JP2009251362A - Three-group zoom lens and imaging apparatus equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-group zoom lens or the like where respective lens groups have lens components two by two, and which is advantageous in terms of securement of a variable power ratio, brightness and optical performance. <P>SOLUTION: The three-group zoom lens comprises the lens groups having negative, positive and positive power in order from an object side to an image side. When varying power from a wide angle end to a telephoto end, the second lens group moves to narrow a space between the first lens group and the second lens group and to widen a space between the second lens group and the third lens group. The first lens group comprises two lens components, that is, a negative front side lens component and a positive rear side lens component in order from the object side. The second lens group comprises two lens components, that is, a positive front side lens component and a negative rear side lens component in order from the object side. The third lens group comprises two lens components, that is, a front side lens component and a positive rear side lens component in order from the object side. A brightness diaphragm is arranged nearer to an image side than the first lens group and nearer to the object side than the rear side lens component in the second lens group, and moves in an optical axis direction integrally with the second lens group when varying power from the wide angle end to the telephoto end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a three-unit zoom lens including a first lens unit having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power in order from the object side. Furthermore, the present invention relates to an imaging apparatus provided with such a three-group zoom lens.

In recent years, digital cameras that shoot a subject using an image sensor such as a CCD or CMOS instead of a silver salt film camera have become mainstream. Furthermore, it has come to have a number of categories in a wide range from high-functional types for business use to compact popular types.
Users of 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, a wide-angle field angle characteristic is demanded for an imaging region, and a zoom lens having a high zoom ratio, a wide angle at the wide-angle end, and a good optical performance is demanded.

As a zoom lens that is compact when the lens is retracted and that can easily secure a zoom ratio, the first lens unit having negative refractive power, the second lens group having positive refractive power, and the third lens having positive refractive power are arranged in order from the object side. A three-group zoom lens composed of three lens groups is known.
Among such a three-group zoom lens, Patent Documents 1 and 2 disclose a three-group zoom lens in which each lens group is constituted by a plurality of lens components and has good optical performance.

JP 2006-195064 A JP 2007-148052 A

However, the zoom lens disclosed in Patent Document 1 has a large total number of lens components of 7 and a zoom ratio of less than 3.
Although the zoom lens disclosed in Patent Document 2 has a small number of lens components, it has a large F number.

  In view of such a problem, an object of the present invention is to provide a three-group zoom lens that is advantageous in securing a zoom ratio, brightness, and optical performance while reducing the number of lens components of each lens group by two. Is. Furthermore, it aims at providing the imaging device provided with such a 3 group zoom lens.

In order to solve the above-described problems and achieve the object, the three-group zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, The third lens unit has a refractive power, and the second lens unit moves during zooming from the wide-angle end to the telephoto end, and the distance between the first lens unit and the second lens unit is narrowed. When the distance between the third lens group is wide and the lens component has only two lens bodies on the optical axis that are in contact with air, the object side surface and the image side surface,
In order from the object side, the first lens group includes two lens components, a lens surface on the object side that is concave on the object side, and a front lens component having negative refractive power and a rear lens component having positive refractive power.
The second lens group, in order from the object side, consists of two lens components, a front lens component of positive refractive power and an image side lens surface concave on the image side, and a rear lens component of negative refractive power,
The third lens group, in order from the object side, consists of two lens components, a front lens component whose object side lens surface is concave on the object side and a rear lens component of positive refractive power,
The aperture stop is disposed on the image side of the first lens unit and on the object side of the rear lens component in the second lens unit, and the aperture stop is used for the second lens unit during zooming from the wide angle end to the telephoto end. And move in the optical axis direction.

The three-group zoom lens according to the present invention employs negative, positive, and positive power arrangement. This type is advantageous for securing the angle of view on the wide-angle side and reducing the size of the first lens group in the radial direction, and since the number of lens groups is small, it is possible to reduce the size when retracted and to construct a mechanism for driving the lens group. This is advantageous for simplification.
By making the relationship with each group during zooming as described above, the second lens group has a main zooming action.

With such a basic configuration, in the three-group zoom lens of the present invention, each of the first lens group, the second lens group, and the third lens group has two lens components, and aberration correction and configuration of each lens group are simplified. To achieve both.
The two lens components of the first lens group are composed of a front lens component having negative refractive power and a rear lens component having positive refractive power, with the object-side lens surface being concave on the object side.
Such a configuration is advantageous in reducing the size of the first lens group in the radial direction by using the main point of the first lens group as the object. In addition, correction of chromatic aberration, curvature of field, etc. is facilitated.
In the present invention, the most object side surface of the first lens unit is a concave surface at least near the optical axis.
This makes it easier to reduce spherical aberration, especially near the telephoto end where the axial beam diameter increases, by bearing the negative refractive power of the first lens group even on this concave surface, ensuring brightness and increasing the zoom ratio. Is advantageous.

The two lens components of the second lens group are composed of two lens components, a front lens component having a positive refractive power and an image side lens surface concave on the image side and a rear lens component having a negative refractive power. Yes.
With this configuration, the principal point of the second lens group can be easily set closer to the object side, which is advantageous for securing a zooming function by changing the distance between the first lens group and the second lens group. Further, the concave surface of the image side lens surface contributes to correction of aberrations occurring in the second lens group, and at the same time, the function of refracting the off-axis light beam in the direction away from the optical axis ensures the image height and the diameter of the second lens group. This is advantageous for reducing the direction.

  The two lens components of the third lens group are the two lens components of the front lens component whose object side lens surface is concave on the object side and the rear lens component of positive refractive power. With this configuration, it is possible to reduce the incident angle of the off-axis light beam to the third lens group while ensuring the positive refractive power of the third lens group, which is advantageous in reducing off-axis aberrations.

  In particular, when the zoom ratio is increased, the change in the diameter of the light beam incident on the third lens group due to the zooming increases, but with such a shape, the change in the incident angle of the light beam incident on the third lens group is changed. It is suppressed and it becomes easy to reduce the fluctuation | variation of the aberration accompanying zooming.

In the vicinity of the telephoto end, the first lens group and the second lens group are close to each other, so that reduction of spherical aberration or the like in the synthesis system of the first lens group and the second lens group can ensure brightness and a zoom ratio. It is important to secure
In the three-group zoom lens of the present invention, this composition system becomes a negative lens component, a positive lens component, a positive lens component, and a negative lens component from the object side, and each of the object-side and image-side lens surfaces of the composition system is negatively refracted. It becomes a concave surface of force. Such a symmetrical arrangement is advantageous for reducing aberrations such as spherical aberration and curvature of field at the telephoto end.
At the wide-angle end, the opposing lens surfaces of the second lens group and the third lens group are concave surfaces, and the object side and image side lens components in the synthesis system of the second and third lens groups are respectively Since it has a positive refractive power, it is advantageous in reducing aberrations such as field curvature due to a symmetrical refractive power arrangement.

The location of the aperture stop is important in determining the location through which the light flux of each lens group passes. By arranging the aperture stop at the above-mentioned position, the radial direction of the first lens group can be increased even if the angle is widened. The size can be easily reduced, which is advantageous in terms of aberration correction.
In addition, by moving the aperture stop integrally with the second lens group, it becomes easy to simplify the driving mechanism, and the effective diameter of the second lens group can be reduced at both the wide-angle end and the telephoto end. This is advantageous for downsizing and aberration reduction.

In the present invention described above, it is more preferable to satisfy one or more of the following configurations at the same time.
It is preferable that the first lens group and the second lens group satisfy the following conditions.
0.1 <(R _1F + R _2R ) / (R _1F −R _2R ) <1 (3)
However,
R _1F is the paraxial radius of curvature of the lens surface closest to the object in the first lens group,
R _2R is the paraxial radius of curvature of the lens surface on the most image side in the second lens group,
It is.

Conditional expression (3) shows more preferable shapes of the lens surface closest to the object side of the first lens group and the lens surface closest to the image side of the second lens group.
By appropriately suppressing the negative refractive power of the lens surface on the object side of the first lens group, it is advantageous for reducing coma and distortion on the wide angle side.
By avoiding falling below the lower limit and appropriately suppressing the paraxial radius of curvature of the lens surface closest to the object, it becomes easy to suppress the occurrence of excessive distortion on the wide angle side.
It is easy to reduce Petzval sum and spherical aberration by ensuring the negative refractive power of the lens surface closest to the object side without exceeding the upper limit.

The front lens group in the first lens group is preferably a biconcave lens component that satisfies the following conditions.
−0.5 <(R _1F + R _1FR ) / (R _1F −R _1FR ) <1.0 (D)
However,
R _1F is the paraxial radius of curvature of the lens surface closest to the object in the first lens group,
R _1FR is the paraxial radius of curvature of the image side lens surface of the front lens component in the first lens group,
It is.

By making the front lens component in the first lens group a biconcave shape, negative refractive power can be shared by a plurality of lens surfaces, which is advantageous for reducing spherical aberration in the first lens group.
Conditional expression (D) specifies a preferable shape of the lens component considering the influence on off-axis aberration.
By making sure that the lower limit is not exceeded, the negative refracting power of this lens component on the image side lens surface is secured, and spherical aberration can be suppressed easily. In addition, the absolute value of curvature of the object side lens surface can be easily suppressed, which is advantageous for correcting coma aberration on the wide angle side. Ensuring the negative refractive power of the object side lens surface without exceeding the upper limit is advantageous in reducing spherical aberration and the like.

Moreover, it is preferable that the front lens component and the rear lens component in the first lens group satisfy the following conditions.
−1.8 <f _1F / f _W <−1 (7)
2 <f _1R / f _W <9 (8)
However,
f _1F is the focal length of the front lens component in the first lens group,
f _1R is the focal length of the rear lens component in the first lens group,
f _W is the focal length of the entire three-group zoom lens system at the wide-angle end,
It is.

Conditional expressions (7) and (8) are the optimum focal points of the lens components constituting the first lens group for ensuring the performance even when the zoom ratio is increased to about 4 times while ensuring good productivity. This is a condition indicating the relationship of distance.
By making sure that the lower limit of conditional expression (7) is not exceeded, the occurrence of higher-order spherical aberration is suppressed, and it becomes easier to correct spherical aberration over the entire zoom range. In addition, the shape can be reduced, and the lens can be easily processed.
By not exceeding the upper limit, it is easy to suppress the variation of spherical aberration and field curvature at the time of zooming, which is advantageous in ensuring performance over the entire zooming range.
It becomes easy to prevent the field curvature from being over by appropriately suppressing the positive refractive power so as not to fall below the lower limit of the conditional expression (8). By ensuring the positive refracting power appropriately so as not to exceed the upper limit, it becomes easy to prevent the field curvature from becoming under.

In addition, the object side lens surface of the front lens component in the first lens group is preferably an aspherical surface having a shape in which the negative refractive power becomes weaker as the distance from the optical axis increases.
The lens surface closest to the object has a larger effective diameter at the wide-angle end than at the telephoto end. Therefore, the lens surface having the above-mentioned aspherical shape is advantageous not only for reducing higher-order spherical aberration on the telephoto side but also for reducing coma aberration on the wide-angle side.
Furthermore, if the aspherical surface has a shape in which the negative refracting power becomes weaker and changes to the positive refracting power as it moves away from the optical axis, it is more advantageous for correcting off-axis aberrations.

More preferably, the front lens component in the first lens group has a biconcave shape, and the rear lens component in the first lens group has a convex meniscus shape on the object side.
Negative refractive power can be shared by both sides of the negative lens component, which is advantageous for reducing spherical aberration on the telephoto side. Further, the incident angle of the off-axis light beam near the wide-angle end can be reduced on the object-side lens surface and the image-side lens surface of the rear lens component in the first lens group, which is advantageous for correcting various aberrations near the wide-angle end. It becomes.

Furthermore, it is more preferable that the image side lens surface of the front lens component in the first lens group is an aspheric concave surface.
The effective diameter at the wide angle end of the image side lens surface of the front lens component in the first lens group is larger than the effective diameter at the telephoto end, as is the case with the most object side lens surface. Therefore, this lens surface also has an aspherical shape, which is advantageous not only for reducing high-order spherical aberration on the telephoto side but also for reducing coma aberration on the wide-angle side in cooperation with the aspherical surface on the object side. .

  In addition, it is preferable that the aperture stop be disposed immediately before the front lens component of the second lens group. This makes it easier to further reduce the size of the first lens group. In addition, it is easy to provide a function of refracting light rays from the image-side lens surface of the second lens group in a direction away from the optical axis. In addition, it is easy to reduce the incident angle of the off-axis light beam with respect to the image plane. In addition, the symmetry of the composition system of the first and second lens units with respect to the aperture stop near the telephoto end becomes even better, which is advantageous for correction such as magnification color correction near the telephoto end.

In addition, it is preferable that the third group zoom lens satisfies the following conditions at the wide-angle end.
1 <D ₁₂ / f _W <4 (4)
However,
D ₁₂ is the axial distance from the lens surface on the most image side in the first lens group at the wide-angle end to the most object side lens surface of the second lens group,
f _W is the focal length of the entire system of the three-group zoom lens at the wide angle end,
It is.

Conditional expression (4) specifies the preferable first and second lens group intervals that are advantageous for securing the zoom ratio, optical performance, and miniaturization.
Securing the first and second lens group intervals so as not to fall below the lower limit of conditional expression (4) is advantageous in ensuring a zoom ratio while suppressing the refractive power of each lens group. Since the amount of aberration is easily suppressed, it is advantageous for securing optical performance in the entire zooming region.
By not exceeding the upper limit, it is possible to prevent the first lens group from being too far from the aperture stop, and it is advantageous for downsizing the first lens group in the radial direction.

In addition, it is preferable that the second lens group satisfies the following conditions.
−0.7 <T _2F / f _W <−0.4 (5)
However,
T _2F is the distance on the optical axis from the lens surface closest to the object side of the second lens group to the front principal point of the second lens group, and is negative when the principal point is on the object side of the second lens group. ,
f _W is the focal length of the entire system of the three-group zoom lens at the wide-angle end,
It is.

  By making the front principal point of the second lens group the object side relative to the object side lens surface of the second lens group, it is advantageous for increasing the zoom ratio. Conditional expression (5) specifies a preferable front principal point position of the second lens group. By making sure that the lower limit of conditional expression (5) is not exceeded, it becomes easier to suppress excessive curvature of the lens surface in the second lens group, and by reducing spherical aberration in the second lens group, aberration fluctuations during zooming can be reduced. It becomes easy to suppress. By not exceeding the upper limit, the rear principal point of the first lens group can be made easier than the object, and the negative lens of the first lens group can be designed to be easily processed. Further, it is advantageous for increasing the zoom ratio.

Also, the total number of lenses in the zoom lens when expressed as N _t, it is preferable to satisfy the following condition.
6 ≦ N _t ≦ 8 (9)
By making sure that the lower limit of conditional expression (9) is not exceeded, it becomes easy to ensure the refractive power of each lens group of the zoom lens and to reduce aberrations. By avoiding exceeding the upper limit and reducing the number of lenses, it is advantageous for compactness.

  Moreover, it is preferable that the first lens unit has a front lens component having negative refractive power in which both the object side lens surface and the image side lens surface are aspherical surfaces on the most object side. Thereby, the occurrence of spherical aberration, curvature of field, and distortion can be suppressed, which is more preferable in constructing a compact zoom lens with good aberration correction.

  In the present invention, the total number of lenses included in the second lens group is preferably 3 or less. Accordingly, the number of lenses in the second lens group is three or less, which is advantageous for making the zoom lens compact.

  The second lens group is preferably composed of a single lens having a positive refractive power, a cemented lens having a positive lens and a negative lens. This makes it easy to correct various aberrations when the zoom ratio is increased and the angle is increased.

  The second lens group is preferably composed of a single lens having a positive refractive power and a single lens having a negative refractive power. This is advantageous in reducing the size of the second lens group while suppressing aberrations.

  The second lens group preferably includes a positive lens and a negative lens, and all the negative lenses in the second lens group preferably have a smaller Abbe number than all the positive lenses in the second lens group. This is a preferable configuration for correcting chromatic aberration and curvature of field.

In addition, it is preferable that the second lens group satisfies the following conditions.
n _2pave ≧ 1.59 (10)
ν _2n ≦ 35 (11)
However,
n 2 _pave is the average value of the refractive indexes of all the positive lenses in the second lens group,
ν _2n is the Abbe number of all negative lenses in the second lens group,
It is.

By making the positive lens in the second lens group a high refractive index material that satisfies the conditional expression (10), astigmatism correction can be easily performed.
By using a high dispersion material that satisfies the conditional expression (11) for the negative lens in the second lens group, the chromatic aberration due to the positive lens in the second lens group is canceled, which is advantageous in reducing chromatic aberration.

The most image-side lens in the second lens group is a negative lens having a concave surface facing the image side, and the thickness of the negative lens on the optical axis is the front lens component and the rear side of the second lens group. It is preferable that the distance between the lens component and the lens component is larger than that on the optical axis.
Thereby, the thickness of the second lens group on the optical axis can be reduced. Including a negative lens in the second lens group is advantageous in improving the optical performance by canceling aberrations in the second lens group, and ensuring the thickness of the negative lens with the concave surface facing the image side is not necessary. It becomes easier to correct point aberrations.

  The second lens group preferably includes a positive lens having an aspheric surface. The positive lens in the second lens group has a lens surface with strong positive refractive power in order to ensure the positive refractive power of the second lens group. Therefore, it is preferable to use an aspherical surface for correcting spherical aberration and the like.

Moreover, it is preferable that all the lenses in the third lens group satisfy the following conditions.
n _3ave ≧ 1.4 (12)
ν _3ave ≧ 50 (13)
However,
n _3ave is the average value of the refractive indexes of all the lenses in the third lens group,
ν _3ave is the average value of the Abbe numbers of all the lenses in the third lens group,
It is.

  By making all the lenses in the third lens group high refractive index materials satisfying conditional expression (12), it becomes easy to correct astigmatism, and by using low dispersion materials satisfying conditional expression (13), chromatic aberration is achieved. It becomes advantageous for reduction of.

  Moreover, it is preferable that the total number of lenses included in the third lens group is 2, and any one of them has an aspherical surface. This is advantageous in reducing the size and cost of the third lens group. The use of an aspheric surface is advantageous for astigmatism correction in close-up photography. In order to secure optical performance, it is preferable to make one or both surfaces of the rear lens component of the third lens group an aspherical surface, and to make the absolute value of the paraxial radius of curvature of the image side lens surface smaller than the object side lens surface. .

  The third lens group preferably has at least one resin lens. By constituting the third lens group with at least one resin, the cost can be reduced and the lens can be easily molded.

  Further, it is preferable that both the rear lens component in the second lens group and the front lens component in the third lens group have a meniscus shape having a negative refractive power. This is advantageous for chromatic aberration correction of each lens group. In addition, the symmetry in the composition system of the second and third lens units becomes even better, and it becomes easier to suppress aberrations near the wide-angle end.

  When zooming from the wide-angle end to the telephoto end, the first lens group first moves to the image side and then reverses the moving direction to the object side, and the third lens group moves to the telephoto end relative to the position at the wide-angle end. It is preferably located on the image side. This makes it easy to reduce the overall length of the lens system in use, and thus facilitates reducing the thickness of the lens frame in the optical axis direction. In addition, the first lens group can be provided with a function of reducing fluctuations in the image position during zooming. The third lens group is also provided with a zoom function, which is more advantageous for securing a zoom ratio.

In addition, an imaging apparatus according to the present invention includes a zoom lens and an imaging element that has an imaging surface disposed on the image side thereof and converts an optical image on the imaging surface formed by the zoom lens into an electrical signal. The zoom lens is preferably the above-described three-group zoom lens.
Accordingly, it is possible to provide an imaging apparatus including a zoom lens that is compact and advantageous in securing a zoom ratio, a field angle, and optical performance.

In addition, a signal processing circuit that outputs image data obtained by processing image data obtained by imaging with an imaging device and changing the shape thereof, is provided.
In the state where the third group zoom lens is focused at the wide-angle end and the farthest distance, it is preferable to satisfy the following conditions.
_{0.7 <y 07 / (f w} · tanω 07w) <1.0 ... (14)
However,
When the distance to the farthest point from the center in the effective image pickup plane of the image pickup device and a y _10,
y ₀₇ = 0.7 × y ₁₀
If effective image pickup area changes at the telephoto end from the wide-angle end, y ₁₀ is the maximum value of the possible values, omega _07w enters the image position where the image height is y ₀₇ from the center of the image pickup surface at the wide angle end This is the angle between the incident ray in the object space of the principal ray and the optical axis.

  Focusing on the point that astigmatism correction and barrel distortion correction tend to be in a trade-off relationship when the size is reduced as in the present invention, the zoom of the present invention is allowed to some extent to allow distortion to occur. Image shape distortion can be corrected by an image processing function included in an electronic imaging apparatus using an optical system. This will be described in detail below.

Here, it is assumed that an infinite object is imaged by an optical system having no distortion. In this case, since the image formed has no distortion,
f = y / tan ω (15)
Is established.
Where y is the height of the image point from the optical axis, f is the focal length of the imaging system, ω is the angle with respect to the optical axis in the object direction corresponding to the image point connecting from the center on the imaging surface to the y position. is there.
On the other hand, if the barrel distortion is allowed only when the optical system is near the wide-angle end,
f> y / tan ω (16)
It becomes. That is, if ω and y are constant values, the focal length f at the wide-angle end may be long, and accordingly, design with reduced aberrations can be facilitated. The reason why the lens group corresponding to the first lens group is normally composed of two or more lens components is to make both distortion and astigmatism compatible. This need not be done in the present invention. This is advantageous for correcting astigmatism.

  Therefore, in the electronic imaging device of the present invention, image data obtained by the electronic imaging element is processed by image processing. In this processing, the image data (image shape) is changed so as to correct the barrel distortion. In this way, the finally obtained image data is image data having a shape substantially similar to the object. Therefore, an object image may be output to a CRT or printer based on the image data.

When such image data correction is performed, the effective imaging area at the wide-angle end has a barrel shape. Then, the image data of the barrel-shaped effective imaging area is changed to rectangular image data.
Conditional expression (14) defines the degree of barrel distortion at the zoom wide-angle end. By satisfying conditional expression (14), astigmatism can be corrected without difficulty. Note that an image distorted in a barrel shape is photoelectrically converted by an image sensor to become image data distorted in a barrel shape. However, the image data distorted into a barrel shape is electrically processed by an image processing means which is a signal processing system of the electronic imaging apparatus, corresponding to a change in the shape of the image. In this way, even if the image data finally output from the image processing means is reproduced on the display device, the distortion is corrected and an image substantially similar to the subject shape is obtained.

Here, by suppressing the occurrence of distortion by the zoom lens so as not to fall below the lower limit of the conditional expression (14), when the image distortion due to the distortion of the zoom lens is corrected by the signal processing circuit, the periphery of the corrected image Therefore, it is easy to suppress the deterioration of the sharpness of the peripheral portion of the image.
In addition, by allowing distortion of the zoom lens so as not to exceed the upper limit, it is advantageous for correcting astigmatism of the zoom lens, which is advantageous for reducing the thickness of the zoom lens.
Note that the effective imaging area at the wide-angle end may be determined so as to completely correct the distortion, but considering the influence of the perspective and the peripheral image deterioration, it is appropriate to be around -3% or around -5%. Alternatively, the image data may be changed while leaving barrel distortion.

Moreover, it becomes a more preferable structure by changing the conditional expression mentioned above or mentioned later as follows.
0.2 <(R _1F + R _2R ) / (R _1F −R _2R ) <0.9 (3 ′)
0.25 <(R _1F + R _2R ) / (R _1F −R _2R ) <0.8 (3 ″)
2.5 <D ₁₂ / f _W <3.5 (4 ′)
2 <D ₁₂ / f _W <3 (4 ″)
−0.65 <T _2F / f _W <−0.45 (5 ′)
−0.6 <T _2F / f _W <−0.5 (5 ″)
−1.7 <f _1F / f _W <−1.2 (7 ′)
−1.6 <f _1F / f _W <−1.3 (7 ″)
3.0 <f _1R / f _W <7 (8 ′)
3.5 <f _1R / f _W <8 (8 ″)
n _2pave ≧ 1.50 (10 ′)
n _2pave ≧ 1.52 (10 ″)
ν _2n ≦ 30 (11 ′)
ν _2n ≦ 26 (11 ″)
n _3ave ≧ 1.50 (12 ′)
n _3ave ≧ 1.52 (12 ″)
ν _3ave ≧ 58 (13 ′)
ν _3ave ≧ 80 (13 ″)
_{0.75 <y 07 / (f w} · tanω 07w) <0.99 ... (14 ')
_{0.80 <y 07 / (f w} · tanω 07w) <0.97 ... (14 ")
0.5 <(R _1F + R _1FR ) / (R _1F −R _1FR ) <0.98 (D ′)
0.6 <(R _1F + R _1FR ) / (R _1F −R _1FR ) <0.9 (D ″)

In order to advantageously reduce the cost of the positive lens in the second lens group, it is more preferable to use a material that sets an upper limit for n 2 _pave and satisfies the following conditions.
n 2 _pave ≦ 2.2 (10A)
Furthermore, n _2pave ≦ 1.8 (10A ′)
Is preferably satisfied.

In order to reduce the cost of the negative lens in the second lens group, it is more preferable to use a material that sets a lower limit for ν _2n and satisfies the following conditions.
ν _2n ≧ 10 (11A)
Furthermore, ν _2n ≧ 15 (11A ′)

In order to advantageously reduce the cost of each lens in the third lens group, it is more preferable to set an upper limit on n _3ave and use a material that satisfies the following conditions.
n _3ave ≦ 2.2 (12A)
Furthermore, n _3ave ≦ 1.8 (12A ′)
Is preferably satisfied.

In order to advantageously reduce the cost of each lens in the third lens group, it is more preferable to use a material that sets an upper limit for ν _3ave and satisfies the following conditions.
ν _3ave ≦ 95 (12A)
Furthermore, ν _3ave ≦ 82 (12A ′)
Furthermore, ν _3ave ≦ 58 (12A ″)
Is preferably satisfied.
Only the upper limit value or only the lower limit value of each conditional expression may be used as the new upper limit value and lower limit value.

In addition, the invention of each of the three-group zoom lenses described above or below will be configured in a state of focusing on the farthest object when having the focusing function.
Focusing from an object at a long distance to an object at a short distance extends the entire third group zoom lens toward the object side, extends only the first lens group toward the object side, and extends only the third lens group toward the object side. It is preferable to carry out either

  It is more preferable that a plurality of the above-described inventions are arbitrarily satisfied at the same time. For each conditional expression, only the upper limit value or lower limit value of the numerical range of the more limited conditional expression may be limited. Further, the above-described configurations may be arbitrarily combined.

According to the present invention, it is possible to provide a three-group zoom lens that is advantageous in securing a zoom ratio, brightness, and optical performance while the number of lens components in each lens group is two.
Furthermore, an imaging apparatus including such a three-group zoom lens can be provided.

  Embodiments of a zoom lens and an imaging apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  Examples 1 to 7 of the zoom lens according to the present invention will be described below. FIGS. 1 to 7 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 7, respectively. 1 to 7, the first lens group is G1, the second lens group is G2, the aperture stop is S, the third lens group is G3, the fourth lens group is G4, and the wavelength range is limited to limit infrared light. The parallel flat plate constituting the coated low-pass filter 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.

  In each embodiment, the aperture stop S moves integrally with the third lens group G3. All of the numerical data is data in a state where an object at infinity is focused. 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 (WE), the intermediate zoom state (ST) defined in the present invention, and the telephoto end (TE).

  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 negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. And a third lens group G3 for power.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side after moving to the image side, the second lens group G2 moves only to the object side, and the third lens G3 moves only to the image side. Moving.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side and a biconvex positive lens.

  The aspherical surface is 5 of the both surfaces of the biconcave negative lens of the first lens group G1, the both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the biconvex positive lens of the third lens group G3. Used on the surface.

  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 negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. And a third lens group G3 for power.

  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 only to the object side, and the third lens G3 moves to the object side. It moves to the rear image side and is positioned closer to the image side at the telephoto end than at the wide angle end.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens, a negative meniscus lens having a convex surface facing the object side, and a negative meniscus lens having a convex surface facing the object side. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side, and a positive meniscus lens having a convex surface directed toward the image side.

  An aspherical surface is an image of a positive meniscus lens having a convex surface facing both surfaces of a biconcave negative lens of the first lens group G1, a biconvex positive lens of the second lens group G2, and an image side of the third lens group G3. It is used for 5 surfaces with the side surface.

  As shown in FIG. 3, the zoom lens of Example 3 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. And a third lens group G3 for power.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side after moving to the image side, the second lens group G2 moves only to the object side, and the third lens G3 moves only to the image side. Moving.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens, a cemented lens including a positive meniscus lens having a convex surface facing the object side and a negative meniscus lens having a convex surface facing the object side. The third lens group G3 includes a first positive meniscus lens having a convex surface directed toward the image side, and a second positive meniscus lens having a convex surface directed toward the image side.

  The aspherical surfaces are the first positive meniscus with the convex surfaces facing both surfaces of the biconcave negative lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side of the third lens group G3. It is used for six surfaces, that is, the object side surface of the lens and the image side surface of the first positive meniscus lens having a convex surface facing the image side.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and positive refraction. And a third lens group G3 for power.

  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 only to the object side, and the third lens G3 moves to the object side. It moves to the rear image side and is positioned closer to the image side at the telephoto end than at the wide angle end.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side, and a positive meniscus lens having a convex surface directed toward the image side.

  The aspheric surface includes both surfaces of the biconcave negative lens of the first lens group G1, the object side surface of the positive meniscus lens having a convex surface facing the object side, both surfaces of the biconvex positive lens of the second lens group G2, It is used on six surfaces including the image side surface of a positive meniscus lens having a convex surface facing the image side of the three lens group G3.

  As shown in FIG. 5, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, and positive refraction. And a third lens group G3 for power.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side after moving to the image side, the second lens group G2 moves only to the object side, and the third lens G3 moves only to the image side. Moving.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side, and a positive meniscus lens having a convex surface directed toward the image side.

  The aspherical surface includes both surfaces of the biconcave negative lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, and the image side surface of the negative meniscus lens having a convex surface facing the object side. The three lens groups G3 are used for seven surfaces: an object side surface of a negative meniscus lens having a convex surface facing the image side, and an image side surface of a positive meniscus lens having a convex surface facing the image side.

  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 negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. And a third lens group G3 for power.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side after moving to the image side, the second lens group G2 moves only to the object side, and the third lens G3 moves only to the image side. Moving.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a negative meniscus lens having a convex surface directed toward the object side. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side, and a positive meniscus lens having a convex surface directed toward the image side.

  An aspherical surface is an image of a positive meniscus lens having a convex surface facing both surfaces of a biconcave negative lens of the first lens group G1, a biconvex positive lens of the second lens group G2, and an image side of the third lens group G3. It is used for 5 surfaces with the side surface.

  As shown in FIG. 7, the zoom lens of Example 7 includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and positive refraction. And a third lens group G3 for power.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side after moving to the image side, the second lens group G2 moves only to the object side, and the third lens G3 moves only to the image side. Moving.

  In order from the object side, the first lens group G1 includes a biconcave negative lens and a positive meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a first biconvex positive lens and a cemented lens of a second biconvex positive lens and a biconcave negative lens. The third lens group G3 includes a negative meniscus lens having a convex surface directed toward the image side, and a positive meniscus lens having a convex surface directed toward the image side.

  The aspheric surfaces are both surfaces of the biconcave negative lens of the first lens group G1, both surfaces of the biconvex positive lens of the second lens group G2, the image side surface of the biconcave negative lens, and the image side of the third lens group G3. The negative meniscus lens having a convex surface facing the object side and the positive meniscus lens having a convex surface facing the image side are used for seven surfaces.

Below, the numerical data of each said Example are shown. Symbols are the above, f is the focal length of the entire system, BF is the back focus, f1, f2... Are the focal lengths of the lens groups, IH is the image height, _FNO is the F number, ω is the half field angle, and WE is the wide angle. ST, intermediate focal length state, TE telephoto end, r1, r2..., Radius of curvature of each lens surface, d1, d2..., Spacing between lens surfaces, nd1, nd2. The ratio, νd1, νd2,... Is the Abbe number 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. BF (back focus) represents the distance from the last lens surface to the paraxial image plane in terms of air.

  The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁸ + A ₁₀ y ¹⁰ + A ₁₂ y ¹²
Where r is the paraxial radius of curvature, K is the conic coefficient, and A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are the fourth, sixth, eighth, tenth, and twelfth 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
1 * -75.732 0.80 1.80610 40.92
2 * 6.159 2.19
3 8.286 1.26 1.92286 18.90
4 12.932 Variable
5 (Aperture) ∞ 0.00
6 * 4.218 1.58 1.58313 59.38
7 * -11.614 0.10
8 6.020 1.50 1.92286 18.90
9 2.854 Variable
10 -10.000 0.80 1.52542 55.78
11 -12.633 0.10
12 1570.615 1.68 1.52542 55.78
13 * -7.877 Variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 8.63164e-04, A6 = -1.44594e-05, A8 = -1.79441e-07, A10 = 6.44702e-09
Second side
K = 0.604, A4 = 3.55946e-04, A6 = 8.82553e-06, A8 = -1.63344e-06, A10 = -4.03670e-08
6th page
K = -2.032, A4 = 9.55124e-04, A6 = -3.47908e-05, A8 = -1.61349e-05, A10 = -2.39598e-06
7th page
K = 0.000, A4 = -1.90243e-04, A6 = 5.16487e-05, A8 = -3.86916e-05
13th page
K = -4.289, A4 = -3.77823e-04, A6 = 6.57896e-06, A8 = -1.39603e-07

Group focal length
f1 = -11.20 f2 = 8.59 f3 = 16.71

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 4.63 7.32 16.22
FNO. 2.87 3.59 6.01
Angle of view 2ω 79.87 52.68 24.66
BF (in air) 4.51 4.35 3.65
Total length (in air) 29.73 26.69 29.66
d4 12.70 6.97 1.60
d9 2.50 5.36 14.40
d13 2.86 2.70 2.00


Zoom data (Distortion correction)
WE ST TE
Focal length 4.63 7.32 16.22
FNO. 2.87 3.59 6.01
Angle of view 2ω 78.56 52.68 24.66
Image height 3.52 3.6 3.6

Numerical example 2
Unit: mm

Surface data Surface number rd nd νd
1 * -31.515 0.80 1.80610 40.92
2 * 7.000 2.03
3 9.346 1.28 1.92286 18.90
4 16.817 Variable
5 (Aperture) ∞ 0.50
6 * 4.597 1.74 1.58313 59.38
7 * -10.331 0.10
8 7.257 1.06 1.80400 46.57
9 13.104 0.50 1.80518 25.42
10 3.117 Variable
11 -10.000 0.80 1.52542 55.78
12 -15.879 0.10
13 -61.608 1.61 1.52542 55.78
14 * -7.052 variable
15 ∞ 0.50 1.54771 62.84
16 ∞ 0.50
17 ∞ 0.50 1.51633 64.14
18 ∞ 0.50
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 1.28825e-03, A6 = -2.87635e-05, A8 = 1.43822e-08, A10 = 5.28531e-09
Second side
K = 0.968, A4 = 7.51526e-04, A6 = 1.29461e-05, A8 = -2.77211e-06, A10 = -7.88860e-11
6th page
K = -2.315, A4 = 6.32399e-04, A6 = -7.60844e-05, A8 = -1.44293e-05, A10 = -2.09939e-06
7th page
K = 0.000, A4 = -3.71450e-04, A6 = -1.28789e-05, A8 = -3.03992e-05
14th page
K = -3.360, A4 = -3.71759e-04, A6 = 4.76797e-06, A8 = -1.08593e-07

Group focal length
f1 = -11.69 f2 = 9.00 f3 = 19.40

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 4.75 7.51 16.62
FNO. 2.88 3.53 5.85
Angle of view 2ω 78.82 51.47 23.93
BF (in air) 5.23 5.29 4.15
Total length (in air) 31.38 27.60 30.32
d4 13.33 6.87 1.20
d10 2.30 4.92 14.45
d14 3.58 3.64 2.50

Zoom data (when distortion is corrected electrically)
WE ST TE
Focal length 4.75 7.51 16.62
FNO. 2.88 3.53 5.85
Angle of view 2ω 77.16 51.47 23.93
Image height 3.51 3.6 3.6

Numerical Example 3
Unit: mm

Surface data Surface number rd nd νd
1 * -28.624 0.80 1.80610 40.92
2 * 7.102 1.51
3 8.465 1.25 1.92286 18.90
4 15.000 Variable
5 (Aperture) ∞ 0.50
6 * 4.584 1.68 1.58313 59.38
7 * -15.102 0.10
8 6.386 1.20 1.80610 40.92
9 22.010 0.50 1.80518 25.42
10 3.040 Variable
11 * -13.000 0.80 1.52542 55.78
12 -12.693 0.10
13 -23.585 2.02 1.52542 55.78
14 * -6.191 variable
15 ∞ 0.50 1.54771 62.84
16 ∞ 0.50
17 ∞ 0.50 1.51633 64.14
18 ∞ 0.32
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 9.65210e-04, A6 = -1.84232e-05, A8 = 1.54796e-07
Second side
K = 0.775, A4 = 6.83359e-04, A6 = -1.28637e-05, A8 = 2.06468e-07, A10 = -3.45662e-08
6th page
K = -1.904, A4 = 1.02323e-03, A6 = 5.25597e-07, A8 = -4.66818e-06, A10 = -7.03594e-08
7th page
K = 0.000, A4 = 2.16799e-04, A6 = 2.80625e-05, A8 = -7.06696e-06
11th page
K = 0.000, A4 = -1.21144e-03, A6 = 4.31564e-05
14th page
K = -1.253, A4 = -7.50374e-04, A6 = 2.86564e-05, A8 = -3.30381e-09

Group focal length
f1 = -11.75 f2 = 9.13 f3 = 14.68

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 5.08 8.03 19.71
FNO. 2.69 3.49 6.22
Angle of view 2ω 78.29 51.65 21.69
BF (in air) 4.90 4.11 3.97
Total length (in air) 30.11 28.53 34.15
d4 12.17 7.34 1.30
d10 2.60 6.63 18.43
d14 3.43 2.64 2.50

Zoom data (Distortion correction)
WE ST TE
Focal length 5.08 8.03 19.71
FNO. 2.69 3.49 6.22
Angle of view 2ω 77.16 51.65 21.69
Image height 3.53 3.6 3.6

Numerical Example 4
Unit: mm

Surface data Surface number rd nd νd
1 * -57.999 0.80 1.85135 40.10
2 * 6.200 2.50
3 * 11.815 1.19 2.10225 16.80
4 18.266 Variable
5 (Aperture) ∞ 0.00
6 * 4.296 2.27 1.54969 71.75
7 * -9.050 0.10
8 5.495 1.35 1.92286 20.88
9 2.856 Variable
10 -10.000 0.80 1.52542 55.78
11 -11.124 0.16
12 -15.000 1.68 1.58313 59.38
13 * -5.592 variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 1.48620e-03, A6 = -3.26084e-05, A8 = -1.55682e-07, A10 = 7.46342e-09
Second side
K = 0.392, A4 = 1.55710e-03, A6 = 1.17426e-05, A8 = -2.92298e-07, A10 = -1.27276e-07
Third side
K = 0.000, A4 = 2.81277e-04, A6 = 2.02191e-07, A8 = 0.000, A10 = 2.1004e-08, A12 = 2.0141e-09,
A14 = -1.39554e-10
6th page
K = -2.195, A4 = 1.00603e-03, A6 = -1.08685e-04, A8 = 1.06757e-06, A10 = -1.49012e-06
7th page
K = 0.000, A4 = 1.64463e-04, A6 = -4.05406e-05, A8 = -1.34042e-05
13th page
K = -1.481, A4 = 1.97334e-04, A6 = -1.36749e-05, A8 = 1.20016e-07

Each group focal length
f1 = -9.27 f2 = 8.04 f3 = 14.68

Various data
WE ST TE
Image height 3.85 3.85 3.85
Focal length 4.07 6.43 14.25
FNO. 2.96 3.68 6.17
Angle of view 2ω 87.82 58.31 27.79
BF (in air) 4.39 4.50 4.15
Total length (in air) 29.18 26.52 30.31
d4 11.65 6.36 1.60
d9 2.30 4.83 13.74
d13 2.74 2.85 2.49

Zoom data (when distortion is corrected electrically)
WE ST TE
Focal length 4.07 6.43 14.25
FNO. 2.96 3.68 6.17
Angle of view 2ω 85.92 58.31 27.79
Image height 3.75 3.85 3.85

Numerical Example 5
Unit: mm

Surface data Surface number rd nd νd
1 * -40.267 0.75 1.80610 40.92
2 * 6.106 1.88
3 8.717 1.35 1.92286 18.90
4 16.000 Variable
5 (Aperture) ∞ 0.00
6 * 3.893 1.77 1.55606 64.53
7 * -21.375 0.10
8 6.044 1.50 2.10225 16.80
9 * 3.352 Variable
10 * -10.000 0.80 1.52542 55.78
11 -12.572 0.10
12 -34.726 1.57 1.52542 55.78
13 * -7.254 variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 9.53870e-04A6 = -1.82491e-05, A8 = 9.03444e-09, A10 = 2.97648e-09
Second side
K = 0.480, A4 = 4.91521e-04, A6 = -3.93247e-06, A8 = -7.50240e-07, A10 = -4.68586e-08
6th page
K = -1.448, A4 = 1.68446e-03, A6 = 5.28303e-06, A8 = -1.50101e-05, A10 = 1.40900e-06
7th page
K = 0.000, A4 = -7.33600e-04, A6 = 1.21720e-05, A8 = 1.45238e-06
9th page
K = 0.000, A4 = 3.00679e-03, A6 = 3.47555e-04
10th page
K = 0.000, A4 = -3.33530e-04, A6 = 5.44978e-05
13th page
K = -0.522, A4 = 8.89558e-05, A6 = 3.35121e-05, A8 = 2.97775e-07

Group focal length
f1 = -10.95 f2 = 8.46 f3 = 19.53

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 4.75 7.51 16.63
FNO. 2.96 3.72 6.16
Angle of view 2ω 78.16 51.71 24.00
BF (in air) 4.89 4.45 4.15
Total length (in air) 29.60 26.79 29.65
d4 12.60 7.11 1.60
d9 2.30 5.41 14.09
d13 3.24 2.80 2.50

Zoom data (when distortion is corrected electrically)
WE ST TE
Focal length 4.75 7.51 16.63
FNO. 2.96 3.72 6.16
Angle of view 2ω 77.17 51.71 24.00
Image height 3.54 3.6 3.6

Numerical Example 6
Unit: mm

Surface data Surface number rd nd νd
1 * -101.960 0.80 1.80610 40.92
2 * 6.026 2.24
3 7.927 1.25 1.92286 18.90
4 11.714 Variable
5 (Aperture) ∞ 0.00
6 * 4.320 1.61 1.58313 59.38
7 * -11.280 0.10
8 5.926 1.50 1.92286 18.90
9 2.876 Variable
10 -10.000 0.80 1.49700 81.61
11 -11.321 0.10
12 -44.614 1.56 1.49700 81.61
13 * -7.436 variable
14 ∞ 0.50 1.54771 62.84
15 ∞ 0.50
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 9.19304e-04, A6 = -1.59914e-05, A8 = -2.00653e-07, A10 = 7.26801e-09
Second side
K = 0.576, A4 = 4.20396e-04, A6 = 1.23717e-05, A8 = -1.88963e-06, A10 = -4.69727e-08
6th page
K = -2.144, A4 = 8.73053e-04, A6 = -4.28150e-05, A8 = -1.50232e-05, A10 = -2.57889e-06
7th page
K = 0.000, A4 = -3.19558e-04, A6 = 5.83092e-05, A8 = -3.97480e-05
13th page
K = -6.150, A4 = -1.04910e-03, A6 = 4.05974e-05, A8 = -8.82329e-07

Each group focal length
f1 = -10.90 f2 = 8.47 f3 = 18.63

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 4.61 7.29 16.14
FNO. 2.89 3.60 6.01
Angle of view 2ω 80.24 52.78 24.62
BF (in air) 4.74 4.74 4.15
Total length (in air) 29.73 26.56 29.68
d4 12.71 6.91 1.60
d9 2.30 4.94 13.95
d13 3.09 3.08 2.50


Zoom data (when distortion is corrected electrically)
WE ST TE
Focal length 4.75 7.51 16.63
FNO. 2.96 3.72 6.16
Angle of view 2ω 78.83 51.71 24.00
Image height 3.52 3.6 3.6

Numerical Example 7
Unit: mm

Surface data Surface number rd nd νd
1 * -58.855 0.80 1.80610 40.92
2 * 6.277 2.16
3 9.471 1.17 1.92286 18.90
4 17.000 Variable
5 (Aperture) ∞ 0.60
6 * 4.351 1.82 1.58313 59.38
7 * -20.893 0.10
8 7.239 1.49 1.81600 46.62
9 -9.912 0.51 1.90366 31.31
10 * 3.664 variable
11 * -13.918 0.80 1.52542 55.78
12 -14.157 0.10
13 -28.285 1.75 1.52542 55.78
14 * -7.381 Variable
15 ∞ 0.50 1.54771 62.84
16 ∞ 0.50
17 ∞ 0.50 1.51633 64.14
18 ∞ 0.32
Image plane (imaging plane)

Aspheric data first surface
K = 0.000, A4 = 4.44012e-04, A6 = -6.81498e-06, A8 = 5.22166e-08
Second side
K = -1.079, A4 = 7.59676e-04, A6 = 3.19513e-06
6th page
K = -1.617, A4 = 1.55861e-03, A6 = -3.53530e-06
7th page
K = 0.000, A4 = -8.59697e-05, A6 = 3.53598e-05, A8 = -1.81923e-06
10th page
K = 0.000, A4 = 2.43339e-03, A6 = 9.59757e-05, A8 = 3.89963e-05
11th page
K = 0.000, A4 = -4.22139e-04, A6 = 1.92221e-05
14th page
K = -1.578, A4 = -1.73317e-04, A6 = 8.80572e-06, A8 = 7.74930e-08

Various data
WE ST TE
Image height 3.6 3.6 3.6
Focal length 5.08 8.03 19.71
FNO. 2.71 3.46 6.23
Angle of view 2ω 78.36 51.44 21.73
BF (in air) 4.94 4.42 3.97
Total length (in air) 31.86 29.41 34.65
d4 13.00 7.46 1.30
d10 2.60 6.23 18.07
d14 3.47 2.94 2.50

Group focal length
f1 = -11.54 f2 = 9.26 f3 = 18.09

Zoom data (when distortion is corrected electrically)
WE ST TE
Focal length 4.75 7.51 16.63
FNO. 2.96 3.72 6.16
Angle of view 2ω 77.16 51.71 24.00
Image height 3.52 3.6 3.6

  Aberration diagrams at the time of focusing on an object point at infinity in Examples 1 to 7 are shown in FIGS. In these aberration diagrams, (a) is a wide-angle end, (b) is an intermediate state, (c) is spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (CC) at the telephoto end. ). In each figure, “ω” indicates a half angle of view.

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

Example 1 Example 2 Example 3 Example 4
(R _1F + R _2R ) / (R _1F -R _2R ) 0.708286 0.312301 0.304093 0.52098
D ₁₂ / f _W 2.740741 2.49317 2.911911 2.862238
T _2F / f _W -0.57821 -0.55624 -0.61719 -0.593
f _1F / _fW -1.51838 -1.48216 -1.37574 -1.60732
f _1R / _fW 4.77198 4.43364 3.79665 6.80152
N _t 6 7 7 6
n _2pave 1.58313 1.693565 1.694615 1.54969
ν _2n 18.9 25.42 25.42 20.88
n _3ave 1.52542 1.52542 1.52542 1.554275
ν _3ave 55.7771 55.7771 55.7771 57.57855
y ₀₇ / (f _w・_{tanω 07w} ) 0.980239 0.942645 0.930925 0.960465
_{(R 1F + R 1FR) /} (R 1F -R 1FR) 0.849576 0.636506 0.636506 0.80685
Scaling ratio 3.5 3.5 3.88 3.5
ω _07w (°) 29.02295 29.37106 29.67779 32.80801

Example 5 Example 6 Example 7 Example 8
(R _1F + R _2R ) / (R _1F -R _2R ) 0.431284 1.014621 0.793904 0.551778
D ₁₂ / f _W 2.652638 2.807932 2.756339 2.908675
T _2F / f _W -0.581 -0.61533 -0.59716 -0.68372
f _1F / f _W -1.37477 -1.59581 -1.52561 -1.37751
f _1R / f _W 4.01257 4.82112 4.97151 4.24424
N _t 6 6 6 7
n _2pave 1.55606 1.58313 1.58313 1.699565
ν _2n 16.8 18.9 18.9 31.31
n _3ave 1.52542 1.52542 1.497 1.52542
ν _3ave 55.7771 55.7771 81.61 55.7771
y ₀₇ / (f _w・_{tanω 07w} ) 0.951067 0.961141 0.954629 0.953373
_{(R 1F + R 1FR) /} (R 1F -R 1FR) 0.73666 1.033541 0.888397 0.807262
Zoom ratio 3.5 3.5 3.5 3.88
ω _07w (°) 29.15364 28.91341 29.79002 29.09408

(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. 15, 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, correction is performed by moving each point on the circumference (image height) of any other radius r (ω) in a substantially radial direction and concentrically so as to have the radius r ′ (ω). To do.

For example, in FIG. 15, a point P ₁ on the circumference of an arbitrary radius r ₁ (ω) located inside the circle of radius R is a radius r ₁ ′ (ω) circle to be corrected toward the center of the circle. Move to 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 radius r ₂ ′ (ω) circumference to be corrected in a direction away from the center of the circle. It is moved to the point Q ₂ of the above.

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

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

  The optical system is ideally rotationally symmetric with respect to the optical axis, that is, distortion is also generated 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 on the circumference of the circle of R (image height) is fixed, and the other points on the circumference of the circle (image height) of radius r (ω) are moved in a substantially radial direction to obtain a radius r ′ ( If correction can be performed by moving the concentric circles so that ω), 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 possessed by 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.

  Such a method is particularly distorted with respect to the optical axis due to a manufacturing error of an optical system or an electronic imaging element in an electronic imaging device included in a zoom lens, and the circle with the radius R drawn on the optical image is It is effective for correction when it becomes asymmetric. Further, it 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 preferably satisfies the following conditional expression so that the image after distortion correction does not have an extremely short amount of light at both ends in the short side direction.

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

Preferably, the radius R 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 the actual number of images, but the effect of reducing the size is ensured even if the angle 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.

  However, in that 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 extraneous data necessary for correction on 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 approximately 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 satisfying the above is obtained, and uniformly multiply the correction amount for each focal distance 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.
Where y is the height of the image point from the optical axis (image height), f is the focal length of the imaging system (in the present invention, the zoom lens), and ω is the image point connected from the center on the imaging surface to the y position. It is an angle (subject half field angle) with respect to the optical axis in the corresponding object direction.

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

(Digital camera)
16 to 18 are conceptual diagrams of the configuration of the digital camera according to the present invention in which the zoom lens as described above is incorporated in the photographing optical system 141. FIG. FIG. 16 is a front perspective view showing the appearance of the digital camera 140, FIG. 17 is a rear front view thereof, and FIG. 18 is a schematic cross-sectional view showing the configuration of the digital camera 140. However, in FIGS. 16 and 18, the photographing optical system 141 is not retracted. In this example, the digital camera 140 includes a photographing optical system 141 having a photographing optical path 142, a finder optical system 143 having a finder optical path 144, a shutter button 145, a flash 146, a liquid crystal display monitor 147, a focal length change button 161, When the photographic optical system 141 is retracted, including the setting change switch 162, the photographic optical system 141, the finder optical system 143, and the flash 146 are covered with the cover 160 by sliding the cover 160. When the cover 160 is opened and the camera 140 is set to the photographing state, the photographing optical system 141 is brought into the non-collapsed state of FIG. 16, and when the shutter button 145 arranged on the upper part of the camera 140 is pressed, photographing is performed in conjunction therewith. Photographing is performed through the optical system 141, for example, the zoom lens of the first embodiment. An object image formed by the photographic optical system 141 is formed on the imaging surface of the CCD 149 through a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 149 is displayed as an electronic image on a liquid crystal display monitor 147 provided on the back of the camera via the processing means 151. Further, the processing means 151 is connected to a recording means 152 so that a photographed electronic image can be recorded. The recording unit 152 may be provided separately from the processing unit 151, or may be configured to perform recording / writing electronically using a flexible disk, a memory card, an MO, or the like. Further, instead of the CCD 149, a silver salt camera in which a silver salt film is arranged may be configured.

  Further, a finder objective optical system 153 is disposed on the finder optical path 144. The finder objective optical system 153 includes a plurality of lens groups (three groups in the figure) and two prisms, and includes a zoom optical system whose focal length changes in conjunction with the zoom lens of the photographing optical system 141. The object image formed by the finder objective optical system 153 is formed on the field frame 157 of the erecting prism 155 that is an image erecting member. Behind the erecting prism 155, an eyepiece optical system 159 that guides the erect image to the observer eyeball E is disposed. A cover member 150 is disposed on the exit side of the eyepiece optical system 159.

  The digital camera 140 configured in this way has the imaging optical system 141 according to the present invention, which is extremely thin when retracted, and has high zooming performance and extremely stable imaging performance in the entire zooming range. Miniaturization and wide angle can be realized.

(Internal circuit configuration)
FIG. 19 is a block diagram showing the internal circuitry of the main part of the digital camera 140. In the following description, the processing means includes, for example, the CDS / ADC unit 124, the temporary storage memory 117, the image processing unit 118, and the like, and the storage means includes, for example, the storage medium unit 119.

  As shown in FIG. 19, the digital camera 140 is connected to the operation unit 112, the control unit 113 connected to the operation unit 112, and the control signal output port of the control unit 113 via buses 114 and 115. An imaging drive circuit 116, a temporary storage memory 117, an image processing unit 118, a storage medium unit 119, a display unit 120, and a setting information storage memory unit 121 are provided.

  The temporary storage memory 117, the image processing unit 118, the storage medium unit 119, the display unit 120, and the setting information storage memory unit 121 are configured so that data can be input or output with each other via the bus 122. In addition, a CCD 149 and a CDS / ADC unit 124 are connected to the imaging drive circuit 116.

  The operation unit 112 includes various input buttons and switches, and is a circuit that notifies the control unit of event information input from the outside (camera user) via these input buttons and switches.

  The control unit 113 is a central processing unit composed of, for example, a CPU and the like. The control unit 113 includes a program memory (not shown) and is input from the camera user via the operation unit 112 according to a program stored in the program memory. This is a circuit that controls the entire digital camera 140 in response to an instruction command.

  The CCD 149 receives an object image formed through the photographing optical system 141 according to the present invention. The CCD 149 is an image pickup element that is driven and controlled by the image pickup drive circuit 116, converts the light amount of each pixel of the object image into an electrical signal, and outputs the electric signal to the CDS / ADC unit 124.

  The CDS / ADC unit 124 amplifies the electric signal input from the CCD 149 and performs analog / digital conversion, and temporarily stores the raw video data (Bayer data, hereinafter referred to as RAW data) that has just been subjected to the amplification and digital conversion. This is a circuit for outputting to the storage memory 117.

  The temporary storage memory 117 is a buffer made of, for example, SDRAM or the like, and is a memory device that temporarily stores the RAW data output from the CDS / ADC unit 124. The image processing unit 118 reads out the RAW data stored in the temporary storage memory 117 or the RAW data stored in the storage medium unit 119, and performs various corrections including distortion correction based on the image quality parameter designated from the control unit 113. It is a circuit that performs image processing electrically.

  The recording medium unit 119 detachably mounts a card-type or stick-type recording medium made of, for example, a flash memory, and RAW data transferred from the temporary storage memory 117 to the card-type or stick-type flash memory. This is a control circuit of an apparatus for recording and holding image data processed by the image processing unit 118.

  The display unit 120 includes a liquid crystal display monitor, and is a circuit that displays an image, an operation menu, and the like on the liquid crystal display monitor. The setting information storage memory unit 121 stores a ROM unit in which various image quality parameters are stored in advance, and an image quality parameter selected by an input operation of the operation unit 112 among the image quality parameters read from the ROM unit. RAM section is provided. The setting information storage memory unit 121 is a circuit that controls input and output to these memories.

  In the digital camera 140 configured in this way, the imaging optical system 141 has a sufficiently wide angle range and a compact configuration according to the present invention, and the imaging performance is extremely stable at a high zoom ratio and in a full zoom ratio range. Therefore, high performance, downsizing, and wide angle can be realized. In addition, fast focusing operation on the wide-angle side and the telephoto side is possible.

  As described above, the three-group zoom lens according to the present invention is suitable for a lens that is advantageous for securing the angle of view, the zoom ratio, and the optical performance.

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. It is the same figure as FIG. 1 of Example 2 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 3 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 4 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 5 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 6 of the zoom lens of this invention. It is the same figure as FIG. 1 of Example 7 of the zoom lens of this 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. FIG. 10 is an aberration diagram for Example 7 upon focusing on an object point at infinity. It is a figure explaining correction | amendment of a distortion aberration. It is a front perspective view which shows the external appearance of the digital camera incorporating the zoom lens by this invention. It is a rear perspective view of the digital camera. It is sectional drawing of the said digital camera. It is a block diagram of the internal circuit of the main part of the digital camera.

Explanation of symbols

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Brightness stop F ... Low pass filter C ... Cover glass I ... Image surface 112 ... Operation part 113 ... Control part 114 ... Bus 115 ... Bus 116 ... Imaging drive circuit 117 ... Temporary storage memory 118 ... Image processing part 119 ... Storage medium part 120 ... Display part 121 ... Setting information storage memory part 122 ... Bus 124 ... CDS / ADC part 140 ... Digital camera 141 ... Optical optical system 142 ... Optical optical path 143 ... Finder optical system 144 ... Optical path for finder 145 ... Shutter button 146 ... Flash 147 ... LCD monitor 149 ... CCD
150: cover member 151 ... processing means 152 ... recording means 153 ... finder objective optical system 155 ... erecting prism 157 ... field frame 159 ... eyepiece optical system 160 ... cover 161 ... focal length change button 162 ... setting change switch

Claims (27)

From the object side to the image side,
A first lens unit having negative refractive power;
A second lens unit having positive refractive power,
It consists of a third lens group with positive refractive power,
When zooming from the wide-angle end to the telephoto end,
The second lens group moves;
An interval between the first lens group and the second lens group is narrowed,
The distance between the second lens group and the third lens group is widened,
When the lens component has only two lens bodies on the optical axis in contact with air, the object side surface and the image side surface,
The first lens group is sequentially from the object side.
The lens surface on the object side is concave on the object side, and consists of two lens components, a front lens component having negative refractive power and a rear lens component having positive refractive power,
The second lens group is in order from the object side.
The front lens component having a positive refractive power and the image side lens surface are concave on the image side, and are composed of two lens components, a rear lens component having a negative refractive power,
The third lens group is in order from the object side.
It consists of two lens components, a front lens component whose object side lens surface is concave on the object side and a rear lens component of positive refractive power,
An aperture stop is disposed on the image side of the first lens group and on the object side of the rear lens component in the second lens group, and the aperture stop is zoomed from the wide-angle end to the telephoto end. In this case, the three-group zoom lens moves in the optical axis direction integrally with the second lens group. 2. The three-group zoom lens according to claim 1, wherein the first lens group and the second lens group satisfy the following condition.
0.1 <(R _1F + R _2R ) / (R _1F −R _2R ) <1.0 (3)
However,
R _1F is the paraxial radius of curvature of the lens surface closest to the object in the first lens group,
R _2R is the paraxial radius of curvature of the lens surface on the most image side in the second lens group,
It is. The three-group zoom lens according to claim 1 or 2, wherein the front lens group in the first lens group is a biconcave lens component that satisfies the following condition.
−0.5 <(R _1F + R _1FR ) / (R _1F −R _1FR ) <1.0 (D)
However,
R _1F is the paraxial radius of curvature of the lens surface closest to the object in the first lens group,
R _1FR is the paraxial radius of curvature of the image side lens surface of the front lens component in the first lens group,
It is. 4. The three-group zoom lens according to claim 1, wherein the front lens component and the rear lens component in the first lens group satisfy the following condition. 5.
−1.8 <f _1F / f _W <−1 (7)
2 <f _1R / f _W <9 (8)
However,
f _1F is the focal length of the front lens component in the first lens group,
f _1R is the focal length of the rear lens component in the first lens group,
f _W is the focal length of the entire three-group zoom lens system at the wide-angle end,
It is.   5. The object-side lens surface of the front lens component in the first lens group is an aspherical surface having a shape in which negative refractive power decreases as the distance from the optical axis increases. The three-group zoom lens described in the item.   6. The object-side lens surface of the front lens component in the first lens group is an aspherical surface having a shape in which negative refractive power becomes weaker and changes to positive refractive power as the distance from the optical axis increases. 3 group zoom lens. The front lens component in the first lens group has a biconcave shape,
7. The three-group zoom lens according to claim 5, wherein the rear lens component in the first lens group has a meniscus shape convex toward the object side.   8. The third group zoom lens according to claim 5, wherein an image side lens surface of the front lens component in the first lens group is an aspheric concave surface. 9.   9. The three-group zoom lens according to claim 1, wherein the aperture stop is disposed immediately before the front lens component of the second lens group. 10. The three-group zoom lens according to claim 1, wherein the three-group zoom lens satisfies the following condition at a wide-angle end.
1 <D ₁₂ / f _W <4 (4)
However,
D ₁₂ is the axial distance from the lens surface on the most image side in the first lens group at the wide-angle end to the most object side lens surface of the second lens group,
f _W is the focal length of the entire system of the three-group zoom lens at the wide-angle end,
It is. 11. The three-unit zoom lens according to claim 1, wherein the second lens group satisfies the following condition.
−0.7 <T _2F / f _W <−0.4 (5)
However,
T _2F is the distance on the optical axis from the lens surface closest to the object side of the second lens group to the front principal point of the second lens group, and is negative when the principal point is on the object side of the second lens group. ,
f _W is the focal length of the entire system of the three-group zoom lens at the wide-angle end,
It is. 12. The three-unit zoom lens according to claim 1, wherein the following conditional expression is satisfied when the total number of lenses in the three-group zoom lens is expressed as N _t : 12.
6 ≦ N _t ≦ 8 (9)   13. The first lens group according to claim 1, wherein the object side lens surface and the image side lens surface have an aspherical front lens component having a negative refractive power on the most object side. The three-group zoom lens described.   14. The three-group zoom lens according to claim 1, wherein the total number of lenses included in the second lens group is three or less.   15. The three-group zoom lens according to claim 14, wherein the second lens group includes a single lens having a positive refractive power, a cemented lens having a positive lens and a negative lens.   15. The three-group zoom lens according to claim 14, wherein the second lens group includes a single lens having a positive refractive power and a single lens having a negative refractive power.   2. The second lens group includes a positive lens and a negative lens, and all negative lenses in the second lens group have an Abbe number smaller than all positive lenses in the second lens group. The three-group zoom lens according to at least one of Items 16 to 16. 18. The three-unit zoom lens according to claim 14, wherein the second lens group satisfies the following condition.
n _2pave ≧ 1.59 (10)
ν _2n ≦ 35 (11)
However,
n 2 _pave is the average value of the refractive indexes of all the positive lenses in the second lens group,
ν _2n is the Abbe number of all negative lenses in the second lens group,
It is. The most image side lens in the second lens group is a negative lens having a concave surface facing the image side,
The thickness of the negative lens on the optical axis is larger than the distance on the optical axis between the front lens component and the rear lens component of the second lens group. The three-group zoom lens according to at least one of the above.   The third lens group zoom lens according to any one of claims 1 to 19, wherein the second lens group includes a positive lens having an aspherical surface. 21. The three-group zoom lens according to claim 1, wherein all the lenses in the third lens group satisfy the following condition.
n _3ave ≧ 1.4 (12)
ν _3ave ≧ 50 (13)
However,
n _3ave is the average value of the refractive indexes of all the lenses in the third lens group,
ν _3ave is the average value of the Abbe numbers of all the lenses in the third lens group,
It is.   22. The three-group zoom according to claim 1, wherein the total number of lenses included in the third lens group is two, and any one of the lenses has an aspherical surface. lens.   23. The three-group zoom lens according to claim 1, wherein the third lens group includes at least one resin lens.   24. At least one of claims 1 to 23, wherein both the rear lens component in the second lens group and the front lens component in the third lens group have a meniscus shape having a negative refractive power. The three-group zoom lens described in 1. When zooming from the wide-angle end to the telephoto end, the first lens group first moves to the image side and then reverses the moving direction to the object side.
25. The third group zoom lens according to claim 1, wherein the third lens group is positioned on the image side at a telephoto end with respect to a position at a wide angle end. A zoom lens,
An imaging device having an imaging surface disposed on the image side and converting an optical image on the imaging surface formed by the zoom lens into an electrical signal;
An image pickup apparatus, wherein the zoom lens is the three-group zoom lens according to at least one of claims 1 to 25. A signal processing circuit that processes image data obtained by imaging with the imaging element and outputs the image data as a changed shape;
27. The imaging apparatus according to claim 26, wherein the following condition is satisfied in a state in which the third group zoom lens is focused at the wide-angle end and the farthest distance.
_{0.7 <y 07 / (f w} · tanω 07w) <1.0 ... (14)
However,
When the distance to the farthest point from the center in the effective image pickup plane of the image pickup device and a y _10,
y ₀₇ = 0.7 × y ₁₀
If effective image pickup area changes at the telephoto end from the wide-angle end, y ₁₀ is the maximum value of the possible values, omega _07w enters the image position where the image height is y ₀₇ from the center of the image pickup surface at the wide angle end This is the angle between the incident ray in the object space of the principal ray and the optical axis.

Images