JP7301657B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens and an imaging device having the same.

In recent years, along with the sophistication of imaging devices, there has been a demand for zoom lenses that have a high zoom ratio (variable magnification ratio), high optical performance over the entire zoom range, and a short overall lens length, as imaging optical systems used in imaging devices. ing. As a zoom lens that satisfies this requirement, a positive lead type zoom lens in which a lens group having a positive refractive power is arranged closest to the object side is known (Patent Documents 1 and 2).

In Patent Document 1, in order from the object side to the image side, there are a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power. A zoom lens is disclosed which consists of lens groups and the spacing between adjacent lens groups changes during zooming.

In Patent Document 2, in order to shorten the overall length of the lens and reduce the diameter of the lens barrel, the back focal length is set short, and a so-called mirrorless lens is used in which mechanical members are removed from the final surface of the lens to the image plane. A type of zoom lens has been proposed.

In Patent Document 2, in order from the object side to the image side, a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with negative refractive power. A zoom lens is disclosed which consists of a lens group, a fifth lens group with negative refractive power, and a sixth lens group with positive refractive power, and in which the distance between adjacent lens groups changes during zooming.

JP 2013-257508 A JP 2016-157143 A

The zoom lens of Patent Document 1 achieves a zoom magnification of about 10 times by increasing the refractive power of the first lens group and setting a long zooming movement amount from the wide-angle end to the telephoto end. If an attempt is made to achieve a higher zoom ratio in this zoom lens, there is a tendency for deterioration in optical performance in the vicinity of the telephoto end, particularly zoom fluctuations in curvature of field aberration to become noticeable. In addition, the back focus tends to be long, making it difficult to shorten the total length of the lens. In addition, since the first lens group moves out by a large amount during zooming, it is necessary to secure a certain amount of overall lens length at the wide-angle end, which is not preferable from the viewpoint of miniaturizing the overall lens length.

The zoom lens of Patent Document 2 is a so-called mirrorless type zoom lens, and has a relatively short overall lens length. However, since the refractive power of the positive third lens group is too strong and the amount of movement during zooming is large, it is difficult to ensure good optical performance over the entire zoom range.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a compact zoom lens that can easily obtain high optical performance over the entire zoom range at a high zoom ratio, and an imaging apparatus having the zoom lens.

The zoom lens of the present invention comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. , a fourth lens group with positive refractive power, a fifth lens group with positive refractive power, and a rear group including one or more lens groups, and lenses that are adjacent during zooming from the wide-angle end to the telephoto end. A zoom lens in which group intervals change, wherein the rear group includes a sixth lens group with negative refractive power and a seventh lens group with negative refractive power, which are arranged in order from the object side to the image side, ft is the focal length of the zoom lens at the telephoto end, f5 is the focal length of the fifth lens group, f1 is the focal length of the first lens group, skw is the back focus at the wide-angle end , and fw is the focal length of the zoom lens at the wide-angle end. When
4. 374≦ ft/f5<15.0
5.3<f1/skw<30.0
5.0<ft/fw<25.0
satisfies the following conditional expression.

According to the present invention, it is possible to obtain a compact zoom lens that has a high zoom ratio and high optical performance over the entire zoom range.

FIG. 2 is a cross-sectional view of the zoom lens at the wide-angle end of Embodiment 1 of the present invention; Aberration diagrams at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end of Example 1 of the present invention. FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end of Embodiment 2 of the present invention; Aberration diagrams at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end of Example 2 of the present invention. FIG. 10 is a cross-sectional view of a zoom lens at the wide-angle end of Embodiment 3 of the present invention; Aberration diagrams at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end of Example 3 of the present invention. FIG. 4 is a cross-sectional view of a zoom lens at the wide-angle end of Embodiment 4 of the present invention; Aberration diagrams at (A) the wide-angle end, (B) the intermediate zoom position, and (C) the telephoto end of Example 4 of the present invention. FIG. 5 is a cross-sectional view of a zoom lens at the wide-angle end of Embodiment 5 of the present invention; Aberration diagrams of Example 5 of the present invention at (A) wide-angle end, (B) intermediate zoom position, and (C) telephoto end Schematic diagram of the main part of the optical apparatus of the present invention

Preferred embodiments of the present invention are described below with reference to the accompanying drawings.

2. Description of the Related Art There is a strong demand for a zoom lens used in an imaging device to have a short overall lens length, a compact overall lens system, and a high zoom ratio and high optical performance over the entire zoom range. In addition, it is desired that the back focal length be appropriate, and that the lens structure be such that the diameter of the lens barrel becomes small when incorporated into the lens barrel.

In order to satisfy these requirements in a positive lead type zoom lens, it is important to appropriately set each element constituting the zoom lens. For example, it is important to appropriately set the zoom type (the number of lens groups and the sign of the refractive power of each lens group) and the amount of movement of one group that strongly affects the overall length of the lens.

The zoom lens of each embodiment of the present invention comprises a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. This zoom lens has three lens groups, a fourth lens group with positive refractive power, and a fifth lens group with positive refractive power, and the distance between adjacent lens groups changes during zooming.

FIG. 1 is a sectional view of a lens of Example 1 of the present invention. 2A, 2B, and 2C are longitudinal aberration diagrams of the zoom lens of Example 1 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Example 1 is a zoom lens with a zoom ratio of 13.1 and an F number of about 4.12 to 8.12.

FIG. 3 is a sectional view of a lens of Example 2 of the present invention. 4A, 4B, and 4C are longitudinal aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 2, respectively. Example 2 is a zoom lens with a zoom ratio of 12.1 and an F number of about 4.12 to 8.12.

FIG. 5 is a sectional view of a lens of Example 3 of the present invention. 6A, 6B, and 6C are longitudinal aberration diagrams of the zoom lens of Example 3 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Example 3 is a zoom lens with a zoom ratio of 12.1 and an F number of about 4.12 to 8.12.

FIG. 7 is a sectional view of a lens of Example 4 of the present invention. 8A, 8B, and 8C are longitudinal aberration diagrams at the wide-angle end, intermediate zoom position, and telephoto end of the zoom lens of Example 4, respectively. Example 4 is a zoom lens with a zoom ratio of 12.0 and an F number of about 4.12 to 8.12.

FIG. 9 is a sectional view of a lens of Example 5 of the present invention. 10A, 10B, and 10C are longitudinal aberration diagrams of the zoom lens of Example 5 at the wide-angle end, intermediate zoom position, and telephoto end, respectively. Example 5 is a zoom lens with a zoom ratio of 10.8 and an F number of about 4.12 to 8.12.

FIG. 11 is a schematic diagram of the essential parts of the imaging apparatus of the present invention.

The zoom lens of each embodiment is a zoom lens used in an imaging apparatus such as a digital camera, video camera, broadcasting camera, surveillance camera, and silver halide photography camera. The zoom lens of each embodiment can also be used as a projection optical system for a projection device (projector).

In the lens cross-sectional view of each example, the left side is the object side (front) and the right side is the image side (rear). If i is the order of lens groups from the object side, Li indicates the i-th lens group. SP is the aperture stop. IP is the image plane. The image plane IP corresponds to an imaging surface of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor when a zoom lens is used as an imaging device such as a digital camera or a video camera. When a zoom lens is used as an imaging device for a silver-salt film camera, it corresponds to the film surface. When zooming from the wide-angle end to the telephoto end, each lens group is moved as indicated by the arrows. The arrow related to focus indicates the direction of movement during focusing from an infinite distance object to a short distance object.

In the spherical aberration diagrams, Fno is the F-number. Further, the solid line d is the d-line (wavelength 587.6 nm), and the two-dot chain line g is the g-line (wavelength 435.8 nm). In the astigmatism diagrams, the dotted line ΔM is the meridional image plane on the d-line, and the solid line ΔS is the sagittal image plane on the d-line. Distortion aberration diagrams are shown for the d-line. Magnification chromatic aberration diagrams are shown for the g-line. ω is a half angle of view (degrees).

Next, the lens configuration of each example will be described.

In Examples 1 and 2, in order from the object side to the image side, the first lens group L1 with positive refractive power, the second lens group L2 with negative refractive power, the third lens group L3 with positive refractive power, A fourth lens group L4 with positive refractive power, a fifth lens group L5 with positive refractive power, a sixth lens group L6 with negative refractive power, a seventh lens group L7 with negative refractive power, and a seventh lens group L7 with positive refractive power. This is an 8-group zoom lens composed of 8 lens groups L8.

During zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves linearly toward the object side, and the second lens unit L2 moves along a convex locus toward the image side. During zooming, the third lens group L3, the fifth lens group L5 and the seventh lens group L7 move integrally (on the same locus) toward the object side. During zooming, the fourth lens unit L4 moves toward the object side, and the sixth lens unit L6 moves toward the object side. The eighth lens unit L8 is stationary during zooming. The sixth lens group L6 moves during focusing.

Example 3 is an eight-group zoom lens of the same zoom type (the number of lens groups, the sign of the refractive power of each lens group) as in Examples 1 and 2, but the final group, the eighth lens group L8. moves to the image side during zooming.

In the fourth embodiment, in order from the object side to the image side, the first lens unit L1 with positive refractive power, the second lens unit L2 with negative refractive power, the third lens unit L3 with positive refractive power, and the positive refractive power. 4th lens group L4, 5th lens group L5 with positive refractive power, 6th lens group L6 with negative refractive power, and 7th lens group L7 with negative refractive power. be.

In Example 4, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 linearly moves toward the object side, and the second lens unit L2 moves along a convex locus toward the image side. During zooming, the third lens group L3, the fifth lens group L5 and the seventh lens group L7 move integrally (on the same locus) toward the object side. During zooming, the fourth lens unit L4 moves toward the object side, and the sixth lens unit L6 moves toward the object side. During focusing, the sixth lens group L6 moves.

In Example 5, in order from the object side to the image side, a first lens unit L1 with positive refractive power, a second lens unit L2 with negative refractive power, a third lens unit L3 with positive refractive power, and a third lens unit L3 with positive refractive power. It is a seven-group zoom lens composed of a fourth lens group L4, a fifth lens group L5 with positive refractive power, a sixth lens group L6 with negative refractive power, and a seventh lens group L7 with positive refractive power. .

In Example 5, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 linearly moves toward the object side, and the second lens unit L2 moves along a convex locus toward the image side. During zooming, the third lens group L3 and the fifth lens group L5 move integrally (on the same trajectory) toward the object side. During zooming, the fourth lens group L4 moves toward the object side, the sixth lens group L6 moves toward the object side, and the seventh lens group L7 moves toward the object side. The sixth lens group L6 moves during focusing.

The zoom lens of each embodiment mainly performs zooming by moving the first lens group L1 to the fifth lens group L5 during zooming. When zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves toward the object side to reduce the front lens effective diameter at the wide-angle end and increase the zoom ratio. Further, the third lens group L3 to the fifth lens group L5, which are positive refractive power groups, move toward the object side during zooming from the wide-angle end to the telephoto end, thereby obtaining a zooming effect.

In a positive lead type zoom lens, when the overall lens length is to be shortened, it is effective to arrange a lens group having a negative refractive power near the final lens group. If the final lens group has a positive refractive power, the incident angle of the light flux on the image plane can be made low, and the occurrence of so-called shading, such as light loss and coloring at the peripheral image height due to the imaging element, can be reduced.

In addition, by relatively changing the distance between the fourth lens group and the fifth lens group, which have positive refractive power on the image side of the third lens group L3, during zooming, the image can be Aberrations such as surface curvature are corrected over the entire zoom range.

In each embodiment, it is preferable to satisfy one or more of the following conditional expressions (1) to (9).

4.2<ft/f5<15.0 (1)
5.3<f1/skw<30.0 (2)
3.0<f1/|m2|<50.0 (3)
0.3<f4/f5<3.0 (4)
-3.0<m4/f4<-0.3 (5)
-2.00<f2/ft<-0.01 (6)
3.0<TTDw/skw<20.0 (7)
-8.0<POw/fw<-1.0 (8)
5.0<ft/fw<25.0 (9)
Here, the focal length at the telephoto end is ft, the focal length of the fifth lens group is f5, the focal length of the first lens group is f1, and the back focus at the wide-angle end is skw. Let m2 be the amount of movement of the second lens group when zooming from the wide-angle end to the telephoto end, f4 be the focal length of the fourth lens group, and m4 be the amount of movement of the fourth lens group when zooming from the wide-angle end to the telephoto end. there is Also, the focal length of the second lens group is f2, the distance (optical total length) on the optical axis from the surface closest to the object (first lens surface) of the zoom lens at the wide-angle end to the image plane is TTDw, and the zoom at the wide-angle end is Let fw be the focal length of the lens, and POw be the distance from the image plane to the position of the exit pupil at the wide-angle end.

The total optical length TTDw at the wide-angle end is the sum of the distance from the first lens surface on the object side to the final lens surface plus the value of the back focal length converted to air. The back focus is the air-equivalent length from the final lens surface to the image plane. The position of the exit pupil is the distance from the image plane. The sign of the distance of the position of the exit pupil is negative when positioned on the object side of the image plane, and positive when positioned on the image side of the image plane. The amount of movement of the lens group corresponds to the difference between the position on the optical axis at the wide-angle end and the position on the optical axis at the telephoto end. is positive, and negative is when the lens group is positioned closer to the object side at the telephoto end than at the wide-angle end.

Next, the technical meanings of the above conditional expressions (1) to (9) will be explained.

Conditional expression (1) defines the focal length of the fifth lens group and the telephoto end focal length in order to increase the magnification and correct aberrations in the entire zoom range.

If the focal length f5 of the fifth lens group becomes smaller than the upper limit of conditional expression (1), although this contributes to increasing the magnification, the refractive power of the fifth lens group becomes too strong, causing aberration fluctuations in curvature of field. becomes difficult to control. In addition, it is sensitive to performance deterioration due to an error in the direction of the optical axis and an eccentricity error, which is undesirable. Alternatively, if the telephoto end focal length ft exceeds the upper limit of conditional expression (1) and becomes too large, it becomes difficult to suppress axial chromatic aberration and lateral chromatic aberration at the telephoto end, which is not preferable.

Exceeding the lower limit of conditional expression (1) and increasing the focal length f5 of the fifth lens group is not preferable because it does not contribute sufficiently to suppressing fluctuations in zooming and zooming aberrations. Alternatively, if the focal length ft becomes too small beyond the lower limit of conditional expression (1), it becomes difficult to obtain a desired zoom magnification.

Conditional expression (2) defines the focal length f1 of the first lens group and the back focus skw at the wide-angle end in order to reduce the total lens length.

If the wide-angle end back focus skw becomes small beyond the upper limit of conditional expression (2), the mechanical layout of the connecting portion between the lens and the camera becomes difficult. Alternatively, if the focal length f1 of the first lens group increases beyond the upper limit of conditional expression (2), it is necessary to increase the amount of movement of the first lens group in order to obtain high magnification. unfavorable from this point of view.

Exceeding the lower limit of conditional expression (2) and increasing the back focus skw is not preferable because it is disadvantageous in reducing the overall length of the lens, which is the objective. Alternatively, if the focal length of the first lens group f1 becomes too small beyond the lower limit of conditional expression (2), this is advantageous for reducing the overall length of the lens at the telephoto end, but it may cause longitudinal chromatic aberration and spherical aberration at the telephoto end. This is not preferable because correction of aberration becomes difficult.

Conditional expression (3) prescribes the zooming movement amount m2 of the second lens group, which is the main variable magnification group, and the focal length f1 of the first lens group, in order to achieve both a reduction in overall lens length and aberration correction. .

When the amount of movement of the second lens group becomes small beyond the upper limit of conditional expression (3), the share of zooming of the second lens group becomes small. It is not desirable because it must be increased. Alternatively, if the focal length f1 of the first lens group increases beyond the upper limit of conditional expression (3), it is necessary to increase the amount of movement of the first lens group. .

Exceeding the lower limit of conditional expression (3) and increasing the amount of zooming movement of the second lens group is advantageous for achieving high magnification, but it is not preferable because fluctuations in curvature of field tend to increase during zooming. Alternatively, if the focal length f1 of the first lens group becomes too small beyond the lower limit of conditional expression (3), it becomes difficult to suppress axial chromatic aberration and spherical aberration at the telephoto end, which is not preferable.

Conditional expression (4) defines the focal lengths f4 and f5 of the fourth lens group and the fifth lens group in order to perform good aberration correction in the rear group located closer to the image side than the third lens group.

If the ratio (balance relationship) of the focal lengths of the fourth lens group and the fifth lens group is lost beyond the upper limit and the lower limit of conditional expression (4), aberration fluctuations during zooming will be It becomes difficult to correct for both groups. In addition, if the focal length of one of the lens groups becomes small, the sensitivity to decentration increases, which is not preferable from the viewpoint of manufacturing error.

Conditional expression (5) prescribes the focal length f4 and the zooming movement amount m4 of the fourth lens group in order to achieve both a high variable magnification ratio and suppression of aberration fluctuations by the fourth lens group.

When the focal length f4 of the fourth lens group becomes small beyond the lower limit of conditional expression (5), the refractive power of the fourth lens group becomes too strong, and the Petzval sum increases, resulting in curvature of field aberration and astigmatism. worsens and is not desirable. Alternatively, if the zooming movement amount m4 of the fourth lens group increases beyond the lower limit of conditional expression (5), it is necessary to secure a group interval closer to the image side than the third lens group, which is preferable from the viewpoint of overall length reduction. do not have.

When the focal length f4 of the fourth lens group increases beyond the upper limit of conditional expression (5), it is necessary to increase the focal length of the other lens groups or increase the amount of movement in order to obtain a high zoom ratio. There is, and it is not preferable from the viewpoint of high magnification. Alternatively, if the amount of movement of the fourth lens group becomes small beyond the upper limit of conditional expression (5), it becomes difficult to correct fluctuations in field curvature aberration during zooming, which is undesirable.

Conditional expression (6) defines the focal length f2 and telephoto end focal length ft of the second lens group in order to reduce the size and weight of the movable group on the image side of the second lens group and shorten the total length of the lens. .

If the focal length f2 of the second lens group is shortened beyond the upper limit of conditional expression (6), the luminous flux incident on the transition to the third lens group becomes large, the diameter of the lens increases, and the weight of the zooming group is reduced. unfavorable from Further, if the refractive power of the second lens group is too strong, it is difficult to suppress fluctuations in the curvature of field in zooming, which is undesirable. Alternatively, if the telephoto end focal length ft exceeds the upper limit of conditional expression (6) and becomes too long, it becomes difficult to correct axial chromatic aberration at the telephoto end while maintaining the desired total lens length.

If the focal length f2 of the second lens group becomes longer than the lower limit of conditional expression (6), the moving distance of the second lens group and the subsequent lens groups becomes longer in order to obtain the desired zoom magnification. , it is not preferable because the overall length of the lens is increased. Alternatively, if the telephoto end focal length ft becomes shorter than the lower limit of conditional expression (6), the desired telephoto end field of view cannot be obtained.

Conditional expression (7) is a conditional expression for appropriately setting the overall length and the back focus in order to obtain a zoom lens with a small overall lens length.

If the total lens length TTDw at the wide-angle end increases beyond the upper limit of conditional expression (7), it will no longer be possible to satisfy the problem of reducing the total lens length. Alternatively, if the upper limit of conditional expression (7) is exceeded and the back focus skw becomes too small, the mechanical layout of the connecting portion between the lens and the camera becomes difficult.

If the total lens length TTDw at the wide-angle end becomes smaller than the lower limit of conditional expression (7), the positive refractive power of the entire lens becomes too high, making it difficult to control the Petzval sum and to obtain the desired optical performance. becomes. Alternatively, if the lower limit of conditional expression (7) is exceeded, the back focus skw becomes too large, which is not preferable from the viewpoint of shortening the overall length.

Conditional expression (8) defines the relationship between the exit pupil position POw at the wide-angle end and the focal length fw of the entire system at the wide-angle end in order to ensure high telecentricity.

If the lower limit of conditional expression (8) is exceeded and the exit pupil POw becomes large, the refracting power of the final group tends to increase, making it difficult to sufficiently suppress curvature of field, which is not preferable.

If the exit pupil POw becomes smaller than the upper limit of conditional expression (8), the angle of incidence of light rays at the peripheral image height on the image plane becomes too large, which is not preferable from the viewpoint of so-called shading. Alternatively, if the upper limit of conditional expression (8) is exceeded, the focal length fw at the wide-angle end increases, making it difficult to achieve a desired zoom magnification, which is not preferable.

Conditional expression (9) is a zoom magnification formula defined to obtain a desired zoom magnification.

If the telephoto end focal length ft exceeds the upper limit of conditional expression (9), it becomes difficult to correct spherical aberration and axial chromatic aberration that occur at the telephoto end while maintaining a compact size of the entire lens system. Alternatively, if the focal length fw at the wide-angle end becomes shorter than the upper limit of conditional expression (9), the size of the front lens increases in order to secure the amount of peripheral light at the wide-angle end, which is undesirable.

If the lower limit of conditional expression (9) is exceeded, the desired zoom magnification cannot be secured. Further, if the wide-angle end focal length fw increases beyond the lower limit of conditional expression (9), a desired wide-angle end field of view cannot be obtained.

In each embodiment, it is more preferable to set the numerical ranges of conditional expressions (1) to (9) as follows.

4.2<ft/f5<13.0 (1a)
5.3<f1/skw<20.0 (2a)
4.0<f1/|m2|<40.0 (3a)
0.5<f4/f5<2.5 (4a)
-2.0<m4/f4<-0.4 (5a)
-1.50<f2/ft<-0.07 (6a)
5.0<TTDw/skw<16.0 (7a)
−7.0<POw/fw<−2.0 (8a)
7.0<ft/fw<20.0 (9a)
More preferably, in each embodiment, if the numerical ranges of conditional expressions (1a) to (9a) are set as follows, the effects implied by the aforementioned conditional expressions can be maximized.

4.3<ft/f5<10.0 (1b)
5.4<f1/skw<15.0 (2b)
7.0<f1/|m2|<30.0 (3b)
0.7<f4/f5<2.0 (4b)
-1.5<m4/f4<-0.5 (5b)
-1.00<f2/ft<-0.05 (6b)
6.0<TTDw/skw<13.0 (7b)
−5.0<POw/fw<−2.5 (8b)
10.0<ft/fw<15.0 (9b)
In Examples 1 to 5, in order to simplify the mechanical structure, the third lens unit L3 and the fifth lens unit L5 can be integrated and moved so as to draw the same trajectory when zooming from the wide-angle end to the telephoto end. preferable.

Also, in order to simplify the mechanical structure and facilitate dust and drip resistance, it is preferable that the final lens group be stationary during zooming. Also, the focusing lens group is required to be as light as possible in order to increase the focusing speed. Therefore, it is preferable that the focus lens group is composed of a cemented lens composed of two lenses or a single lens. Also, in order to suppress image magnification change (breathing) when the focus lens group moves, it is preferable to set the focus lens group closer to the image side than the third lens group.

In order to achieve a high zoom ratio with a wide angle of view while miniaturizing the entire system, the smaller the number of lenses in the first lens unit L1, the greater the incident height of the off-axis light flux passing through the first lens unit L1. can be lowered, and the effective diameter of the first lens unit L1 can be reduced. Therefore, the number of lenses in the first lens unit L1 is preferably four or less.

In order to widen the angle of view, the second lens unit L2 preferably comprises a negative lens, a negative lens, a positive lens, and a negative lens in order from the object side to the image side. By arranging a lens with a positive refractive power, it is possible to converge the luminous flux and reduce the effective diameter of the succeeding lens group. Further, by making the second lens group L2 a lens group with a negative refractive power and by adopting a lens configuration in which the negative lens precedes, a wide angle of view is facilitated.

Also, it is preferable to introduce an aspherical lens into the third lens unit L3 and appropriately set the refractive power of the lens units after the third lens unit L3 and the second lens unit L2. This makes it possible to satisfactorily correct various off-axis aberrations, especially astigmatism and distortion, and effectively correct spherical aberration, coma, etc. when the angle of view is widened and the zoom ratio is increased. .

In each embodiment, by configuring each element as described above, a compact zoom lens having a high zoom ratio and high optical performance over the entire zoom range can be obtained.
[Imaging device]
Next, an embodiment of a digital still camera (imaging device) using the optical system (zoom lens) of the present invention as an imaging optical system will be described with reference to FIG. In FIG. 11, reference numeral 10 denotes a camera main body, and 11 denotes a photographing optical system constituted by any one of the optical systems described in the first to fifth embodiments. Reference numeral 12 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or CMOS sensor, which is built in the camera body and receives and photoelectrically converts an optical image formed by the photographing optical system 11 . The camera body 10 may be a so-called single-lens reflex camera with a quick turn mirror, or a so-called mirrorless camera without a quick turn mirror.

By applying the optical system of the present invention to an imaging apparatus such as a digital still camera, an imaging apparatus having a small lens can be obtained.

Specific numerical data (Numerical Examples 1 to 5) corresponding to Examples 1 to 5 are shown below.

In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial distance (distance on the optical axis) between the m-th surface and the (m+1)-th surface. . However, m is the surface number counted from the light incident side. Also, nd represents the refractive index for the d-line of each optical member, and νd represents the Abbe number of the optical member. The Abbe number νd of a certain material is given by
νd = (Nd-1)/(NF-NC)
is represented by

In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values when the optical system of each example is focused on an object at infinity. "Back focus BF" is the distance on the optical axis from the final lens surface (lens surface closest to the image side) to the paraxial image surface expressed in air conversion length. The “total length of the lens” is the length obtained by adding the back focus to the distance on the optical axis from the foremost lens surface (the lens surface closest to the object side) of the zoom lens to the final lens surface. The term "lens group" is not limited to the case of being composed of a plurality of lenses, but also includes the case of being composed of one lens.

Moreover, when the optical surface is an aspherical surface, an asterisk (*) is attached to the right side of the surface number. The aspherical shape has X as the displacement amount from the surface vertex in the optical axis direction, h as the height from the optical axis in the direction perpendicular to the optical axis, R as the paraxial radius of curvature, k as the conic constant, A4, A6, When A8, A10, and A12 are aspheric coefficients of each order,
x=(h ² /R)/[1+{1−(1+k)(h/R) ² } ^1/2 +A4×h ⁴ +A6×h ⁶ +A8×h ⁸ +A10×h ¹⁰ +A12×h ¹²
is represented by "e±XX" in each aspheric coefficient means "×10± ^XX ".

Table 1 shows the relationship between each conditional expression described above and each numerical example.

[Numerical Example 1]
unit mm

Surface data surface number rd nd νd
1 136.708 1.60 1.83481 42.7
2 54.068 5.92 1.49700 81.5
3 -569.135 0.15
4 55.333 4.63 1.49700 81.5
5 -4300.270 (variable)
6 166.264 1.10 1.91082 35.3
7 19.083 5.16
8 -31.928 0.90 1.53775 74.7
9 67.182 0.15
10 32.747 4.41 1.84666 23.8
11 -48.674 0.69
12 -29.870 0.85 1.77250 49.6
13 133.724 (variable)
14 (Aperture) ∞ 0.40
15* 17.137 4.34 1.58313 59.4
16* -48.368 3.00
17 129.627 0.76 1.76200 40.1
18 20.939 (variable)
19 26.948 0.60 1.91082 35.3
20 13.176 3.82 1.72916 54.1
21 -122.128 (variable)
22 -46.685 0.75 1.85150 40.8
23 18.016 3.98 1.48749 70.2
24 -29.317 1.17
25 25.869 3.50 1.69680 55.5
26 -52.465 (variable)
27 82.743 1.50 1.92286 18.9
28 -250.809 0.78 1.74400 44.8
29 17.626 (variable)
30* -39.861 1.50 1.53110 55.9
31* -10000.000 (variable)
32 -338.910 2.23 1.90366 31.3
33 -68.440 (variable)
Image plane ∞

15th surface of aspheric data
K = 0.00000e+000 A4 = -2.38477e-005 A6 = 1.12703e-008 A8 = -6.40359e-010
A10 = -1.97712e-013

16th side
K = 0.00000e+000 A4 = 1.55260e-005 A6 = 1.06896e-008 A8 = -2.45437e-010
A10 = -2.69603e-012

30th side
K = 0.00000e+000 A4 = -2.10266e-004 A6 = 1.50725e-006 A8 = -1.13121e-008
A10 = 8.10044e-011

31st side
K = 0.00000e+000 A4 = -2.05775e-004 A6 = 1.56933e-006 A8 = -1.03786e-008
A10 = 5.19188e-011

Various data zoom ratio 13.11
Wide Angle Medium Telephoto Focal Length 18.49 59.57 242.50
F number 4.12 6.60 8.12
Half angle of view (degrees) 33.67 12.91 3.22
Image height 12.32 13.66 13.66
Overall lens length 123.50 155.31 187.11
BF 10.16 10.16 10.16

d5 0.85 27.49 60.73
d13 31.93 16.43 1.60
d18 8.52 4.45 1.76
d21 1.64 5.71 8.40
d26 2.28 1.23 1.87
d29 13.41 14.46 13.82
d31 0.80 21.46 34.85
d33 10.16 10.16 10.16

Zoom lens group data group Starting surface Focal length
1 1 101.94
2 6 -16.73
3 14 45.05
4 19 38.76
5 22 39.67
6 27 -33.60
7 30 -75.36
8 32 94.53

[Numerical Example 2]
unit mm

Surface data surface number rd nd νd
1 135.813 1.60 1.83481 42.7
2 54.021 6.12 1.49700 81.5
3 -659.684 0.15
4 55.151 4.71 1.49700 81.5
5 -7330.449 (variable)
6 187.948 1.10 1.91082 35.3
7 18.803 5.13
8 -31.993 0.90 1.53775 74.7
9 74.377 0.15
10 33.081 4.41 1.84666 23.8
11 -48.897 0.74
12 -30.206 0.85 1.77250 49.6
13 142.565 (variable)
14 (Aperture) ∞ 0.40
15* 17.690 4.01 1.58313 59.4
16* -66.769 2.90
17 60.080 0.73 1.76200 40.1
18 20.483 (variable)
19 27.015 0.60 1.91082 35.3
20 13.170 4.14 1.72916 54.1
21 -110.969 (variable)
22 -47.225 0.75 1.85150 40.8
23 18.864 3.30 1.48749 70.2
24 -36.543 0.36
25 28.444 3.35 1.69680 55.5
26 -49.205 (variable)
27 72.392 1.37 1.92286 18.9
28 -3354.746 0.78 1.74400 44.8
29 17.983 (variable)
30* -46.495 1.50 1.53110 55.9
31* -10000.000 (variable)
32 -347.725 2.19 1.90366 31.3
33 -69.639 (variable)
Image plane ∞

15th surface of aspheric data
K = 0.00000e+000 A4 = -2.03272e-005 A6 = -2.23135e-008 A8 = -2.64438e-010
A10 = -2.44606e-012

16th side
K = 0.00000e+000 A4 = 1.27031e-005 A6 = -3.75774e-008 A8 = 5.16997e-010
A10 = -9.28439e-012

30th side
K = 0.00000e+000 A4 = -2.16539e-004 A6 = 1.40858e-006 A8 = -1.23141e-008
A10 = 8.48579e-011

31st side
K = 0.00000e+000 A4 = -2.10443e-004 A6 = 1.43432e-006 A8 = -1.01489e-008
A10 = 5.01868e-011

Various data Zoom ratio 12.12
Wide Angle Medium Telephoto Focal Length 18.57 59.27 225.00
F number 4.12 6.60 8.12
Half angle of view (degrees) 33.56 12.98 3.47
Image height 12.32 13.66 13.66
Overall lens length 123.50 155.11 186.72
BF 11.44 11.44 11.44

d5 0.85 27.75 60.21
d13 32.22 16.13 2.14
d18 8.18 4.32 1.78
d21 1.46 5.32 7.86
d26 2.43 1.53 2.50
d29 13.89 14.79 13.82
d31 0.80 21.61 34.75
d33 11.44 11.44 11.44

Zoom lens group data group Starting surface Focal length
1 1 103.02
2 6 -16.72
3 14 45.05
4 19 38.09
5 22 51.44
6 27 -35.77
7 30 -87.96
8 32 96.00

[Numerical Example 3]
unit mm

Surface data surface number rd nd νd
1 127.420 1.60 1.83481 42.7
2 49.985 6.46 1.49700 81.5
3 -411.297 0.15
4 51.871 4.87 1.49700 81.5
5 -1203.579 (variable)
6 218.688 1.10 1.91082 35.3
7 18.311 4.79
8 -32.008 0.90 1.53775 74.7
9 53.486 0.15
10 28.998 4.34 1.84666 23.8
11 -48.719 1.17
12 -27.466 0.85 1.77250 49.6
13 105.495 (variable)
14 (Aperture) ∞ 0.40
15* 17.862 4.05 1.58313 59.4
16* -83.856 3.01
17 60.162 1.80 1.76200 40.1
18 21.176 (variable)
19 29.802 0.60 1.91082 35.3
20 14.138 3.41 1.72916 54.1
21 -87.282 (variable)
22 -49.908 0.75 1.85150 40.8
23 17.260 6.73 1.48749 70.2
24 -27.840 0.15
25 24.328 4.30 1.69680 55.5
26 -53.545 (variable)
27 147.682 1.41 1.92286 18.9
28 -209.227 0.78 1.74400 44.8
29 21.208 (variable)
30* -37.422 1.50 1.53110 55.9
31* -10000.000 (variable)
32 -605.729 1.96 1.90366 31.3
33 -86.220 (Variable)
Image plane ∞

15th surface of aspheric data
K = 0.00000e+000 A4 = -1.45579e-005 A6 = 1.39385e-007 A8 = -1.72463e-009
A10 = 4.11594e-011

16th side
K = 0.00000e+000 A4 = 1.85404e-005 A6 = 1.29171e-007 A8 = -5.59522e-010
A10 = 3.51871e-011

30th side
K = 0.00000e+000 A4 = -1.04337e-004 A6 = 1.33651e-006 A8 = -4.92090e-009
A10 = 1.83890e-011

31st side
K = 0.00000e+000 A4 = -9.79616e-005 A6 = 1.30590e-006 A8 = -6.03519e-009
A10 = 2.31593e-011

Various data Zoom ratio 12.10
Wide Angle Medium Telephoto Focal Length 18.60 56.56 225.00
F number 4.12 6.60 8.12
Half angle of view (degrees) 33.52 13.58 3.47
Image height 12.32 13.66 13.66
Overall lens length 126.19 157.98 189.78
BF 16.74 16.74 16.74

d5 0.85 24.61 53.65
d13 27.20 13.82 1.60
d18 9.66 5.11 1.78
d21 1.99 6.55 9.87
d26 1.62 1.20 1.29
d29 10.12 10.54 10.44
d31 0.79 22.20 37.18
d33 16.74 16.74 16.74

Zoom lens group data group Starting surface Focal length
1 1 91.21
2 6 -14.90
3 14 45.05
4 19 38.74
5 22 32.15
6 27 -36.09
7 30 -70.73
8 32 111.05

[Numerical Example 4]
unit mm

Surface data surface number rd nd νd
1 138.939 1.60 1.83481 42.7
2 53.983 6.38 1.49700 81.5
3 -430.310 0.15
4 54.870 5.55 1.49700 81.5
5 -2870.147 (variable)
6 190.618 1.10 1.91082 35.3
7 17.554 4.42
8 -32.438 0.90 1.53775 74.7
9 63.082 0.15
10 27.435 4.15 1.84666 23.8
11 -48.905 0.56
12 -27.122 0.85 1.77250 49.6
13 76.755 (variable)
14 (Aperture) ∞ 0.40
15* 16.476 4.53 1.58313 59.4
16* -42.536 3.02
17 150.080 1.63 1.76200 40.1
18 20.043 (variable)
19 28.525 0.60 1.91082 35.3
20 13.793 3.93 1.72916 54.1
21 -157.090 (variable)
22 -40.731 0.75 1.85150 40.8
23 18.438 7.11 1.48749 70.2
24 -20.954 2.56
25 24.962 4.38 1.69680 55.5
26 -75.379 (variable)
27 238.284 1.55 1.92286 18.9
28 -111.896 0.78 1.74400 44.8
29 23.126 (variable)
30* -105.117 1.50 1.53110 55.9
31* -10000.000 (variable)
Image plane ∞

15th surface of aspheric data
K = 0.00000e+000 A4 = -3.22073e-005 A6 = 2.01013e-007 A8 = -7.08972e-009
A10 = 6.65770e-011

16th side
K = 0.00000e+000 A4 = 1.33606e-005 A6 = 1.92613e-007 A8 = -5.69066e-009
A10 = 4.92341e-011

30th side
K = 0.00000e+000 A4 = -1.29623e-004 A6 = 1.05234e-006 A8 = -4.81453e-009
A10 = 3.01246e-011

31st side
K = 0.00000e+000 A4 = -1.32259e-004 A6 = 1.11548e-006 A8 = -5.99362e-009
A10 = 3.28776e-011

Various data Zoom ratio 11.99
Wide Angle Medium Telephoto Focal Length 18.77 54.34 224.98
F number 4.12 6.60 8.12
Half angle of view (degrees) 33.28 14.11 3.47
Image height 12.32 13.66 13.66
Total lens length 125.34 159.37 193.39
BF 15.91 38.92 49.49

d5 0.85 25.68 60.99
d13 27.27 13.46 1.60
d18 8.51 5.33 1.84
d21 1.60 4.78 8.27
d26 2.07 1.20 1.24
d29 10.56 11.43 11.39
d31 15.91 38.92 49.49

Zoom lens group data group Starting surface Focal length
1 1 98.84
2 6 -14.73
3 14 40.55
4 19 42.94
5 22 30.66
6 27 -37.70
7 30 -200.04

[Numerical Example 5]
unit mm

Surface data surface number rd nd νd
1 127.739 1.60 1.83481 42.7
2 52.606 6.06 1.49700 81.5
3 -710.769 0.15
4 55.859 5.39 1.49700 81.5
5 -1309.701 (variable)
6 286.137 1.10 1.91082 35.3
7 19.336 4.81
8 -37.188 0.90 1.53775 74.7
9 65.023 0.15
10 29.522 4.46 1.84666 23.8
11 -53.348 0.61
12 -31.150 0.85 1.77250 49.6
13 79.061 (variable)
14 (Aperture) ∞ 0.40
15* 17.779 3.96 1.58313 59.4
16* -63.070 2.00
17 63.816 1.80 1.76200 40.1
18 21.184 (variable)
19 31.369 0.60 1.91082 35.3
20 14.951 3.34 1.72916 54.1
21 -156.497 (variable)
22 -74.434 0.75 1.85150 40.8
23 18.025 6.96 1.48749 70.2
24 -22.922 3.09
25 20.689 4.78 1.69680 55.5
26 -287.639 (variable)
27 -78.369 1.76 1.92286 18.9
28 -34.130 0.78 1.74400 44.8
29 18.660 (variable)
30* 70.863 2.00 1.53110 55.9
31* 633.434 (variable)
Image plane ∞

15th surface of aspheric data
K = 0.00000e+000 A4 = -3.98123e-005 A6 = 3.75965e-008 A8 = -7.40412e-009
A10 = 1.54341e-011

16th side
K = 0.00000e+000 A4 = -1.01592e-005 A6 = 6.98255e-008 A8 = -8.51312e-009
A10 = 2.99960e-011

30th side
K = 0.00000e+000 A4 = -8.67742e-005 A6 = 2.18244e-007 A8 = -5.38043e-010
A10 = 1.31259e-012

31st side
K = 0.00000e+000 A4 = -1.02267e-004 A6 = 2.15688e-007 A8 = -9.10522e-010
A10 = 1.26346e-012

Various data Zoom ratio 10.76
Wide Angle Medium Telephoto Focal Length 18.59 52.07 199.98
F number 4.12 6.60 8.12
Half angle of view (degrees) 33.53 14.70 3.91
Image height 12.32 13.66 13.66
Overall lens length 123.65 155.08 186.50
BF 13.00 35.85 45.58

d5 0.85 23.18 58.31
d13 29.04 15.63 1.60
d18 9.31 6.23 3.80
d21 4.01 7.10 9.53
d26 3.28 1.22 1.53
d29 5.86 7.58 7.85
d31 13.00 35.85 45.58

Zoom lens group data group Starting surface Focal length
1 1 99.51
2 6 -16.34
3 14 43.29
4 19 46.60
5 22 28.57
6 27 -21.32
7 30 150.05

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist.

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group

Claims (17)

A first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. A zoom lens that consists of four lens groups, a fifth lens group with positive refractive power, and a rear group that includes one or more lens groups. The distance between adjacent lens groups changes during zooming from the wide-angle end to the telephoto end. is a lens,
The rear group includes a sixth lens group with negative refractive power and a seventh lens group with negative refractive power, which are arranged in order from the object side to the image side,
ft is the focal length of the zoom lens at the telephoto end, f5 is the focal length of the fifth lens group, f1 is the focal length of the first lens group, skw is the back focus at the wide-angle end , and skw is the focal length of the zoom lens at the wide-angle end. When the distance is fw ,
4. 374≦ ft/f5<15.0
5.3<f1/skw<30.0
5.0<ft/fw<25.0
A zoom lens that satisfies the following conditional expression: When the amount of movement of the second lens group during zooming from the wide-angle end to the telephoto end is m2,
3.0<f1/|m2|<50.0
2. The zoom lens according to claim 1, wherein: When the focal length of the fourth lens group is f4,
0.3<f4/f5<3.0
3. The zoom lens according to claim 1, wherein: When the focal length of the fourth lens group is f4, and the amount of movement of the fourth lens group during zooming from the wide-angle end to the telephoto end is m4,
-3.0<m4/f4<-0.3
4. The zoom lens according to any one of claims 1 to 3, wherein: When the focal length of the second lens group is f2,
-2.00<f2/ft<-0.01
5. The zoom lens according to any one of claims 1 to 4, wherein: When the distance on the optical axis from the surface closest to the object side of the zoom lens at the wide-angle end to the image plane is TTDw,
3.0<TTDw/skw<20.0
6. The zoom lens according to any one of claims 1 to 5, wherein: When the distance from the image plane to the exit pupil at the wide-angle end is POw, and the focal length of the zoom lens at the wide-angle end is fw,
-8.0<POw/fw<-1.0
7. The zoom lens according to any one of claims 1 to 6, wherein: 8. The zoom lens according to any one of claims 1 to 7 , wherein the third lens group and the fifth lens group move so as to draw the same trajectory during zooming from the wide-angle end to the telephoto end. A first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a third lens group with positive refractive power, which are arranged in order from the object side to the image side. A zoom lens that consists of four lens groups, a fifth lens group with positive refractive power, and a rear group that includes one or more lens groups. The distance between adjacent lens groups changes during zooming from the wide-angle end to the telephoto end. is a lens,
The rear group includes a sixth lens group with negative refractive power and a seventh lens group with negative refractive power, which are arranged in order from the object side to the image side,
When zooming from the wide-angle end to the telephoto end, the third lens group and the fifth lens group move so as to draw the same trajectory,
When the focal length of the zoom lens at the telephoto end is ft, the focal length of the fifth lens group is f5, the focal length of the first lens group is f1, and the back focus at the wide-angle end is skw,
4.2<ft/f5<15.0
5.3<f1/skw<30.0
A zoom lens that satisfies the following conditional expression: The rear group further has a positive refractive power eighth lens group arranged closest to the image side,
10. The zoom lens according to any one of claims 1 to 9, wherein the eighth lens group does not move during zooming. 11. The zoom lens according to any one of claims 1 to 10, wherein the lens group arranged closer to the image side than the fifth lens group moves during focusing. 12. The zoom lens according to claim 11 , wherein the lens group that moves during focusing comprises a cemented lens composed of two lenses or a single lens. 13. The zoom lens according to any one of claims 1 to 12 , wherein the first lens group comprises four or less lenses. 14. The second lens group according to any one of claims 1 to 13 , wherein the second lens group is composed of a negative lens, a negative lens, a positive lens, and a negative lens arranged in order from the object side to the image side. The zoom lens described in the item. 15. The zoom lens according to any one of claims 1 to 14 , wherein the third lens group includes an aspherical lens. 6.112≤ft/f5<15.0
16. The zoom lens according to any one of claims 1 to 15, wherein the following conditional expression is satisfied. A zoom lens according to any one of claims 1 to 16;
and an imaging device for receiving an image formed by the zoom lens.

Images