JP7695801B2 - Zoom lens and imaging device - Google Patents

Description

This invention relates to a zoom lens and an imaging device, and in particular to a zoom lens and an imaging device suitable for a small imaging device using a solid-state imaging element or the like.

In recent years, imaging devices using solid-state imaging elements, such as digital still cameras and digital video cameras, have become widespread. As a result, optical systems have become more compact and more powerful, and compact imaging device systems have become increasingly popular. However, it has been difficult to miniaturize the optical system while maintaining high optical performance for zoom lenses used in surveillance cameras, video cameras, digital still cameras, single-lens reflex cameras, mirrorless single-lens cameras, and other devices that require a short overall length and a compact optical system.

Therefore, Patent Document 1 proposes a zoom lens having, in order 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.

Patent No. 6040890

However, in the zoom lens having a negative-positive-negative-negative refractive power arrangement of Patent Document 1, the negative refractive power of the first lens group is weaker than the positive refractive power of the second lens group, so it is necessary to place a lens with a large lens diameter closest to the object in the first lens group, which poses the problem of insufficient miniaturization of the optical system in the radial direction.

The objective of the present invention is to provide a zoom lens and imaging device that are smaller and have higher optical performance.

In order to solve the above problems, the following invention was conceived as a result of extensive research.

The zoom lens of the present invention 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 including a lens group LpMax which has the strongest positive refractive power among the lens groups included in the intermediate group, and which performs magnification or focusing by changing the spacing between adjacent lens groups, and is characterized in that it satisfies the following conditional formula:
0.05 ≦ |f1|/|fpMax| ≦ 0.80...(1)
however,
f1: focal length of the first lens group fpMax: focal length of the lens group LpMax

The zoom lens of the present invention 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 including a lens group LpMax which has the strongest positive refractive power among the lens groups included in the intermediate group, and which performs magnification or focusing by changing the spacing between adjacent lens groups, and is characterized in that it satisfies the following conditional formula:
βpw ≦ -0.58...(2)
however,
βpw: composite lateral magnification of the intermediate group when focusing on infinity at the wide-angle end

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

The present invention makes it possible to provide a zoom lens and imaging device that are smaller and have high optical performance across the entire zoom range.

1A and 1B are cross-sectional views of a zoom lens according to a first embodiment of the present invention at the wide-angle end and the telephoto end when focused on infinity. 4A to 4C are longitudinal aberration diagrams of the zoom lens of the first embodiment when focused on infinity at the wide-angle end. 4A to 4C are longitudinal aberration diagrams of the zoom lens of Example 1 when focused on infinity in an intermediate focal length state. 4A to 4C are longitudinal aberration diagrams of the zoom lens of Example 1 when focused on an object at infinity at the telephoto end. 1 is a cross-sectional view of a zoom lens according to a second embodiment of the present invention at the wide-angle end and at the telephoto end when focused on infinity. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 2 when focused on an object at infinity at the wide-angle end. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 2 when focused on infinity in an intermediate focal length state. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 2 when focused on an object at infinity at the telephoto end. 11A and 11B are cross-sectional views of a zoom lens according to a third embodiment of the present invention at the wide-angle end and the telephoto end when focused on infinity. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 3 when focused on an object at infinity at the wide-angle end. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 3 when focused on infinity in an intermediate focal length state. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 3 when focused on an object at infinity at the telephoto end. 13A and 13B are cross-sectional views of a zoom lens according to a fourth embodiment of the present invention at the wide-angle end and the telephoto end when focused on infinity. 13A to 13C are longitudinal aberration diagrams of the zoom lens of Example 4 when focused on an object at infinity at the wide-angle end. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 4 when focused on infinity in an intermediate focal length state. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 4 when focused on an object at infinity at the telephoto end. 13A and 13B are cross-sectional views of a zoom lens according to a fifth embodiment of the present invention at the wide-angle end and at the telephoto end when focused on infinity. 13A to 13C are longitudinal aberration diagrams of the zoom lens of Example 5 when focused on an object at infinity at the wide-angle end. 13A and 13B are longitudinal aberration diagrams of the zoom lens of Example 5 when focused on infinity in an intermediate focal length state. 13A to 13C are longitudinal aberration diagrams of the zoom lens of Example 5 when focused on an object at infinity at the telephoto end.

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 of the zoom lens The zoom lens of this embodiment is configured, in order from the object side, with 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. The middle group includes a lens group LpMax, which has the strongest positive refractive power among the lens groups included in the middle group. The zoom lens is configured to perform magnification or focusing by changing the interval between adjacent lens groups.

The zoom lens has a negative refractive power in the first lens group and a positive refractive power in the intermediate group, which gives it a diverging effect on the object side and a converging effect on the image side. In this way, by adopting a so-called retrofocus configuration in the optical configuration of the zoom lens, it is possible to widen the angle of view at the wide-angle end without increasing the size of the zoom lens. In other words, the zoom lens has a power (refractive power) arrangement suitable for a wide-angle zoom lens.

In addition, in order to shorten the overall optical length of the zoom lens of this embodiment, it is preferable to adopt a so-called telephoto type refractive power arrangement. That is, it is preferable to arrange a lens group with positive refractive power on the object side and a lens group with negative refractive power on the image side. In this zoom lens, on the image side of the first lens group, in order from the object side, an intermediate group with positive refractive power as a whole, a lens group Ln with negative refractive power, and a final lens group with negative refractive power are provided. By adopting such a refractive power arrangement, it is possible to make the image side of the first lens group a power arrangement with a strong telephoto tendency. That is, the zoom lens can 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, and it is possible to shorten the overall optical length of the entire zoom lens.

The optical configuration of each lens group is explained below.

(1) First Lens Group As described above, the first lens group is disposed closest to the object among the lens groups constituting the zoom lens, and as long as it has negative refractive power, its specific lens configuration is not particularly limited. In addition, it is preferable that the first lens group has a lens L1p having positive refractive power, which is disposed closest to the image side in the group. This is because, if this lens L1p or its image-side lens surface satisfies a predetermined conditional expression described later, the lens diameter of the lens disposed closest to the object side in the group can be made smaller.

(2) Intermediate group The intermediate group is arranged closer to the image side than the first lens group, and is composed of one or more lens groups. As long as it has a positive refractive power as a whole, the specific lens groups and the configuration of the lenses in each group are not particularly limited. The intermediate group only needs to include at least one lens group having a positive refractive power in the group, and may have two or more lens groups having a positive refractive power, or may have one or more lens groups having a positive refractive power and one or more lens groups having a negative refractive power. In the present invention, the lens group having the strongest positive refractive power among the lens groups included in the intermediate group is called the lens group LpMax.

(3) Lens group Ln
The lens group Ln is arranged closer to the image side than the intermediate group and has a negative refractive power, so long as the lens group Ln has no particular limitations on its specific lens configuration. In order to operate the lens group Ln at high speed, it is preferable that the lens group Ln is a single lens having a negative refractive power. In order to correct the curvature of field, it is preferable that the lens arranged closest to the image side in the group is a meniscus lens.

(4) Final Lens Group The final lens group is disposed closest to the image among the lens groups constituting the zoom lens, and the specific lens configuration is not particularly limited as long as it has negative refractive power. In order to make the optical system compact, it is preferable that the final lens group be made up of two lenses, that is, a lens having positive refractive power and a lens having negative refractive power, in that order from the object side.

(5) Focus group In the zoom lens, the presence or absence of a focus group is not particularly limited. If the zoom lens is provided with a focus group, at least one of the lenses constituting the zoom lens is used as the focus group, and the focus group can be moved in the optical axis direction during focusing to focus on a subject. In the zoom lens, the position and refractive power of the lens used as the focus group are not particularly limited.

(6) Anti-vibration group In the zoom lens, the presence or absence of an anti-vibration group is not particularly limited. When the anti-vibration group is provided in the zoom lens, at least one of the lenses constituting the zoom lens is made into an anti-vibration group, and the anti-vibration group is moved in a direction substantially perpendicular to the optical axis to perform image shift (so-called camera shake correction), which is preferable in terms of miniaturizing the optical system, since the entire zoom lens unit including the lens barrel can be made small. Note that the zoom lens unit includes, in addition to the zoom lens, a drive mechanism (zoom drive mechanism) for relatively moving each lens group during magnification change, a drive mechanism (focus drive mechanism) for moving the focus group in the optical axis direction during focusing, and a lens barrel that accommodates these.

(7) Aperture Stop In the zoom lens, the position of the aperture stop is not particularly limited. However, the aperture stop referred to here refers to the aperture stop that determines the light beam diameter of the zoom lens, i.e., the aperture stop that determines the F-number of the zoom lens.

In this zoom lens, it is preferable to place the aperture stop closer to the image side than the first lens group in order to reduce the size of the aperture unit, and it is even more preferable to place it within the intermediate group in order to reduce the size even further.

(8) Lens Group Configuration The number of lens groups constituting the zoom lens is not particularly limited, and various lens group configurations can be adopted, such as a five-group zoom lens having a first lens group having negative refractive power, an intermediate group consisting of a second lens group having positive refractive power and a third lens group having positive refractive power, a lens group Ln consisting of a fourth lens group having negative refractive power, and a final lens group consisting of a fifth lens group having negative refractive power, a six-group zoom lens having an intermediate group consisting of 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 positive refractive power, and having positive refractive power as a whole, a lens group Ln consisting of the fifth lens group having negative refractive power, and a final lens group consisting of a sixth lens group having negative refractive power. In other words, the specific lens group configuration of the zoom lens is not particularly limited as long as it has, in order from the object side, a first lens group having negative refractive power, an intermediate group having positive refractive power, a lens group Ln having negative refractive power, and a final lens group having negative refractive power.

1-2. Operation (1) Operation during Magnification Change In this zoom lens, the interval between adjacent lens groups changes when the magnification is changed from the wide-angle end to the telephoto end.

In the zoom lens, as long as the air spacing between adjacent lens groups changes when changing magnification from the wide-angle end to the telephoto end, there are no particular limitations on the increase or decrease in the air spacing between each lens group. In addition, when changing magnification, all of the lens groups constituting the zoom lens may be moved in the optical axis direction, or some of the lens groups may be fixed in the optical axis direction and the remaining lens groups may be moved in the optical axis direction, and there are no particular limitations on whether or not each lens group moves and the direction of movement.

(2) Operation during focusing When a focus group is provided in the zoom lens, the position, refractive power, direction of movement, etc. of the focus group are not particularly limited, but it is preferable to use the lens group Ln as the focus group and move the lens group Ln toward the image side when focusing from infinity to a close object. This is because the lens group Ln is disposed closer to the image than the intermediate group, and the variation in the angle of incidence of light is small, so that the variation in the angle of view during focusing can be suppressed.

1-3. Conditional Expressions It is preferable that the zoom lens of the present invention employs the above-mentioned configuration and satisfies either the conditional expression (1) or the conditional expression (2) described below.

1-3-1. Conditional expression (1)
0.05 ≦ |f1|/|fpMax| ≦ 0.80...(1)
however,
f1: focal length of the first lens group fpMax: focal length of the lens group LpMax

The above-mentioned conditional formula (1) is a formula for defining the ratio between the focal length of the first lens group and the focal length of the lens group LpMax that has the strongest positive refractive power among the lens groups included in the intermediate group. By satisfying the conditional formula (1), it is possible to widen the angle of view at the wide-angle end, and also to suppress aberration fluctuations during zooming. In other words, by satisfying the above-mentioned conditional formula (1), it is possible 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, if the numerical value of conditional formula (1) is less than the lower limit, the power of the first lens group becomes too strong relative to the power of the intermediate group, making it difficult to correct coma aberration and distortion aberration, and making it difficult to realize a zoom lens with high optical performance, which is undesirable. On the other hand, if the numerical value of conditional formula (1) exceeds the upper limit, the power of the first lens group becomes too weak relative to the power of the intermediate group, which is undesirable. In other words, in order to achieve a wide angle of view at the wide-angle end, it becomes necessary to place the lens with the largest lens diameter closest to the object among the lenses constituting the first lens group, which is undesirable because it becomes difficult to achieve a compact size in the radial direction.

To obtain these effects, the lower limit of conditional formula (1) is preferably 0.10, more preferably 0.15, and even more preferably 0.20. The upper limit of conditional formula (1) is preferably 0.75, more preferably 0.70, and even more preferably 0.65.

1-3-2. Conditional expression (2)
βpw ≦ -0.58...(2)
however,
βpw: Composite lateral magnification of the middle group when focusing on infinity at the wide-angle end

The above-mentioned conditional formula (2) is a formula for defining the composite lateral magnification of the middle group when focusing on infinity at the wide-angle end. By satisfying conditional formula (2), the power of the first lens group can be strengthened, and the angle of view can be widened at the wide-angle end while keeping the first lens group small in the radial direction. This makes it possible to suppress aberration fluctuations during zooming. In other words, it is possible to realize a zoom lens that has a wide angle of view at the wide-angle end, is small in size, and has high optical performance.

On the other hand, if the numerical value of conditional formula (2) exceeds the upper limit, the power of the first lens group cannot be increased, and in order to achieve a wide angle of view at the wide-angle end, it is necessary to place the lens with the largest lens diameter among the lenses constituting the first lens group closest to the object, which is undesirable because it becomes difficult to achieve a compact size in the radial direction.

To obtain these effects, the upper limit value of conditional formula (2) is more preferably -0.60, even more preferably -0.62, even more preferably -0.64, and even more preferably -0.66.

It is preferable that the zoom lens of the present invention satisfies either conditional expression (1) or conditional expression (2) described above, and also satisfies at least one of the following conditional expressions.

1-3-3. Conditional expression (3)
-1.50 ≦ f1/fw ≦ -0.05 ... (3)
however,
f1: focal length of the first lens group fw: focal length of the zoom lens when focused at infinity at the wide-angle end

The above-mentioned conditional formula (3) is a formula for defining the focal length of the first lens group. By satisfying conditional formula (3), the angle of view at the wide-angle end can be made wider, and aberration fluctuations during zooming can be suppressed. In other words, a zoom lens with a wide angle of view at the wide-angle end and high optical performance can be realized.

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

To obtain these effects, the lower limit of conditional formula (3) is more preferably -1.45, even more preferably -1.40, even more preferably -1.35, even more preferably -1.30, and even more preferably -1.25. The upper limit of conditional formula (3) is more preferably -0.10, even more preferably -0.15, and even more preferably -0.20.

1-3-4. Conditional expression (4)
-4.0 ≦ fn/fpMax ≦ -1.5 ... (4)
however,
fn: focal length of lens group Ln fpMax: focal length of lens group LpMax

The above-mentioned conditional formula (4) is a formula for defining the ratio between the focal length of the lens group Ln and the focal length of the lens group LpMax. By satisfying the conditional formula (4), it is possible to achieve a high telephoto effect in the optical system on the image side of the first lens group (the optical system consisting of the intermediate group, the lens group Ln, and the final lens group), thereby realizing a reduction in the overall optical length.

On the other hand, if the numerical value of conditional expression (4) is less than the lower limit, the power of lens group Ln becomes too strong, which is undesirable as it becomes difficult to correct distortion and coma aberration. Also, if the power of lens group Ln becomes too strong, the height of the marginal rays passing through the final lens group arranged closer to the image than lens group Ln becomes high, which makes it necessary to arrange a lens with a large lens diameter closest to the image in the final lens group, which makes it difficult to achieve a compact size in the radial direction, which is undesirable. On the other hand, if the numerical value of conditional expression (4) exceeds the upper limit, the overall length of the optical system becomes long, which is undesirable as it becomes difficult to achieve a compact zoom lens.

To obtain these effects, the lower limit of conditional formula (4) is more preferably -3.9, even more preferably -3.8, even more preferably -3.7, and even more preferably -3.6. The upper limit of conditional formula (4) is more preferably -1.6, even more preferably -1.7, and even more preferably -1.8.

1-3-5. Conditional expression (5)
0.05 ≦ frt/ft ≦ 1.50 (5)
however,
frt: composite focal length from the middle 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-mentioned conditional formula (5) is a formula for defining the composite focal length from the middle lens group to the final lens group when focusing on infinity at the telephoto end. By satisfying conditional formula (5), it is possible to achieve both compactness and high optical performance of the zoom lens.

On the other hand, if the numerical value of conditional expression (5) is less than the lower limit, it is undesirable because it becomes difficult to correct distortion, coma, and spherical aberration. On the other hand, if the numerical value of conditional expression (5) exceeds the upper limit, it becomes necessary to increase the diameter of the lens closest to the object in the first lens group, which is undesirable because it makes it impossible to reduce the size of the zoom lens.

To obtain these effects, 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 expression (6)
1.00≦βn1≦5.00 (6)
however,
βn1: lateral magnification of the lens unit Ln when focusing on infinity at the wide-angle end

The above-mentioned conditional expression (6) is an expression for defining the lateral magnification of the lens group Ln when focusing on infinity at the wide-angle end. By satisfying conditional expression (6), it is possible to realize 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 (6) is less than the lower limit, the amount of movement of lens group Ln when changing magnification from the wide-angle end to the telephoto end becomes too large, so the overall length of the optical system becomes long, and it is not possible to miniaturize the zoom lens, which is not preferable. On the other hand, if the value of conditional expression (6) exceeds the upper limit, the lateral magnification of lens group Ln becomes too high, so it becomes difficult to correct distortion and curvature of field, which is not preferable.

To obtain these effects, the lower limit of conditional formula (6) is more preferably 1.10, even more preferably 1.20, and even more preferably 1.30. The upper limit of conditional formula (6) is more preferably 4.90, even more preferably 4.80, and even more preferably 4.70.

1-3-7. Conditional expression (7)
1.00 ≦ βn12 ≦ 5.00 (7)
however,
βn12: The combined lateral magnification of the lens group Ln and the final lens group when focusing on infinity at the wide-angle end

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

On the other hand, if the numerical value of conditional expression (7) is less than the lower limit, the amount of movement of lens group Ln and the final lens group when changing magnification from the wide-angle end to the telephoto end becomes too large, so the overall length of the optical system becomes long and it becomes difficult to miniaturize the zoom lens, which is undesirable. On the other hand, if the numerical value of conditional expression (7) exceeds the upper limit, the combined lateral magnification of lens group Ln and the final lens group becomes too high, which is undesirable because it becomes difficult to correct distortion and curvature of field.

To obtain these effects, the lower limit of conditional formula (7) is more preferably 1.10, even more preferably 1.20, and even more preferably 1.30. The upper limit of conditional formula (7) is more preferably 4.90, even more preferably 4.80, and even more preferably 4.70.

1-3-8. Conditional expression (8)
When focusing from infinity to a close object is performed by moving the lens group Ln in the optical axis direction, it is preferable to satisfy the following conditional expression.
0.60≦|{1−(βn1×βn1)}×(βn2×βn2)|≦15.0 ... (8)
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-mentioned conditional formula (8) is a formula for specifying the absolute value of the focus sensitivity of the lens group Ln that moves on the optical axis during focusing, i.e., the amount of movement of the image plane when the lens group Ln moves a unit amount. By satisfying conditional formula (8), it is possible to shorten the amount of movement of the focus group (lens group Ln) during focusing from infinity to a close distance (close object), and a zoom lens with a short optical length can be realized.

On the other hand, if the value of conditional expression (8) is less than the lower limit, the amount of movement of lens group Ln when focusing from an infinite object to a close object becomes large, making it difficult to reduce the overall optical length, which is not preferable. On the other hand, if the value of conditional expression (8) exceeds the upper limit, the amount of movement of lens group Ln to correct the positional shift of the focal position becomes too small, which is not preferable, as it requires highly accurate control.

In order to obtain these effects, the lower limit of conditional formula (8) is more preferably 0.65, and even more preferably 0.70. The upper limit of conditional formula (8) is more preferably 14.0, and even more preferably 13.0, and even more preferably 12.0.

1-3-9. Conditional formula (9)
1.00≦ |CrG1r/fw| ...(9)
however,
CrG1r: radius of curvature of the lens surface in the first lens group closest to the image side fw: focal length of the zoom lens when focusing at infinity at the wide-angle end

The above-mentioned conditional expression (9) is an expression for defining the radius of curvature of the lens surface in the first lens group closest to the image side. By satisfying conditional expression (9), it becomes easier to correct spherical aberration and curvature of field, and it is possible to achieve compactness while achieving high performance.

On the other hand, if the value of conditional expression (9) is less than the lower limit, the field curvature will be overcorrected and it will be necessary to increase the diameter of the lens closest to the object in the first lens group, which is undesirable as it will be difficult to reduce the size of the zoom lens.

To obtain these effects, it is more preferable that the lower limit of conditional formula (9) is 1.50, more preferably 2.00, even more preferably 2.50, even more preferably 3.00, and even more preferably 3.50.

1-3-10. Conditional expression (10)
0.65 ≦ (fw×tanω)/BFw ≦ 2.30 (10)
however,
fw: focal length of the zoom lens when focusing on infinity at the wide-angle end ω: half angle of view of the zoom lens when focusing on infinity at the wide-angle end BFw: distance on the optical axis between the lens surface closest to the image side and the image plane of the zoom lens when focusing on infinity at the wide-angle end

The above-mentioned conditional formula (10) is a formula for defining the ratio of the angle of view at the wide-angle end to the distance between the lens surface closest to the image side of the zoom lens at the wide-angle end and the image plane (the back focus of the optical system). By satisfying conditional formula (10), it is possible to realize high optical performance throughout the entire zoom range and to shorten the overall optical length.

If the value of conditional expression (10) is less than the lower limit, it is undesirable because it is necessary to increase the angle of incidence of off-axis rays on the image plane. In other words, it is undesirable because it becomes necessary to reduce the focal length of the final lens group, which makes it difficult to correct coma and distortion. Alternatively, it becomes necessary to increase the lens diameter of the final lens group, which is undesirable because it is not possible to reduce the size of the zoom lens. If the value of conditional expression (10) exceeds the upper limit, the total length of the optical system becomes too long, which is undesirable because it is not possible to reduce the size of the zoom lens.

To obtain these effects, the lower limit of conditional formula (10) is more preferably 0.70, even more preferably 0.75, even more preferably 0.80, even more preferably 0.85, and even more preferably 0.90. The upper limit of conditional formula (10) is more preferably 2.20, even more preferably 2.10, even more preferably 2.00, even more preferably 1.90, and even more preferably 1.80.

1-3-11. Conditional formula (11)
It is preferable that the zoom lens of the present invention has at least one lens LpMp having a positive refractive power in the lens unit LpMax and satisfies the following conditional expression:
45.0 ≦ νdLpMp ≦ 98.0 (11)
however,
νdLpMp: Abbe number at d line of lens LpMp

The above-mentioned conditional formula (11) is a formula for defining the Abbe number at the d-line of the lens LpMp included in the lens group LpMax. By satisfying the conditional formula (11), it becomes easier to correct the axial chromatic aberration and spherical aberration, and it is possible to achieve a compact size while achieving high performance.

If the value of conditional expression (11) is less than the lower limit, it becomes difficult to correct axial chromatic aberration, which is not preferable. If the value of conditional expression (11) is more than the upper limit, the lens becomes expensive, which is not preferable from the perspective of reducing costs.

To obtain these effects, the lower limit of conditional formula (11) is more preferably 50.0, even more preferably 55.0, and even more preferably 60.0. The upper limit of conditional formula (11) is more preferably 95.0, even more preferably 90.0, and even more preferably 85.0.

1-3-12. Conditional formula (12)
It is preferable that the zoom lens of the present invention has at least one lens L1p having positive refractive power in the first lens group and satisfies the following conditional expression:
20.0 ≦ νdL1p ≦ 50.0 (12)
however,
νdL1p: Abbe number at d line of lens L1p

The above-mentioned conditional formula (12) is a formula for defining the Abbe number at the d-line of the lens L1p having a positive refractive power included in the first lens group. In the lens group having a negative refractive power, it is common to use high dispersion glass for the lens having a positive refractive power and low dispersion glass for the lens having a negative refractive power to correct the lateral chromatic aberration. However, high dispersion glass for which the numerical value of the above-mentioned conditional formula (12) is less than the lower limit is expensive, and is therefore not preferable in terms of reducing costs. In addition, if the numerical value of the above-mentioned conditional formula (12) exceeds the upper limit, it is not preferable because it is difficult to correct the lateral chromatic aberration even if low dispersion glass is used for the lens having a negative refractive power. In other words, by having the structure of the zoom lens satisfy the conditional formula (12), it is possible to reduce costs while ensuring good image surface characteristics.

To obtain these effects, the lower limit of conditional formula (12) is more preferably 22.0, even more preferably 24.0, and even more preferably 26.0. The upper limit of conditional formula (12) is more preferably 47.0, even more preferably 44.0, and even more preferably 41.0.

1-3-13. Conditional formula (13)
It is preferable that the zoom lens of the present invention has at least one lens L1p having positive refractive power in the first lens group and satisfies the following conditional expression:
1.70≦NdL1p≦2.20 (13)
however,
NdL1p: Refractive index of lens L1p at d line

The above-mentioned conditional formula (13) is a formula for defining the refractive index at the d-line of the lens L1p having a positive refractive power included in the first lens group. In a lens group having a negative refractive power, it is common to use a high refractive index glass for the lens having a positive refractive power and a low refractive index glass for the lens having a negative refractive power to correct the Petzval sum. Here, if the numerical value of the above-mentioned conditional formula (13) is less than the lower limit, it is not preferable because it becomes difficult to correct the image surface. In addition, high refractive index glass having a refractive index that exceeds the upper limit of the numerical value of the conditional formula (13) is expensive, and is therefore not preferable in terms of reducing costs. In other words, by satisfying the conditional formula (13), it is possible to reduce costs while ensuring good image surface properties.

To obtain these effects, the lower limit of conditional formula (13) is preferably 1.75, more preferably 1.80, and even more preferably 1.85. The upper limit of conditional formula (13) is preferably 2.15, more preferably 2.10, and even more preferably 2.05.

1-3-14. Conditional formula (14)
|BFt-BFw|/TLw ≦ 0.30...(14)
however,
BFt: Distance on the optical axis between the lens surface closest to the image side of the zoom lens and the image plane when focusing on infinity at the telephoto end. BFw: Distance on the optical axis between the lens surface closest to the image side of the zoom lens and the image plane when focusing on infinity at the wide-angle end. TLw: Total optical length of the zoom lens when focusing on infinity at the wide-angle end.

The above-mentioned conditional formula (14) is a 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. By satisfying conditional formula (14), 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 is possible to shorten the overall optical length at the telephoto end while ensuring a predetermined magnification change.

On the other hand, if the numerical value of conditional formula (14) exceeds the upper limit, the above-mentioned movement amount of the final lens group during zooming (the movement amount of the final lens group toward the object side when zooming from the wide-angle end to the telephoto end) becomes large. 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 doubling the inner barrel portion to be housed in the outer barrel, complicating the lens barrel structure and increasing the outer diameter of the lens barrel (increasing the product size), which is not desirable.

To obtain these effects, the upper limit value of conditional formula (14) is more preferably 0.27, even more preferably 0.24, even more preferably 0.21, and even more preferably 0.18.

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 described above, 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.

Here, there is no particular limitation on the imaging element, and solid-state imaging elements such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used. The imaging device according to the present invention is suitable for imaging devices using such solid-state imaging elements, such as digital cameras and video cameras. Furthermore, the imaging device may be a fixed-lens imaging device in which the lens is fixed to the housing, or it may be an interchangeable-lens imaging device, such as a single-lens reflex camera or a mirrorless single-lens camera.

The imaging device preferably has an image processing unit that electrically processes the captured image data acquired by the imaging element to change the shape of the captured image, and an image correction data storage unit that stores image correction data and an image correction program used to process the captured image data in the image processing unit. When the zoom lens is made smaller, the captured image shape formed on the image formation plane is more likely to be distorted. In this case, it is preferable to store distortion correction data for correcting the distortion of the captured image shape in advance in the image correction data storage unit, and to correct the distortion of the captured image shape in the above-mentioned image processing unit using the distortion correction data stored in the image correction data storage unit. With such an imaging device, the negative refractive power of the lens located closest to the image side in the zoom lens can be strengthened, so that the diameter of the lens located closest to the image side in the zoom lens can be reduced. In other words, with this imaging device, the zoom lens can be made even smaller, and a beautiful captured image can be obtained while the entire imaging device can be made smaller.

Next, the present invention will be specifically explained by showing examples. However, the present invention is not limited to the following examples.

(1) Optical configuration of the zoom lens Figure 1 is a cross-sectional view showing the lens configuration of the zoom lens of Example 1 according to the present invention at the wide-angle end and the telephoto end when focusing on infinity. Note that "IP" in Figure 1 is an image plane (image surface), specifically, an imaging surface of a solid-state imaging element such as a CCD sensor or a CMOS sensor, or a film surface of a silver halide film. In addition, a parallel plate having no substantial refractive power, such as a cover glass "CG", is provided on the object side of the image plane IP. These points are the same in each lens cross-sectional view shown in the other examples, so the explanation will be omitted below.

The zoom lens of Example 1 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. An aperture stop S is disposed adjacent to the object side of the third lens group G3. In this example, the intermediate group is composed of the second lens group G2 and the third lens group G3, and the lens group Ln corresponds to the fourth lens group G4.

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 having a convex shape toward the object side, a negative meniscus lens L102 having a convex shape toward the object side, a biconcave lens L103, and a positive meniscus lens L104 having a convex shape toward the object side. The image-side lens surfaces of the lenses L102 and L104 are as follows:
It is a so-called composite aspheric surface in which an aspheric film is attached to the glass surface. The lens L104 corresponds to the lens "L1p" in the present invention, and the lens surface on the image side of the lens L104 corresponds to the lens surface "CrG1r" in the present invention.

The second lens group G2 is composed of a cemented lens in which a negative meniscus lens L105 with a convex shape facing the object side and a biconvex lens L106 are cemented together.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a cemented lens in which a biconvex lens L107 and a biconcave lens L108 are cemented together, a cemented lens in which a negative meniscus lens L109 with a convex shape toward the object side is cemented together with a positive meniscus lens L110 with a convex shape toward the object side, and a biconvex lens L111. Both surfaces of the lens L111 are aspheric. The third lens group G3 corresponds to the lens group "LpMax" in the present invention, and the lens L111 corresponds to the lens "LpMp" in the present invention.

The fourth lens group G4 is composed of a negative meniscus lens L112 that is convex toward the object side.

The fifth lens group G5 is composed of, from the object side, a biconvex lens L113 and a biconcave lens L114. Both surfaces of the lens L113 are aspheric.

When the zoom lens of Example 1 changes magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side and then toward the object side relative to the image plane, 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.

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

This zoom lens uses lens L111 included in the third lens group G3 as an anti-vibration group, and can perform image stabilization by moving this anti-vibration group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. In the following tables, all the units of length are "mm", and all the units of angle of view are "°". Table 1 shows the surface data of the zoom lens. In Table 1, "surface number" indicates the order of the lens surface counted from the object side, "R" indicates the radius of curvature of the lens surface, "D" indicates the distance on the optical axis of the lens surface, "Nd" indicates the refractive index for the d-line (wavelength λ=587.6 nm), and "ABV" indicates the Abbe number for the d-line. In addition, "ASP" displayed in the column next to the surface number indicates that the lens surface is aspheric, and "S" indicates the aperture stop. Furthermore, "D(10)", "D(13)", etc., shown in the column of the distance on the optical axis of the lens surface mean that the distance on the optical axis of the lens surface is a variable distance that changes when the magnification is changed or when focusing. In addition, "∞ (infinity)" in the radius of curvature means a flat surface. Surfaces 29 and 30 in Table 1 are surface data for the cover glass (CG).

Table 2 is a specification table of the zoom lens. The specification table shows the focal length "f" of the zoom lens when focused at infinity, the F-number "Fno.", the half angle of view "ω", the image height "Y", the total optical length "TL", and the variable distance on the optical axis of the zoom lens when changing magnification and when focused. However, from the left, Table 2 shows the respective values at the wide-angle end, the intermediate focal length state, and the telephoto end.

Table 3 shows the lens surface numbers of each lens group that constitutes the zoom lens and the focal length of each lens group.

Table 4 shows the aspheric coefficients of each aspheric surface. The aspheric coefficients are the values when each aspheric shape is defined by the following formula.

X(Y)=CY ² / [1+{1-(1+K)・C ² Y ² } ^1/2 ]+A ₄・Y ⁴ +A ₆・Y ⁶ +A ₈・Y ⁸ +A ₁₀・Y ¹⁰

In Table 4, "E-a" indicates "×10 ^-a ". In addition, in the above formula, "X" is the amount of displacement from the reference surface in the optical axis direction, "C" is the curvature at the surface vertex, "Y" is the height from the optical axis in a direction perpendicular to the optical axis, "K" is the Conic coefficient, and "A _n " is the n-th order aspheric coefficient.

Table 21 also shows the values of conditional expressions (1) to (14) and the values used in the calculations of conditional expressions (1) to (14).

The points regarding the above table are the same for the tables shown in the other examples, so we will not repeat the explanation below.

[Table 1]
Surface number RD Nd ABV
Object plane ∞ ∞
1 51.4464 2.0000 1.89085 36.41
2 20.0000 5.7196
3 47.2371 1.5000 1.72916 54.67
4 23.5686 0.2000 1.53610 41.21
5 A.S.P. 19.7552 6.4678
6 -206.9428 1.5000 1.72916 54.67
7 23.0858 1.9587
8 26.8465 4.0557 1.85764 22.33
9 121.5647 0.2000 1.53610 41.21
10 ASP 105.4586 D(10)
11 29.2922 1.0000 1.92108 22.20
12 16.8467 4.9210 1.64109 33.36
13 -216.9562 D(13)
14 S∞2.0000
15 59.2608 4.0417 1.54697 68.55
16 -17.6603 1.0000 1.71375 55.52
17 69.4793 0.1016
18 20.2723 1.0000 1.80899 42.96
19 13.2943 3.8193 1.51650 70.18
20 51.7432 4.1444
21 ASP 34.3114 6.1621 1.48556 80.01
22 ASP -18.9780 D(22)
23 32.3936 1.0000 1.68811 57.08
24 19.0779 D(24)
25 ASP 23.9793 8.9358 1.49700 81.61
26 ASP -18.9694 0.1000
27 -34.6849 1.2000 1.73979 49.98
28 22.9171 D(28)
29 ∞ 2.5000 1.51680 64.20
30∞1.0000

[Table 2]
Wide-angle end Mid-range focal length Telephoto end
f 15.45 21.84 29.11
Fno. 2.88 3.60 4.12
ω 56.70 45.52 36.98
Y 19.97 20.64 21.23
TL 120.00 117.10 119.65
D(10) 10.1655 5.7974 3.1563
D(13) 16.3597 7.5636 2.1111
D(22) 6.1150 3.5611 2.4945
D(24) 3.4600 6.0138 7.0805
D(28) 17.3722 27.6314 38.2786

[Table 3]
Group Surface number Focal length
G1 1-10 -16.25
G2 11-13 55.96
G3 14-22 28.71
G4 23-24 -69.58
G5 25-28 -400.00

[Table 4]
Surface number K A4 A6 A8 A10
5 0.00000E+00 -2.23462E-05 -4.09357E-08 -8.91357E-11 0.00000E+00
10 0.00000E+00 4.48229E-06 6.87070E-09 -5.54223E-11 0.00000E+00
21 0.00000E+00 -2.17920E-05 -5.42256E-09 1.86040E-10 0.00000E+00
22 0.00000E+00 3.69697E-05 -7.19257E-08 2.55987E-10 0.00000E+00
25 0.00000E+00 1.97160E-05 -5.15489E-08 3.03503E-10 -5.84468E-13
26 0.00000E+00 5.13298E-05 -3.64861E-08 2.43868E-10 -2.67122E-13

2 to 4 show longitudinal aberration diagrams of the zoom lens of Example 1 at the wide-angle end, intermediate focal length state, and 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 (%). In the diagrams showing spherical aberration, the vertical axis shows the ratio to the open F-number, the horizontal axis shows defocus, the solid line shows spherical aberration at the d-line (wavelength λ = 587.6 nm), the dashed line shows spherical aberration at the F-line (wavelength λ = 486.1 nm), and the dotted line shows spherical aberration at the C-line (wavelength λ = 656.3 nm). In the diagrams showing astigmatism, the vertical axis shows half angle of view, the horizontal axis shows defocus, the four-dot chain line shows sagittal image plane (S) for the d-line, and the solid line shows meridional image plane (M) for the d-line. In the diagrams showing distortion aberration, the vertical axis shows half angle of view, and the horizontal axis shows distortion in %, respectively. The matters relating to these longitudinal aberration diagrams are the same as those shown in the longitudinal aberration diagrams of other examples, so the explanation will be omitted below.

(1) Optical configuration of the zoom lens Figure 5 is a cross-sectional view showing the lens configuration of the zoom lens of Example 2 according to 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. The aperture stop S is disposed adjacent to the object side of the third lens group G3. In this example, the intermediate group is composed of the second lens group G2 and the third lens group G3, and the lens group Ln corresponds to the fourth lens group G4.

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, a negative meniscus lens L203 with a convex shape toward the object side, and a positive meniscus lens L204 with a convex shape toward the object side. The image side lens surfaces of the lenses L202 and L204 are composite aspheric surfaces. The lens L204 corresponds to the lens "L1p" in the present invention, and the image side lens surface of the lens L204 corresponds to the lens surface "CrG1r" in the present invention.

The second lens group G2 is composed of a cemented lens in which a negative meniscus lens L205 with a convex shape facing the object side and a biconvex lens L206 are cemented together.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a cemented lens in which a biconvex lens L207 and a biconcave lens L208 are cemented together, a cemented lens in which a negative meniscus lens L209 with a convex shape on the object side is cemented together with a positive meniscus lens L210 with a convex shape on the object side, and a biconvex lens L211. Both surfaces of the lens L211 are aspheric. The third lens group G3 corresponds to the lens group "LpMax" in the present invention, and the lens L211 corresponds to the lens "LpMp" in the present invention.

The fourth lens group G4 is composed of a negative meniscus lens L212 that is convex toward the object side.

The fifth lens group G5 is composed of, from the object side, a biconvex lens L213 and a biconcave lens L214. Both surfaces of the lens L213 are aspheric.

When the zoom lens of Example 2 changes magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side and then toward the object side relative to the image plane, the second lens group G2 moves toward the image side and then 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.

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

This zoom lens uses lens L211 included in the third lens group G3 as an anti-vibration group, and can perform image stabilization by moving this anti-vibration group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 5 shows surface data of the zoom lens. Table 6 is a table of specifications of the zoom lens. Table 7 shows the surface numbers of the lenses in each lens group constituting the zoom lens and the focal length of each lens group. Table 8 shows the aspheric coefficients of each aspheric surface. Also, FIGS. 6 to 8 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity, respectively. And Table 21 shows the values of conditional expressions (1) to (14) and the values used in the calculation of conditional expressions (1) to (14).

[Table 5]
Surface number RD Nd ABV
Object plane ∞ ∞
1 49.9199 2.0000 1.78436 45.77
2 20.0000 4.8247
3 36.9299 1.5000 1.72916 54.67
4 17.7030 0.2000 1.53610 41.21
5 A.S.P. 17.1820 6.4517
6 100.7210 1.5000 1.72916 54.67
7 20.4815 2.6125
8 28.3348 4.6408 1.71736 29.50
9 115.4139 0.2000 1.53610 41.21
10 ASP 52.1147 D(10)
11 33.8489 1.0000 1.91970 23.36
12 14.8237 6.1699 1.72405 27.25
13 -210.0707 D(13)
14 S∞2.0000
15 24.3756 4.8951 1.53845 72.92
16 -28.4241 1.0000 1.70018 56.32
17 55.9270 2.7897
18 25.6060 1.0000 1.77131 47.50
19 13.9069 3.6869 1.49700 81.61
20 54.8489 3.2852
21 ASP 26.7652 5.8021 1.49710 81.56
22 ASP -23.9208 D(22)
23 34.3910 1.0000 1.69680 55.46
24 17.8455 D(24)
25 ASP 24.0464 8.1846 1.49710 81.56
26 ASP -19.4330 0.1000
27 -34.7778 1.2000 1.72604 54.84
28 23.4576 D(28)
29 ∞ 2.5000 1.51680 64.20
30∞1.0000

[Table 6]
Wide-angle end Mid-range focal length Telephoto end
f 15.46 21.85 29.10
Fno. 2.89 3.61 4.12
Omega 56.72 45.30 36.73
Y 19.97 20.64 21.23
TL 120.62 117.02 118.06
D(10) 4.2008 2.8886 2.0000
D(13) 21.2547 9.7141 2.1000
D(22) 5.0787 3.1436 2.4987
D(24) 3.4065 5.3416 5.9865
D(28) 17.1402 26.3913 35.9284

[Table 7]
Group Surface number Focal length
G1 1-10 -14.84
G2 11-13 57.53
G3 14-22 26.30
G4 23-24 -54.59
G5 25-28 -541.46

[Table 8]
Surface number K A4 A6 A8 A10
5 0.00000E+00 -7.13353E-06 -2.73137E-08 -1.73885E-11 0.00000E+00
10 0.00000E+00 -2.16483E-05 -3.23519E-08 -1.69294E-10 0.00000E+00
21 0.00000E+00 -1.84352E-05 2.43101E-08 8.28668E-11 0.00000E+00
22 0.00000E+00 3.13539E-05 -5.21245E-08 1.08634E-10 0.00000E+00
25 0.00000E+00 1.44636E-05 -3.13467E-08 3.20638E-10 -9.57521E-13
26 0.00000E+00 4.11894E-05 -1.81690E-08 2.54212E-10 -6.03157E-13

(1) Optical configuration of the zoom lens Figure 9 is a cross-sectional view showing the lens configuration of the zoom lens of Example 3 according to 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. An aperture stop S is disposed in the second lens group G2. In this example, the intermediate group corresponds to the second lens group G2, and the lens group Ln corresponds to the third lens group G3.

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 L301 with a convex shape toward the object side, a negative meniscus lens L302 with a convex shape toward the object side, a biconcave lens L303, and a biconvex lens L304. The image side lens surfaces of lenses L302 and L304 are composite aspheric surfaces. Lens L304 corresponds to lens "L1p" in the present invention, and the image side lens surface of lens L304 corresponds to lens surface "CrG1r" in the present invention.

The second lens group G2 is composed of, in order from the object side, a cemented lens in which a negative meniscus lens L305 having a convex shape toward the object side and a biconvex lens L306 are cemented together, an aperture stop S, a cemented lens in which a biconcave lens L307 and a biconvex lens L308 are cemented together, a positive meniscus lens L309 having a convex shape toward the object side, and a biconvex lens L310. Both surfaces of the lens L310 are aspheric. The second lens group G2 corresponds to the lens group "LpMax" in the present invention, and the lens L310 corresponds to the lens "LpMp" in the present invention.

The third lens group G3 is composed of a negative meniscus lens L311 that is concave toward the object side.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens L312 and a biconcave lens L313. Both surfaces of the lens L312 are aspheric.

In the zoom lens of Example 3, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side and then toward the object side relative to the image surface, 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.

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

This zoom lens uses lens L310 included in the second lens group G2 as an anti-vibration group, and can perform image stabilization by moving this anti-vibration group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 9 shows surface data of the zoom lens. Table 10 is a table of specifications of the zoom lens. Table 11 shows the surface numbers of the lenses in each lens group constituting the zoom lens and the focal length of each lens group. Table 12 shows the aspherical coefficients of each aspherical surface. Also, FIGS. 10 to 12 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity, respectively. And Table 21 shows the values of conditional expressions (1) to (14) and the values used in the calculation of conditional expressions (1) to (14).

[Table 9]
Surface number RD Nd ABV
Object plane ∞ ∞
1 45.9665 2.0000 1.91082 35.25
2 20.0000 4.6653
3 35.8656 1.5000 1.72916 54.67
4 19.1538 0.2000 1.53610 41.21
5 A.S.P. 16.9422 7.5065
6 -78.2089 1.5000 1.72916 54.67
7 25.2371 2.0427
8 37.1407 4.9633 1.71736 29.50
9 -62.4250 0.2000 1.53610 41.21
10 ASP -94.7173 D(10)
11 20.0044 1.0000 1.91082 35.25
12 15.5086 4.4513 1.68046 33.39
13 -312.6741 2.1000
14 S∞2.5110
15 -63.1697 1.0000 1.91082 35.25
16 11.7699 4.3762 1.63416 61.14
17 629.8056 0.1000
18 22.9325 2.6332 1.49700 81.61
19 78.5401 4.6758
20 ASP 36.8447 4.2746 1.49710 81.56
21 ASP -22.3539 D(21)
22 -65.7587 1.0000 1.72916 54.67
23 -672.0766 D(23)
24 ASP 48.6211 5.2314 1.49710 81.56
25 ASP -18.8806 0.1182
26 -44.4585 1.2000 1.72916 54.67
27 30.8496 D(27)
28 ∞ 2.5000 1.51680 64.20
29∞1.0000

[Table 10]
Wide-angle end Mid-range focal length Telephoto end
f 15.45 21.85 29.11
Fno. 2.88 3.61 4.12
ω 56.68 43.76 34.79
Y 19.97 20.64 21.23
TL 120.00 115.76 115.50
D(10) 22.4143 10.0680 2.0000
D(21) 3.0925 7.4275 14.3355
D(23) 8.9418 8.9357 6.0656
D(27) 22.8019 26.5746 30.3516

[Table 11]
Group Surface number Focal length
G1 1-10 -17.97
G2 11-21 27.92
G4 22-23 -100.04
G5 24-27 -400.00

[Table 12]
Surface number K A4 A6 A8 A10
5 0.00000E+00 -2.38163E-05 -4.78409E-08 -1.47334E-10 0.00000E+00
10 0.00000E+00 -6.06540E-06 6.24989E-10 -1.49920E-10 0.00000E+00
20 0.00000E+00 -3.54582E-05 -1.04141E-07 -7.27066E-11 0.00000E+00
21 0.00000E+00 -5.56397E-06 -1.05803E-07 -4.01537E-10 0.00000E+00
24 0.00000E+00 -3.56136E-05 1.23145E-07 -2.04005E-09 6.67569E-12
25 0.00000E+00 3.07376E-05 1.28930E-07 -1.98340E-09 6.50202E-12

(1) Optical configuration of the zoom lens Figure 13 is a cross-sectional view showing the lens configuration of the zoom lens of Example 4 according to 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 positive refractive power, a fifth lens group G5 having negative refractive power, and a sixth lens group G6 having negative refractive power. The aperture stop S is disposed adjacent to the object side of the third lens group G3. In this example, the intermediate group is composed of the second lens group G2, the third lens group G3, and the fourth lens group G4, and the lens group Ln corresponds to the fifth lens group G5.

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 toward the object side, a negative meniscus lens L402 with a convex shape toward the object side, a biconcave lens L403, and a positive meniscus lens L404 with a convex shape toward the object side. The image side lens surfaces of the lenses L402 and L404 are composite aspheric surfaces. The lens L404 corresponds to the lens "L1p" in the present invention, and the image side lens surface of the lens L404 corresponds to the lens surface "CrG1r" in the present invention.

The second lens group G2 is composed of a cemented lens in which a negative meniscus lens L405 with a convex shape facing the object side and a biconvex lens L406 are cemented together.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a cemented lens in which a biconvex lens L407 and a biconcave lens L408 are cemented together, and a cemented lens in which a negative meniscus lens L409 with a convex shape toward the object side is cemented together with a positive meniscus lens L410 with a convex shape toward the object side.

The fourth lens group G4 is composed of a biconvex lens L411. Both surfaces of the lens L411 are aspheric. The fourth lens group G4 corresponds to the lens group "LpMax" in the present invention, and the lens L411 corresponds to the lens "LpMp" in the present invention.

The fifth lens group G5 is composed of a negative meniscus lens L412 that is convex toward the object side.

The sixth lens group G6 is composed of, in order from the object side, a biconvex lens L413 and a biconcave lens L414. Both surfaces of the lens L413 are aspheric.

In the zoom lens of Example 4, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 does not move relative to the image plane and remains 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.

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

This zoom lens uses L411, which constitutes the fourth lens group G4, as an anti-vibration group, and can perform image stabilization by moving this anti-vibration group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 13 shows surface data of the zoom lens. Table 14 is a table of specifications of the zoom lens. Table 15 shows the surface numbers of the lenses in each lens group constituting the zoom lens and the focal length of each lens group. Table 16 shows the aspherical coefficients of each aspherical surface. Also, FIGS. 14 to 16 show longitudinal aberration diagrams of the zoom lens at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity, respectively. And Table 21 shows the values of conditional expressions (1) to (14) and the values used in the calculation of conditional expressions (1) to (14).

[Table 13]
Surface number RD Nd ABV
Object plane ∞ ∞
1 42.8582 2.0000 1.91082 35.25
2 20.0000 5.9132
3 57.1247 1.5000 1.73647 53.21
4 24.1922 0.2000 1.53610 41.21
5 A.S.P. 20.5048 6.9517
6 -106.4452 1.5000 1.73014 54.47
7 23.2844 1.9588
8 25.9803 3.7932 1.85056 24.21
9 134.1277 0.2000 1.53610 41.21
10 ASP 123.9146 D(10)
11 27.7803 1.0000 1.91733 25.65
12 16.0429 4.1181 1.64065 33.41
13 -950.9894 D(13)
14 S∞2.8785
15 43.3018 4.0046 1.54824 71.30
16 -20.4613 1.0000 1.71210 53.95
17 42.4758 0.2273
18 23.8726 1.0000 1.80697 38.92
19 15.7558 3.8401 1.51721 76.95
20 355.5760 D(20)
21 ASP 27.4262 7.0734 1.48614 82.92
22 ASP -21.2352 D(22)
23 38.1860 1.0000 1.68905 57.02
24 18.4614 D(24)
25 ASP 25.2455 9.4359 1.50250 76.18
26 ASP -17.1401 0.1150
27 -27.1371 1.2000 1.72791 54.74
28 25.1493 D(28)
29 ∞ 2.5000 1.51680 64.20
30∞1.0000

[Table 14]
Wide-angle end Mid-range focal length Telephoto end
f 15.45 21.85 29.10
Fno. 2.88 3.61 4.14
Omega 56.69 45.61 36.70
Y 19.97 20.64 21.23
TL 120.00 120.00 120.00
D(10) 9.2631 5.9048 2.3457
D(13) 15.3884 8.8201 4.7874
D(20) 5.8497 4.3952 3.1279
D(22) 4.9839 2.1108 2.7002
D(24) 3.0300 7.0471 5.5293
D(28) 17.0751 27.3122 37.0998

[Table 15]
Group Surface number Focal length
G1 1-10 -16.41
G2 11-13 59.86
G3 14-20 401.05
G4 21-22 25.85
G5 23-24 -52.97
G6 25-28 -400.00

[Table 16]
Surface number K A4 A6 A8 A10
5 0.00000E+00 -2.15513E-05 -3.54019E-08 -1.03182E-10 0.00000E+00
10 0.00000E+00 8.64701E-06 6.06914E-09 -3.21414E-12 0.00000E+00
21 0.00000E+00 -1.79955E-05 5.40156E-09 1.53060E-10 0.00000E+00
22 0.00000E+00 4.21377E-05 -8.37172E-08 4.00374E-10 0.00000E+00
25 0.00000E+00 1.97469E-05 -6.09841E-08 3.24007E-10 -1.67902E-13
26 0.00000E+00 5.31544E-05 -1.54076E-08 2.14204E-10 6.55586E-13

(1) Optical configuration of the zoom lens Figure 17 is a cross-sectional view showing the lens configuration of the zoom lens of Example 5 according to 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. The aperture stop S is disposed adjacent to the object side of the third lens group G3. In this example, the intermediate group is composed of the second lens group G2, the third lens group G3, and the fourth lens group G4, and the lens group Ln corresponds to the fifth lens group G5.

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 L501 with a convex shape toward the object side, a negative meniscus lens L502 with a convex shape toward the object side, a biconcave lens L503, and a biconvex lens L504. The image-side lens surfaces of lenses L502 and L504 are composite aspheric surfaces. Lens L504 corresponds to lens "L1p" in the present invention, and the image-side lens surface of lens L504 corresponds to lens surface "CrG1r" in the present invention.

The second lens group G2 is composed of a cemented lens in which a negative meniscus lens L505 with a convex shape facing the object side and a biconvex lens L506 are cemented together.

The third lens group G3 is composed of, in order from the object side, an aperture stop S, a negative meniscus lens L507 with a concave shape toward the object side, and a cemented lens in which a biconvex lens L508 and a biconcave lens L509 are cemented together.

The fourth lens group G4 is composed of, in order from the object side, a cemented lens in which a negative meniscus lens L510 with a convex shape toward the object side and a positive meniscus lens L511 with a convex shape toward the object side are cemented together, and a biconvex lens L512. Both surfaces of the lens L512 are aspheric. The fourth lens group G4 corresponds to the lens group "LpMax" in the present invention, and the lens L512 corresponds to the lens "LpMp" in the present invention.

The fifth lens group G5 is composed of a negative meniscus lens L513 that is convex toward the object side.

The sixth lens group G6 is composed of, from the object side, a biconvex lens L514 and a biconcave lens L515. Both surfaces of the lens L515 are aspheric.

In the zoom lens of Example 5, when changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side and then toward the object side relative to the image plane, 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.

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

This zoom lens uses lens L512 included in the fourth lens group G4 as an anti-vibration group, and can perform image stabilization by moving this anti-vibration group in a direction perpendicular to the optical axis.

(2) Numerical Examples Next, numerical examples to which specific numerical values of the zoom lens are applied will be described. Table 17 shows surface data of the zoom lens. Table 18 is a table of specifications of the zoom lens. Table 19 shows the surface numbers of the lenses in each lens group constituting the zoom lens and the focal length of each lens group. Table 20 shows the aspherical coefficients of each aspherical surface. Also, FIGS. 18 to 20 show longitudinal aberration diagrams of the zoom lens of Example 5 at the wide-angle end, the intermediate focal length state, and the telephoto end when focusing on infinity, respectively. And Table 21 shows the values of conditional expressions (1) to (14) and the values used in the calculation of conditional expressions (1) to (14).

[Table 17]
Surface number RD Nd ABV
Object plane ∞ ∞
1 64.4935 2.0000 1.80420 46.50
2 20.0000 5.8149
3 44.3380 1.5000 1.72916 54.67
4 21.1456 0.2000 1.53610 41.21
5 A.S.P. 19.2295 7.5156
6 -150.7078 1.5000 1.72916 54.67
7 30.8746 2.0751
8 39.1591 4.7734 1.85883 30.00
9 -122.1827 0.2000 1.53610 41.21
10 ASP -337.0680 D(10)
11 25.7483 1.0000 1.91082 35.25
12 16.7808 3.8598 1.63680 49.15
13 -108.4616 D(13)
14 S∞2.7762
15 -36.6701 1.0000 1.82332 36.47
16 -663.6925 0.1000
17 24.1845 3.9673 1.54571 51.63
18 -33.7101 1.0000 1.72916 54.67
19 119.1041 D(19)
20 29.2776 1.0000 1.83338 40.48
21 13.7692 4.4721 1.49700 81.61
22 158.7714 2.5000
23 ASP 30.8545 5.1765 1.49710 81.56
24 ASP -33.1652 D(24)
25 29.6714 1.0000 1.73357 53.78
26 20.5408 D(26)
27 21.5900 8.4030 1.53350 56.48
28 -29.7187 0.1000
29 ASP -57.0454 1.2000 1.76029 49.12
30 ASP 20.4524 D(30)
31 ∞ 2.5000 1.51680 64.20
32∞1.0000

[Table 18]
Wide-angle end Mid-range focal length Telephoto end
f 15.45 21.85 29.10
Fno. 2.88 3.60 4.12
ω 56.68 44.98 36.07
Y 19.97 20.64 21.23
TL 120.00 116.50 117.59
D(10) 20.3946 9.6191 2.0000
D(13) 4.3222 5.1184 5.3378
D(19) 5.4505 3.2882 2.5000
D(24) 2.0059 2.0030 4.6652
D(26) 3.4503 4.3535 6.1135
D(30) 17.7429 25.4839 30.3398

[Table 19]
Group Surface number Focal length
G1 1-10 -20.57
G2 11-13 40.26
G3 14-19 -100.00
G4 20-24 32.69
G5 25-26 -95.42
G6 27-30 -400.00

[Table 20]
Surface number K A4 A6 A8 A10
5 0.00000E+00 -1.33896E-05 -4.03264E-08 -4.74820E-12 0.00000E+00
10 0.00000E+00 -7.18688E-06 -4.32457E-09 -4.62078E-11 0.00000E+00
23 0.00000E+00 -1.87086E-05 4.43421E-08 1.89540E-10 0.00000E+00
24 0.00000E+00 9.14539E-06 9.72993E-09 4.52486E-11 0.00000E+00
29 0.00000E+00 -1.25529E-05 3.09804E-08 -3.76634E-10 0.00000E+00
30 0.00000E+00 3.30936E-06 4.84433E-08 -5.50774E-10 0.00000E+00

[Table 21]
Example 1 Example 2 Example 3 Example 4 Example 5
Conditional expression (1) |f1| / |fpMax| 0.57 0.56 0.64 0.63 0.63
Conditional expression (2) βpw -0.63 -0.70 -0.61 -0.62 -0.61
Conditional expression (3) f1/fw -1.23 -0.96 -1.16 -1.06 -1.33
Conditional expression (4) fn/fpMax -2.70 -2.08 -3.58 -2.05 -2.92
Conditional expression (5) frt / ft 1.02 0.96 1.03 0.95 0.98
Conditional expression (6) βn1 1.39 1.65 1.41 1.69 1.38
Conditional expression (7) βn12 1.29 1.49 1.42 1.52 1.24
Conditional formula (8) |{1-(βn1×βn1)}×(βn2×βn2)|
0.80 1.40 1.00 1.50 0.73
Conditional expression (9) | CrG1r / fw | 1981.08 3.37 6.13 8.02 21.82
Conditional expression (10) (fw×tanω) / BFw 1.19 1.19 0.92 1.19 1.15
Conditional expression (11) νdLpMp 80.01 81.56 81.56 82.92 81.56
Conditional expression (12) νdL1p 22.33 29.50 29.50 24.21 30.00
Conditional expression (13) NdL1p 1.86 1.72 1.72 1.85 1.86
Conditional expression (14) |BFt - BFw| / TLw 0.16 0.16 0.06 0.17 0.10
frt 29.55 27.94 30.01 27.54 28.62
BFw 19.80 19.80 25.46 19.74 20.40
BFt 39.65 38.59 33.01 39.76 33.00

The present invention makes it possible to provide a zoom lens and imaging device that are compact and have high optical performance.

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group G5 Fifth lens group G6 Sixth lens group CG Cover glass IP Imaging surface (image surface)
S Aperture W Wide-angle end T Telephoto end FNo. F-number ω Half angle of view

Claims (14)

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 includes a lens group LpMax,
the lens group LpMax has the strongest positive refractive power among the lens groups included in the intermediate group,
A zoom lens that changes magnification or focuses by changing the distance between adjacent lens groups,
the final lens group moves from the image side to the object side along the optical axis during zooming from the wide-angle end to the telephoto end,
A zoom lens characterized by satisfying the following conditional expressions:
0.05 ≦ |f1|/|fpMax| ≦ 0.65...(1)
however,
f1: focal length of the first lens group fpMax: focal length of the lens group LpMax 2. The zoom lens according to claim 1, which satisfies the following condition:
-1.50 ≦ f1/fw ≦ -0.05 ... (3)
however,
f1: focal length of the first lens group fw: focal length of the zoom lens when focused on infinity at the wide-angle end 3. The zoom lens according to claim 1, which satisfies the following condition:
-4.0 ≦ fn/fpMax ≦ -1.5 ... (4)
however,
fn: focal length of the lens group Ln fpMax: focal length of the lens group LpMax The zoom lens according to any one of claims 1 to 3, which satisfies the following conditional expression:
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 The zoom lens according to any one of claims 1 to 4, which satisfies the following conditional expression:
1.00 ≦ βn1 ≦ 5.00 (6)
however,
βn1: lateral magnification of the lens unit Ln when focusing on infinity at the wide-angle end The zoom lens according to any one of claims 1 to 5, which satisfies the following conditional expression:
1.00 ≦ βn12 ≦ 5.00 (7)
however,
βn12: The combined lateral magnification of the lens group Ln and the final lens group when focusing on infinity at the wide-angle end 7. The zoom lens according to claim 1, wherein the lens group Ln moves along the optical axis when focusing from infinity to a close object, and satisfies the following condition:
0.6≦|{1−(βn1×βn1)}×(βn2×βn2)|≦15.0 ... (8)
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 zoom lens according to any one of claims 1 to 7, which satisfies the following conditional expression:
1.00≦ |CrG1r/fw| ...(9)
however,
CrG1r: radius of curvature of the lens surface of the first lens group closest to the image side fw: focal length of the zoom lens when focusing on infinity at the wide-angle end The zoom lens according to any one of claims 1 to 8, which satisfies the following conditional expression:
0.65 ≦ (fw×tanω)/BFw ≦ 2.30 (10)
however,
fw: focal length of the zoom lens when focusing on infinity at the wide-angle end ω: half angle of view of the zoom lens when focusing on infinity at the wide-angle end BFw: distance on the optical axis between the lens surface closest to the image and the image plane of the zoom lens when focusing on infinity at the wide-angle end 10. The zoom lens according to claim 1, wherein the lens group LpMax has at least one lens LpMp having a positive refractive power, and the following conditional expression is satisfied:
45.0 ≦ νdLpMp ≦ 98.0 (11)
however,
νdLpMp: Abbe number at d line of the lens LpMp The zoom lens according to any one of claims 1 to 10, wherein the first lens group has at least one lens L1p having a positive refractive power, and satisfies the following conditional expression: 1<$1 mn>1<$1mn> 1 .
20.0 ≦ νdL1p ≦ 50.0 (12)
however,
νdL1p: Abbe number at the d line of the lens L1p The zoom lens according to any one of claims 1 to 11, wherein the first lens group has at least one lens L1p having a positive refractive power, and satisfies the following conditional expression: 1<$1 mn>1<$1mn> 1 .
1.70≦NdL1p≦2.20 (13)
however,
NdL1p: refractive index of the lens L1p at the d line The zoom lens according to any one of claims 1 to 12, which satisfies the following conditional expression:
|BFt-BFw|/TLw ≦ 0.30...(14)
however,
BFt: The distance on the optical axis between the lens surface closest to the image side of the zoom lens and the image plane when focusing on infinity at the telephoto end. BFw: The distance on the optical axis between the lens surface closest to the image side of the zoom lens and the image plane when focusing on infinity at the wide-angle end. TLw: The total optical length of the zoom lens when focusing on infinity at the wide-angle end. An imaging device comprising the zoom lens according to any one of claims 1 to 13, and an image sensor on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal.

Images