JP7512078B2 - 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 cameras become more compact, there is a demand for optical systems with smaller zoom lenses.

Patent Documents 1 and 2 disclose inventions relating to optical systems for telephoto zoom lenses for mirrorless interchangeable-lens cameras. In these zoom lenses, the focus group is located closer to the image side than the aperture, thereby making the focus mechanism more compact.

Patent document 3 discloses an invention relating to an optical system for a high-magnification zoom lens for a so-called mirrorless single-lens camera. In this zoom lens, the entire second lens group is arranged as a focus group, ensuring good optical performance throughout the entire zoom range.

JP 2014-016601 A JP 2013-037105 A JP 2018-197774 A

In the zoom lenses described in Patent Documents 1 and 2, the lens group on the image side of the focus group is large, and the overall product is not sufficiently compact and lightweight. In addition, in the zoom lens described in Patent Document 3, the lens diameter of the second lens group is large, which results in a large focus mechanism and insufficient compactness and weight reduction.

Therefore, the objective of the present invention is to provide a small and lightweight zoom lens and imaging device.

In order to solve the above-mentioned problems, the zoom lens of the present invention comprises, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups, a Gf lens group having negative refractive power, and a rear group including at least a Gn lens group having negative refractive power, and is a zoom lens that varies magnification by changing the spacing between adjacent lens groups, wherein a composite refractive power from the intermediate group to the rear group is positive, at least the second lens group moves along the optical axis during magnification variation, and the intermediate group is defined as group A on the object side and group B on the image side, with the maximum air spacing at the telephoto end as the boundary, and satisfies the following conditional formula:
0.1<FA/FB<4.0 ... (1)
1.0< Lff/TAtoB < 5.7 ... (2)
−18.0<ffr/fw<−0.1 ... (3)
0.0 < |fw/m2| < 2000.0 ... (4)
however,
FA: composite focal length of the A group at the telephoto end FB: composite focal length of the B group at the telephoto end Lff: total optical length of the middle group at the telephoto end TAtoB: maximum air space at the telephoto end of the middle group ffr: composite focal length at the telephoto end of all lenses located on the image side of the Gf lens group fw: focal length at the wide-angle end of the zoom lens m2: amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end Here, the amount of movement is considered positive in the direction from the object side to the image side.

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 provides a small and lightweight zoom lens and imaging device.

1 is a cross-sectional view of a zoom lens at a wide-angle end according to a first embodiment of the present invention. 5A to 5C are diagrams illustrating various aberrations at the wide-angle end of the zoom lens of Example 1. 5A to 5C are diagrams illustrating various aberrations of the zoom lens of Example 1 in an intermediate focal length state. 5A to 5C are diagrams illustrating various aberrations at the telephoto end of the zoom lens of Example 1. FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end according to a second embodiment of the present invention. 8A to 8C are diagrams illustrating various aberrations at the wide-angle end of the zoom lens of Example 2. 8A to 8C are diagrams illustrating various aberrations of the zoom lens of Example 2 in an intermediate focal length state. 8A to 8C are diagrams illustrating various aberrations at the telephoto end of the zoom lens of Example 2. FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end according to a third embodiment of the present invention. 11A to 11C are diagrams illustrating various aberrations at the wide-angle end of the zoom lens of Example 3. 11A to 11C are diagrams illustrating various aberrations of the zoom lens of Example 3 in an intermediate focal length state. 11A to 11C are diagrams illustrating various aberrations at the telephoto end of the zoom lens of Example 3. FIG. 11 is a cross-sectional view of a zoom lens at a wide-angle end according to a fourth embodiment of the present invention. 13A to 13C are diagrams illustrating various aberrations at the wide-angle end of the zoom lens of Example 4. 13A to 13C are diagrams illustrating various aberrations of the zoom lens of Example 4 in an intermediate focal length state. 13A to 13C are diagrams illustrating various aberrations at the telephoto end of the zoom lens of Example 4. 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 a zoom lens that is made up of, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups, a Gf lens group having negative refractive power, and a rear group including at least a Gn lens group having negative refractive power, and changes the spacing between adjacent lens groups to change the magnification. In addition, the composite refractive power from the intermediate group to the rear group is positive, and the intermediate group is made up of an A group on the object side and a B group on the image side, with the maximum air space at the telephoto end as the boundary. This lens configuration allows for an overall small size and light weight.

(1) First Lens Group The first lens group is a lens group having a positive refractive power, and the specific configuration is not particularly limited as long as it has at least one positive lens. Also, having at least one negative lens is preferable because it makes it easier to suppress chromatic aberration and obtain good optical performance. Also, having a cemented lens of a positive lens and a negative lens is preferable because it makes it easier to suppress chromatic aberration and to suppress the sensitivity of each lens.

Here, "lens group" refers to a group consisting of one lens or multiple adjacent lenses that move along the optical axis by the same amount and along the same trajectory when changing magnification. When a lens group is composed of multiple lenses, the distance on the optical axis between the lenses included in that lens group does not change when changing magnification. In addition, the distance on the optical axis between adjacent lens groups changes when changing magnification.

(2) Second Lens Group The second lens group is a lens group having negative refractive power, and its specific configuration is not particularly limited as long as it has one or more negative lenses. It is preferable to have a cemented lens of a positive lens and a negative lens in the second lens group, since it is easier to suppress chromatic aberration and obtain good optical performance. In addition, the second lens group moves on the optical axis when zooming from the wide-angle end to the telephoto end, making it possible to reduce the size of the first lens group and the amount of movement of other lens groups. In order to obtain the above effect, the second lens group moves down to the image side when zooming, which is effective in reducing the size of the subsequent groups and allows the size of the entire product system to be reduced.

(3) Composite group from the middle group to the rear group The composite group from the middle group to the rear group has positive refractive power as a whole, and the specific group configuration is not particularly limited as long as it has three or more lens groups. As long as it has at least one positive lens group and two negative lens groups, the other lens groups may have either negative or positive refractive power.

By constructing the composite group from the middle group to the rear group from three or more lens groups, the distance on the optical axis between each lens group can be changed when changing magnification, which increases the design freedom for the position to which each lens group can be moved when changing magnification. As a result, it becomes easier to suppress aberration fluctuations, and a zoom lens with high optical performance can be obtained. In addition, by arranging an aperture diaphragm in the composite group from the middle group to the rear group, the aperture diaphragm can be made small, making it easy to achieve radial miniaturization and weight reduction.

(4) Gf lens group The Gf lens group is a lens group having negative refractive power, and as long as it has one or more negative lenses, its specific configuration is not particularly limited. The Gf lens group is configured to include one or more positive lenses, which makes it easy to suppress the occurrence of axial chromatic aberration caused by movement during focusing, and to obtain good optical performance. It is preferable to cement a positive lens and a negative lens together, since it is easy to suppress the sensitivity between the lenses. It is also preferable to configure the lens from the object side to a positive lens and a negative lens, since it is easy to suppress axial aberration. It is also preferable to configure the lens from a positive lens and a negative lens, since it is possible to reduce the size of the entire product system. It is also preferable that the lens closest to the image side of the Gf lens group has a concave shape toward the image side.

(4) Gn lens group The Gn lens group is a lens group having negative refractive power, and is arranged closer to the image side than the Gf lens group. The specific configuration of the Gn lens group is not particularly limited. By moving toward the object side when changing magnification from the wide-angle end to the telephoto end, it is possible to change magnification efficiently, and it is preferable to easily reduce the overall length of the product. In addition, it is preferable that the lens closest to the object side of the Gn lens group has a concave shape toward the object side.

1-2. Operation (1) Magnification change The zoom lens employs the above-mentioned configuration, and when changing the magnification, the magnification is changed by changing the distance on the optical axis between the first lens group, the second lens group, and the multiple lens groups included in the intermediate group to the rear group. At that time, it is preferable that the distance on the optical axis between the first lens group and the second lens group is maximum at the telephoto end, and the distance on the optical axis between the second lens group and the intermediate group is minimum at the telephoto end. By moving each lens group in this way, it becomes easy to obtain good optical performance over the entire range of magnification change without forcibly increasing the power.

In addition, when changing magnification from the wide-angle end to the telephoto end, the Gn lens group moves along the same trajectory as one of the lens groups included in the intermediate group, which is preferable because it simplifies the mechanical structure that moves the Gn lens group and makes it easier to make the entire product smaller and lighter.

(2) Focusing In this zoom lens, when focusing from infinity to a close distance, the Gf lens group is moved along the optical axis. By using the Gf lens group as the focus group, it becomes easy to obtain a zoom lens with little variation in field curvature over the entire range of object distances from infinity to a close distance.

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 formula (1)
0.1 <FA/FB<4.0 ... (1)
however,
FA: composite focal length of A group at the telephoto end FB: composite focal length of B group at the telephoto end

The above conditional expression (1) specifies the ratio of the composite focal length of group A to the composite focal length of group B at the telephoto end of the zoom lens. By satisfying conditional expression (1), the group closer to the image side than the intermediate group can be made smaller, making it easier to miniaturize the entire product system.

On the other hand, if the value of conditional formula (1) is below the lower limit, the composite focal length of group A becomes shorter than the appropriate value, making it difficult to correct the spherical aberration and coma aberration that occur in group A with the entire optical system, and making it difficult to obtain good optical performance throughout the entire zoom range. On the other hand, if the value of conditional formula (1) is above the upper limit, the composite focal length of group A becomes longer than the appropriate value, the height of the light rays passing through the group on the image side of group A becomes high, making it impossible to miniaturize the subsequent groups and making it difficult to miniaturize the entire product system.

In order to obtain the above effect, the lower limit of conditional formula (1) is preferably 0.20, and more preferably 0.30. The upper limit of conditional formula (1) is preferably 3.20, more preferably 2.00, and even more preferably 1.20. When adopting these preferred lower or upper limits, the inequality sign with equality (≦) may be replaced with an inequality sign (<). The same principle applies to the other conditional formulas.

1-3-2. Conditional Expression (2)
1.0< Lff/TAtoB < 5.7 ... (2)
however,
Lff: total optical length of the middle group at the telephoto end TAtoB: maximum air gap of the middle group at the telephoto end

Conditional formula (2) specifies the ratio of the total optical length of the intermediate group at the telephoto end of the zoom lens to the maximum air gap of the intermediate group at the telephoto end. By satisfying conditional formula (2), the convergence effect obtained in the intermediate group makes it possible to lower the height of the light rays passing through the subsequent groups, making it easier to miniaturize the entire product system.

On the other hand, if the value of conditional formula (2) is equal to or greater than the upper limit, the overall optical length of the intermediate group becomes too long, making it difficult to shorten the overall optical length. The distance on the optical axis between group A and group B becomes too short, making it difficult to reduce the diameter of the subsequent groups, making it difficult to miniaturize the entire product system.

To obtain the above effect, the lower limit of conditional formula (2) is preferably 1.20, and more preferably 1.40. The upper limit of conditional formula (2) is preferably 5.00, and more preferably 4.50.

1-3-3. Conditional expression (3)
−18.0< ffr / fw< −0.1 ... (3)
however,
ffr: composite focal length at the telephoto end of all lenses arranged on the image side of the Gf lens group fw: focal length at the wide-angle end of the zoom lens

The above conditional formula (3) specifies the ratio of the composite focal length at the telephoto end of all the lenses in the group located on the image side of the Gf lens group of the zoom lens to the focal length at the wide-angle end. By satisfying conditional formula (3), it becomes easier to shorten the exit pupil at the telephoto end and reduce the outer diameter of the lens group close to the image plane, thereby making it possible to miniaturize the entire product system.

On the other hand, if the value of conditional formula (3) is below the lower limit, it indicates that the composite focal length of the group on the image side of the Gf lens group is longer than the appropriate value, the exit pupil becomes longer at the telephoto end, the outer diameter of the lens group close to the image surface becomes smaller, and it becomes difficult to miniaturize the entire product system. On the other hand, if the value of conditional formula (3) is above the upper limit, it indicates that the composite focal length of the group on the image side of the Gf lens group is shorter than the appropriate value, it becomes difficult to correct aberrations such as curvature of field and distortion, and many lenses are required for aberration correction, making it difficult to miniaturize the entire product system.

To obtain the above effect, the lower limit of conditional formula (3) is preferably -5.00, more preferably -4.00, and even more preferably -3.00. The upper limit of conditional formula (3) is preferably -0.5, and even more preferably -1.00.

1-3-3. Conditional expression (4)
0.1 < |fw/m2| < 2000.0 ... (4)
however,
fw: focal length at the wide-angle end of the zoom lens; m2: amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end. Here, the amount of movement is in the direction from the object side to the image side. is considered positive.

The above conditional expression (4) defines the ratio between the focal length at the wide-angle end of the zoom lens and the amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end. By satisfying conditional expression (4), it becomes easy to reduce the size of the first lens group and the amount of movement of each lens group.

On the other hand, if the value of conditional expression (4) is equal to or less than the lower limit, the amount of movement of the second lens group becomes large, making it difficult to reduce the size of the entire product. On the other hand, if the value of conditional expression (4) is equal to or greater than the upper limit, the amount of movement of the second lens group becomes small, and in order to obtain a predetermined zoom magnification, it is necessary to compensate for the change in magnification with other groups. As a result, the amount of movement of the other groups during magnification change becomes large, making it difficult to reduce the size of the entire product.

To obtain the above effect, the lower limit of conditional formula (4) is preferably 1.0, more preferably 2.0, and even more preferably 3.0. The upper limit of conditional formula (4) is preferably 1000.0, more preferably 100.0, even more preferably 50.0, and even more preferably 20.0.

1-3-3. Conditional formula (4)'
0.1 < fw/m2 < 2000.0 ... (4)'
however,
fw: focal length at the wide-angle end of the zoom lens; m2: amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end. Here, the amount of movement is in the direction from the object side to the image side. is considered positive.

The above conditional formula (4)' stipulates the ratio between the focal length at the wide-angle end of the zoom lens and the amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end. By satisfying conditional formula (4)', the second lens group moves down toward the eyepiece side when changing magnification, which is effective in reducing the size of the subsequent groups and also makes it easier to reduce the size of the entire product system.

In order to obtain the above effect, the lower limit of conditional formula (4)' is preferably 1.0, more preferably 2.0, and even more preferably 3.0. The upper limit of conditional formula (4)' is preferably 1000.0, more preferably 100.0, even more preferably 50.0, and even more preferably 20.0.

1-3-3. Conditional expression (5)
−5.0 < β2t < −0.1 (5)
however,
β2t: lateral magnification of the second lens group at the telephoto end

The above conditional formula (5) specifies the lateral magnification of the second lens group at the telephoto end. By satisfying conditional formula (5), the amount of movement of each lens group during magnification change is optimized, making it possible to shorten the overall optical length, and by facilitating aberration correction throughout the entire zoom range, it becomes easier to simplify the lens configuration and reduce the weight of the entire product.

On the other hand, if the value of conditional formula (5) is equal to or less than the lower limit, it indicates that the lateral magnification of the second lens group is greater than the appropriate value, and the spherical aberration and coma aberration occurring in the first lens group are magnified more than the appropriate values, so that a large number of lenses are required for aberration correction, making it difficult to reduce the weight of the entire product system. On the other hand, if the value of conditional formula (5) is equal to or greater than the upper limit, it indicates that the lateral magnification of the second lens group is smaller than the appropriate value, and in order to obtain a predetermined zoom magnification, it is necessary to compensate for the magnification change with lens groups other than the second lens group, and the amount of movement of each lens group during magnification change becomes large, making it difficult to reduce the size of the entire product system.

To obtain the above effect, the lower limit of conditional formula (5) is preferably -4.0, more preferably -2.8, and even more preferably -2.0. The upper limit of conditional formula (5) is preferably -0.3, and even more preferably -0.5.

1-3-4. Conditional expression (6)
1.0 < β2t / β2w < 7.0 (6)
however,
β2w: lateral magnification of the second lens group at the wide-angle end β2t: lateral magnification of the second lens group at the telephoto end

The above conditional formula (6) is a conditional formula for defining the ratio of the lateral magnification of the second lens group at the telephoto end to the lateral magnification of the second lens group at the wide-angle end. By satisfying conditional formula (6), the amount of movement of each lens group during magnification change is optimized, making it possible to shorten the overall optical length. Furthermore, it becomes easier to correct aberrations throughout the entire zoom range, simplifying the lens configuration, and making it easier to reduce the weight of the entire product.

On the other hand, if the value of conditional expression (6) is equal to or less than the lower limit, the amount of movement of the second lens group during zooming becomes smaller than the appropriate value, and in order to obtain a predetermined zoom ratio, it is necessary to increase the amount of movement of lens groups other than the second lens group or to strengthen the refractive power. As a result, a large number of lenses are required to correct aberrations, making it difficult to reduce the size and weight of the entire product. On the other hand, if the value of conditional expression (6) is equal to or greater than the upper limit, the amount of movement of the second lens group during zooming becomes larger than the appropriate value, making it difficult to reduce the size of the entire product.

In order to obtain the above effect, the lower limit of conditional formula (6) is preferably 1.50, more preferably 1.75, and even more preferably 2.00. The upper limit of conditional formula (6) is preferably 5.60, more preferably 4.5, and even more preferably 3.50.

1-3-5. Conditional expression (7)
−10.0 < (1 − βf × βf) × βfr × βfr < −1 (7)
however,
βf: lateral magnification of the Gf lens group at the telephoto end βfr: composite lateral magnification of all lenses arranged on the image side of the Gf lens group at the telephoto end

Conditional formula (7) specifies the lateral magnification at the telephoto end of the Gf lens group and all lenses arranged on its image side, and the calculated value is a conditional formula for specifying the so-called backlash magnification of the Gf lens group. By satisfying conditional formula (7), the amount of movement of the focus group during focusing can be optimized, making it easy to reduce the size and weight of the entire optical system.

On the other hand, if the value of conditional formula (7) is below the lower limit, the backlash magnification of the focus group becomes larger than the appropriate value, and it becomes necessary to strengthen the refractive power of each lens group more than the appropriate value. As a result, a large number of lenses are required to correct aberrations, making it difficult to reduce the weight of the entire product. On the other hand, if the value of conditional formula (7) is above the upper limit, the backlash magnification of the focus group becomes smaller than the appropriate value, and the amount of movement of the focus group when focusing on a close object becomes large, which results in a larger focus mechanism and makes it difficult to reduce the size of the entire product.

To obtain the above effect, the lower limit of conditional formula (7) is preferably -9.30, more preferably -8.50, and even more preferably -8.00. The upper limit of conditional formula (7) is preferably -2.00.

1-3-6. Conditional expression (8)
1.1 < f1/fw < 10.0 (8)

The above conditional expression (8) is a conditional expression for defining the ratio between the focal length of the first lens group and the focal length at the wide-angle end of the zoom lens. By satisfying conditional expression (8), it is possible to shorten the total optical length, and it becomes easy to reduce the weight of the first lens group, which has the largest outer diameter in the entire optical system.

On the other hand, if the value of conditional formula (8) is equal to or less than the lower limit, the focal length of the first lens group will be shorter than the appropriate value, which is effective in reducing the overall optical length, but the spherical aberration and coma aberration generated by each surface will be greater than the appropriate value. As a result, a large number of lenses will be required to correct the aberrations, making it difficult to reduce the weight of the entire product system. On the other hand, if the value of conditional formula (8) is equal to or greater than the upper limit, the composite focal length of the first lens group will be longer than the appropriate value, making it difficult to reduce the overall optical length and the amount of extension of the first lens group during zooming, and making it difficult to reduce the size of the entire product system.

In order to obtain the above effect, the lower limit of conditional formula (8) is preferably 1.50. The upper limit of conditional formula (7) is preferably 6.00, more preferably 5.00, and even more preferably 4.00.

1-3-7. Conditional expression (9)
1.65 < Nd1n < 2.50 (9)
however,
Nd1n: the refractive index of the negative lens having the highest refractive index in the first lens group

Conditional formula (9) is a conditional formula for specifying the refractive index of the negative lens with the highest refractive index in the first lens group. By satisfying conditional formula (9), it is possible to optimize the spherical aberration and coma aberration that occur in the first lens group, and it becomes easy to achieve a reduction in the size and weight of the entire product system.

On the other hand, when the value of conditional expression (9) is equal to or less than the lower limit, the over-spherical aberration generated by the negative lens is under-corrected relative to the under-spherical aberration generated by the first lens group. As a result, a large number of lenses are required in the subsequent lens groups to correct the aberration, making it difficult to reduce the weight of the entire product system. On the other hand, when the value of conditional expression (9) is equal to or greater than the upper limit, the over-spherical aberration generated by the negative lens is over-corrected relative to the under-spherical aberration generated by the first lens group. As a result, a large number of lenses are required in the subsequent lens groups to correct the aberration, making it difficult to reduce the weight of the entire product system.

In order to obtain the above effect, the lower limit of conditional formula (9) is preferably 1.70, and more preferably 1.75. The upper limit of conditional formula (9) is preferably 2.10, and more preferably 2.0, and even more preferably 1.94.

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.

Next, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

(1) Optical Configuration FIG. 1 shows a lens cross-sectional view of the zoom lens of Example 1. As shown in FIG. 1, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an intermediate group consisting of a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a rear group consisting of a fifth lens group G5 having negative refractive power. The third lens group G3 has an aperture stop S disposed therein. In addition, the composite refractive power from the intermediate group to the rear group is positive. Here, the fourth lens group G4 is a Gf lens group that moves along the optical axis during focusing, and the fifth lens group is a Gn lens group.

When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 each move toward the object side on the optical axis. In addition, the third lens group G3 and the fifth lens group G5 move on the same trajectory. The configuration of each lens group is explained below.

The first lens group G1 is composed of, in order from the object side, a cemented lens formed by cementing together a negative meniscus lens L1 and a positive meniscus lens L2, both of which have a convex surface facing the object side, and a biconvex lens L3.

The second lens group G2 is composed of, in order from the object side, a negative meniscus lens L4 with its convex surface facing the object side, a positive meniscus lens L5, a cemented lens formed by cementing a biconcave lens L6 and a biconvex lens L7, and a negative meniscus lens L8 with its concave surface facing the object side.

The third lens group G3 is composed of, in order from the object side, a biconvex lens L9, a biconvex lens L10, a cemented lens formed by cementing a biconvex lens L11 and a biconcave lens L12, an aperture stop S, a cemented lens formed by cementing a negative meniscus lens L13 and a biconvex lens L14, a biconvex lens L15, a biconcave lens L16, and a biconvex lens L17. In the intermediate group of Example 1, group A is composed of lenses with surface numbers 15 to 21 shown in the lens data table below, and group B is composed of lenses with surface numbers 23 to 31.

The fourth lens group G4 is composed of, in order from the object side, a cemented lens formed by cementing together a positive meniscus lens L18 and a negative meniscus lens L19 with its concave surface facing the image side.

The fifth lens group G5 is composed of a negative meniscus lens L20 that is concave on the object side. This lens L20 has a composite aspheric surface.

In FIG. 1, "I" indicates the image plane, and more specifically, indicates the imaging surface of a solid-state imaging device such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. Also, a cover glass CG or the like is provided on the object side of I. This is the same in the lens cross-sectional views shown in the other embodiments, so further explanation will be omitted.

(2) Numerical Examples Numerical Examples to which specific numerical values of the zoom lens are applied will now be described. The "lens data,""specificationtable,""variableinterval,""asphericcoefficient," 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 4.

In the "Lens Data" section, "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 "νd" is the Abbe number at the d-line. In the "surface number" column, "ASPH" 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(0)", "d(6)", 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 "radius of curvature" column, "inf." means infinity, meaning that the lens surface is flat.

In the "Specifications Table," "f" is the focal length of the zoom lens, "FNo." is the F-number, and "ω" is the half angle of view. The values shown are for the wide-angle end, mid-focal length, and telephoto end, respectively.

In "Variable Distance," values at the wide-angle end, mid-focal length, and telephoto end when focusing on infinity are shown. The same applies to 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" represents 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 when focusing on an object at infinity at the wide-angle end, intermediate focal length, and telephoto end. 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 diagram, the solid line shows the spherical aberration at the d-line (wavelength 587.56 nm), and the dashed line shows the spherical aberration at the g-line (wavelength 435.84 nm). In the astigmatism diagram, 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 (T) of the d-line. In the distortion aberration diagram, 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 other embodiments, so explanations will be omitted below.

(Lens data)
Surface number RD Nd νd
1 140.280 1.000 1.83400 37.34
2 71.818 5.191 1.49700 81.61
3 1453.759 0.200
4 86.386 4.987 1.49700 81.61
5 -671.717 D(5)
6 279.897 0.800 1.87070 40.73
7 31.807 3.435
8 34.685 2.449 1.85478 24.80
9 48.743 3.732
10 -54.863 0.800 1.72916 54.67
11 52.358 3.920 1.85478 24.80
12 -122.362 0.937
13 -54.826 0.800 1.87070 40.73
14 -137.141 D(14)
15 88.192 3.216 1.63854 55.45
16 -126.808 0.200
17 61.272 2.938 1.56883 56.04
18 -1597.002 0.200
19 40.271 4.336 1.61800 63.39
20 -100.891 0.800 1.95375 32.32
21 76.735 12.860
22S inf. 5.980
23 78.059 0.800 1.95375 32.32
24 16.446 5.028 1.61800 63.39
25 -160.736 0.200
26 95.695 2.592 1.63930 44.87
27 -78.586 1.251
28 -27.998 0.800 1.72916 54.67
29 69.575 0.200
30 41.954 5.336 1.65412 39.68
31 -27.825 D(31)
32 45.168 2.181 1.84666 23.78
33 102.549 0.800 1.72916 54.67
34 21.310 D(34)
35ASPH -30.909 0.100 1.51460 49.96
36 -35.423 0.800 1.59349 67.00
37 -88.558 D(37)
38 inf. 2.500 1.51680 64.20
Image surface inf. 1.000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 51.552 122.4417 290.9854
F No. 4.7089 6.4897 6.4952
ω 23.4944 9.7363 4.1286

(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 A12
35 0.0000 7.03119E-06 9.43985E-09 7.14036E-12 7.39190E-15 1.72441E-17

(Lens group data)
Group Number Focal Length
G1 135.967
G2 -31.217
G3 41.088
G4 -64.284
G5 -82.605

(1) Optical Configuration FIG. 5 shows a lens cross-sectional view of the zoom lens of Example 2. As shown in FIG. 5, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an intermediate group consisting of a third lens group G3 having positive refractive power and a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, and a rear group consisting of a sixth lens group G6 having negative refractive power. An aperture stop S is disposed in the fourth lens G4. In addition, the composite refractive power from the intermediate group to the rear group is positive. Here, the fifth lens group G5 is a Gf lens group that moves along the optical axis when focusing, and the sixth lens group is a Gn lens group.

When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, and the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 each move toward the object side on the optical axis. In addition, the fourth lens group G4 and the sixth lens group G6 move on the same trajectory. The configuration of each lens group is explained below.

The first lens group G1 is composed of, in order from the object side, a cemented lens formed by cementing together a negative meniscus lens L1 with its convex surface facing the object side and a biconvex lens L2, and a biconvex lens L3.

The second lens group G2 is composed of, in order from the object side, a cemented lens formed by cementing together a biconcave lens L4, a biconcave lens L5 and a biconvex lens L6, and a negative meniscus lens L7 with its concave surface facing the object side.

The third lens group G3 is composed of, in order from the object side, a biconvex lens L8, a biconvex lens L9, a biconvex lens L10, and a cemented lens formed by cementing together a biconcave lens L11. In this embodiment, group A is the third lens group G3.

The fourth lens group G4 is composed of an aperture stop, a cemented lens formed by cementing a negative meniscus lens L12 and a biconvex lens L13, a cemented lens formed by cementing a negative meniscus lens L14, a cemented lens formed by cementing a positive meniscus lens L15 and a biconcave lens L16, and a biconvex lens L17. These lenses L16 and L17 have aspheric shapes. In this embodiment, group B is the fourth lens group G4.

The fifth lens group G5 is composed of, in order from the object side, a cemented lens formed by cementing together a positive meniscus lens L18 and a negative meniscus lens L19 with its concave surface facing the image side.

The sixth lens group G6 is composed of a negative meniscus lens L20 that has a concave surface facing the object side. This lens L20 has a composite aspheric surface.

(2) Numerical Examples Numerical examples using specific numerical values of the zoom lens are shown below. Also, longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, the intermediate focal length, and the telephoto end are shown in Fig. 6, Fig. 7, and Fig. 8.

(Lens data)
Surface number RD Nd νd
1 217.1079 1.0000 1.87070 40.73
2 90.4950 7.4730 1.43700 95.10
3 -386.3192 0.2000
4 90.0885 6.9871 1.49700 81.61
5 -650.7101 D(5)
6 -603.1690 0.8000 1.91082 35.25
7 39.0857 4.6492
8 -62.4702 0.8000 1.59282 68.62
9 42.1177 5.6943 1.85478 24.80
10 -74.7101 1.3563
11 -44.7356 0.8000 1.91082 35.25
12 -102.6544 D(12)
13 90.6161 3.4091 1.61800 63.39
14 -280.4369 0.2000
15 47.1512 5.7492 1.49700 81.61
16 -506.8687 8.8446
17 32.8121 5.4460 1.61800 63.39
18 -118.0118 0.8000 2.00100 29.13
19 87.9349 D(19)
20S inf. 7.1522
21 67.4803 0.8000 2.00100 29.13
22 16.9646 6.6008 1.61340 44.27
23 -21.7845 0.8000 2.00100 29.13
24 -65.7583 1.0000
25 -77.4598 3.2111 1.85478 24.80
26 -21.8522 0.8000 1.77387 47.25
27ASPH 39.7020 1.2050
28ASPH 28.9875 5.8563 1.63930 44.87
29 -31.6072 D(29)
30 44.6723 2.5740 1.85478 24.80
31 195.7795 0.8000 1.72916 54.67
32 20.5423 D(32)
33ASPH -22.5854 0.1000 1.51460 49.96
34 -26.4686 0.8000 1.84263 42.59
35 -44.1143 D(35)
36 inf. 2.5000 1.51680 64.20
Image surface inf. 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 51.5451 141.3119 387.9155
F No. 4.6040 6.0190 6.4986
ω 23.3081 8.4793 3.1194

(variable interval)
Wide-angle end Mid-range Telephoto end
D(5) 1.0000 37.3753 75.6505
D(12) 51.0014 22.1315 1.0000
D(19) 1.5339 3.2464 6.7679
D(29) 0.9845 6.6961 3.0860
D(32) 26.5718 20.8603 24.4704
D(35) 14.4998 36.1300 49.7531

(Aspherical coefficients)
Face number K A4 A6 A8 A10 A12
27 0.0000 -5.50054E-06 6.48593E-09 -9.01927E-11 -4.13584E-15 1.99064E-15
28 0.0000 -1.59705E-05 6.66374E-09 1.16544E-11 -6.99629E-13 3.75875E-15
33 0.0000 1.43601E-05 2.28089E-08 2.57195E-11 -5.45627E-14 4.59464E-16

(Lens group data)
Group Number Focal Length
G1 150.777
G2 -35.087
G3 39.769
G4 99.715
G5 -63.536
G6 -63.392

(1) Optical Configuration FIG. 9 shows a lens cross-sectional view of the zoom lens of Example 3. As shown in FIG. 9, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an intermediate group consisting of a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, and a rear group consisting of a fifth lens group G5 having negative refractive power. The third lens group G3 has an aperture stop S disposed therein. In addition, the composite refractive power from the intermediate group to the rear group is positive. Here, the fourth lens group G4 is a Gf lens group that moves along the optical axis during focusing, and the fifth lens group is a Gn lens group.

When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, and the third lens group G3, the fourth lens group G4, and the fifth lens group G5 each move toward the object side on the optical axis. In addition, the third lens group and the fifth lens group move on the same trajectory. The configuration of each lens group is explained below.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L1 with its convex surface facing the object side and a cemented lens formed by cementing together a biconvex lens L2.

The second lens group G2 is composed of, from the object side, a cemented lens formed by cementing a biconvex lens L3 and a biconcave lens L4 together, and a negative meniscus lens L5 with its concave surface facing the object side.

The third lens group G3 is composed of, in order from the object side, a biconvex lens L6, a cemented lens formed by cementing a biconvex lens L7 and a biconcave lens L8, an aperture stop S, a cemented lens formed by cementing a negative meniscus lens L9 and a biconvex lens L10, a biconcave lens L11, and a biconvex lens L12.

The fourth lens group G4 is composed of, in order from the object side, a biconvex lens L13 and a cemented lens formed by cementing a biconcave lens L14 to the image side.

The fifth lens group G5 is composed of a negative meniscus lens L15 that has a concave surface facing the object side. This lens L15 has a composite aspheric surface.

(2) Numerical Examples Numerical examples using specific numerical values of the zoom lens are shown below. Also, longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, the intermediate focal length, and the telephoto end are shown in Fig. 10, Fig. 11, and Fig. 12.

(Lens data)
Surface number RD Nd νd
1 97.3810 1.0000 1.83400 37.34
2 65.3564 6.0969 1.49700 81.61
3 -357.4593 D(3)
4 521.6104 3.6395 1.84666 23.78
5 -56.0589 0.8000 1.72916 54.67
6 71.2731 3.1101
7 -55.1365 0.8000 1.83481 42.72
8 -607.3141 D(8)
9 65.5883 3.8714 1.63854 55.45
10 -88.9316 0.2000
11 35.7714 4.9105 1.61997 63.88
12 -78.6426 0.8000 1.90366 31.34
13 91.4486 13.4138
14S inf. 5.9970
15 29.3555 0.8000 1.90366 31.34
16 12.8554 5.3881 1.61997 63.88
17 -1289.1248 1.0948
18 -39.1085 0.8000 1.80420 46.50
19 24.8823 0.2000
20 22.8459 7.0000 1.68893 31.16
21 -31.8355 D(21)
22 103.1500 2.2711 1.71736 29.50
23 -179.1975 0.8000 1.48749 70.44
24 19.2094 D(24)
25ASPH -59.7119 0.1000 1.51460 49.96
26 -84.0434 0.8000 1.83481 42.72
27 -210.1086 D(27)
28 inf. 2.5000 1.51680 64.20
Image surface inf. 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 72.1249 144.9063 290.9111
F No. 4.5378 5.7122 6.6499
ω 17.0633 8.3186 4.1549

(variable interval)
Wide-angle end Mid-range Telephoto end
D(3) 1.0000 43.9217 78.1773
D(8) 42.9273 20.097 1.0000
D(21) 0.9934 4.8635 6.9051
D(24) 33.1863 29.3162 27.2746
D(27) 14.4999 27.3721 44.2499

(Aspherical coefficients)
Face number K A4 A6 A8 A10 A12
25 0.0000 7.77961E-06 2.18096E-09 2.15496E-11 -5.60681E-14 8.26596E-17

(Lens group data)
Group Number Focal Length
G1 208.489
G2 -48.948
G3 41.843
G4 -59.501
G5 -118.579

(1) Optical configuration FIG. 13 shows a lens cross-sectional view of the zoom lens of Example 4. As shown in FIG. 13, the zoom lens is composed of, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, an intermediate group consisting of a third lens group G3 having positive refractive power and a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, and a rear group consisting of a seventh lens group G7 having negative refractive power. The third lens group G3 has an aperture stop S disposed therein. In addition, the composite refractive power from the intermediate group to the rear group is positive. Here, the fifth lens group G5 is a Gf lens group that moves along the optical axis during focusing, and the seventh lens group is a Gn lens group.

When changing magnification from the wide-angle end to the telephoto end, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, and the third lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 each move toward the object side on the optical axis. The configuration of each lens group is explained below.

The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L1 with its convex surface facing the object side and a cemented lens formed by cementing together a biconvex lens L2.

The second lens group G2 is composed of, from the object side, a biconcave lens L3 and a cemented lens formed by cementing a positive meniscus lens L4.

The third lens group G3 is composed of, in order from the object side, a biconvex lens L5, a cemented lens formed by cementing a biconvex lens L6 and a biconcave lens L7, and an aperture stop S.

The fourth lens group G4 is composed of a biconvex lens L8.

The fifth lens group G5 is composed of, in order from the object side, a cemented lens formed by cementing together a positive meniscus lens L9 and a negative meniscus lens L10 with its concave surface facing the image side.

The sixth lens group G6 is composed of a positive meniscus lens L11 that has a concave surface facing the object side.

The seventh lens group G7 is composed of, in order from the object side, a cemented lens formed by cementing a positive meniscus lens L12 and a biconcave lens L13. In Example 4, the sixth lens group G6 and the seventh lens group G7 are all lenses arranged closer to the image side than the Gf lens group.

(2) Numerical Examples Numerical examples using specific numerical values of the zoom lens are shown below. Also, longitudinal aberration diagrams of the zoom lens when focusing on an object at infinity at the wide-angle end, the intermediate focal length, and the telephoto end are shown in Fig. 14, Fig. 15, and Fig. 16.

(Lens data)
Surface number RD Nd νd
1 80.2310 1.2000 1.65412 39.68
2 51.4611 6.9283 1.49700 81.61
3 -588.1180 D(3)
4 -83.1445 0.8000 1.77250 49.60
5 34.3555 3.1575 1.84666 23.78
6 93.2074 D(6)
7 42.4229 4.8058 1.48749 70.44
8 -75.5189 0.2000
9 36.3497 4.5183 1.48749 70.44
10 -98.8617 0.8000 1.90366 31.34
11 72.1939 2.0261
12S inf. D(12)
13ASPH 190.4294 2.6151 1.51680 64.20
14 -106.2288 D(14)
15 56.7162 1.5046 1.61340 44.27
16 61.3493 0.8000 1.49700 81.61
17 26.7503 D(17)
18 -167.6227 2.8673 1.51680 64.20
19 -35.1637 D(19)
20 -35.9906 3.1114 1.90200 25.26
21 -23.0202 0.8000 1.72916 54.67
22 157.9046 D(22)
23 inf. 2.5000 1.51680 64.20
Image surface inf. 1.0000

(Specifications table)
Wide-angle end Mid-range Telephoto end
f 73.0328 129.9833 289.7757
F No. 4.2908 4.9963 6.4530
ω 16.5755 9.1923 4.1390

(variable interval)
Wide-angle end Mid-range Telephoto end
D(3) 1.9648 38.6419 63.8017
D(6) 34.9313 23.3251 1.0000
D(12) 1.0000 4.1649 18.9593
D(14) 6.7538 1.0043 1.0187
D(17) 15.7987 23.2263 27.3620
D(19) 24.9698 20.1269 1.1823
D(22) 14.5000 26.7013 53.5073

(Aspherical coefficients)
Face number K A4 A6 A8 A10 A12
13 0.0000 -6.15279E-06 -8.73064E-10 -3.52033E-11 2.16752E-13 0.00000E+00

(Lens group data)
Group Number Focal Length
G1 168.411
G2 -61.141
G3 61.649
G4 132.344
G5 -48.792
G6 85.474
G7 -45.269

[Table 1]
Example 1 Example 2 Example 3 Example 4
Conditional formula (1) FA/FB 0.638 0.399 0.455 0.466
Condition (2) Lff/TAtoB 2.481 4.201 2.291 1.617
Condition (2) ffr/fw -1.602 -1.230 -1.644 -1.337
Condition (4) |fw/m2| 10.095 5.418 5.923 14.388
Condition (5) β2t -0.859 -1.003 -0.673 -1.637
Condition (6) β2t/β2w 2.627 3.134 2.061 2.656
Condition (7) (1-βf×βf)×βfr×βfr -6.152 -7.582 -5.996 -2.963
Condition (8) f1/fw 2.637 2.925 2.891 2.306
Condition (9) Nd1n 1.834 1.871 1.834 1.654

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.

Gr: Middle group to rear group Gff: Middle group Gf: Gf lens group (focus group)
Gfr ... rear group S ... aperture stop CG ... cover glass I ... 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 1 ... imaging device 2 ... camera 3 ... lens 21 ... CCD sensor or CMOS sensor 22 ... cover glass 31 ... aperture stop IP ... image surface

Claims (14)

A zoom lens that varies magnification by changing the spacing between adjacent lens groups, the zoom lens including, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups, a Gf lens group having negative refractive power, and a rear group including at least a Gn lens group having negative refractive power, and the composite refractive power from the intermediate group to the rear group is positive,
At least the second lens group moves along the optical axis during zooming,
the Gf lens group includes at least one cemented lens,
A zoom lens that satisfies the following condition when the intermediate group is group A on the object side and group B on the image side, with the maximum air space at the telephoto end as the boundary:
0.1<FA/FB<4.0 ... (1)
1.0< Lff/TAtoB ≦4.201 ... (2)
−18.0<ffr/fw<−0.1 ... (3)
0.0 < |fw/m2| < 2000.0 ... (4)
however,
FA: composite focal length of the A group at the telephoto end FB: composite focal length of the B group at the telephoto end Lff: total optical length of the middle group at the telephoto end TAtoB: maximum air space at the telephoto end of the middle group ffr: composite focal length at the telephoto end of all lenses located on the image side of the Gf lens group fw: focal length at the wide-angle end of the zoom lens m2: amount of movement on the optical axis of the second lens group when changing magnification from the wide-angle end to the telephoto end Here, the amount of movement is considered positive in the direction from the object side to the image side. A zoom lens that varies magnification by changing the spacing between adjacent lens groups, the zoom lens including, in order from the object side, a first lens group having positive refractive power, a second lens group having negative refractive power, an intermediate group including one or more lens groups, a Gf lens group having negative refractive power, and a rear group including at least a Gn lens group having negative refractive power, and the composite refractive power from the intermediate group to the rear group is positive,
At least the second lens group moves along the optical axis during zooming,
the Gf lens group includes at least one cemented lens,
The Gn lens group moves toward the object side when zooming from the wide-angle end to the telephoto end,
A zoom lens that satisfies the following condition when the intermediate group is group A on the object side and group B on the image side, with the maximum air space at the telephoto end as the boundary:
0.1<FA/FB<2.00 ... (1)
1.0< Lff/TAtoB < 5.7 ... (2)
−18.0< ffr/fw<−0.1 ... (3)
0.0 < |fw/m2| < 2000.0 ... (4)
however,
FA: composite focal length at the telephoto end of the A group
FB: composite focal length of the B group at the telephoto end
Lff: total optical length at the telephoto end of the middle group
TA to B: Maximum air gap at the telephoto end of the middle group
ffr: composite focal length at the telephoto end of all lenses arranged on the image side of the Gf lens group
fw: focal length at the wide-angle end of the zoom lens
m2: Amount of movement of the second lens group on the optical axis when changing magnification from the wide-angle end to the telephoto end
Here, the amount of movement is defined as positive in the direction from the object side to the image side. 3. The zoom lens according to claim 1, which satisfies the following condition:
−2.8 < β2t < −0.5 (5)
however,
β2t: lateral magnification of the second lens group at the telephoto end 4. The zoom lens according to claim 1 , which satisfies the following condition:
1.0 < β2t / β2w < 7.0 (6)
β2w: lateral magnification of the second lens group at the wide-angle end β2t: lateral magnification of the second lens group at the telephoto end 5. The zoom lens according to claim 1, which satisfies the following condition:
−10.0 < (1 − βf × βf) × βfr × βfr < −1.0 (7)
however,
βf: lateral magnification of the Gf lens group at the telephoto end βfr: composite lateral magnification of all lenses arranged on the image side of the Gf lens group at the telephoto end 6. The zoom lens according to claim 1, which satisfies the following condition:
1.1 < f1/fw < 10.0 (8)
however,
f1: focal length of the first lens group 7. The zoom lens according to claim 1, wherein the first lens group has at least one negative lens, and the negative lens having the highest refractive index among the at least one negative lens satisfies the following condition:
1.65 < Nd1n < 2.50 (9)
however,
Nd1n: the refractive index of the negative lens having the highest refractive index in the first lens group The zoom lens according to claim 1 , wherein the Gf lens group includes at least one positive lens. The zoom lens according to any one of claims 1 to 8, wherein the Gf lens group is composed of one negative lens and one positive lens. The zoom lens according to any one of claims 1 to 9, wherein the Gf lens group has, in order from the object side, a positive lens and a negative lens. The zoom lens according to any one of claims 1 to 10, wherein an aperture stop is disposed within the intermediate group to the rear group. 12. The zoom lens according to claim 1, wherein the Gn lens group moves along the same locus as one of the lens groups included in the intermediate group during zooming from the wide-angle end to the telephoto end. 13. The zoom lens according to claim 1, wherein the Gf lens group moves along the optical axis during focusing. 14. An imaging apparatus comprising: the zoom lens according to claim 1; and an imaging element that converts an optical image formed by the zoom lens into an electrical signal.

Images