easy to suppress distortion aberration and coma aberration and achieve good optical performance.

1-2. Operation (1) Varying Magnification The zoom lens employs the above-described configuration, and varies magnification by changing the distances on the optical axis between the first lens group, an intermediate group consisting of one or more lens groups, the lens group LN, and the final lens group. By moving each lens group in this manner, it becomes easy to obtain good optical performance over the entire range of magnification without forcibly increasing the power of each lens group.

In addition, by adopting the above configuration and making the final lens group and at least one other lens group follow the same path during magnification change, it is possible to simplify the mechanical structure, making it easier to miniaturize the entire zoom lens.

(2) Focusing In the zoom lens, it is preferable that the lens group LN moves along the optical axis toward the object side when focusing from infinity to a close distance. The lens group LN is disposed closer to the image side than the intermediate group, and the fluctuation in the angle of incidence of light is small, making it easy to suppress fluctuations in the angle of view when focusing.

1-3. Conditional Expressions It is desirable that the zoom lens has the above-mentioned configuration and satisfies at least one of the following conditional expressions.

1-3-1. Conditional expression (1)
-1.20 ≦ f1/fpt ≦ -0.05 (1)
however,
f1: focal length of the first lens group fpt: focal length of the middle lens group when focusing at infinity at the telephoto end

The above conditional formula (1) specifies the ratio between the focal length of the first lens group and the composite focal length of the middle group at the telephoto end. By satisfying conditional formula (1), the angle of view at the wide-angle end can be widened, and aberration fluctuations during zooming can be suppressed. In other words, it is easy to realize a zoom lens that has a wide angle of view at the wide-angle end and high optical performance.

On the other hand, when the value of conditional formula (1) is less than the lower limit, the refractive power of the first lens group may be too weak relative to the refractive power of the intermediate group, or the refractive power of the intermediate group may be too strong relative to the refractive power of the first lens group. When the refractive power of the first lens group is relatively weak, in order to achieve a wide angle of view at the wide-angle end, it is necessary to arrange lenses with a large lens diameter, particularly on the object side, among the lenses constituting the first lens group, and it becomes difficult to achieve a compact size in the radial direction.

Furthermore, if the refractive power of the intermediate group becomes relatively weak, the overall optical length of the zoom lens must be increased. For these reasons, if the value of conditional expression (1) is below the lower limit, it is difficult to realize a small zoom lens with high optical performance, which is undesirable. On the other hand, if the value of conditional expression (1) exceeds the upper limit, the refractive power of the first lens group becomes too strong relative to the refractive power of the intermediate group. In this case, it becomes difficult to correct coma aberration and distortion aberration, making it difficult to realize a zoom lens with high optical performance.

To obtain the above effect, the lower limit of conditional formula (1) is preferably -1.15, more preferably -1.10, and even more preferably -1.05. The upper limit of conditional formula (1) is preferably -0.10, more preferably -0.15, and even more preferably -0.20. When adopting these preferred lower or upper limits, the inequality sign with equality (≦) in conditional formula (1) may be replaced with an inequality sign (<). The same principle applies to the other conditional formulas.

1-3-2. Conditional expression (2)
0.05 ≦ fpMax/fw ≦ 1.25 (2)
however,
fpMax: focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group fw: focal length of the zoom lens at the wide-angle end when focusing on infinity

The above conditional formula (2) specifies the ratio of the focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group to the focal length of the zoom lens at the wide-angle end. By satisfying conditional formula (2), it is possible to achieve a power arrangement with a stronger telephoto tendency, making it easier to shorten the overall optical length.

On the other hand, if the value of conditional expression (2) is less than the lower limit, the refractive power of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group will be too strong, making it difficult to correct spherical aberration, which is undesirable. On the other hand, if the value of conditional expression (2) exceeds the upper limit, the overall length will be too long, making it difficult to reduce the size of the entire zoom lens.

To obtain the above effect, the lower limit of conditional formula (2) is preferably 0.10, more preferably 0.15, and even more preferably 0.25. The upper limit of conditional formula (2) is preferably 1.25, more preferably 1.20, even more preferably 1.15, and even more preferably 1.05.

1-3-3. Conditional expression (3)
-3.00 ≦ f1/fw ≦ -1.00 (3)
however,
f1: focal length of the first lens group fw: focal length of the zoom lens at the wide-angle end when focused on infinity

The above conditional expression (3) specifies the ratio between the focal length of the first lens group and the focal length of the zoom lens when focused on infinity at the wide-angle end. By satisfying conditional expression (3), the angle of view can be widened at the wide-angle end state, making it easier to suppress aberration fluctuations when changing magnification. In other words, it is easy to realize a zoom lens that has a wide angle of view at the wide-angle end, is compact, and has high optical performance.

On the other hand, if the value of conditional expression (3) is below the lower limit, then in order to achieve a wide angle of view at the wide-angle end, it is necessary to place a lens with a large lens diameter, particularly on the object side, among the lenses constituting the first lens group, making it difficult to achieve a compact size in the radial direction. On the other hand, if the value of conditional expression (3) exceeds the upper limit, the refractive power of the first lens group becomes too strong, making it difficult to correct coma aberration and distortion aberration, and making it difficult to compact a zoom lens with high optical performance.

To obtain the above effect, the lower limit of conditional formula (3) is preferably -2.90, more preferably -2.80, and even more preferably -2.70. The upper limit of conditional formula (3) is preferably -1.10, more preferably -1.15, and even more preferably -1.20.

1-3-4. Conditional expression (4)
-1.50 ≦ fn1/ft ≦ -0.05 (4)
however,
fn1: focal length of the lens group LN ft: focal length of the zoom lens at the telephoto end when focused on infinity

The above conditional expression (4) specifies the ratio of the focal length of the lens group LN to the focal length of the zoom lens at the telephoto end when focusing on infinity. By satisfying conditional expression (4), it is possible to achieve a power arrangement with a strong telephoto tendency, making it easier to shorten the overall optical length.

On the other hand, if the value of conditional expression (4) is less than the lower limit, the overall length becomes too long, making it difficult to reduce the size. On the other hand, if the value of conditional expression (4) exceeds the upper limit, the refractive power of the lens group LN becomes too strong, making it difficult to correct distortion and coma.

To obtain the above effect, the lower limit of conditional formula (4) is preferably -1.45, and more preferably -1.35. The upper limit of conditional formula (4) is preferably -0.10, and more preferably -0.15, and even more preferably -0.20.

1-3-5. Conditional expression (5)
0.05 ≦ frt/ft ≦ 1.50 (5)
however,
frt: composite focal length from the middle lens group to the final lens group when focusing on infinity at the telephoto end ft: focal length of the zoom lens when focusing on infinity at the telephoto end

The above conditional expression (5) specifies the composite focal length from the middle group to the final lens group when focusing on infinity at the telephoto end, and the focal length of the zoom lens when focusing on infinity at the telephoto end. Satisfying conditional expression (5) makes it easy to achieve both compactness and optical performance of the zoom lens.

On the other hand, if the value of conditional expression (5) is below the lower limit, it becomes difficult to correct distortion, coma, and spherical aberration. On the other hand, if the value of conditional expression (5) exceeds the upper limit, the lens on the object side in the first lens group becomes large in diameter, making it difficult to achieve compact size.

To obtain the above effect, the lower limit of conditional formula (5) is preferably 0.10, more preferably 0.15, and even more preferably 0.20. The upper limit of conditional formula (5) is preferably 1.45, more preferably 1.40, and even more preferably 1.35.

1-3-6. Conditional formula (6)
-1.50 ≦ fn12/ft ≦ -0.05 (6)
however,
fn12: composite focal length from the lens group LN to the final lens group when focusing on infinity at the telephoto end ft: focal length of the zoom lens when focusing on infinity at the telephoto end

The above conditional expression (6) is a conditional expression for defining the ratio of the composite focal length from the lens group LN to the final lens group when focusing on infinity at the telephoto end to the focal length of the zoom lens when focusing on infinity at the telephoto end. By satisfying the conditional expression, it is possible to have a power arrangement with a strong telephoto tendency, and it becomes easier to shorten the overall optical length.

On the other hand, if the value of conditional expression (6) is less than the lower limit, the total optical length becomes long, making it difficult to achieve compact size. On the other hand, if the value of conditional expression (6) exceeds the upper limit, the refractive power of the final lens group becomes too strong, making it difficult to correct distortion and coma.

To obtain the above effect, the lower limit of conditional formula (6) is preferably -1.40, and more preferably -1.35. The upper limit of conditional formula (6) is preferably -0.10, and more preferably -0.15, and even more preferably -0.20.

1-3-7. Conditional expression (7)
1.00 ≦ βn1 ≦ 5.00 (7)
however,
βn1: lateral magnification of the lens unit LN when focusing on infinity at the wide-angle end

The above conditional expression (7) is a conditional expression for defining the lateral magnification of the lens group LN when focusing on infinity at the wide-angle end. By satisfying conditional expression (7), it becomes easier to achieve high optical performance throughout the entire zoom range and to shorten the overall optical length.

On the other hand, if the value of conditional expression (7) is less than the lower limit, the amount of movement of the lens group LN during zooming from the wide-angle end to the telephoto end becomes too large, resulting in an increase in overall length and making it difficult to achieve compact size. On the other hand, if the value of conditional expression (7) exceeds the upper limit, the lateral magnification of the lens group LN becomes too high, making it difficult to correct distortion and curvature of field.

In order to obtain the above effect, the lower limit of conditional formula (7) is preferably 1.10, and more preferably 1.20. The upper limit of conditional formula (7) is preferably 4.90, and more preferably 4.80, and even more preferably 4.70.

1-3-8. Conditional expression (8)
1.00 ≦ βn12 ≦ 5.00 (8)
however,
βn12: composite lateral magnification from the lens unit LN to the final lens unit when focusing on infinity at the wide-angle end

The above conditional expression (8) is a conditional expression for defining the composite lateral magnification from the lens group LN to the final lens group when focusing on infinity at the wide-angle end. By satisfying conditional expression (8), it becomes easier to achieve high optical performance throughout the entire zoom range and to shorten the overall optical length.

On the other hand, if the value of conditional expression (8) is less than the lower limit, the amount of movement of the lens group LN during zooming from the wide-angle end to the telephoto end becomes too large, resulting in an increase in overall length and making it difficult to achieve compact size. On the other hand, if the value of conditional expression (8) exceeds the upper limit, the lateral magnification of the lens group LN becomes too high, making it difficult to correct distortion and curvature of field.

In order to obtain the above effect, the lower limit of conditional formula (8) is preferably 1.10, and more preferably 1.20. The upper limit of conditional formula (8) is preferably 4.90, and more preferably 4.80, and even more preferably 4.70.

1-3-9. Conditional formula (9)
1.0≦|{1-(βn1×βn1)}×(βn2×βn2)|≦15.0...(9)
however,
βn1: lateral magnification of the lens group LN when focusing on infinity at the wide-angle end βn2: lateral magnification of the final lens group when focusing on infinity at the wide-angle end

The above conditional expression (9) is an expression for defining the absolute value of the focus sensitivity of the lens group LN that moves on the optical axis during focusing, that is, the amount of movement of the image plane when the lens group LN moves by a unit amount.
By satisfying conditional expression (9), it is possible to reduce the amount of focus movement required when focusing from infinity to a close distance, and it becomes easy to shorten the overall optical length.

On the other hand, if the value of conditional expression (9) is less than the lower limit, the amount of movement when focusing from infinity to a close distance becomes large, making it difficult to reduce the overall optical length. On the other hand, if the value of conditional expression (9) exceeds the upper limit, the amount of movement of the lens group LN for correcting the positional deviation of the focal position becomes too small, making it difficult to achieve high-precision control.

In order to obtain the above effect, the lower limit of conditional formula (9) is preferably 1.20, and more preferably 1.30. The upper limit of conditional formula (9) is preferably 14.0, and more preferably 13.0, and even more preferably 12.0.

1-3-10. Conditional expression (10)
1.00≦｜CrG1r/fw｜・・・・・・(10)
however,
CrG1r: radius of curvature of the surface of the first lens group closest to the image side fw: focal length of the zoom lens at the wide-angle end when focused on infinity

The above conditional expression (10) is a conditional expression for defining the ratio of the radius of curvature of the surface of the first lens group closest to the image side to the focal length of the zoom lens at the wide-angle end when focusing on infinity. By satisfying conditional expression (10), it becomes easy to correct spherical aberration and curvature of field, and to achieve compactness while achieving high performance.

On the other hand, if the value of conditional expression (10) is less than the lower limit, the field curvature will be overcorrected, and the lens on the object side in the first lens group will have a large diameter, making it difficult to achieve compact size.

To obtain the above effect, the lower limit of conditional formula (10) is preferably 1.10, more preferably 1.20, and even more preferably 1.30.

1-3-11. Conditional formula (11)
0.65 ≦ (fw×tanω)/BFw ≦ 2.30 (11)
however,
fw: focal length of the zoom lens at the wide-angle end when focusing on infinity; ω: half angle of view of the zoom lens at the wide-angle end when focusing on infinity; BFw: air equivalent length on the optical axis from the surface closest to the image side to the image plane at the wide-angle end when focusing on infinity

The above conditional expression (11) is a conditional expression that specifies the half angle of view when the zoom lens is focused on infinity at the wide-angle end and the air-equivalent length on the optical axis from the surface closest to the image side to the image plane. By satisfying conditional expression (11), it is possible to achieve high optical performance throughout the entire zoom range, and it is also easy to shorten the overall optical length.

On the other hand, if the value of conditional expression (11) is less than the lower limit, the angle of incidence of the off-axis light rays on the image plane must be increased. This requires the focal length of the final lens group to be reduced, making it difficult to correct coma and distortion. Alternatively, the lens diameter of the final lens group must be increased, making it difficult to achieve compact size. On the other hand, if the value of conditional expression (11) exceeds the upper limit, the overall length becomes too long, making it difficult to achieve compact size.

To obtain the above effect, the lower limit of conditional formula (11) is preferably 0.70, more preferably 0.75, even more preferably 0.85, and even more preferably 0.90. The upper limit of conditional formula (11) is more preferably 2.10, even more preferably 2.00, even more preferably 1.90, and even more preferably 1.80.

1-3-12. Conditional formula (12)
45.0 ≦ νdLpMp ≦ 98.0 (12)
however,
νdLpMp: Abbe number at d line of lens LpMp included in lens unit LpMax having the strongest positive refractive power in the intermediate group

The above conditional expression (12) is an expression for defining the Abbe number at the d-line of the lens LpMp included in the lens group LpMax that has the strongest positive refractive power in the intermediate group. By satisfying conditional expression (12), it becomes easy to achieve both axial chromatic aberration and spherical aberration.

On the other hand, if the value of conditional expression (12) is below the lower limit, it becomes difficult to correct axial chromatic aberration. On the other hand, if the value of conditional expression (12) exceeds the upper limit, the lens becomes expensive, which is not desirable from the perspective of cost reduction.

In order to obtain the above effect, the lower limit of conditional formula (12) is preferably 50.0, and more preferably 60.0. The upper limit of conditional formula (12) is preferably 95.0, and more preferably 90.0, and even more preferably 85.0.

1-3-13. Conditional formula (13)
20.0 ≦ νdL1p ≦ 50.0 (13)
however,
νdL1p: Abbe number at d line of lens L1p

The above conditional formula (13) is a formula for defining the Abbe number at the d-line of at least one lens L1p having positive refractive power included in the first lens group. By satisfying conditional formula (13), it becomes easy to achieve low costs while ensuring good image surface quality.

On the other hand, if the value of conditional formula (13) is below the lower limit, it becomes difficult to reduce costs because low-dispersion glass is expensive. On the other hand, if the value of conditional formula (13) is above the upper limit, it becomes difficult to reduce costs because high-dispersion glass is expensive.

To obtain the above effect, the lower limit of conditional formula (13) is preferably 23.0, more preferably 26.0, and even more preferably 29.0. The upper limit of conditional formula (13) is preferably 47.0, more preferably 44.0, and even more preferably 41.0.

1-3-14. Conditional formula (14)
1.70 ≦ NdL1p ≦ 2.20 (14)
however,
NdL1p: refractive index of lens L1p at d line

The above conditional expression (14) is an expression for defining the refractive index at the d-line of the lens L1p, which is included in at least one of the first lens group and has positive refractive power. By satisfying conditional expression (14), it becomes easy to achieve low costs while ensuring good image surface characteristics.

On the other hand, if the value of conditional formula (14) is below the lower limit, it becomes difficult to reduce costs because low-refractive-index glass is expensive. On the other hand, if the value of conditional formula (14) exceeds the upper limit, it becomes difficult to reduce costs because high-refractive-index glass is expensive.

In order to obtain the above effect, the lower limit of conditional formula (14) is preferably 1.75, more preferably 1.80, and even more preferably 1.85. The upper limit of conditional formula (14) is preferably 2.15, more preferably 2.10, and even more preferably 2.05.

1-3-15. Conditional formula (15)
-3.00 ≦ fLnL/ft ≦ -0.05 (15)
however,
fLnL: focal length of lens LnL ft: focal length of the zoom lens at the telephoto end when focused on infinity

The above conditional expression (15) is a conditional expression for defining the ratio of the focal length of the lens LnL arranged closest to the image side in the final lens group to the focal length of the zoom lens when focused on infinity at the telephoto end. By satisfying conditional expression (15), it becomes easy to realize a compact zoom lens with a short back focus.

On the other hand, if the value of conditional expression (15) is less than the lower limit, the height from the optical axis of the marginal rays passing through the lens LnL becomes large, which makes it difficult to reduce the size of the lens. On the other hand, if the value of conditional expression (15) exceeds the upper limit, the refractive power of the lens LnL becomes too strong, making it difficult to correct distortion and coma.

To obtain the above effect, the lower limit of conditional formula (15) is preferably -2.90, more preferably -2.80, and even more preferably -2.70. The upper limit of conditional formula (15) is preferably -0.10, more preferably -0.15, and even more preferably -0.20.

1-3-16. Conditional formula (16)
|BFt-BFw|/TLw ≦ 0.30 (16)
however,
BFw: Air-equivalent length on the optical axis from the surface closest to the image side to the image plane when focusing on infinity at the wide-angle end of the zoom lens. BFt: Air-equivalent length on the optical axis from the surface closest to the image side to the image plane when focusing on infinity at the telephoto end of the zoom lens. TLw: Total optical length of the zoom lens when focusing on infinity at the wide-angle end.

The above conditional formula (16) is a conditional formula for regulating the amount of movement of the final lens group toward the object side when changing magnification from the wide-angle end to the telephoto end. Here, the total optical length refers to the total length on the optical axis from the lens closest to the object side among the lenses constituting the zoom lens to the image plane, and is a numerical value including the cover glass and IR cut filter etc. that are located in between. By satisfying conditional formula (16), the refractive power of the final lens group is appropriate, and the amount of movement during magnification change is within an appropriate range. Therefore, it becomes easy to shorten the total optical length at the telephoto end while maintaining a predetermined magnification ratio.

On the other hand, if the value of conditional expression (16) exceeds the upper limit, the above-mentioned movement amount of the final lens group during zooming increases. In this case, if the lens barrel has a nested structure in which the inner barrel portion is housed in the outer barrel portion, designing the lens barrel length to match the overall optical length at the wide-angle end would require the inner barrel portion to be housed in two parts in the outer barrel, complicating the lens barrel structure and increasing the outer diameter of the lens barrel, making it difficult to reduce the size.

To obtain the above effect, the upper limit value of conditional formula (16) is preferably 0.27, more preferably 0.21, and even more preferably 0.18.

1-3-17. Conditional formula (17)
-0.50 ≦ fpMax/f1 ≦ -0.05 (17)
however,
fpMax: focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group f1: focal length of the first lens group

The above conditional expression (17) specifies the ratio between the focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group and the focal length of the first lens group. By satisfying conditional expression (17), it is possible to enhance the variable magnification effect of the lens group LpMax. It is also possible to shorten the amount of movement of each lens group during magnification, making it easier to achieve a shorter overall optical length.

On the other hand, when the value of conditional expression (17) is less than the lower limit, the refractive power of the first lens group becomes too strong relative to the refractive power of the lens group LpMax, or the refractive power of the lens group LpMax becomes too weak relative to the refractive power of the first lens group. When the refractive power of the lens group LpMax becomes relatively weak, it is necessary to increase the total optical length of the zoom lens. When the refractive power of the first lens group becomes relatively weak, in order to achieve a wide angle of view at the wide-angle end, it is necessary to arrange lenses with a large lens diameter, particularly on the object side, among the lenses constituting the first lens group, and it becomes difficult to achieve a compact size in the radial direction. On the other hand, when the value of conditional expression (17) exceeds the upper limit, the refractive power of the lens group LpMax becomes too strong relative to the refractive power of the first lens group. In this case, it becomes difficult to correct spherical aberration, and it becomes difficult to realize a zoom lens with high optical performance.

To obtain the above effect, the lower limit of conditional formula (17) is preferably -0.48, more preferably -0.46, and even more preferably -0.44. The upper limit of conditional formula (17) is preferably -0.10, more preferably -0.15, and even more preferably -0.20.

1-3-18. Conditional formula (18)
0.40 ≦ fpt/ft ≦ 2.00 (18)
however,
fpt: focal length of the middle group at the telephoto end ft: focal length of the zoom lens at the telephoto end when focused on infinity

The above conditional expression (18) specifies the ratio between the focal length of the middle group at the telephoto end and the focal length of the zoom lens when focused on infinity at the telephoto end. By satisfying conditional expression (18), it is possible to achieve a power arrangement with a strong telephoto tendency, making it easier to shorten the overall optical length.

On the other hand, if the value of conditional expression (18) is less than the lower limit, the refractive power of the middle group becomes too strong, making it difficult to correct spherical aberration, which is undesirable. On the other hand, if the value of conditional expression (18) exceeds the upper limit, the overall length becomes too long, making it difficult to achieve compact size.

To obtain the above effect, the lower limit of conditional formula (18) is preferably -0.45, more preferably -0.50, and even more preferably -0.65. The upper limit of conditional formula (18) is preferably 1.90, more preferably 1.80, even more preferably 1.70, and even more preferably 1.50.

1-3-19. Conditional formula (19)
-1.35 ≦ fn1/fpt ≦ -0.05 (19)
however,
fpt: focal length of the intermediate group at the telephoto end fn1: focal length of the lens group LN

The above conditional expression (19) specifies the ratio between the focal length of the lens group LN and the focal length of the intermediate group at the telephoto end. By satisfying conditional expression (19), it is possible to achieve a power arrangement with a strong telephoto tendency, making it easier to achieve a shorter overall optical length.

On the other hand, if the value of conditional expression (19) is less than the lower limit, the refractive power of the lens group LN becomes too strong, making it difficult to correct distortion and coma, which is undesirable. Also, the height of the peripheral rays in the final lens group, which is located on the image side of the lens group LN, becomes high. Furthermore, the final lens group will have a lens with a large lens diameter located on the image side, making it difficult to achieve a compact size in the radial direction. On the other hand, if the value of conditional expression (19) exceeds the upper limit, the overall length will become too long, making it difficult to achieve a compact size.

To obtain the above effect, the lower limit of conditional formula (19) is preferably -1.30, more preferably -1.25, and even more preferably -0.65. The upper limit of conditional formula (19) is preferably -0.10, more preferably -0.15, and even more preferably -0.20.

2. Imaging Device Next, an imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the zoom lens according to the present invention and an imaging element that converts an optical image formed by the zoom lens into an electrical signal. It is preferable that the imaging element is provided on the image side of the zoom lens.

Here, the imaging element is not particularly limited, and solid-state imaging elements such as a CCD (Charge Coupled Device) sensor and a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging elements, such as digital cameras and video cameras. The imaging device can be applied to various imaging devices, such as single-lens reflex cameras, mirrorless single-lens cameras, digital still cameras, surveillance cameras, car-mounted cameras, and drone-mounted cameras. These imaging devices may be lens-interchangeable imaging devices, or lens-fixed imaging devices in which the lens is fixed to the housing. In particular, the zoom lens according to the present invention is suitable for use as a zoom lens in an imaging device equipped with a large-sized imaging element such as a full-size. The zoom lens is small and lightweight overall, and has high optical performance, so that high-quality images can be obtained even when used as a zoom lens for such imaging devices.

Figure 25 is a diagram showing a schematic example of the configuration of an imaging device 1. The camera 2 has a detachable zoom lens 3, an imaging element 21 (CCD sensor or CMOS sensor) arranged on the imaging plane IP of the zoom lens 3, and a cover glass 22 arranged on the object side of the imaging element 21. The zoom lens 3 has an aperture stop 31.

Next, the present invention will be specifically described with reference to Reference Examples and Examples, but the present invention is not limited to the following Examples.
[Reference Example 1 ]

1 is a cross-sectional view of a zoom lens according to Reference Example 1 of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 first moves toward the image side and then moves toward the object side, the second lens group G2 moves toward the object side, the third lens group G3 does not move and remains fixed, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 moves toward the object side. Also, when zooming, the fourth lens group G4 and the sixth lens group G6 move on the same orbit.

When focusing from an object at infinity to a close object, the fifth lens group G5 moves from the object side to the image side along the optical axis.

The aperture stop S is located adjacent to the object side of the third lens group G3.

In this reference example , the intermediate group refers to a group consisting of the second lens group G2, the third lens group G3, and the fourth lens group G4, the lens group LpMax refers to the fourth lens group G4, the lens group LN refers to the fifth lens group G5, and the final lens group refers to the sixth lens group G6. The fourth lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L101 with a convex shape facing the object side, a biconcave lens L102, and a positive meniscus lens L103 with a convex shape facing the object side and aspheric surfaces on both sides.

The second lens group G2 is composed of, from the object side, a biconvex lens L104 having aspheric surfaces on both sides, a negative meniscus lens L105 with a concave shape facing the object side, and a biconvex lens L106.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a biconcave lens L107 having an aspheric surface on the object side, a biconvex lens L108, and a biconcave lens L109.

The fourth lens group G4 is composed of, from the object side, a biconvex lens L110, a biconvex lens L111, and a biconvex lens L112 having aspheric surfaces on both sides.

The fifth lens group G5 is composed of, in order from the object side, a negative meniscus lens L113 with a convex shape facing the object side, and a positive meniscus lens L114 with a convex shape facing the object side and an aspheric surface on the object side.

The sixth lens group G6 is composed of, in order from the object side, a biconvex lens L115 and a negative meniscus lens L116 with a concave shape facing the object side.

In this reference example , L1p in the present application refers to the lens L103, LpMp refers to the lens L111, LnL refers to the lens L116, and CrGLf refers to the image side surface of the lens L103.

In FIG. 1, "IP" is an image plane, and more specifically, indicates the imaging surface of a solid-state imaging element such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. Also, on the object side of the image plane IP, a parallel plate with no substantial refractive power, such as a cover glass CG, is provided. Also, in FIG. 1, the reference numerals for the lenses that make up each lens group are omitted. These points are the same in the lens cross-sectional views shown in the other embodiments, so further explanation will be omitted.

(2) Numerical examples
Next, a numerical example to which specific numerical values of the zoom lens are applied will be described. The "lens data", "specification table", "variable interval", "aspheric coefficient", and "lens group data" are shown below. In addition, the values of each conditional expression (Table 1) and the numerical values used to calculate the values of each conditional expression (Table 2) are shown after Example 6.

In (Lens Data), "Surface Number" is the order of the lens surface counted from the object side, "R" is the radius of curvature of the lens surface, "D" is the lens thickness or air space on the optical axis, "Nd" is the refractive index at the d-line (wavelength λ = 587.6 nm), and "ABV" is the Abbe number at the d-line. In the "Surface Number" column, "ASP" next to the surface number indicates that the lens surface is aspheric, and "S" indicates that the surface is an aperture stop. In the "D" column, "D(6)", "D(12)", etc. indicate that the spacing on the optical axis of the lens surface is a variable spacing that changes when the magnification is changed. In the "Range of Curvature" column, "0.0000" means infinity, and that the lens surface is flat.

In the specifications table, "f" is the focal length of the zoom lens, "Fno" is the F-number, "W" is the half angle of view, "Y" is the image height, and "TL" is the total optical length. The values shown are for the wide-angle end, mid-focal length, and telephoto end, respectively.

(Variable interval) shows the values when focusing on infinity at the wide-angle end, mid-focal length, and telephoto end. The same applies to the other examples.

(Aspherical coefficient) indicates the aspherical coefficient when the aspherical shape is defined as follows, where x is the amount of displacement from the reference surface in the optical axis direction, r is the paraxial radius of curvature, H is the height from the optical axis in a direction perpendicular to the optical axis, k is the conical coefficient, and An is the n-th order aspherical coefficient. In the "Aspherical coefficient" table, "E±XX" indicates exponential notation, meaning "×10 ^±XX ."

The details in these tables are the same as those in the tables shown in the other examples, so we will not repeat the explanation below.

2, 3, and 4 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity. The longitudinal aberration diagrams shown in each diagram are, from the left side of the drawing, spherical aberration (mm), astigmatism (mm), and distortion aberration (%), respectively. In the spherical aberration diagrams, the solid line shows the spherical aberration at the d-line (wavelength 587.6 nm), the dashed line shows the spherical aberration at the F-line (wavelength 486.1 nm), and the dotted line shows the spherical aberration at the C-line (wavelength 656.3 nm). In the astigmatism diagrams, the vertical axis shows the half angle of view (ω) and the horizontal axis shows the defocus, the solid line shows the sagittal image plane (S) of the d-line, and the dashed line shows the meridional image plane (M) of the d-line. In the distortion aberration diagrams, the vertical axis shows the half angle of view (ω) and the horizontal axis shows the distortion aberration. These matters are the same in each aberration diagram shown in the other examples, so explanations will be omitted below.

(Lens data)
Surface number RD Nd ABV
1 124.1004 2.0000 1.69680 55.46
2 32.7464 10.5157
3 -346.5647 2.0000 1.49700 81.61
4 47.0039 2.8357
5 ASP 64.0822 3.9531 1.88202 37.22
6 A.S.P. 213.0728 D(6)
7 ASP 229.6363 4.0489 1.72916 54.67
8 ASP -67.1566 1.6500
9 -63.2719 1.5000 1.92286 20.88
10 -2259.4237 0.1000
11 66.3043 5.6238 1.72916 54.67
12 -76.8959 D(12)
13 S 0.0000 3.3554
14 ASP -60.0156 0.2000 1.53610 41.21
15 -62.4762 1.2000 1.70154 41.15
16 45.4814 1.6081
17 48.1506 3.6658 1.98613 16.48
18 -991.4188 4.3046
19 -34.3709 1.2000 1.78472 25.72
20 1578.8626 D(20)
21 57.1212 3.8884 1.49700 81.61
22 -625.9645 0.1000
23 32.6298 8.3899 1.49700 81.61
24 -53.2937 0.1000
25 ASP 137.3913 2.3668 1.88202 37.22
26 ASP -152.6159 D(26)
27 197.2996 1.2000 1.85883 30.00
28 32.7802 2.0643
29 ASP 40.1582 0.2000 1.53610 41.21
30 42.4092 2.2574 1.72916 54.67
31 58.5890 D(31)
32 62.1969 8.3641 1.49700 81.61
33 -31.5909 6.3018
34 -27.0088 1.5000 1.83400 37.34
35 0.0000 D(35)
36 0.0000 2.5000 1.51680 64.20
37 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 25.78 35.45 48.51
Fno 2.06 2.06 2.06
W 41.07 31.21 23.00
Y 20.61 21.63 21.63
TL 150.05 145.05 144.82

(variable interval)
Wide-angle end Mid-range Telephoto end
D(5) 1.0000 29.5878 60.1049
D(14) 40.7065 16.2511 1.0000
D(31) 0.9807 9.3356 8.9082
D(34) 30.4459 22.091 22.5184
D(37) 14.4999 32.4611 49.0997

(Aspherical coefficients)
Face number K A4 A6 A8 A10
5 -6.01225E+00 1.52917E-06 3.46595E-09 -7.48207E-12 6.68959E-15
6 5.69139E+00 -2.68169E-06 4.29674E-09 -8.47722E-12 7.09503E-15
7 0.00000E+00 -7.10488E-07 -9.43179E-10 -2.96672E-12 0.00000E+00
8 0.00000E+00 8.01634E-07 -1.01577E-09 -2.30382E-12 0.00000E+00
14 0.00000E+00 5.29970E-06 -2.26478E-09 1.47060E-12 0.00000E+00
25 0.00000E+00 -1.03549E-05 -2.65374E-09 2.20566E-10 -6.43627E-13
26 0.00000E+00 2.11307E-06 3.44455E-09 2.26640E-10 -6.86047E-13
29 0.00000E+00 -3.10161E-07 3.58551E-09 -3.63278E-11 0.00000E+00

(Lens group data)
Group Surface Number Focal Length
G1 1-6 -56.82
G2 7-12 50.68
G3 14-20 -33.56
G4 21-26 23.74
G5 27-31 -61.94
G6 32-35 -500.00

5 is a cross-sectional view of a zoom lens according to Example 2 of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 does not move and is fixed, the second lens group G2 moves toward the object side, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 moves toward the object side. Also, when zooming, the fourth lens group G4 and the sixth lens group G6 move on the same orbit.

When focusing from an object at infinity to a close object, the fifth lens group G5 moves from the object side to the image side along the optical axis.

The aperture stop S is located adjacent to the object side of the third lens group G3.

In this embodiment, the intermediate group refers to a group consisting of the second lens group G2, the third lens group G3, and the fourth lens group G4, the lens group LpMax refers to the fourth lens group G4, the lens group LN refers to the fifth lens group G5, and the final lens group refers to the sixth lens group G6. The fourth lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L201 with a convex shape toward the object side, a negative meniscus lens L202 with a convex shape toward the object side, and a positive meniscus lens L203 with a convex shape toward the object side and aspheric surfaces on both sides.

The second lens group G2 is composed of, in order from the object side, a biconvex lens L204 having aspheric surfaces on both sides, a negative meniscus lens L205 with a concave shape facing the object side, and a biconvex lens L206.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a cemented lens formed by cementing a biconcave lens L207 and a biconvex lens L208, and a biconcave lens L209 having an aspheric surface on the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens L210, a cemented lens formed by cementing a negative meniscus lens L211 with a convex shape facing the object side and a biconvex lens L212, and a biconvex lens L213 having aspheric surfaces on both sides.

The fifth lens group G5 is composed of a negative meniscus lens L214 that is convex toward the object side.

The sixth lens group G6 is composed of, in order from the object side, a biconvex lens L215 and a negative meniscus lens L216 with a concave shape facing the object side.

In this embodiment, L1p refers to lens L203, LpMp refers to lens L210, LnL refers to lens L216, and CrGLf refers to the image side surface of lens L203.

(2) Numerical Examples Next, as numerical examples to which specific numerical values of the zoom lens are applied, "Lens Data", "Specification Table", "Variable Distance", "Aspheric Coefficient", and "Lens Group Data" are shown. Also, Fig. 6, Fig. 7, and Fig. 8 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity.

(Lens data)
Surface number RD Nd ABV
1 113.2329 2.0000 1.69680 55.46
2 28.9918 14.5759
3 1100.4655 2.0000 1.49700 81.61
4 40.9545 3.8366
5 ASP 67.6631 4.9844 1.88202 37.22
6 A.S.P. 263.7182 D(6)
7 ASP 353.4183 3.5852 1.70338 56.13
8 ASP -72.9016 2.3235
9 -46.8700 1.5000 1.92286 20.88
10 -100.4699 0.1000
11 108.2828 4.7848 1.72916 54.67
12 -61.7328 D(12)
13 S 0.0000 2.6692
14 -79.9400 1.2000 1.69453 33.74
15 24.8547 3.9977 1.92286 20.88
16 -226.1765 2.8711
17 ASP -32.1322 1.2000 1.78431 29.92
18 115.3058 D(18)
19 30.3491 4.1422 1.56061 69.42
20 -488.3397 0.1000
21 64.3308 1.0000 1.92123 22.09
22 30.6549 6.0126 1.49715 81.57
23 -47.3036 0.1000
24 ASP 47.7491 3.2661 1.60787 63.65
25 ASP -150.4366 D(25)
26 1000.2287 1.2000 1.49700 81.61
27 28.9539 D(27)
28 106.6910 4.9866 1.54830 50.74
29 -45.8170 2.2484
30 -35.8488 1.5000 1.69842 55.08
31 -1854.8498 D(31)
32 0.0000 13.1500
33 0.0000 2.5000 1.51680 64.20
34 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 20.60 32.56 48.51
Fno 2.88 2.88 2.88
W 48.36 33.40 23.02
Y 19.68 21.63 21.63
TL 150.00 150.00 150.00

(variable interval)
Wide-angle end Mid-range Telephoto end
D(6) 36.5041 18.4579 2.2359
D(12) 2.0000 16.1729 28.1780
D(18) 7.0006 4.7795 2.0000
D(25) 5.8909 2.3950 2.5056
D(27) 5.6703 9.1662 9.0555
D(31) 0.1000 6.1943 13.1907

(Aspherical coefficients)
Face number K A4 A6 A8 A10
5 -2.41245E+00 1.68633E-06 1.86228E-09 -3.84080E-13 3.03302E-15
6 9.66380E+00 -1.19783E-06 8.14054E-10 3.91400E-13 3.30443E-16
7 0.00000E+00 -3.29731E-06 6.24380E-09 -1.31483E-11 0.00000E+00
8 0.00000E+00 -2.61691E-06 6.16884E-09 -1.23535E-11 0.00000E+00
17 0.00000E+00 4.93529E-06 7.76897E-09 -4.63230E-11 0.00000E+00
24 0.00000E+00 -7.39682E-06 -3.12310E-08 -1.33183E-10 5.47014E-13
25 0.00000E+00 1.16420E-05 -2.36695E-08 -1.11278E-10 7.57203E-13

(Lens group data)
Group Number Focal Length
G1 1-6 -52.16
G2 7-12 51.85
G3 14-18 -37.90
G4 19-25 23.21
G5 26-27 -60.02
G6 28-31 -866.15

9 is a cross-sectional view of a zoom lens according to a third embodiment of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a fifth lens group G5 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 first moves toward the image side and then moves toward the object side, the second lens group G2 moves toward the object side, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 moves toward the object side.

When focusing from an object at infinity to a close object, the fourth lens group G4 moves from the object side to the image side along the optical axis.

The aperture stop S is located adjacent to the object side of the third lens group G3.

In this embodiment, the intermediate group refers to a group consisting of the second lens group G2 and the third lens group G3, the lens group LpMax refers to the third lens group G3, the lens group LN refers to the fourth lens group G4, and the final lens group refers to the fifth lens group G5. The third lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of, in order from the object side, a biconcave lens L301, a negative meniscus lens L302 with a convex shape facing the object side, and a biconvex lens L303 with aspheric surfaces on both sides.

The second lens group G2 is composed of, in order from the object side, a biconvex lens L304 having aspheric surfaces on both sides, a negative meniscus lens L305 with a concave shape facing the object side, and a biconvex lens L306.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a cemented lens formed by cementing a biconcave lens L307 and a biconvex lens L308, a biconcave lens L309 having an aspheric surface on the object side, a biconvex lens L310, a cemented lens formed by cementing a negative meniscus lens L311 having a convex shape facing the object side and a biconvex lens L312, and a biconvex lens L313 having aspheric surfaces on both sides.

The fourth lens group G4 is composed of a biconcave lens L314.

The fifth lens group G5 is composed of, in order from the object side, a positive meniscus lens L315 with a concave shape facing the object side and a negative meniscus lens L316 with a concave shape facing the object side.

In this embodiment, L1p refers to lens L303, LpMp refers to lens L310, LnL refers to lens L316, and CrGLf refers to the image side surface of lens L303.

(2) Numerical Examples Next, as numerical examples to which specific numerical values of the zoom lens are applied, "Lens Data", "Specification Table", "Variable Distance", "Aspheric Coefficient", and "Lens Group Data" are shown. Also, Figs. 10, 11, and 12 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity.

(Lens data)
Surface number RD Nd ABV
1 -2236.7015 2.0000 1.69680 55.46
2 27.3449 11.7237
3 249.8646 2.0000 1.49700 81.61
4 56.2626 4.3892
5 ASP 666.8413 5.8788 1.88202 37.22
6 A.S.P. -90.7339 D(6)
7 ASP 122.9237 3.6737 1.72917 54.67
8 ASP -99.3509 3.5122
9 -34.6395 1.5000 1.92286 20.88
10 -66.3126 0.1000
11 290.8205 8.4371 1.72916 54.67
12 -41.4174 D(12)
13 S 0.0000 2.8414
14 -44.7019 1.2000 1.70085 34.48
15 29.9927 4.4622 1.92286 20.88
16 -91.2906 2.1384
17 ASP -125.1747 1.2000 1.78796 30.34
18 31.8452 5.9742
19 40.8206 4.9661 1.56823 68.35
20 -82.6639 0.1000
21 104.6105 1.0000 1.91901 23.79
22 38.6544 7.4729 1.50803 78.95
23 -27.9405 0.1000
24 ASP 237.9555 4.1714 1.63691 60.91
25 ASP -35.1031 D(25)
26 -156.7844 1.2000 1.49700 81.61
27 24.6262 D(27)
28 -240.7169 5.5480 1.63943 33.54
29 -24.7233 0.1000
30 -30.8315 1.5000 2.00100 29.13
31 -739.3576 D(31)
32 0.0000 13.1500
33 0.0000 2.5000 1.51680 64.20
34 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 20.60 29.12 38.81
Fno 2.88 2.88 2.88
W 48.36 37.03 27.97
Y 19.68 21.63 21.63
TL 150.00 144.53 146.59

(variable interval)
Wide-angle end Mid-range Telephoto end
D(6) 31.6350 12.9055 2.0000
D(12) 2.0000 13.2119 22.3626
D(25) 4.6309 3.4430 2.0000
D(27) 6.6861 7.1924 7.8817
D(31) 1.2088 3.9403 8.5061

(Aspherical coefficients)
Face number K A4 A6 A8 A10
5 1.00000E+01 9.69921E-06 -9.70199E-09 1.60672E-11 -1.36358E-14
6 -1.56748E+00 5.20654E-06 -9.88038E-09 1.29752E-11 -1.36136E-14
7 0.00000E+00 -9.03623E-06 -4.56900E-09 2.22950E-11 0.00000E+00
8 0.00000E+00 -8.12098E-06 1.98512E-09 2.01792E-11 0.00000E+00
17 0.00000E+00 -1.89534E-05 1.21170E-08 -1.05762E-10 0.00000E+00
24 0.00000E+00 -6.50834E-06 -4.31965E-08 1.99772E-10 3.36191E-14
25 0.00000E+00 8.96935E-06 -3.60234E-08 1.65609E-10 2.62714E-13

(Lens group data)
Group Number Focal Length
G1 1-6 -56.93
G2 7-12 49.69
G3 14-25 23.69
G4 26-27 -42.73
G5 28-31 -127.05

13 is a cross-sectional view of a zoom lens according to Example 4 of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves toward the object side.

When focusing from an object at infinity to a close object, the third lens group G3 moves from the object side to the image side along the optical axis.

The aperture stop S is located in the second lens group G2.

In this embodiment, the intermediate group refers to the second lens group G2, the lens group LpMax refers to the second lens group G2, the lens group LN refers to the third lens group G3, and the final lens group refers to the fourth lens group G4. The second lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L401 with a convex shape facing the object side, a biconcave lens L402 with an aspheric surface on the image side, and a positive meniscus lens L403 with a convex shape facing the object side and aspheric surfaces on both sides.

The second lens group G2 is composed of, in order from the object side, a positive meniscus lens L404 with a convex shape toward the object side, an aperture stop S, a cemented lens in which a negative meniscus lens L405 with a convex shape toward the object side and a positive meniscus lens L406 with a convex shape toward the object side are cemented together, and a biconvex lens L407 with aspheric surfaces on both sides.

The third lens group G3 is composed of a biconcave lens L408.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens L409, a negative meniscus lens L410 with a concave shape facing the object side, and a negative meniscus lens L411 with a concave shape facing the object side and aspherical surfaces on both sides.

In this embodiment, L1p refers to lens L403, LpMp refers to lens L407, LnL refers to lens L411, and CrGLf refers to the image side surface of lens L403.

(2) Numerical Examples Next, as numerical examples to which specific numerical values of the zoom lens are applied, "Lens Data", "Specification Table", "Variable Distance", "Aspheric Coefficient", and "Lens Group Data" are shown. Also, Figs. 14, 15, and 16 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity.

(Lens data)
Surface number RD Nd ABV
1 60.6706 2.0000 1.69680 55.46
2 22.0000 12.1130
3 -203.7986 2.0000 1.49700 81.61
4 ASP 21.5856 3.6638
5 ASP 32.6755 5.2332 1.88202 37.22
6 A.S.P. 61.9904 D(6)
7 37.8621 2.9348 1.72916 54.67
8 178.6874 2.3629
9 S 0.0000 3.7933
10 22.4993 1.2000 1.91124 34.42
11 12.8888 6.5006 1.57505 67.44
12 85.8581 10.0754
13 ASP 27.3823 5.7808 1.49700 81.61
14 ASP -24.7300 D(14)
15 -61.8097 1.2000 1.72916 54.67
16 34.4138 D(16)
17 375.9690 5.0605 1.68460 43.79
18 -19.8398 0.2986
19 -24.9204 1.5000 1.91082 35.25
20 -64.7824 4.3005
21 ASP -30.3891 1.5000 1.85135 40.10
22 ASP -84.9035 D(22)
23 0.0000 13.1500
24 0.0000 2.5000 1.51680 64.20
25 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 20.60 29.15 38.80
Fno 2.88 2.88 2.88
W 48.28 36.90 27.98
Y 20.03 21.59 21.63
TL 123.99 113.14 107.70

(variable interval)
Wide-angle end Mid-range Telephoto end
D(6) 30.1383 13.2308 2.0000
D(14) 2.0001 3.7100 5.9959
D(16) 3.5842 5.4743 7.4542
D(22) 0.1000 2.5597 4.0776

(Aspherical coefficients)
Face number K A4 A6 A8 A10
4 -4.07902E+00 5.20396E-05 -1.01831E-07 1.84887E-10 0.00000E+00
5 -6.79657E+00 2.83309E-05 -5.33579E-08 1.19865E-10 -1.46658E-14
6 3.44746E+00 -1.91082E-06 -1.05921E-08 5.89406E-11 -8.29321E-14
13 0.00000E+00 -2.44644E-05 -3.39046E-08 -3.44484E-10 0.00000E+00
14 0.00000E+00 5.31260E-06 -3.71272E-08 -3.31959E-10 0.00000E+00
21 0.00000E+00 -9.04175E-05 5.73366E-08 -9.26258E-11 0.00000E+00
22 0.00000E+00 -6.68157E-05 1.69679E-07 -9.20940E-11 0.00000E+00

(Lens group data)
Group Surface Number Focal Length
G1 1-6 -29.66
G2 7-14 25.13
G3 15-16 -30.16
G4 17-22 -400.01

17 is a cross-sectional view of a zoom lens according to a fifth embodiment of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 does not move and is fixed, the second lens group G2 moves toward the object side, the aperture stop S does not move and is fixed, the third lens group G3 moves toward the image side, the fourth lens group G4 does not move and is fixed, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 does not move and is fixed.

When focusing from an object at infinity to a close object, the fifth lens group G5 moves from the object side to the image side along the optical axis.

The aperture stop S is disposed independently between the second lens group G2 and the third lens group G3.

In this embodiment, the intermediate group refers to a group consisting of the second lens group G2, the third lens group G3, and the fourth lens group G4, the lens group LpMax refers to the fourth lens group G4, the lens group LN refers to the fifth lens group G5, and the final lens group refers to the sixth lens group G6. The fourth lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of, in order from the object side, a biconcave lens L501, a negative meniscus lens L502 with an aspheric surface on the image side and a convex shape on the object side, and a negative meniscus lens L503 with a convex shape on the object side.

The second lens group G2 is composed of a cemented lens in which a biconvex lens L504 and a negative meniscus lens L505 with a concave object side are cemented together, and a biconvex lens L506.

The third lens group G3 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave lens L507 and a biconvex lens L508 together, a biconcave lens L509 having an aspheric surface on the object side, and a positive meniscus lens L510 with a convex shape facing the object side.

The fourth lens group G4 is composed of, from the object side, a biconvex lens L511 having aspheric surfaces on both sides, and a cemented lens formed by cementing a biconvex lens L512 and a negative meniscus lens L513 having a concave shape facing the object side.

The fifth lens group G5 is composed of a biconcave lens L514 having aspheric surfaces on both sides.

The sixth lens group G6 is composed of, in order from the object side, a positive meniscus lens L515 with a concave shape facing the object side and a biconcave lens L516.

In this embodiment, L1p refers to lens L503, LpMp refers to lens L511, LnL refers to lens L516, and CrGLf refers to the image side surface of lens L503.

(2) Numerical Examples Next, as numerical examples to which specific numerical values of the zoom lens are applied, "Lens Data", "Specification Table", "Variable Distance", "Aspheric Coefficient", and "Lens Group Data" are shown. Also, Figs. 18, 19, and 20 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity.

(Lens data)
Surface number RD Nd ABV
1 -432.5690 2.0000 1.65534 44.20
2 44.8660 4.3979
3 83.2788 2.0000 1.49700 81.61
4 ASP 31.4343 4.4655
5 63.9196 3.1569 1.75404 28.91
6 174.6629 D(6)
7 69.3596 6.5632 1.58528 66.16
8 -56.0044 1.0000 1.92286 20.88
9 -113.4602 2.6930
10 44.5856 5.5502 1.59382 66.96
11 -681.0575 D(11)
12S 0.0000D(12)
13 -174.8844 1.0000 1.83913 35.38
14 40.7918 3.9572 1.85347 22.43
15 -47.1043 1.5540
16 ASP -24.4495 1.2000 1.91004 35.29
17 47.4411 0.3120
18 46.9147 2.0248 1.92286 20.88
19 83.1280 D(19)
20 ASP 60.2483 5.8432 1.58749 65.90
21 ASP -26.0922 0.0744
22 70.2837 6.9800 1.49700 81.61
23 -25.0067 1.0000 1.89211 21.51
24 -40.0619 D(24)
25 ASP -168.1626 1.0000 1.69260 53.24
26 ASP 76.7232 D(26)
27 -173.3234 4.3046 1.91925 23.76
28 -36.8857 0.1892
29 -48.8379 1.0000 1.75776 25.64
30 53.3950 15.9159
31 0.0000 2.5000 1.51680 64.20
32 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 28.85 46.44 72.67
Fno 2.88 2.88 2.88
W 38.14 24.64 15.79
Y 19.91 21.63 21.63
TL 140.00 140.00 140.00

(variable interval)
Wide-angle end Mid-range Telephoto end
D(6) 27.2265 14.5929 2.1783
D(11) 2.2955 14.9291 27.3436
D(12) 2.1782 6.4295 11.7481
D(19) 11.7372 7.4859 2.1673
D(24) 8.4438 5.2820 4.4632
D(26) 6.4369 9.5988 10.4176

(Aspherical coefficients)
Face number K A4 A6 A8 A10
4 0.00000E+00 -4.12067E-06 -3.05369E-09 -1.84090E-12 0.00000E+00
16 0.00000E+00 7.62098E-06 1.35010E-08 -2.35354E-11 0.00000E+00
20 0.00000E+00 -3.02504E-06 -6.95946E-09 6.02111E-12 0.00000E+00
21 0.00000E+00 1.16203E-05 -8.87540E-09 2.23704E-12 0.00000E+00
25 0.00000E+00 3.92682E-06 -4.92977E-08 1.21563E-10 0.00000E+00
26 0.00000E+00 3.84781E-06 -2.70552E-08 8.56004E-11 0.00000E+00

(Lens group data)
Group Surface Number Focal Length
G1 1-6 -55.58
G2 7-11 42.25
G3 13-19 -29.60
G4 20-24 23.24
G5 25-26 -75.94
G6 27-30 -100.00

21 is a cross-sectional view of a zoom lens according to Example 6 of the present invention at the wide-angle end and the telephoto end when focusing on infinity. The zoom lens is composed of, in order from the object side, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, and a seventh lens group G7 having negative refractive power.

When zooming from the wide-angle end to the telephoto end, the first lens group G1 does not move and is fixed, the second lens group G2 moves toward the image side, the third lens group G3 moves toward the object side, the aperture stop S does not move and is fixed, the fourth lens group G4 moves toward the image side, the fifth lens group G5 does not move and is fixed, the sixth lens group G6 moves toward the object side, and the seventh lens group G7 does not move and is fixed.

When focusing from an object at infinity to a close object, the sixth lens group G6 moves from the object side to the image side along the optical axis.

The aperture stop S is disposed independently between the third lens group G3 and the fourth lens group G4.

In this embodiment, the intermediate group refers to a group consisting of the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5, the lens group LpMax refers to the fifth lens group G5, the lens group LN refers to the sixth lens group G6, and the final lens group refers to the seventh lens group G7. The fifth lens group is the lens group with the strongest positive refractive power among the lens groups included in the intermediate group. The configuration of each lens group will be described below.

The first lens group G1 is composed of a plano-concave lens L601 whose object side is flat.

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens L602 with an aspheric surface on the image side and a convex shape toward the object side, and a positive meniscus lens L603 with a convex shape toward the object side.

The third lens group G3 is composed of a cemented lens in which a biconvex lens L604 and a negative meniscus lens L605 with a concave object side shape are cemented together, and a biconvex lens L606.

The fourth lens group G4 is composed of, in order from the object side, a cemented lens formed by cementing a biconcave lens L607 and a biconvex lens L608, a biconcave lens L609 having an aspheric surface on the object side, and a positive meniscus lens L610 with a convex shape facing the object side.

The fifth lens group G5 is composed of, from the object side, a biconvex lens L611 having aspheric surfaces on both sides, and a cemented lens formed by cementing a biconvex lens L612 and a negative meniscus lens L613 having a concave shape facing the object side.

The sixth lens group G6 is composed of, from the object side, a biconcave lens L614 having aspheric surfaces on both sides.

The seventh lens group G7 is composed of, in order from the object side, a negative meniscus lens L615 with a convex shape facing the object side.

In this embodiment, LpMp refers to lens L611, LnL refers to lens L615, and CrGLf refers to the image side surface of lens L601.

(2) Numerical Examples Next, as numerical examples to which specific numerical values of the zoom lens are applied, "Lens Data", "Specification Table", "Variable Distance", "Aspheric Coefficient", and "Lens Group Data" are shown. Also, Figs. 22, 23, and 24 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length, and the telephoto end when focusing on infinity.

(Lens data)
Surface number RD Nd ABV
1 0.0000 2.0000 1.65595 43.41
2 31.5382 D(2)
3 46.1135 2.0000 1.55440 48.77
4 ASP 28.5329 2.2812
5 41.5798 3.4352 1.91920 23.80
6 70.6455 D(6)
7 70.3251 4.5885 1.58682 65.98
8 -55.2713 1.0000 1.92286 20.88
9 -132.0319 0.0000
10 46.8701 3.7754 1.59774 66.43
11 -166.9787 D(11)
12S 0.0000D(12)
13 -70.8026 1.0000 1.80147 43.76
14 146.7866 2.5860 1.86552 22.13
15 -55.7713 2.2797
16 ASP -29.3436 0.2000 1.53610 41.21
17 -28.1516 1.0000 1.90560 35.54
18 53.1008 0.3683
19 49.9701 2.3681 1.92286 20.88
20 198.2902 D(20)
21 ASP 58.1368 5.9408 1.59805 64.69
22 ASP -26.0328 0.0000
23 47.0802 6.1303 1.49700 81.61
24 -33.4750 1.0000 1.86259 22.20
25 -90.6067 D(25)
26 ASP -55.0870 1.0000 1.59807 66.39
27 ASP 137.2913 D(27)
28 329.2435 1.0000 1.77402 44.32
29 62.5860 0.0000
30 0.0000 16.1500
31 0.0000 2.5000 1.51680 64.20
32 0.0000 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 28.84 45.11 72.75
Fno 4.12 4.12 4.12
W 38.13 25.27 15.78
Y 19.92 21.63 21.63
TL 130.00 130.00 130.00

(variable interval)
Wide-angle end Mid-range Telephoto end
D(2) 4.0563 6.0563 8.0757
D(6) 31.8607 17.6273 2.0000
D(11) 2.0000 14.2334 27.8414
D(12) 2.2673 5.6919 10.6665
D(20) 10.3992 6.9746 2.0000
D(25) 9.4245 5.2401 2.5877
D(27) 6.3885 10.5729 13.2253

(Aspherical coefficients)
No. K A4 A6 A8 A10
4 0.00000E+00 -3.61525E-06 -3.55159E-09 -6.20392E-12 0.00000E+00
16 0.00000E+00 2.80091E-06 -3.35294E-10 -1.75681E-11 0.00000E+00
21 0.00000E+00 -3.59063E-06 1.32767E-09 1.32009E-11 0.00000E+00
22 0.00000E+00 7.92222E-06 -1.41905E-09 3.59304E-11 0.00000E+00
26 0.00000E+00 -2.81203E-06 4.19731E-08 -1.27591E-10 0.00000E+00
27 0.00000E+00 -2.09918E-06 4.88511E-08 -1.25865E-10 0.00000E+00

(Lens group data)
Group Surface Number Focal Length
G1 1-2 -48.07
G2 3-6 426.48
G3 7-11 40.07
G4 13-20 -33.33
G5 21-25 24.24
G6 26-27 -65.61
G7 28-29 -100.00

[Table 1]
Conditional Expression Reference Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
Conditional expression (1) f1/fpt -1.06 -1.01 -1.10 -1.18 -0.69 -0.65
Conditional expression (2) fpMax/fw 0.92 1.13 1.15 1.22 0.81 0.84
Conditional expression (3) f1/fw -2.20 -2.53 -2.76 -1.44 -1.93 -1.67
Conditional expression (4) fn1/ft -1.28 -1.24 -1.10 -0.78 -1.05 -0.90
Conditional expression (5) frt/ft 0.86 0.97 1.30 0.64 0.50 0.43
Conditional expression (6) fn12/ft -0.91 -1.08 -0.78 -0.65 -0.55 -0.50
Conditional expression (7) βn1 1.78 1.50 1.60 2.03 1.33 1.35
Conditional expression (8) βn12 1.50 1.44 1.84 1.98 1.59 1.61
Conditional formula (9) |{1-(βn1×βn1)}×(βn2×βn2)|
1.55 1.15 2.05 2.97 1.10 1.18
Conditional expression (10) | CrG1r/fw | 8.26 12.80 4.41 3.01 6.05 1.09
Conditional expression (11) (fw×tanω)/BFw 1.42 1.46 1.36 1.45 1.22 1.20
Conditional expression (12) νdLpMp 81.61 69.42 68.35 81.61 65.90 64.69
Conditional expression (13) νdL1p 37.22 37.22 37.22 37.22 28.91 -
Conditional expression (14) NdL1p 1.88 1.88 1.88 1.88 1.75 -
Condition (15) fLnL/ft -0.67 -1.08 -0.83 -1.45 -0.46 -1.37
Conditional expression (16) |BFt-BFw|/TLw 0.03 0.09 0.05 0.03 0.00 0.00
Conditional expression (17) fpMax/f1 -0.42 -0.44 -0.42 -0.85 -0.42 -0.50
Conditional expression (18) fpt/ft 1.10 1.06 1.33 0.65 1.11 1.01
Conditional expression (19) fn1/fpt -1.06 -1.01 -1.10 -1.18 -0.69 -0.65

The zoom lens according to the present invention can be suitably used as an imaging optical system for imaging devices such as film cameras, digital still cameras, and digital video cameras.

S ... aperture stop CG ... cover glass IP ... image surface G1 ... first lens group G2 ... second lens group G3 ... third lens group G4 ... fourth lens group G5 ... fifth lens group G6 ... sixth lens group G7 ... seventh lens group (W) ... wide-angle end (T) ... telephoto end 1 ... imaging device 2 ... camera 3 ... lens 21 ... imaging element (CCD sensor or CMOS sensor)

Claims (15)

The optical system is composed of, in order from the object side, a first lens group having negative refractive power, an intermediate group consisting of one or more lens groups and having positive refractive power as a whole, a lens group LN having negative refractive power, and a final lens group having negative refractive power,
the intermediate group is composed of, in order from the object side, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, or is composed of, in order from the object side, a second lens group having positive refractive power, and a third lens group having positive refractive power,
When changing magnification, the spacing between adjacent lens groups changes,
A zoom lens characterized by satisfying the following conditional expressions:
-1.20 ≦ f1/fpt ≦ -0.05 (1)
0.05 ≦ fpMax/fw ≦ 1.25 (2)
-3.00 ≦ f1/fw ≦ -1.93 (3)
however,
f1: focal length of the first lens group fpt: focal length of the intermediate group when focusing on infinity at the telephoto end fpMax: focal length of the lens group with the strongest positive refractive power among the lens groups included in the intermediate group fw: focal length of the zoom lens when focusing on infinity at the wide-angle end 2. The zoom lens according to claim 1, which satisfies the following condition:
-1.50 ≦ fn1/ft ≦ -0.05 (4)
however,
fn1: focal length of the lens group LN ft: focal length of the zoom lens at the telephoto end when focused on infinity 3. The zoom lens according to claim 1, which satisfies the following condition:
0.05 ≦ frt/ft ≦ 1.50 (5)
however,
frt: composite focal length from the intermediate lens group to the final lens group when focusing on infinity at the telephoto end ft: focal length of the zoom lens when focusing on infinity at the telephoto end 4. The zoom lens according to claim 1, which satisfies the following condition:
-1.50 ≦ fn12/ft ≦ -0.05 (6)
however,
fn12: composite focal length from the lens group LN to the final lens group when focusing on infinity at the telephoto end ft: focal length of the zoom lens when focusing on infinity at the telephoto end 5. The zoom lens according to claim 1, which satisfies the following condition:
1.00 ≦ βn1 ≦ 5.00 (7)
however,
βn1: lateral magnification of the lens unit LN when focusing on infinity at the wide-angle end 6. The zoom lens according to claim 1, which satisfies the following condition:
1.00 ≦ βn12 ≦ 5.00 (8)
however,
βn12: composite lateral magnification from the lens unit LN to the final lens unit when focusing on infinity at the wide-angle end 7. The zoom lens according to claim 1, wherein focusing from infinity to a close object is performed by moving the lens unit LN in the optical axis direction, and the following conditional expression is satisfied:
1.0≦|{1-(βn1×βn1)}×(βn2×βn2)|≦15.0...(9)
however,
βn1: lateral magnification of the lens group LN when focusing on infinity at the wide-angle end βn2: lateral magnification of the final lens group when focusing on infinity at the wide-angle end 8. The zoom lens according to claim 1, which satisfies the following condition:
1.00≦｜CrG1r/fw｜・・・(10)
however,
CrG1r: radius of curvature of the surface of the first lens group closest to the image side 9. The zoom lens according to claim 1, which satisfies the following condition:
0.65 ≦ (fw×tanω)/BFw ≦ 2.30 (11)
however,
ω: Half angle of view when focusing on infinity at the wide-angle end of the zoom lens BFw: Air equivalent length on the optical axis from the surface closest to the image side to the image plane when focusing on infinity at the wide-angle end of the zoom lens 10. The zoom lens according to claim 1, wherein the lens group having the strongest positive refractive power among the lens groups included in the intermediate group has at least one lens LpMp having positive refractive power, and satisfies the following conditional expression:
45.0 ≦ νdLpMp ≦ 98.0 (12)
however,
νdLpMp: Abbe number at d line of the lens LpMp 11. The zoom lens according to claim 1, wherein the first lens group has at least one lens L1p having a positive refractive power, and satisfies the following condition: 1<$1 mn>1<$1mn> 1 .
20.0 ≦ νdL1p ≦ 50.0 (13)
however,
νdL1p: Abbe number at d line of the lens L1p 12. The zoom lens according to claim 1, wherein the first lens group includes at least one lens L1p having a positive refractive power, and the following conditional expression is satisfied: 1<$1 mn>1<$1mn> 1 .
1.70 ≦ NdL1p ≦ 2.20 (14)
however,
NdL1p: refractive index of the lens L1p at the d line 13. The zoom lens according to claim 1, further comprising a lens LnL having negative refractive power, the lens LnL being located closest to the image side of the final lens group, and satisfying the following conditional expression:
-3.00 ≦ fLnL/ft ≦ -0.05 (15)
however,
fLnL: focal length of the lens LnL ft: focal length of the zoom lens at the telephoto end when focused on infinity 14. The zoom lens according to claim 1, which satisfies the following condition:
|BFt-BFw|/TLw ≦ 0.30 (16)
however,
BFw: Air-equivalent length on the optical axis from the surface closest to the image side to the image plane when focusing on infinity at the wide-angle end of the zoom lens. BFt: Air-equivalent length on the optical axis from the surface closest to the image side to the image plane when focusing on infinity at the telephoto end of the zoom lens. TLw: Total optical length on the optical axis when focusing on infinity at the wide-angle end of the zoom lens. An imaging device comprising the zoom lens according to any one of claims 1 to 14, and an imaging element on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal.

Images