JP5948130B2 - Zoom lens and imaging apparatus using the same - Google Patents

Description

  The present invention relates to a zoom lens and an imaging apparatus using the same, and particularly suitable for a compact digital camera.

  In recent years, digital cameras that shoot a subject using a solid-state imaging device such as a CCD or CMOS instead of a silver salt film camera have become mainstream. Furthermore, digital cameras have come to have a number of categories in a wide range from high-functional types for business use to compact popular types.

Users of such popular digital cameras have a desire to enjoy shooting in a wide range of scenes anytime and anywhere.
For this reason, digital cameras with a small size in the thickness direction are favored because they are easy to carry in small products, especially clothes and bag pockets. There is a demand for further miniaturization.

In addition, digital cameras that can perform image processing such as widening the sensitivity range of the dynamic range so that shooting can be performed even in high light and dark conditions have been proposed, which enables shooting regardless of shooting conditions. It is coming.
When shooting in a dark place, it is possible to electronically correct the brightness to some extent, but if a lens with a large lens aperture is used, shooting in a dark place can be supported, and there may be conditions for shooting. Will spread.

In addition, with a lens with a large lens diameter, clear shooting is possible even with a small amount of incident light, so it is possible to increase the shutter speed more quickly in continuous shooting of moving subjects, etc. In recent years, lenses with large lens apertures have attracted attention because they provide options.
In addition, there is still a demand for a high zoom ratio from the viewpoint of expanding the photographing area, and further higher zoom ratio is expected.

  As a prior art that constitutes such a zoom lens having a relatively high zoom ratio and a large aperture, there are a positive first lens group, a negative second lens group, a positive third lens group, and a positive first lens group from the object side. A zoom lens having four lens groups is disclosed (Patent Document 1).

JP 2010-217478 A

  However, in the case of a bright zoom lens having a relatively small F number at the wide-angle end of 1.85 as in the zoom lens described in Patent Document 1, a large pupil diameter and high aberration performance are required. It was difficult.

  The present invention has been made in view of the above, and an object of the present invention is to provide a zoom lens having a large aperture and a high zoom ratio, and having a high aberration performance and a compact configuration. .

In order to solve the above-described problems and achieve the object, a zoom lens according to the present invention includes, in order from the object side , a first lens group having a positive refractive power and a second lens group having a negative refractive power. , A third lens group having a positive refractive power and a fourth lens group having a positive refractive power, or a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a first lens having a positive refractive power. The third lens group includes a third lens group, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power . The third lens group, in order from the object side, includes a first lens component having a positive refractive power and a negative refraction. And the following conditional expressions (1-1) , (2), (3) , and (4-1) are satisfied.
2 <| f _{3_2} / f _{3_1} | ≦ 3.72 (1-1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
1.9 <f ₃ / f _W ≦ 2.40 (4-1)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
f ₃ is the focal length of the third lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is.
Further, another zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. A fourth lens group having positive refractive power, or a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a first lens group having negative refractive power. 4 lens group and a fifth lens group having positive refractive power, and the third lens group, in order from the object side, includes a first lens component having positive refractive power and a second lens component having negative refractive power. The following conditional expressions (1), (2), (3-1), (4-2), and (5-1) are satisfied.
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.4 (3-1)
1.9 <f ₃ / f _W <3 (4-2)
Σd _3G / f _T <0.3 (5-1)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
f ₃ is the focal length of the third lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
Σd _3G is the total length of the third lens group,
f _T is the focal length of the entire zoom lens system at the telephoto end,
The lens component is a single lens or a cemented lens,
It is.
Further, another zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. A fourth lens group having positive refractive power, or a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a first lens group having negative refractive power. 4 lens group and a fifth lens group having positive refractive power, and the third lens group, in order from the object side, includes a first lens component having positive refractive power and a second lens component having negative refractive power. The following conditional expressions (1), (2), (3), (5-1), and (9-1) are satisfied.
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
Σd _3G / f _T <0.3 (5-1)
3.1 <f _T / f _W <8 (9-1)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
Σd _3G is the total length of the third lens group,
f _T is the focal length of the entire zoom lens system at the telephoto end,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is.
Further, another zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. A fourth lens group having positive refractive power, or a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a first lens group having negative refractive power. 4 lens group and a fifth lens group having positive refractive power, and the third lens group, in order from the object side, includes a first lens component having positive refractive power and a second lens component having negative refractive power. When the lens group closest to the image side is the fourth lens group, the fourth lens group consists of a single lens, and when the lens group closest to the image side is the fifth lens group, the fifth lens group consists of a single lens. The following conditional expressions (1), (2), (3), and (5-1) are satisfied.
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
Σd _3G / f _T <0.3 (5-1)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
Σd _3G is the total length of the third lens group,
f _T is the focal length of the entire zoom lens system at the telephoto end,
The lens component is a single lens or a cemented lens,
It is.
Further, another zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. A fourth lens group having positive refractive power, or a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a first lens group having negative refractive power. 4 lens group and a fifth lens group having positive refractive power, and the third lens group, in order from the object side, includes a first lens component having positive refractive power and a second lens component having negative refractive power. The following conditional expressions (1), (2), (3), (8-1), and (9-1) are satisfied.
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
L _T / f _T <3 (8-1)
3.1 <f _T / f _W <8 (9-1)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
L _T is the total length of the entire zoom lens system at the telephoto end,
f _T is the focal length of the entire zoom lens system at the telephoto end,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is.

  An image pickup apparatus according to the present invention includes a zoom lens and an image pickup element having an image pickup surface that is disposed on an image side of the zoom lens and receives an image formed by the zoom lens, and the zoom lens is the zoom lens described above. It is characterized by being.

  The zoom lens according to the present invention can provide a zoom lens having a compact configuration with a large aperture and a high zoom ratio, a high aberration performance, and a reduced lens diameter and number of components.

FIG. 2 is a lens cross-sectional view at the wide-angle end (a), the intermediate state (b), and the telephoto end (c) when focusing on an object point at infinity according to the first exemplary embodiment of the zoom lens of the present invention. FIG. 5 is a lens cross-sectional view at a wide angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to a second embodiment of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to a third embodiment of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Embodiment 4 of the zoom lens of the present invention. FIG. 6 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 5 of the zoom lens of the present invention. FIG. 10 is a lens cross-sectional view at a wide-angle end (a), an intermediate state (b), and a telephoto end (c) when focusing on an object point at infinity according to Example 6 of the zoom lens of the present invention. FIG. 6 is an aberration diagram for Example 1 upon focusing on an object point at infinity. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 4 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object point at infinity. FIG. 10 is an aberration diagram for Example 6 upon focusing on an object point at infinity. It is a figure explaining correction | amendment of a distortion aberration. 1 is a cross-sectional view of a compact camera as an image pickup apparatus using a zoom lens of the present invention and using a small CCD or CMOS as an image pickup device. FIG. It is a front perspective view which shows the external appearance of the digital camera as an imaging device. It is a back perspective view showing the appearance of a digital camera as an imaging device. It is a block diagram which shows the internal circuit of the principal part of a digital camera.

Embodiments of a zoom lens according to the present invention and an image pickup apparatus using the same will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In the following description, the lens component is a single lens or a cemented lens.
First, prior to the description of the examples, the effects of the zoom lens of the present embodiment will be described.

A zoom lens according to an embodiment of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power, The third lens group includes, in order from the object side, a first lens component having a positive refractive power and a second lens component having a negative refractive power, and satisfies the following conditional expressions (1), (2), and (3) It is characterized by doing.
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f _{3_2} is the focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
It is.

In the case of a bright lens, since a pupil diameter is large and high aberration performance is required, it is difficult to achieve a compact configuration.
In order from the object side, there are a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power, and the third lens group is positive in order from the object side. When it is composed of a first lens component with refractive power and a second lens component with negative refractive power, high performance and compactness can be achieved by appropriately setting conditional expressions (1), (2), and (3). It can be set as a simple structure.

Conditional expression (1) defines the ratio of the focal lengths of the first lens component having a positive refractive power and the second lens component having a negative refractive power among the lens components constituting the third lens group.
If the upper limit of conditional expression (1) is exceeded, the refractive power of the first lens component becomes excessively large, and the occurrence of spherical aberration, coma aberration, etc. becomes large, which is not preferable.
If the lower limit of conditional expression (1) is not reached, the refractive power of the second lens component becomes too large, the refractive power of the entire third lens group becomes small, and the zoom ratio cannot be increased, or If an attempt is made to increase the ratio, the amount of movement of the third lens group increases, making it difficult to adopt a compact configuration.

Conditional expression (2) defines the variable magnification burden of the second lens group and the third lens group in an appropriate ratio among the lens groups responsible for variable magnification.
Exceeding the upper limit of conditional expression (2) is not preferable because the variable magnification burden of the second lens group becomes excessively large, and the occurrence of field curvature and lateral chromatic aberration at the wide-angle end increases. Moreover, the burden on optical design, such as increasing the number of lenses to suppress aberrations, increases, which is disadvantageous for miniaturization.
On the other hand, if the lower limit of conditional expression (2) is not reached, the zooming burden of the third lens unit becomes too large, the occurrence of various aberrations such as spherical aberration and coma increases, and the fluctuation of axial chromatic aberration increases, which is preferable. Absent.

Conditional expression (3) is an expression that prescribes the F number at the wide-angle end.
If the upper limit of conditional expression (3) is exceeded, the F-number at the wide-angle end will increase and the lens will not be bright.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (4) is satisfied.
1.9 <f ₃ / f _W <5 (4)
here,
f ₃ is the focal length of the third lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
It is.

Conditional expression (4) defines the focal length of the third lens group, and is normalized by the focal length of the entire zoom lens system at the wide angle end.
If the upper limit of conditional expression (4) is exceeded, the refractive power of the third lens group becomes too small, the amount of movement of the third lens group due to trying to achieve a zoom ratio increases, and the overall length of the zoom lens becomes longer. It becomes difficult to take a compact configuration.
On the other hand, if the lower limit of conditional expression (3) is not reached, the refractive power of the third lens group becomes too large, and various aberrations such as spherical aberration and coma aberration occur in the third lens group, which is not preferable.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (5) is satisfied.
Σd _3G / f _T <0.4 (5)
here,
Σd _3G is the total length of the third lens group,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.

Conditional expression (5) is an expression that prescribes the total length of the third lens unit, and is normalized by the focal length of the entire zoom lens system at the telephoto end.
If the upper limit of conditional expression (5) is exceeded, the total length of the third lens group becomes too long, which is not suitable for miniaturization.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (6) is satisfied.
0.6 <f _{3_1} / f ₃ <1.2 (6)
here,
f _{3_1} is the focal length of the first lens component in the third lens group,
f ₃ is the focal length of the third lens group,
It is.

Conditional expression (6) defines the refractive power of the first lens component and is normalized by the focal length of the third lens group.
If the upper limit of conditional expression (6) is exceeded, the refractive power of the first lens component becomes excessively small, and the refractive power of the entire third lens group becomes small, so that the third lens group is moved in order to achieve a high zoom ratio. It is necessary to increase the amount and is not suitable for miniaturization.
On the other hand, if the lower limit of conditional expression (6) is not reached, the refractive power of the first lens component becomes too large, and the amount of spherical aberration generated becomes undesirably large.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (7) is satisfied.
1.2 <| f _{3_2} / f ₃ | <5 (7)
here,
f _{3_2} is the focal length of the second lens component in the third lens group,
f ₃ is the focal length of the third lens group,
It is.

Conditional expression (7) defines the refractive power of the second lens component and is normalized by the focal length of the third lens group.
If the upper limit of conditional expression (7) is exceeded, the refractive power of the second lens component will be excessively small, making it difficult to correct higher-order coma. In addition, since the principal point of the third lens group cannot be put forward, it is difficult to reduce the lens diameter and it is difficult to adopt a compact configuration.
If the lower limit of conditional expression (7) is not reached, the refractive power of the second lens component becomes too large, and the refractive power of the entire third lens group becomes small. It is necessary to increase the amount of movement, which is not suitable for downsizing.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (8) is satisfied.
L _T / f _T <3.3 (8)
here,
L _T is the total length of the entire zoom lens system at the telephoto end,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.

Conditional expression (8) defines the total length of the entire zoom lens system at the telephoto end, and is normalized by the focal length of the entire zoom lens system at the telephoto end.
If the upper limit of conditional expression (8) is exceeded, the total length of the entire zoom lens system at the telephoto end becomes too long, making it unsuitable for miniaturization.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (9) is satisfied.
3.1 <f _T / f _W <10 (9)
here,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.

  Conditional expression (9) defines the zoom ratio of the zoom lens, and it is necessary for the zoom lens to take a value equal to or greater than the lower limit in order to maintain a high zoom ratio.

In the zoom lens according to the embodiment of the present invention, it is preferable that the following conditional expression (10) is satisfied.
−5 <f ₂ / f _W <−1.5 (10)
here,
f ₂ is the focal length of the second lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
It is.

Conditional expression (10) defines the focal length of the second lens group, and is normalized by the focal length of the entire zoom lens system at the wide angle end.
If the lower limit of conditional expression (10) is not reached, the refractive power of the second lens group becomes small and the entire length of the entire zoom lens system becomes long, which is not suitable for miniaturization.
If the upper limit of conditional expression (10) is exceeded, the refractive power of the second lens group will increase, so that field curvature and lateral chromatic aberration will increase at the wide angle end.

  An imaging apparatus according to an embodiment of the present invention includes a zoom lens, and an imaging element that includes an imaging surface that is disposed on an image side of the zoom lens and receives an image formed by the zoom lens. It is characterized by being any zoom lens.

  For conditional expression (1), it is more preferable to set the upper limit value to 3.5, and further to 3. Further, the lower limit value is more preferably 2.1, and further preferably 2.15.

  For conditional expression (2), it is more preferable to set the upper limit value to 0.75, and further to 0.6. Further, the lower limit value is more preferably 0.3, and further preferably 0.35.

  For conditional expression (3), it is more preferable to set the upper limit value to 2.4, and further to 2.36.

  For conditional expression (4), it is more preferable to set the upper limit value to 4, and further to 3. Further, the lower limit value is more preferably 2.1, and further preferably 2.2.

  For conditional expression (5), the upper limit value is more preferably 0.35, and even more preferably 0.3.

  For conditional expression (6), it is more preferable to set the upper limit value to 1.1 and further to 1. Further, it is more preferable that the lower limit value is 0.7, and further 0.8.

  For conditional expression (7), it is more preferable to set the upper limit value to 4, further 3.5. Moreover, it is more preferable that the lower limit value is 1.4, and further 1.6.

  For conditional expression (8), it is more preferable to set the upper limit value to 3, and further to 2.8.

  For conditional expression (9), it is more preferable to set the upper limit value to 8, further 6. Further, it is more preferable that the lower limit value is 3.3, and further 3.6.

  For conditional expression (10), it is more preferable to set the upper limit value to −1.52. The lower limit value is more preferably −3.

  Examples 1 to 6 of the zoom lens according to the present invention will be described below. FIGS. 1 to 6 show lens cross-sectional views of the wide-angle end (a), the intermediate focal length state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 6, respectively. 1 to 6, the first lens group is G1, the second lens group is G2, the third lens group is G3, the fourth lens group is G4, the fifth lens group is G5, and the brightness (aperture) stop is S. The parallel flat plate constituting the low-pass filter provided with the wavelength band limiting coat for limiting the infrared light is indicated by F, the parallel flat plate of the cover glass of the electronic image sensor is indicated by C, and the image plane is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action. The parallel plate F may not have the function of a low-pass filter.

  The numerical data is data in a state where the subject is focused on an object at infinity. The unit of length of each numerical value is mm, and the unit of angle is ° (degree). Further, the zoom data are values at the wide angle end (wide angle), the intermediate focal length state (intermediate), and the telephoto end (telephoto).

  As shown in FIG. 1, the zoom lens according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the object side. The aperture stop S moves together with the third lens group G3.

  In order from the object side, the first lens group G1 includes a biconvex positive lens L1. The second lens group G2 includes a negative meniscus lens L2 having a convex surface directed toward the object side, a biconcave negative lens L3, and a biconvex positive lens L4. The third lens group G3 includes a biconvex positive lens L5 (first lens component), a cemented lens (second lens) of a positive meniscus lens L6 having a convex surface facing the object side and a negative meniscus lens L7 having a convex surface facing the object side. Component). The fourth lens group G4 includes a positive meniscus lens L8 having a convex surface directed toward the object side.

  The aspheric surfaces are provided on the three surfaces of the biconvex positive lens L5 and the object-side surface of the positive meniscus lens L8.

  As shown in FIG. 2, the zoom lens according to the second embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the object side. The aperture stop S moves together with the third lens group G3.

  In order from the object side, the first lens group G1 includes a biconvex positive lens L1. The second lens group G2 includes a negative meniscus lens L2 having a convex surface directed toward the object side, a biconcave negative lens L3, and a biconvex positive lens L4. The third lens group G3 includes a biconvex positive lens L5 (first lens component), a cemented lens (second lens) of a positive meniscus lens L6 having a convex surface facing the object side and a negative meniscus lens L7 having a convex surface facing the object side. Component). The fourth lens group G4 includes a positive meniscus lens L8 having a convex surface directed toward the object side.

  The aspheric surfaces are provided on the three surfaces of the biconvex positive lens L5 and the object-side surface of the positive meniscus lens L8.

  As shown in FIG. 3, the zoom lens according to the third exemplary embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the object side. The aperture stop S moves together with the third lens group G3.

In order from the object side, the first lens group G1 includes a biconvex positive lens L1. The second lens group G2 includes a biconcave negative lens L2, a biconcave negative lens L3, and a biconvex positive lens L4. The third lens group G3 includes a biconvex positive lens L5 (first lens component) and a cemented lens (second lens component) of the biconvex positive lens L6 and the biconcave negative lens L7. The fourth lens group G4 includes a positive meniscus lens L8 having a convex surface directed toward the object side.
In Example 3, the thirteenth through fourteenth surfaces are joint surfaces.

  The aspheric surfaces are provided on the three surfaces of the biconvex positive lens L5 and the object-side surface of the positive meniscus lens L8.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the object side after moving to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the object side. The aperture stop S moves together with the third lens group G3.

  In order from the object side, the first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 includes a negative meniscus lens L2 having a convex surface facing the object side, a biconcave negative lens L3, and a positive meniscus lens L4 having a convex surface facing the object side. The third lens group G3 includes a biconvex positive lens L5 (first lens component), a cemented lens (second lens) of a positive meniscus lens L6 having a convex surface facing the object side and a negative meniscus lens L7 having a convex surface facing the object side. Component). The fourth lens group G4 includes a positive meniscus lens L8 having a convex surface directed toward the object side.

  The aspheric surfaces are provided on the three surfaces of the biconvex positive lens L5 and the object-side surface of the positive meniscus lens L8.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the object side. The aperture stop S moves together with the third lens group G3.

  In order from the object side, the first lens group G1 includes a cemented lens including a negative meniscus lens L1 having a convex surface directed toward the object side and a positive meniscus lens L2 having a convex surface directed toward the object side. The second lens group G2 includes a negative meniscus lens L3 having a convex surface facing the object side, a biconcave negative lens L4, and a positive meniscus lens L5 having a convex surface facing the object side. The third lens group G3 includes a biconvex positive lens L6 (first lens component) and a cemented lens (second lens component) of the biconvex positive lens L7 and the biconcave negative lens L8. The fourth lens group G4 includes a positive meniscus lens L9 having a convex surface directed toward the object side.

  The aspheric surfaces are provided on the four surfaces of the object side surface of the biconcave negative lens L4, both surfaces of the biconvex positive lens L6, and the object side surface of the positive meniscus lens L9.

  As shown in FIG. 6, the zoom lens of Example 6 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a brightness (aperture) stop. S, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side after moving to the image side. The second lens group G2 moves to the image side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the image side after moving to the object side. The fifth lens group G5 moves to the image side after moving to the object side. The aperture stop S moves together with the third lens group G3.

  In order from the object side, the first lens group G1 includes a biconvex positive lens L1. The second lens group G2 includes a negative meniscus lens L2 having a convex surface directed toward the object side, a biconcave negative lens L3, and a biconvex positive lens L4. The third lens group G3 includes a biconvex positive lens L5 (first lens component), a cemented lens (second lens) of a positive meniscus lens L6 having a convex surface facing the object side and a negative meniscus lens L7 having a convex surface facing the object side. Component). The fourth lens group G4 includes a negative meniscus lens L8 having a convex surface directed toward the object side. The fifth lens group G5 is composed of a biconvex positive lens L9.

  The aspheric surfaces are provided on the four surfaces of the biconvex positive lens L5, the object side surface of the negative meniscus lens L8, and the object side surface of the biconvex positive lens L9.

  Below, the numerical data of each said Example are shown. Symbols are the above, fb is back focus, f1, f2... Are focal lengths of each lens group, FNO is F number, ω is half angle of view, r is radius of curvature of each lens surface, d is between each lens surface The interval, nd is the refractive index of the d-line of each lens, and νd is the Abbe number of the d-line of each lens. The total lens length described later is obtained by adding back focus to the distance from the lens front surface to the lens final surface. fb (back focus) represents the distance from the last lens surface to the paraxial image plane in terms of air.

Each aspheric shape is expressed by the following formula (I) using each aspheric coefficient in each embodiment.
Here, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + k) · (Y / r) ² } ^1/2 ] + A ₄ × Y ⁴ + A ₆ × Y ⁶ + A ₈ × Y ⁸ + A ₁₀ × Y ¹⁰ ( I)
here,
r is the paraxial radius of curvature,
k is the cone coefficient,
A ₄ , A ₆ , A ₈ , and A ₁₀ are fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, respectively.
In the aspheric coefficient, “e−n” (n is an integer) indicates “10 ⁻ⁿ ”.

Numerical example 1
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 29.118 2.12 1.49700 81.54
2 -185.547 Variable
3 158.650 0.70 1.88300 40.76
4 7.484 3.39
5 -23.072 0.60 1.88300 40.76
6 81.972 0.20
7 19.828 1.47 1.92286 18.90
8 -140.176 Variable
9 (Aperture) ∞ 0.10
10 * 7.800 1.83 1.58313 59.38
11 * -32.444 0.10
12 6.925 2.00 1.88300 40.76
13 31.679 0.45 1.80810 22.76
14 4.235 Variable
15 * 9.220 1.80 1.52542 55.78
16 70.000 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 10th surface
K = 0.000
A4 = -2.30165e-04, A6 = -1.15925e-06, A8 = -2.79567e-08
11th page
K = 0.000
A4 = 9.05424e-05, A6 = 5.46552e-07
15th page
K = 0.000
A4 = -1.77126e-04, A6 = 9.17940e-07

Zoom data
Wide angle Medium Telephoto focal length 5.06 9.82 19.43
FNO. 2.05 2.44 2.98
Angle of view 2ω 76.02 43.77 22.44
fb (in air) 4.53 6.80 9.52
Total length (in air) 44.12 42.31 49.93

d2 0.30 5.80 13.79
d8 18.35 7.50 1.45
d14 6.19 7.45 10.41
d16 3.00 5.28 7.99

Group focal length
f1 = 50.81 f2 = -9.82 f3 = 11.92 f4 = 20.01

Numerical example 2
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 27.257 2.06 1.49700 81.54
2 -143.042 Variable
3 218.088 0.70 1.88300 40.76
4 7.353 3.45
5 -20.320 0.60 1.88300 40.76
6 171.432 0.20
7 21.069 1.50 1.92286 18.90
8 -109.751 Variable
9 (Aperture) ∞ 0.10
10 * 8.911 1.69 1.58313 59.38
11 * -30.393 0.10
12 7.410 2.45 1.88300 40.76
13 86.809 0.45 1.80810 22.76
14 4.576 Variable
15 * 8.914 1.80 1.52542 55.78
16 70.000 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 10th surface
K = 0.000
A4 = -2.03812e-04, A6 = 3.89448e-07, A8 = -5.60558e-09
11th page
K = 0.000
A4 = 4.54452e-05, A6 = 1.51240e-06
15th page
K = 0.000
A4 = -2.02610e-04, A6 = -4.57528e-07

Zoom data
Wide angle Medium Telephoto focal length 5.06 9.82 19.43
FNO. 2.05 2.43 2.97
Angle of view 2ω 76.15 43.79 22.32
fb (in air) 4.63 7.22 9.87
Total length (in air) 44.59 42.00 49.49

d2 0.30 5.20 12.92
d8 18.32 7.29 1.45
d14 6.25 7.20 10.16
d16 3.10 5.69 8.34

Group focal length
f1 = 46.25 f2 = -9.48 f3 = 12.12 f4 = 19.24

Numerical Example 3
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 42.186 2.07 1.49700 81.54
2 -87.337 Variable
3 -4069.895 0.70 1.88300 40.76
4 8.235 3.69
5 -23.719 0.60 1.88300 40.76
6 394.297 0.20
7 22.297 1.59 1.92286 18.90
8 -183.777 Variable
9 (Aperture) ∞ 0.10
10 * 7.434 2.22 1.58313 59.38
11 * -30.784 0.10
12 8.159 2.15 1.88300 40.76
13 -42.052 0.01 1.56384 60.67
14 -42.052 0.60 1.80518 25.42
15 4.407 Variable
16 * 8.807 1.80 1.52542 55.78
17 43.392 Variable
18 ∞ 0.30 1.54771 62.90
19 ∞ 0.50
20 ∞ 0.50 1.51633 64.10
21 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 10th surface
K = 0.000
A4 = -2.92208e-04, A6 = -4.61047e-06, A8 = -7.55152e-08
11th page
K = 0.000
A4 = 1.13948e-04, A6 = -3.51648e-06
16th page
K = 0.000
A4 = -1.69962e-04

Zoom data
Wide angle Medium Telephoto focal length 5.05 9.89 19.43
FNO. 2.00 2.41 2.99
Angle of view 2ω 76.66 42.82 22.19
fb (in air) 4.49 6.49 8.88
Total length (in air) 45.64 44.17 51.93

d2 0.30 6.91 15.10
d8 19.42 7.87 1.45
d15 5.61 7.09 10.68
d17 3.00 5.00 7.39

Group focal length
f1 = 57.54 f2 = -10.69 f3 = 12.13 f4 = 20.66

Numerical Example 4
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 20.051 2.02 1.49700 81.54
2 187.279 Variable
3 60.222 0.70 1.88300 40.76
4 6.923 3.26
5 -21.750 0.60 1.88300 40.76
6 96.915 0.20
7 17.396 1.39 1.92286 18.90
8 211.623 Variable
9 (Aperture) ∞ 0.10
10 * 7.347 1.99 1.58313 59.38
11 * -26.375 0.10
12 7.950 2.12 1.91082 35.25
13 1794.936 0.45 1.80810 22.76
14 4.350 Variable
15 * 9.728 1.80 1.52542 55.78
16 70.000 Variable
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 10th surface
K = 0.000
A4 = -3.40623e-04, A6 = -1.06642e-06, A8 = -4.53670e-08
11th page
K = 0.000
A4 = 9.85056e-05, A6 = 1.32195e-06
15th page
K = 0.000
A4 = -1.04711e-04, A6 = 1.04972e-06

Zoom data
Wide angle Medium telephoto focal length 5.06 11.08 24.29
FNO. 2.01 2.48 3.13
Angle of view 2ω 76.27 39.63 18.27
fb (in air) 4.33 7.65 9.44
Total length (in air) 44.04 41.88 52.73

d2 0.30 5.96 14.87
d8 18.53 6.55 1.45
d14 6.16 6.99 12.25
d16 2.80 6.12 7.91

Group focal length
f1 = 45.00 f2 = -9.09 f3 = 11.55 f4 = 21.29

Numerical Example 5
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 23.117 0.60 1.92286 18.90
2 19.000 3.04 1.69680 55.53
3 567.677 Variable
4 158.228 0.50 1.88300 40.76
5 8.057 4.30
6 * -23.534 0.40 1.74320 49.34
7 52.059 0.20
8 17.996 1.40 1.92286 18.90
9 108.881 Variable
10 (Aperture) ∞ 0.10
11 * 9.561 2.49 1.74320 49.29
12 * -42.664 0.10
13 8.376 2.09 1.88300 40.76
14 -261.069 0.40 1.80810 22.76
15 4.980 Variable
16 * 12.097 1.60 1.52542 55.78
17 107.953 Variable
18 ∞ 0.30 1.51633 64.14
19 ∞ 0.50
20 ∞ 0.50 1.51633 64.14
21 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 6th surface
K = 0.000
A4 = -1.51119e-05, A6 = -1.33372e-06, A8 = 2.50393e-08, A10 = -3.94915e-10
11th page
K = 0.000
A4 = -1.38545e-04, A6 = -5.62868e-07, A8 = 4.99891e-08
12th page
K = 0.000
A4 = 7.32966e-05, A6 = 5.50415e-07, A8 = 4.47338e-08
16th page
K = 0.000
A4 = -1.54731e-04, A6 = 4.07330e-07, A8 = 3.77271e-09

Zoom data
Wide angle Medium Telephoto focal length 6.10 11.83 23.42
FNO. 2.35 2.72 3.26
Angle of view 2ω 75.78 42.83 21.79
fb (in air) 4.33 7.31 9.34
Total length (in air) 47.13 43.69 47.73

d3 0.30 4.70 10.45
d9 18.00 7.11 1.00
d15 7.29 7.35 9.71
d17 2.80 5.79 7.81

Group focal length
f1 = 37.00 f2 = -9.40 f3 = 11.96 f4 = 25.76

Numerical Example 6
Unit mm

Surface data Surface number rd nd νd
Object ∞ ∞
1 26.721 2.10 1.49700 81.54
2 -124.956 Variable
3 1203.804 0.40 1.88300 40.76
4 7.349 3.10
5 -19.235 0.40 1.88300 40.76
6 299.582 0.20
7 22.220 1.45 1.92286 18.90
8 -69.837 Variable
9 (Aperture) ∞ 0.10
10 * 9.000 2.30 1.58313 59.38
11 * -15.837 0.20
12 6.500 2.00 1.88300 40.76
13 146.230 0.40 1.80810 22.76
14 4.124 Variable
15 * -10.683 0.40 1.49700 81.54
16 -288.659 Variable
17 * 7.732 2.30 1.52542 55.78
18 -32.661 Variable
19 ∞ 0.30 1.51633 64.14
20 ∞ 0.50
21 ∞ 0.50 1.51633 64.14
22 ∞ 0.50
Image plane (imaging plane) ∞

Aspheric data 10th surface
K = 0.000
A4 = -3.04097e-04, A6 = 2.44348e-06, A8 = -3.88587e-07
11th page
K = 0.000
A4 = 5.83875e-05, A6 = 2.41183e-06, A8 = -3.46382e-07
15th page
K = 0.000
A4 = 2.16233e-04, A6 = -6.69265e-06, A8 = 3.07916e-07
17th page
K = 0.000
A4 = -4.34037e-04, A6 = 1.05542e-06, A8 = -6.59403e-08

Zoom data
Wide angle Medium Telephoto focal length 5.06 9.82 19.43
FNO. 2.00 2.31 3.13
Angle of view 2ω 76.14 43.44 22.13
fb (in air) 3.70 5.75 5.03
Total length (in air) 44.43 41.47 44.43

d2 0.30 5.30 9.32
d8 18.48 7.11 1.44
d14 2.00 3.14 10.49
d16 4.59 4.82 2.80
d18 2.18 4.22 3.50

Group focal length
f1 = 44.50 f2 = -9.43 f3 = 10.05 f4 = -22.33 f5 = 12.14

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 6 are shown in FIGS. In these aberration diagrams, (a) to (d) are the wide-angle end, (e) to (h) are the intermediate focal length states, and (i) to (l) are the spherical aberration (SA) and astigmatism at the telephoto end. Aberration (AS), distortion (DT), and lateral chromatic aberration (CC) are shown. In each figure, “ω” indicates a half angle of view.

Next, the values of the conditional expressions in each example are listed.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6
1 | f _{3_2} / f _{3_1} | 2.72 3.25 2.19 2.34 2.75 3.72
2 (β _2T / β _2W ) / (β _3T / β _3W )
0.39 0.38 0.40 0.43 0.57 0.43
3 Fno (W) 2.05 2.05 2.00 2.01 2.35 2.00
4 f ₃ / f _w 2.36 2.40 2.40 2.28 1.96 1.99
5 Σd _3G / f _T 0.23 0.24 0.26 0.19 0.22 0.25
6 f _{3_1} / f ₃ 0.92 0.99 0.87 0.87 0.90 1.01
7 | f _{3_2} / f ₃ | 2.50 3.22 1.89 2.05 2.46 3.77
8 L _T / f _T 2.57 2.55 2.67 2.17 2.04 2.29
9 f _T / f _w 3.84 3.84 3.85 4.80 3.84 3.84
10 f ₂ / f _w -1.94 -1.87 -2.12 -1.80 -1.54 -1.86

In order to cut off unnecessary light such as ghosts and flares, a flare stop other than the brightness stop may be arranged.
You may arrange | position in any place between each lens group of a zoom lens, or between the zoom lens group of the most image side, and an image surface. The frame member may be configured to cut flare rays, or another member may be configured. Also, it may be printed directly on the optical system, painted, or bonded with a seal. Further, the shape may be any shape such as a circle, an ellipse, a rectangle, a polygon, or a range surrounded by a function curve. Further, not only harmful light flux but also light flux such as coma flare around the screen may be cut.

  Each lens may be provided with an antireflection coating to reduce ghosts and flares. A multi-coat is desirable because it can effectively reduce ghost and flare. Further, infrared cut coating may be performed on the lens surface, cover glass, or the like. The brightness (shading) at the periphery of the image may be reduced by shifting the micro lens of the CCD. For example, the design of the CCD microlens may be changed according to the incident angle of the light beam at each image height. Further, the amount of decrease in the peripheral portion of the image may be corrected by image processing.

  In order to prevent the occurrence of ghost and flare, it is common practice to apply an antireflection coating to the air contact surface of the lens. On the other hand, the refractive index of the adhesive is sufficiently higher than the refractive index of air on the cemented surface of the cemented lens. For this reason, the reflectance is often the same as or lower than that of a single-layer coating, and it is rare to apply a coating. However, if an anti-reflection coating is also applied to the joint surface, ghosts and flares can be further reduced, and still better images can be obtained. In recent years, high refractive index glass materials have become widespread and have been used extensively in camera optical systems due to their high aberration correction effects. However, when high refractive index glass materials are used as cemented lenses, reflection on the cemented surface is ignored. It becomes impossible. In such a case, it is particularly effective to provide an antireflection coating on the joint surface.

The effective usage of the bonding surface coat is disclosed in JP-A-2-27301, JP-A-2001-324676, JP-A-2005-92115, USP 7116482, and the like. These documents particularly describe the cemented lens surface coating in the first lens group of the positive leading zoom lens, and the cemented lens surface in the lens group closest to the object in the embodiment of the present invention is also disclosed in these documents. You just have to do it. As a coating material to be used, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , HfO ₂ , and CeO having a relatively high refractive index are selected according to the refractive index of the base lens and the refractive index of the adhesive. ₂ , a coating material such as SnO ₂ , In ₂ O ₃ , ZnO, Y ₂ O ₃ , a coating material such as MgF ₂ , SiO ₂ , Al ₂ O ₃ having a relatively low refractive index, etc. The film thickness may be set so as to satisfy the above. Similar to the coating on the air contact surface of the lens, the bonding surface coat may be a multi-coat. By appropriately combining two or more layers of coating materials and film thicknesses, it becomes possible to further reduce the reflectance and control the spectral characteristics and angular characteristics of the reflectance. Needless to say, it is effective to perform the cemented surface coating on the lens cemented surfaces other than the most object side lens group based on the same concept.

In the above-described embodiments, focusing is preferably performed by moving the fourth lens group G4, but may be performed by the following (B-1), (B-2), and (B-3).
(B-1) Focusing is performed with a lens group other than the fourth lens group G4.
(B-2) Focusing is performed by moving a plurality of lens groups.
(B-3) Focusing may be performed by extending the entire lens system, or focusing may be performed by extending or retracting some lenses.

(Correction of distortion)
By the way, when the zoom lens of the present invention is used, image distortion is digitally corrected electrically. The basic concept for digitally correcting image distortion will be described below.

  For example, as shown in FIG. 13, the magnification on the circumference (image height) of the radius R inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface is fixed, and this circumference is The standard for correction. Then, other distortion points are corrected by moving each point on the circumference (image height) of an arbitrary radius r (ω) in a substantially radial direction. More specifically, the points on each circumference are moved concentrically so that an arbitrary radius r (ω) becomes a radius r ′ (ω).

For example, in FIG. 13, the point P ₁ on the circumference of an arbitrary radius r ₁ (ω) located inside the circle of radius R is the radius r ₁ ′ (ω) to be corrected toward the center of the circle. It is moved to a point P ₂ on the circumference. A point Q ₁ on the circumference of an arbitrary radius r ₂ (ω) located outside the circle of radius R is a circle of radius r ₂ ′ (ω) to be corrected in a direction away from the center of the circle. It is moved to the point Q ₂ on the circumference.

Here, r ′ (ω) can be expressed as follows.
r ′ (ω) = α · f · tan ω
here,
ω is the half angle of view of the subject,
f is the focal length of the imaging optical system (in the present invention, the zoom lens),
α is 0 or more and 1 or less,
It is.

Here, if the ideal image height corresponding to the circle (image height) of radius R is Y,
α = R / Y = R / (f · tan ω),
It becomes.

  Since the optical system is ideally rotationally symmetric with respect to the optical axis, distortion also occurs rotationally symmetric with respect to the optical axis. Therefore, as described above, when the optically generated distortion aberration is electrically corrected, the radius inscribed in the long side of the effective imaging surface around the intersection of the optical axis and the imaging surface on the reproduced image. The magnification is corrected by fixing the magnification on the circumference of the circle of R (image height) and moving each other point on the circumference of the circle (image height) with radius r (ω) in a substantially radial direction. If possible, it is considered advantageous in terms of data amount and calculation amount.

  However, the optical image is no longer a continuous amount (due to sampling) when captured by the electronic image sensor. Therefore, strictly speaking, the circle with the radius R drawn on the optical image is not an accurate circle unless the pixels on the electronic image sensor are arranged radially.

  That is, in the shape correction of the image data represented for each discrete coordinate point, there is no circle that can fix the magnification. Therefore, it is preferable to use a method of determining the coordinates (Xi ′, Yj ′) of the movement destination for each pixel (Xi, Yj). When two or more points (Xi, Yj) have moved to the coordinates (Xi ′, Yj ′), the average value of the values of each pixel is taken. If there is no moving point, interpolation may be performed using the values of the coordinates (Xi ′, Yj ′) of some surrounding pixels.

  In such a method, particularly in an electronic image pickup apparatus having a zoom lens, image distortion is significant with respect to the optical axis due to manufacturing errors of an optical system and an electronic image pickup element, and a circle with a radius R drawn on the optical image is generated. It is effective for correction when it becomes asymmetric. Further, such a method is effective for correction when a geometric distortion or the like occurs when a signal is reproduced as an image in an image sensor or various output devices.

  In the electronic imaging apparatus of the present invention, in order to calculate the correction amount r ′ (ω) −r (ω), r (ω), that is, the relationship between the half field angle and the image height, or the real image height r and the ideal image height. The relationship between r ′ / α may be recorded on a recording medium built in the electronic imaging apparatus.

  Note that the radius R should satisfy the following conditional expression in order to prevent the image after distortion correction from having an extremely short amount of light at both ends in the short side direction.

0 ≦ R ≦ 0.6Ls
Here, Ls is the length of the short side of the effective imaging surface.

The radius R preferably satisfies the following conditional expression.
0.3Ls ≦ R ≦ 0.6Ls
Furthermore, it is most advantageous to make the radius R coincide with the radius of the inscribed circle in the short side direction of the substantially effective imaging surface. In the case of correction in which the magnification is fixed in the vicinity of the radius R = 0, that is, in the vicinity of the axis, there is a slight disadvantage in terms of image quality, but the effect of reducing the size is ensured even if the angle of view is widened. it can.

The focal length section that needs to be corrected is divided into several focal zones. And approximately near the telephoto end in the divided focal zone,
r ′ (ω) = α · f · tan ω
You may correct | amend with the same correction amount as the case where the correction result which satisfies is obtained.

  Here, in this case, some barrel distortion remains at the wide-angle end in the divided focal zone. Further, if the number of divided zones is increased, it becomes unnecessary to store the unique data necessary for correction in the recording medium, which is not preferable. Therefore, one or several coefficients related to each focal length in the divided focal zone are calculated in advance. This coefficient may be determined on the basis of simulation or actual measurement.

And near the telephoto end in the divided zone,
r ′ (ω) = α · f · tan ω
It is also possible to calculate a correction amount when a correction result that satisfies the above is obtained, and to apply a coefficient uniformly for each focal distance to the correction amount to obtain a final correction amount.

By the way, if there is no distortion in the image obtained by imaging an object at infinity,
f = y / tan ω
Is established.
Here, y is the height (image height) of the image point from the optical axis, f is the focal length of the imaging system (in the present invention, the zoom lens), and ω is the image point connecting from the center on the imaging surface to the y position. Is an angle (subject half-field angle) with respect to the optical axis in the object direction corresponding to.

If the imaging optical system has barrel distortion,
f> y / tan ω
It becomes. That is, if the focal length f of the imaging optical system and the image height y are constant, the value of ω increases.

FIG. 14 is a cross-sectional view of a compact camera 1 as an image pickup apparatus using the zoom lens of the present invention and using a small CCD or CMOS as an image pickup device. An imaging lens system 2 is arranged in the lens barrel of the compact camera 1, and an imaging element surface 4 and a back monitor 5 are arranged on the body.
Here, the lens barrel 2 may be provided with a mount so that the imaging lens system 2 can be attached to and detached from the body of the single-lens mirrorless camera. For this mount portion, for example, a screw type or bayonet type mount is used.

  As the imaging lens system 2 of the compact camera 1 having such a configuration, for example, the zoom lens of the present invention shown in the first to sixth embodiments is used.

  FIG. 15 and FIG. 16 are conceptual diagrams of the configuration of an imaging apparatus according to the present invention in which a zoom lens is incorporated in the photographing optical system 41. FIG. 15 is a front perspective view showing an appearance of a digital camera 40 as an image pickup apparatus, and FIG. 16 is a rear perspective view of the same.

  The digital camera 40 of this embodiment includes a photographing optical system 41 positioned on the photographing optical path 42, a shutter button 45, a liquid crystal display monitor 47, and the like. When the shutter button 45 disposed on the upper part of the digital camera 40 is pressed, In conjunction with this, photographing is performed through the photographing optical system 41, for example, the zoom lens of the first embodiment. An object image formed by the photographing optical system 41 is formed on an image sensor (photoelectric conversion surface) provided in the vicinity of the imaging surface. The object image received by the image sensor is displayed on the liquid crystal display monitor 47 provided on the back of the camera as an electronic image by the processing means. In addition, the photographed electronic image can be recorded in a recording unit.

(Internal circuit configuration)
FIG. 17 is a block diagram showing an internal circuit of a main part of the digital camera 40. In the following description, the processing means described above is configured by, for example, the CDS / ADC unit 24, the temporary storage memory 17, the image processing unit 18, and the like, and the storage unit is configured by a storage medium unit or the like.

  As shown in FIG. 17, the digital camera 40 is connected to the operation unit 12, the control unit 13 connected to the operation unit 12, and the control signal output port of the control unit 13 via buses 14 and 15. An imaging drive circuit 16, a temporary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21 are provided.

  The temporary storage memory 17, the image processing unit 18, the storage medium unit 19, the display unit 20, and the setting information storage memory unit 21 can mutually input and output data via the bus 22. In addition, a CCD 49 and a CDS / ADC unit 24 are connected to the imaging drive circuit 16.

  The operation unit 12 includes various input buttons and switches, and notifies the control unit 13 of event information input from the outside (camera user) via these buttons. The control unit 13 is a central processing unit composed of, for example, a CPU, and has a built-in program memory (not shown) and controls the entire digital camera 40 according to a program stored in the program memory.

  The CCD 49 is an image pickup device that is driven and controlled by the image pickup drive circuit 16, converts the light amount of each pixel of the object image formed via the image pickup optical system 41 into an electric signal, and outputs the electric signal to the CDS / ADC unit 24.

  The CDS / ADC unit 24 amplifies the electrical signal input from the CCD 49 and performs analog / digital conversion, and raw video data (Bayer data, hereinafter referred to as RAW data) obtained by performing the amplification and digital conversion. Is output to the temporary storage memory 17.

  The temporary storage memory 17 is a buffer made of, for example, SDRAM, and is a memory device that temporarily stores RAW data output from the CDS / ADC unit 24. The image processing unit 18 reads out the RAW data stored in the temporary storage memory 17 or the RAW data stored in the storage medium unit 19, and includes distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs various image processing electrically.

  The recording medium unit 19 detachably mounts a card type or stick type recording medium made of, for example, a flash memory, and the RAW data transferred from the temporary storage memory 17 and the image processing unit 18 to these flash memories. Image-processed image data is recorded and held.

  The display unit 20 includes a liquid crystal display monitor 47 and the like, and displays captured RAW data, image data, an operation menu, and the like. The setting information storage memory unit 21 includes a ROM unit that stores various image quality parameters in advance, and a RAM unit that stores image quality parameters read from the ROM unit by an input operation of the operation unit 12.

  The digital camera 40 configured as described above is significantly larger than the first mode in which zooming is possible and focusing including infinity is possible by adopting the zoom lens of the present invention as the photographing optical system 41. It is possible to set the second mode that enables obtaining the photographing magnification, and it is possible to obtain an imaging apparatus that is advantageous for both miniaturization and high performance.

As described above, the zoom lens according to the present invention is useful for securing optical performance and reducing the size while having a high zoom ratio.
An example of the invention different from the present invention is shown below.
(Additional item 1)
From the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
Have
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
A zoom lens characterized by satisfying the following conditional expressions (1), (2), and (3):
2 <| f _{3_2} / f _{3_1} | <5 (1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
here,
f _{3_1} is a focal length of the first lens component in the third lens group,
f _{3_2} is a focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
It is.
(Appendix 2)
2. The zoom lens according to appendix 1, wherein the following conditional expression (4) is satisfied.
1.9 <f ₃ / f _W <5 (4)
here,
f ₃ is the focal length of the third lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
It is.
(Additional Item 3)
The zoom lens according to Additional Item 1 or Additional Item 2, wherein the following conditional expression (5) is satisfied.
Σd _3G / f _T <0.4 (5)
here,
Σd _3G is the total length of the third lens group,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.
(Appendix 4)
The zoom lens according to any one of additional items 1 to 3, wherein the following conditional expression (6) is satisfied.
0.6 <f _{3_1} / f ₃ <1.2 (6)
here,
f _{3_1} is a focal length of the first lens component in the third lens group,
f ₃ is the focal length of the third lens group,
It is.
(Appendix 5)
The zoom lens according to any one of additional items 1 to 4, wherein the following conditional expression (7) is satisfied.
1.2 <| f _{3_2} / f ₃ | <5 (7)
here,
f _{3_2} is a focal length of the second lens component in the third lens group,
f ₃ is the focal length of the third lens group,
It is.
(Appendix 6)
The zoom lens according to any one of additional items 1 to 5, wherein the following conditional expression (8) is satisfied.
L _T / f _T <3.3 (8)
here,
L _T is the total length of the entire zoom lens system at the telephoto end,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.
(Appendix 7)
The zoom lens according to any one of supplementary items 1 to 6, wherein the following conditional expression (9) is satisfied.
3.1 <f _T / f _W <10 (9)
here,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
f _T is the focal length of the entire zoom lens system at the telephoto end,
It is.
(Appendix 8)
The zoom lens according to any one of additional items 1 to 7, wherein the following conditional expression (10) is satisfied.
−5 <f ₂ / f _W <−1.5 (10)
here,
f ₂ is the focal length of the second lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
It is.
(Appendix 9)
A zoom lens, and an image pickup device including an image pickup surface that is disposed on an image side of the zoom lens and receives an image formed by the zoom lens;
An imaging apparatus, wherein the zoom lens is the zoom lens according to any one of additional items 1 to 8.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group G5 ... 5th lens group S ... Brightness stop F ... Light quantity reduction filter C ... Cover glass I ... Image plane 1 ... Compact camera 2 ... imaging lens system 4 ... imaging element surface 5 ... back monitor 12 ... operation unit 13 ... control units 14, 15 ... bus 16 ... imaging drive circuit 17 ... temporary storage memory 18 ... image processing unit 19 ... storage medium unit 20 Display unit 21 Setting information storage memory unit 22 Bus 24 CDS / ADC unit 40 Digital camera 41 Shooting optical system 42 Shooting optical path 45 Shutter button 47 Liquid crystal display monitor 49 CCD

Claims (13)

In order from the object side ,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having a positive refractive power,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having negative refractive power;
A fifth lens unit having positive refractive power ,
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
A zoom lens characterized by satisfying the following conditional expressions (1-1) , (2), (3) , and (4-1) .
2 <| f _{3_2} / f _{3_1} | ≦ 3.72 (1-1)
0.1 <(β _2T / β _2W ) / (β _3T / β _3W ) <0.8 (2)
Fno (W) <2.5 (3)
1.9 <f ₃ / f _W ≦ 2.40 (4-1)
here,
f _{3_1} is a focal length of the first lens component in the third lens group,
f _{3_2} is a focal length of the second lens component in the third lens group,
β _2W is the lateral magnification at the wide angle end of the second lens group,
β _2T is the lateral magnification at the telephoto end of the second lens group,
β _3W is the lateral magnification at the wide angle end of the third lens group,
β _3T is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
f ₃ is the focal length of the third lens group,
f _W is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is. In order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having a positive refractive power,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having negative refractive power;
A fifth lens unit having positive refractive power,
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
A zoom lens satisfying the following conditional expressions (1), (2), (3-1), (4-2), and (5-1).
2 <| f _{3_2} / F _{3_1} | <5 (1)
0.1 <(β _2T / Β _2W ) / (Β _3T / Β _3W <0.8 (2)
Fno (W) <2.4 (3-1)
1.9 <f _Three / F _W <3 (4-2)
Σd _3G / F _T <0.3 (5-1)
here,
f _{3_1} Is the focal length of the first lens component in the third lens group,
f _{3_2} Is the focal length of the second lens component in the third lens group,
β _2W Is the lateral magnification at the wide angle end of the second lens group,
β _2T Is the lateral magnification at the telephoto end of the second lens group,
β _3W Is the lateral magnification at the wide-angle end of the third lens group,
β _3T Is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
f _Three Is the focal length of the third lens group,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
Σd _3G Is the total length of the third lens group,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
The lens component is a single lens or a cemented lens,
It is. In order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having a positive refractive power,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having negative refractive power;
A fifth lens unit having positive refractive power,
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
A zoom lens characterized by satisfying the following conditional expressions (1), (2), (3), (5-1), and (9-1).
2 <| f _{3_2} / F _{3_1} | <5 (1)
0.1 <(β _2T / Β _2W ) / (Β _3T / Β _3W <0.8 (2)
Fno (W) <2.5 (3)
Σd _3G / F _T <0.3 (5-1)
3.1 <f _T / F _W <8 (9-1)
here,
f _{3_1} Is the focal length of the first lens component in the third lens group,
f _{3_2} Is the focal length of the second lens component in the third lens group,
β _2W Is the lateral magnification at the wide angle end of the second lens group,
β _2T Is the lateral magnification at the telephoto end of the second lens group,
β _3W Is the lateral magnification at the wide-angle end of the third lens group,
β _3T Is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
Σd _3G Is the total length of the third lens group,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is. In order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having a positive refractive power,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having negative refractive power;
A fifth lens unit having positive refractive power,
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
When the most image side lens group is the fourth lens group, the fourth lens group is a single lens,
When the most image side lens group is the fifth lens group, the fifth lens group is a single lens,
A zoom lens characterized by satisfying the following conditional expressions (1), (2), (3), and (5-1).
2 <| f _{3_2} / F _{3_1} | <5 (1)
0.1 <(β _2T / Β _2W ) / (Β _3T / Β _3W <0.8 (2)
Fno (W) <2.5 (3)
Σd _3G / F _T <0.3 (5-1)
here,
f _{3_1} Is the focal length of the first lens component in the third lens group,
f _{3_2} Is the focal length of the second lens component in the third lens group,
β _2W Is the lateral magnification at the wide angle end of the second lens group,
β _2T Is the lateral magnification at the telephoto end of the second lens group,
β _3W Is the lateral magnification at the wide-angle end of the third lens group,
β _3T Is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
Σd _3G Is the total length of the third lens group,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
The lens component is a single lens or a cemented lens,
It is. In order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having a positive refractive power,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having negative refractive power;
A fifth lens unit having positive refractive power,
The third lens group is in order from the object side.
A first lens component having positive refractive power;
A second lens component having negative refractive power;
Consists of
A zoom lens characterized by satisfying the following conditional expressions (1), (2), (3), (8-1), and (9-1).
2 <| f _{3_2} / F _{3_1} | <5 (1)
0.1 <(β _2T / Β _2W ) / (Β _3T / Β _3W <0.8 (2)
Fno (W) <2.5 (3)
L _T / F _T <3 (8-1)
3.1 <f _T / F _W <8 (9-1)
here,
f _{3_1} Is the focal length of the first lens component in the third lens group,
f _{3_2} Is the focal length of the second lens component in the third lens group,
β _2W Is the lateral magnification at the wide angle end of the second lens group,
β _2T Is the lateral magnification at the telephoto end of the second lens group,
β _3W Is the lateral magnification at the wide-angle end of the third lens group,
β _3T Is the lateral magnification at the telephoto end of the third lens group,
Fno (W) is the F number at the wide-angle end,
L _T Is the total length of the entire zoom lens system at the telephoto end,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
The lens component is a single lens or a cemented lens,
It is. The zoom lens according to any one of claims 3 to 5, wherein the following conditional expression (4) is satisfied.
1.9 <f _Three / F _W <5 (4)
here,
f _Three Is the focal length of the third lens group,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
It is. The zoom lens according to claim 1, wherein the following conditional expression (5) is satisfied.
Σd _3G / F _T <0.4 (5)
here,
Σd _3G Is the total length of the third lens group,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
It is. The zoom lens according to any one of claims 1 to 4, wherein the following conditional expression (8) is satisfied.
L _T / F _T <3.3 (8)
here,
L _T Is the total length of the entire zoom lens system at the telephoto end,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
It is. 5. The zoom lens according to claim 1, wherein the following conditional expression (9) is satisfied.
3.1 <f _T / F _W <10 (9)
here,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
f _T Is the focal length of the entire zoom lens system at the telephoto end,
It is. The zoom lens according to any one of claims 1 to 9, wherein the following conditional expression (6) is satisfied.
0.6 <f _{3_1} / F _Three <1.2 (6)
here,
f _{3_1} Is the focal length of the first lens component in the third lens group,
f _Three Is the focal length of the third lens group,
It is. The zoom lens according to any one of claims 1 to 10, wherein the following conditional expression (7) is satisfied.
1.2 <| f _{3_2} / F _Three | <5 (7)
here,
f _{3_2} Is the focal length of the second lens component in the third lens group,
f _Three Is the focal length of the third lens group,
It is. The zoom lens according to any one of claims 1 to 11, wherein the following conditional expression (10) is satisfied.
−5 <f ₂ / F _W <-1.5 (10)
here,
f ₂ Is the focal length of the second lens group,
f _W Is the focal length of the entire zoom lens system at the wide-angle end,
It is. A zoom lens, and an image pickup device having an image pickup surface disposed on the image side of the zoom lens and receiving an image formed by the zoom lens
The zoom lens according to claim 1, wherein the zoom lens is the zoom lens according to claim 1.

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