JP2012108279A - Zoom lens having optical path folding member, and image pickup apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens compatibly attaining the retention of high optical performance and cost reduction in the zoom lens of a negative preceding type having an optical path folding member in the optical path; and to provide an image pickup apparatus.SOLUTION: This zoom lens includes, in order from an object side to an image side, at least a first lens group of a negative refractive power, a second lens group of a positive refractive power, and a third lens group having a lens. An interval between the first lens group and the second lens group is narrower in a telephoto end than that in a wide-angle end, and an interval between the second lens group and the third lens group changes when varying power from the wide-angle end to the telephoto end. The first lens group comprises, in order from the object side, a front-side sub lens group of a negative refractive power, the optical path folding member, and a rear-side sub lens group of a positive refractive power. The front sub lens group includes a negative lens, the rear-side sub lens group includes a positive lens, and the negative lens and the positive lens are plastic lenses.

Description

  The present invention relates to a zoom lens having an optical path bending member in an optical path, and an image pickup apparatus including the zoom lens.

  2. Description of the Related Art Conventionally, zoom lenses are known in which an optical system is thinned by arranging a reflecting member in the optical path and bending the optical path. In particular, as a zoom lens type, a lens unit having a negative refractive power is arranged closest to the object side (hereinafter referred to as a negative leading type), and a reflecting member is arranged in the lens group having a negative refractive power. The set type is known. On the other hand, a zoom lens of a type in which a lens group having a positive refractive power is disposed closest to the object side (hereinafter, positive leading type) is also known.

  Compared to a positive leading zoom lens, the negative leading zoom lens has the advantage of reducing the number of lens groups, and the advantages of decentering the lens group, for example, making it easier to suppress degradation of imaging performance. . Many conventional zoom lenses of the negative leading type have a zoom ratio of about 3 times, but recently, a zoom lens with a high zoom ratio as in Patent Document 1 has been realized.

JP 2010-160278 A

  However, in the zoom lens disclosed in Patent Document 1, the first lens group includes a negative lens, a reflecting member, and a cemented lens. Here, since each lens is made of glass, the cost is increased. For this reason, the zoom lens of Patent Document 1 is disadvantageous in terms of reducing costs while maintaining optical performance.

  In view of such a problem, the present invention is a negative leading type zoom lens having an optical path bending member in the optical path. The zoom lens has both high optical performance maintenance and low cost, and the zoom lens. An object is to provide an imaging device.

In order to solve the above problems, a 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, and a third lens having a lens. And at least a lens group,
The distance between the first lens group and the second lens group is narrower at the telephoto end than at the wide angle end,
During zooming from the wide-angle end to the telephoto end, the distance between the second lens group and the third lens group changes,
The first lens group, in order from the object side, includes a front sub lens group having a negative refractive power, an optical path bending member, and a rear sub lens group having a positive refractive power,
The front sub-lens group includes a negative lens;
The rear sub-lens group includes a positive lens;
The negative lens and the positive lens are plastic lenses.

  The zoom lens of the present invention is a negative leading type zoom lens, and has an optical path bending member in the optical system, which is advantageous for thinning and miniaturization of the optical system. Further, the first lens group having a negative refractive power and the second lens group having a positive refractive power have a zooming function. In order to achieve a high zoom ratio in such a configuration, it is necessary to ensure the zooming capability of the first lens group and the second lens group. For this purpose, it is preferable to secure a certain amount of negative refractive power in the first lens group. In terms of cost, it is preferable to realize cost reduction in the first lens group.

  Therefore, in the zoom lens according to the present invention, the first lens group includes a front sub lens group having a negative refractive power, an optical path bending member, and a rear sub lens group having a positive refractive power, and further includes a front sub lens group. Has a negative lens. By doing so, it is easy to suppress the occurrence of axial aberration in the vicinity of the telephoto end while securing the negative refractive power in the first lens group.

  In the zoom lens according to the present invention, the rear sub-lens group has a positive lens. By having a positive lens, various aberrations in the first lens group are reduced.

  Furthermore, in the zoom lens of the present invention, the glass material of the negative lens of the front sub lens group and the positive lens of the rear sub lens group is made of plastic. By doing in this way, the cost of an optical system can be reduced.

  Plastic is advantageous in that the cost can be reduced, but it is disadvantageous in that the focal length of the lens changes greatly with changes in temperature. However, when the two lenses are plastic lenses as described above, the front sub-lens group is a negative lens and the rear sub-lens group is a positive lens. Can cancel each other. Therefore, both cost reduction and optical performance can be ensured.

  As described above, in the zoom lens of the present invention, the plastic lens is used as the lens in the first lens group, which is advantageous in terms of cost reduction.

In the zoom lens according to the present invention, in the above configuration, at least one of the negative lens of the front sub lens group and the positive lens of the rear sub lens group satisfies the following conditional expressions (1) and (2). preferable.
-0.3 <N _1FN -N _1RP <0.2 (1)
_{10.5 <ν 1FN -ν 1RP <50} (2)
However,
N _1FN is the refractive index at the d-line of the negative lens of the front sub-lens group,
N _1RP is the refractive index at the d-line of the positive lens in the rear sub-lens group,
ν _1FN is the Abbe number of the negative lens in the front sub-lens group,
ν _1RP is the Abbe number of the positive lens in the rear sub-lens group,
It is.

  Conditional expression (1) specifies a preferable range of the refractive index difference between the negative lens and the positive lens. Conditional expression (2) specifies a preferable range of the Abbe number difference between the negative lens and the positive lens. Satisfying conditional expressions (1) and (2) is advantageous in terms of aberration correction, cost reduction, and miniaturization.

If conditional expression (2) is satisfied in a state where it does not fall below the lower limit of conditional expression (1), the cost of the glass material can be reduced.
Further, by making sure that the upper limit of conditional expression (1) is not exceeded, the entrance pupil position can be made shallow (the entrance pupil is positioned on the object side), which is advantageous for downsizing the optical system.

By making sure that the lower limit of conditional expression (2) is not exceeded, it is easy to efficiently suppress the occurrence of chromatic aberration in the first lens group.
Further, by making sure that the upper limit of conditional expression (2) is not exceeded, it is advantageous for reducing the cost of the glass material.

  In the zoom lens according to the present invention, in the above configuration, the front sub-lens group includes one negative lens, the rear sub-lens group includes at least two lenses, and the positive lens of the rear sub-lens group includes It is preferable that there is only one sheet.

  In this case, since the first lens group can be composed of three lenses, the cost of the optical system can be reduced.

In the zoom lens according to the present invention, it is preferable that the negative lens of the front sub-lens group and the positive lens of the rear sub-lens group satisfy the following conditional expressions (3) to (5) in the above configuration.
150E-7 / ° C <α _FN <1000E-7 / ° C (3)
150E-7 / ° C <α _RP <1000E-7 / ° C (4)
0 / ° C ≤ | α _FN -α _RP | ≤200E-7 / ° C (5)
However,
α _FN is the average linear expansion coefficient of the negative lens of the front sub-lens group,
α _RP is the average linear expansion coefficient of the positive lens in the rear sub-lens group,
Here, “E-7” indicates “× 10 ⁻⁷ ”.

Conditional expressions (3) and (4) specify a preferable range for the average linear expansion coefficient of the negative lens of the front sub-lens group and the positive lens of the rear sub-lens group.
By making it not fall below the lower limit of conditional expressions (3) and (4), a low-cost plastic material can be used. Therefore, it is easy to reduce the cost while maintaining the performance of the optical system.
In addition, by making sure that the upper limits of conditional expressions (3) and (4) are not exceeded, it is possible to prevent the focal length and aberration from changing with temperature from increasing in each lens.

  Conditional expression (5) specifies a preferable range for the difference in average linear expansion coefficient between the two plastic lenses. As described above, the lenses in the front sub-lens group are negative lenses, and the lenses in the rear sub-lens group are positive lenses. Therefore, by satisfying conditional expression (5), changes in focal length due to temperature changes can be canceled with each other.

  By making so as not to exceed the upper limit of conditional expression (5), it is possible to cancel the change in the focal length of the two lenses (negative lens and positive lens). Therefore, it is possible to suppress performance degradation of the optical system due to temperature changes. Note that the lower limit of conditional expression (5) is not exceeded.

  The average linear expansion coefficient is defined by JIS standards and is defined as follows.

  In the zoom lens of the present invention, in the above configuration, it is preferable that the negative lens of the front sub-lens group is a biconcave single lens. Since the lens surface has a biconcave shape, the range of negative refracting power can be widened, so securing the refracting power is advantageous.

  In the zoom lens of the present invention, it is preferable that the biconcave single lens of the front sub lens group is a double-sided aspheric lens.

  By making the biconcave single lens of the front sub-lens group into a double-sided aspheric lens, it is possible to provide both the object side surface and the image side surface with an aspherical aberration correction function. Therefore, it is advantageous for ensuring both the refractive power of the biconcave single lens and the optical performance. In particular, it is easy to suppress off-axis aberrations at the wide-angle end, and it is advantageous for correction of higher-order field curvature at the wide-angle end. Further, since the material of the biconcave single lens is plastic, it is easy to form an aspherical surface as compared with a glass aspherical lens. Furthermore, since it is comprised with the plastic, cost can be reduced.

  In the zoom lens according to the present invention, the object-side surface shape of the biconcave single lens of the front sub-lens group is an aspherical shape whose negative curvature decreases as the distance from the optical axis increases. The surface shape is preferably an aspherical shape in which the positive curvature increases as the distance from the optical axis increases.

  In this way, spherical aberration can be corrected well near the telephoto end, and off-axis aberrations such as coma can be corrected near the wide-angle end, which is advantageous for both of these aberration corrections. Further, since the lens surface on the object side can be prevented from protruding toward the object side, the effective diameter of the lens can be reduced. As a result, the optical system can be reduced in size.

In the zoom lens of the present invention, it is preferable that the aspheric shape of the object side surface and the image side surface of the biconcave single lens satisfy the following conditional expressions (6) and (7).
−0.1 <ΔASP _FNO / f _FN <0 (6)
−0.1 <ΔASP _FNI / f _FN <0 (7)
However,
f _FNO is the focal length of the biconcave single lens,
ΔASP _FNO is the amount of aspherical deviation at the axial marginal ray height at the telephoto end on the object side surface of the biconcave single lens,
ΔASP _FNI is the amount of aspherical deviation at the axial marginal ray height at the telephoto end on the object side of the biconcave single lens,
And
The amount of aspherical deviation is the distance in the optical axis direction from the reference sphere to the aspherical surface, where the aspherical surface apex is the apex and the radius of curvature is the paraxial curvature radius of the aspherical surface. The case where the sphere is on the image side is a positive sign,
It is.

Conditional expressions (6) and (7) specify a preferable range of the aspherical deviation amount of the aspherical surface of the biconcave single lens.
By not exceeding the upper limit of conditional expressions (6) and (7), it is possible to prevent the amount of aspherical deviation from being insufficient on both surfaces of the biconcave single lens. Thereby, the aspherical shape required in the lens peripheral part is obtained. As a result, spherical aberration can be satisfactorily corrected near the telephoto end, and off-axis aberrations such as coma can be corrected near the wide-angle end.
Further, by making sure that the lower limit of conditional expressions (6) and (7) is not exceeded, it is possible to prevent the aspherical deviation amount from becoming excessive on both surfaces of the biconcave single lens. Thereby, it becomes easy to ensure the molding accuracy of the aspherical shape, and it becomes easy to suppress the occurrence of decentration aberration when the lens is decentered.

In the zoom lens according to the present invention, it is preferable that, in the above-described configuration, the biconcave single lens of the front sub lens group satisfies the following conditional expression (8).
−1 <(r _1FNO + r _1FNI ) / (r _1FNO −r _1FNI ) <0.7 (8)
However,
r _1FNO is the paraxial radius of curvature of the object side surface of the biconcave single lens of the front sub-lens group,
r _1FNI is the paraxial radius of curvature of the image side surface of the biconcave single lens of the front sub-lens group,
It is.

Conditional expression (8) specifies a preferable range of the shape of the biconcave single lens. By satisfying conditional expression (8), the optical system can be reduced in size and performance can be secured.
By making it not fall below the lower limit of conditional expression (8), it becomes a biconcave shape and it becomes easy to ensure negative power. In addition, since the incident angle of the off-axis chief ray incident on the object side surface of the biconcave single lens can be suppressed small, the off-axis aberration can be efficiently suppressed.
Further, by making sure that the upper limit of conditional expression (8) is not exceeded, the entrance pupil can be made shallow (the entrance pupil is positioned on the object side), so that the optical system can be miniaturized.

In the zoom lens according to the present invention, it is preferable that, in the above-described configuration, the biconcave single lens in the front sub lens group satisfies the following conditional expression (9).
0.03 < _D1FNon / _D1FNoff <0.31 (9)
However,
D _1FNoff is the thickness on the optical axis of the biconcave single lens of the front sub-lens group,
D _1FNon is the thickness in the direction along the optical axis at the position of the maximum effective diameter of the biconcave single lens of the front sub-lens group,
It is.

Conditional expression (9) specifies a preferable range of the lens thickness of the biconcave single lens. By satisfying conditional expression (9), it is possible to obtain a lens having a required radius of curvature while ensuring the strength of the lens.
By avoiding falling below the lower limit of conditional expression (9), the thickness of the biconcave single lens on the optical axis can be prevented from becoming too thin. In this case, since the strength of the lens can be ensured, the manufacture becomes easy.
Also, by making sure that the upper limit of conditional expression (9) is not exceeded, the difference in lens thickness between the on-axis and the periphery can be kept large. As a result, the radius of curvature of the lens can be further reduced, so that the refractive power of the lens can be sufficiently secured even when a glass material having a low refractive index is used. For example, even if a glass material having a low refractive index is used for the lens, the light beam can be bent greatly, which is advantageous for widening the angle of view.

In the zoom lens according to the present invention, it is preferable that the following conditional expressions (10) and (11) are satisfied in the above configuration.
0.1 <f _1FN / f _1G <10 (10)
−16 <f _1RP / f _1G <−1.2 (11)
However,
f _1G is the focal length of the first lens group,
f _1FN is the focal length of the biconcave lens of the front sub-lens group,
f _1RP is the focal length of the positive lens in the rear sub-lens group,
It is.

Conditional expression (10) specifies a preferable range for the refractive power of the biconcave single lens of the front sub-lens group.
By making it not fall below the lower limit of conditional expression (10), it is possible to prevent the refractive power of the biconcave single lens from becoming excessive. As a result, the amount of various aberrations generated in the biconcave single lens can be reduced.
Moreover, it can prevent that the refractive power of a biconcave single lens runs short by making it not exceed the upper limit of conditional expression (10). Since the front sub lens group bears much of the negative refractive power of the first lens group, it is possible to ensure the negative refractive power of the first lens group.

Conditional expression (11) specifies a preferable range of the refractive power of the positive lens in the rear sub-lens group.
By making sure that the lower limit of conditional expression (11) is not exceeded, it is possible to prevent the refractive power of the positive lens from being insufficient. In this case, since various aberrations generated in the negative lens of the first lens group can be corrected by the positive lens, various aberrations in the first lens group can be corrected satisfactorily.
Further, by making sure that the upper limit of conditional expression (11) is not exceeded, it is possible to prevent the refractive power of the positive lens from becoming excessive. As a result, it is possible to prevent the negative refractive power of the entire first lens group from being reduced, so that an appropriate negative refractive power can be secured in the first lens group.

In the zoom lens according to the present invention, in the above configuration, it is preferable that the positive lens in the rear sub-lens group satisfies the following conditional expression (12).
0.02 <D _1RP / D _1G <0.3 (12)
However,
D _1RP is the thickness on the optical axis measured along the optical axis of the positive lens of the rear sub-lens group,
D _1G is the thickness on the optical axis measured along the optical axis of the first lens group,
It is.

Conditional expression (12) specifies a preferable range of the thickness measured along the optical axis of the positive lens of the rear sub-lens group. By satisfying conditional expression (12), it is possible to satisfactorily correct lateral chromatic aberration at the wide-angle end and the telephoto end.
By making sure that the lower limit of conditional expression (12) is not exceeded, the thickness of the positive lens on the optical axis can be prevented from becoming too thin. In this case, since the strength of the lens can be ensured, the manufacture becomes easy. In addition, since the lens thickness is secured, the lens surface can have a shape with a small radius of curvature, so that the refractive power can be secured.
In addition, by preventing the upper limit of conditional expression (12) from being exceeded, the thickness of the positive lens on the optical axis can be prevented from becoming too thick. As a result, it is possible to efficiently correct lateral chromatic aberration at the wide-angle end and the telephoto end.

In the zoom lens of the present invention, it is preferable that the positive lens of the rear sub lens group is a double-sided aspheric lens.
Since the positive lens of the rear side sub lens group is a plastic lens, both surfaces can be aspherical at low cost. Thereby, both performance improvement and cost reduction of the optical system can be achieved.

  In the zoom lens of the present invention, it is preferable that the rear side sub lens group is composed of only one positive lens. In this way, the number of lenses can be reduced, which is further advantageous for cost reduction.

  In the zoom lens according to the present invention, it is preferable that the rear sub lens group includes only one positive lens and one negative lens, and the negative lens is disposed on the image side of the positive lens. In this way, it is possible to correct monochromatic aberrations and chromatic aberrations better.

In the zoom lens of the present invention, the air layer sandwiched between the positive lens and the negative lens in the rear sub-lens group has positive refractive power, and the positive lens and the negative lens in the rear sub-lens group satisfy the following conditions: It is preferable to satisfy (13).
-1 <( _r1RPI + _r1RNO ) / ( _{r1RPI- r1RNO} ) <1 (13)
However,
r _1RPI is the paraxial radius of curvature of the image side surface of the positive lens in the rear sub-lens group,
r _1RNO is the paraxial radius of curvature of the object side surface of the negative lens in the rear sub-lens group,
It is.

Conditional expression (13) specifies a preferable shape factor for the shape of the air layer formed between the positive lens and the negative lens of the rear sub-lens group.
By making sure that the lower limit of conditional expression (13) is not exceeded, it becomes easy to suppress curvature of field at the wide-angle end.
Further, by making sure that the upper limit of conditional expression (13) is not exceeded, it becomes easier to suppress chromatic aberration at the telephoto end.

In the zoom lens according to the present invention, it is preferable that the negative lens of the rear side sub lens group satisfies the following conditional expression (14).
0.1 <f _1RN / f _1G <10 (14)
However,
f _1RN is the focal length of the negative lens in the rear sub-lens group,
f _1G is the focal length of the first lens group,
It is.

  Conditional expression (14) specifies a preferable range of the refractive power of the negative lens of the rear sub-lens group. As described above, the first lens group includes the biconcave single lens of the front sub lens group, the positive lens and the negative lens of the rear sub lens group. Therefore, the negative refractive power of the first lens group can be appropriately dispersed in the two negative lenses. By satisfying conditional expression (14), an appropriate negative refractive power can be secured in the negative lens of the rear sub-lens group. As a result, the negative refractive power in the first lens group can be borne in a well-balanced manner by the biconcave single lens in the front sub lens group and the negative lens in the rear sub lens group. That is, chromatic aberration can be suppressed while ensuring the negative refractive power of the first lens group.

By making sure that the lower limit of conditional expression (14) is not exceeded, it is possible to prevent the refractive power of the negative lens of the rear sub-lens group from becoming excessive. This facilitates correction of aberrations in the negative lens of the rear sub lens group.
In addition, by making sure that the upper limit of conditional expression (14) is not exceeded, it is possible to prevent the refractive power of the negative lens of the rear sub-lens group from being insufficient. This eliminates the burden of extra refracting power in the biconcave single lens of the front sub-lens group, so that the occurrence of aberrations in the front sub-lens group can be suppressed.

  In the zoom lens of the above invention, focusing can be achieved by extending the first lens group to the object side, but is not limited thereto. The lens group to be extended may be any of the lens groups located on the image side of the second lens group. In particular, since the third lens group and subsequent lens groups can be reduced in weight, it is preferable to perform focusing by extending these lens groups. Alternatively, focusing may be performed by moving the image sensor in the optical axis direction.

  Further, the zooming from the wide-angle end to the telephoto end may be performed with the first lens group and the image sensor fixed. Other configurations may include a configuration in which the first lens group is fixed to the imaging apparatus body and the imaging element moves, or a configuration in which the imaging element is fixed to the imaging apparatus and the first lens group moves. That is, the total lens length may be changed when zooming from the wide-angle end to the telephoto end.

  It is more preferable that the above-mentioned constituent requirements satisfy a plurality at the same time.

  In addition, the imaging apparatus of the present invention includes a zoom lens, an imaging element disposed on the image side of the zoom lens, and an image processing unit that processes a signal from the imaging element, and the zoom lens is any one of the above-described zoom lenses. It is characterized by being a zoom lens.

  In the zoom lens of the present invention, barrel distortion occurs near the wide-angle end. The barrel type distortion is generated in the effective image pickup area of the image pickup device. Therefore, a barrel-type distortion is generated in the image of the subject imaged by the image sensor. Therefore, the image pickup apparatus of the present invention is provided with an image processing unit that corrects the barrel distortion. The image of the subject corrected to a rectangle is reproduced, displayed, and saved by the image processing unit.

  If distortion is performed for each color signal in the image processing unit, the chromatic aberration of magnification can be electrically corrected. In addition, the peripheral light attenuation correction, the blur correction, and the various aberration corrections may be performed by the image processing unit.

  Further, it is preferable that the above conditional expressions are further as follows. By doing in this way, the effect demonstrated by each conditional expression can be acquired more effectively.

It is preferable to set the lower limit of conditional expression (1) to -0.25, more preferably -0.2, and further more preferably -0.15.
The upper limit of conditional expression (1) is preferably 0.15, more preferably 0.1, further 0.05, and even more preferably -0.05.
It is preferable to set the lower limit of conditional expression (2) to 15, more preferably 20, and even more preferably 25.
It is preferable to set the upper limit of conditional expression (2) to 45 2, further 40, and further 33.
The lower limit of conditional expression (3) is preferably 200E-7, more preferably 300E-7, even more preferably 400E-7, and even more preferably 500E-7.
The upper limit of conditional expression (3) is preferably 900E-7, more preferably 800E-7, and even more preferably 700E-7.
The lower limit of conditional expression (4) is preferably 200E-7, more preferably 300E-7, even more preferably 400E-7, and even more preferably 500E-7.
The upper limit of conditional expression (4) is preferably 900E-7, more preferably 800E-7, and even more preferably 700E-7.
The upper limit of conditional expression (5) is preferably 170E-7, more preferably 150E-7, further 120E-7, and even more preferably 80E-7.
It is preferable to set the lower limit of conditional expression (6) to -0.05, more preferably -0.01, more preferably -0.005, and even more preferably -0.001.
The upper limit of conditional expression (6) is preferably -0.0001, more preferably -0.0003, and further preferably -0.0005.
It is preferable to set the lower limit of conditional expression (7) to -0.05, more preferably -0.01, more preferably -0.005, and even more preferably -0.001.
The upper limit of conditional expression (7) is preferably −0.0001, more preferably −0.0002, and further preferably −0.0004.
The lower limit of conditional expression (8) is preferably −0.7, more preferably −0.5, and further preferably −0.35.
The upper limit of conditional expression (8) is preferably 0.5, more preferably 0.32, and even more preferably 0.1.
The lower limit of conditional expression (9) is preferably 0.06, more preferably 0.1, and further preferably 0.15.
The upper limit of conditional expression (9) is preferably 0.27, more preferably 0.24, and even more preferably 0.22.
The lower limit of conditional expression (10) is preferably 0.3, more preferably 0.41, and even more preferably 0.5.
It is preferable to set the upper limit of conditional expression (10) to 5, more preferably 3, more preferably 1, and even more preferably 0.7.
The lower limit of conditional expression (11) is preferably −10, more preferably −5, and further preferably −3.5.
It is preferable that the upper limit of conditional expression (11) is −1.5, more preferably −1.7, further −1.8, and further −1.9.
The lower limit of conditional expression (12) is preferably 0.05, more preferably 0.07, and further preferably 0.1.
The upper limit of conditional expression (12) is preferably 0.25, more preferably 0.19, and further preferably 0.15.
The lower limit of conditional expression (13) is preferably −0.9, more preferably −0.8, and further preferably −0.75.
It is preferable to set the upper limit of conditional expression (13) to 0.7, further 0.4, further 0, more preferably -0.3, and further more preferably -0.6.
It is preferable to set the lower limit of conditional expression (14) to 1, more preferably 1.5, further 2, and even 2.5.
It is preferable to set the upper limit of conditional expression (14) to 8, more preferably 6, and further to 4.

  In the above description, the focal length is a paraxial focal length. In addition, the configuration and conditional expressions of the optical system in the above description are the configurations in the state where the object at the farthest distance is in focus (when focusing on an object at infinity) unless otherwise defined in a zoom lens capable of focusing. Or a conditional expression.

  According to the present invention, in a zoom lens having a negative leading type and having an optical path bending member in the optical path, a zoom lens that maintains both high optical performance and low cost, and an imaging device including the zoom lens are provided. be able to.

FIG. 3 is a lens cross-sectional view at the wide-angle end (a), the intermediate focal length state (b), and the wide-angle end (c) when focusing on an object point at infinity according to the first embodiment of the zoom lens of the present invention. It is a figure similar to FIG. 1 of 2nd Example of the zoom lens of this invention. It is the same figure as FIG. 1 of 3rd Example of the zoom lens of this invention. It is a figure similar to FIG. 1 of 4th Example of the zoom lens of this invention. FIG. 6 is a view similar to FIG. 1 of a fifth embodiment of the zoom lens of the present invention. It is a figure similar to FIG. 1 of 6th Example 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. 1 is a front perspective view showing an overview of a digital camera incorporating a zoom lens according to the present 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.

  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 6 of the zoom lens according to the present invention will be described below. 1 to 6 show lens cross-sectional views at the wide-angle end (a), the intermediate focal length state (b), and the wide-angle end (c) when focusing on an object point at infinity according to 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, the infrared light cut filter is F, and the cover The glass is indicated by C and the image plane is indicated by I.

  Here, the infrared light cut filter F may be a low-pass filter provided with a coat (multilayer film) for cutting infrared light. The cover glass C is a parallel plate of the electronic image sensor. In addition, you may give the coat which cuts infrared light on 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 bass filter.

  In each embodiment, the aperture stop S moves integrally with the second lens group G2. The numerical data is data in a state in which the object (object) at infinity is in focus. The unit of length of each numerical value is mm, and the angle is ° (degrees). Focusing is performed by moving the most image-side lens in any of the embodiments. Further, zoom data is values at the wide-angle end (WE), the intermediate focal length state (ST), and the telephoto end (TE).

  In all embodiments, focusing is preferably performed by moving the third lens group G3. In the zoom lenses of Examples 1 to 3, focusing from a long distance to a short distance is performed by moving the third lens group G3 having a positive refractive power toward the object side. In the zoom lens of Example 4, focusing from a long distance to a short distance is performed by moving the third lens group G3 having a negative refractive power toward the image side. Note that the focusing is not limited to this, and the imaging element may be moved in the optical axis direction.

  As can be seen from the lens cross-sectional view, the movement of each lens group is shown with the imaging surface as a reference (fixed). Therefore, in the zoom lenses of Examples 1 to 3, 5, and 6, it is illustrated that the first lens group G1 moves during zooming. However, if the first lens group G1 is fixed at the time of zooming, the confidentiality of the imaging apparatus can be improved. Therefore, at the time of zooming, it is preferable that the position of the first lens group G1 is fixed and the image sensor is moved. In the zoom lens of Example 4, both the first lens group G and the image sensor are fixed at the time of zooming.

  In each embodiment, the reflecting member corresponds to an optical path bending member. Specifically, this reflecting member is a prism. A mirror may be used instead of the prism.

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

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The fourth lens group G4 is fixed. Thus, the zoom lens of Example 1 is a four-group zoom lens in which the distance between the lens groups changes.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, a reflecting member, and a biconvex positive lens. The second lens group G2 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group G3 is composed of a biconvex positive lens. The fourth lens group G4 is composed of a positive meniscus lens having a concave surface directed toward the object side.

  The aspherical surfaces include both sides of a biconcave negative lens of the first lens group G1, both sides of a biconvex positive lens, both sides of a biconvex positive lens of the second lens group G2, and a biconvex positive lens of the third lens group G3. Are used for a total of eight surfaces including the image side surface and the object side surface of the positive meniscus lens having a concave surface facing the object side of the fourth lens group G4.

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

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The fourth lens group G4 is fixed. Thus, the zoom lens of Example 2 is a four-group zoom lens in which the distance between the lens groups changes.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, a reflecting member, and a positive meniscus lens having a concave surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group G3 is composed of a biconvex positive lens. The fourth lens group G4 is composed of a positive meniscus lens having a concave surface directed toward the object side.

  The aspherical surfaces include both surfaces of a biconcave negative lens of the first lens group G1, both surfaces of a positive meniscus lens having a concave surface facing the object side, both surfaces of a biconvex positive lens of the second lens group G2, and a third lens group. It is used for a total of eight surfaces including the image side surface of the G3 biconvex positive lens and the object side surface of the positive meniscus lens with the concave surface facing the object side of the fourth lens group G4.

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

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. Thus, the zoom lens of Example 3 is a three-group zoom lens in which the distance between the lens groups changes.

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

  The aspherical surfaces include both surfaces of a biconcave negative lens of the first lens group G1, both surfaces of a positive meniscus lens having a concave surface facing the object side, both surfaces of a biconvex positive lens of the second lens group G2, and a third lens group. It is used for a total of 7 surfaces including the image side surface of the G3 biconvex positive lens.

  As shown in FIG. 4, the zoom lens of Example 4 includes, in order from the object side to the image side, a first lens group G1 having a negative refractive power, an aperture stop S, and a second lens group having a positive refractive power. G2, a third lens group G3 having a negative refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are disposed.

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 is fixed. The second lens group G2 moves to the object side. The third lens group G3 moves to the object side. The fourth lens group G4 moves to the image side. The fifth lens group G5 is fixed. Thus, the zoom lens of Example 1 is a 5-group zoom lens in which the distance between the lens groups changes.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, a reflecting member, a biconvex positive lens, and a negative meniscus lens having a convex surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group G3 is composed of a biconcave negative lens. The fourth lens group G4 is composed of a positive meniscus lens having a concave surface directed toward the object side. The fifth lens group G5 is composed of a biconvex positive lens.

  The aspherical surfaces include both sides of the biconcave negative lens of the first lens group G1, both sides of the biconvex positive lens, both sides of the biconvex positive lens of the second lens group G2, and the biconcave negative lens of the third lens group G3. Are used for a total of 10 surfaces, that is, the object side surface of a positive meniscus lens having a concave surface facing the object side of the fourth lens group G4, and both surfaces of the biconvex positive lens of the fifth lens group G5.

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

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The fourth lens group G4 is fixed. Thus, the zoom lens of Example 1 is a four-group zoom lens in which the distance between the lens groups changes.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, a reflecting member, and a positive meniscus lens having a concave surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group G3 is composed of a biconvex positive lens. The fourth lens group G4 is composed of a negative meniscus lens having a concave surface directed toward the object side.

  The aspherical surfaces include both surfaces of a biconcave negative lens of the first lens group G1, both surfaces of a positive meniscus lens having a concave surface facing the object side, both surfaces of a biconvex positive lens of the second lens group G2, and a third lens group. It is used for a total of eight surfaces including the image side surface of the G3 biconvex positive lens and the object side surface of the negative meniscus lens having the concave surface facing the object side of the fourth lens group G4.

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

  At the time of zooming from the wide angle end to the telephoto end, the first lens group G1 moves to the object side. The second lens group G2 moves to the object side. The third lens group G3 moves to the image side. The fourth lens group G4 is fixed. Thus, the zoom lens of Example 1 is a four-group zoom lens in which the distance between the lens groups changes.

  In order from the object side, the first lens group G1 includes a biconcave negative lens, a reflecting member, and a positive meniscus lens having a concave surface directed toward the object side. The second lens group G2 includes a biconvex positive lens and a cemented lens of a biconvex positive lens and a biconcave negative lens. The third lens group G3 is composed of a biconvex positive lens. The fourth lens group G4 is composed of a negative meniscus lens having a concave surface directed toward the object side.

  The aspherical surfaces include both surfaces of a biconcave negative lens of the first lens group G1, both surfaces of a positive meniscus lens having a concave surface facing the object side, both surfaces of a biconvex positive lens of the second lens group G2, and a third lens group. It is used for a total of eight surfaces including the image side surface of the G3 biconvex positive lens and the object side surface of the negative meniscus lens having the concave surface facing the object side of the fourth lens group G4.

Below, the numerical data of each said Example are shown. Symbols other than 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. End, ST is an intermediate focal length state, TE is a telephoto end, r is a radius of curvature of each lens surface, d is a distance between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is an Abbe number of each lens. It is. 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
Here, r is a paraxial radius of curvature, K is a conic coefficient, and A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients. . In the aspheric coefficient, “e−n” (n is an integer) indicates “10 ⁻ⁿ ”.

  In the following numerical examples, the image height at the wide-angle end is smaller than the intermediate focal length state and the image height at the telephoto end. This is because a barrel-type distortion is generated as described above. The value of the total angle of view (2ω) at the wide angle end in the numerical example displays the angle of view corresponding to the image height of the barrel-shaped effective imaging region.

  In the numerical examples, the numerical value indicating the reflecting surface of the reflecting member (prism) is omitted from the data, but the third surface indicates the incident surface of the reflecting member and the fourth surface indicates the emitting surface of the reflecting member. . Therefore, the reflecting surface exists between the third surface and the fourth surface.

Numerical example 1
Unit: mm
Surface data Surface number rd nd υd
Object ∞ ∞
1 * -7.487 0.97 1.53110 55.91
2 * 12.191 1.79
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * 30.132 1.50 1.63493 23.90
6 * -70.000 variable
7 (Aperture) ∞ 0.70
8 * 6.129 2.38 1.49700 81.54
9 * -16.278 0.11
10 11.001 3.49 1.76182 26.52
11 -12.852 0.40 1.84666 23.78
12 4.540 Variable
13 14.287 2.90 1.53110 55.91
14 * -9.746 variable
15 * -20.000 0.61 1.53110 55.91
16 -20.000 0.35
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 2.08019e-03, A6 = -3.26772e-05, A8 = 3.75554e-07
Second side
k = 3.328
A4 = 6.58910e-04, A6 = 1.88880e-05, A8 = -7.45717e-07
5th page
k = 0.000
A4 = -6.95567e-04, A6 = 3.74130e-05, A8 = 1.19289e-07
6th page
k = 0.000
A4 = -5.64334e-04, A6 = 2.76133e-05, A8 = 3.58379e-07
8th page
k = 0.000
A4 = -3.97291e-04, A6 = 9.65125e-07
9th page
k = 0.000
A4 = 4.58180e-04
14th page
k = 0.000
A4 = 4.52981e-04, A6 = 2.25500e-09
15th page
k = 0.000
A4 = -9.19140e-04, A6 = 1.88942e-05

Zoom data
Wide angle Medium Telephoto height 3.74 4.04 4.04
Focal length 5.10 8.91 19.16
FNO. 3.51 5.45 6.96
Angle of view 2ω 78.75 48.16 22.80

d6 11.09 6.77 0.40
d12 1.22 11.03 24.87
d14 3.49 1.85 0.51

fb (in air) 1.71 1.71 1.71
Total length (in air) 39.73 43.51 49.62

Group focal length
f1 = -15.65 f2 = 13.93 f3 = 11.39 f4 = 3550.96

Numerical example 2
Unit: mm
Surface data Surface number rd nd υd
Object ∞ ∞
1 * -7.729 0.97 1.53110 55.91
2 * 12.902 1.85
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * -134.950 1.50 1.63493 23.90
6 * -22.715 variable
7 (Aperture) ∞ 0.70
8 * 6.120 2.45 1.58313 59.46
9 * -14.173 0.10
10 17.067 3.22 1.67790 55.34
11 -17.947 0.52 1.80000 29.84
12 4.546 Variable
13 13.438 3.35 1.51633 64.06
14 * -9.462 variable
15 * -20.000 0.61 1.53110 55.91
16 -20.000 0.35
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 2.04598e-03, A6 = -3.13038e-05, A8 = 3.26785e-07
Second side
k = 4.133
A4 = 8.63342e-04, A6 = 1.65689e-05, A8 = -6.97112e-07
5th page
k = 0.000
A4 = -8.92289e-04, A6 = 2.82135e-05
6th page
k = 0.000
A4 = -7.62040e-04, A6 = 2.03867e-05
8th page
k = 0.000
A4 = -5.15115e-04, A6 = 6.61255e-07
9th page
k = 0.000
A4 = 4.90565e-04
14th page
k = 0.000
A4 = 4.90118e-04, A6 = -2.65331e-06
15th page
k = 0.000
A4 = -4.70846e-04, A6 = 4.96149e-06

Zoom data
Wide angle Medium Telephoto height 3.66 4.04 4.04
Focal length 4.93 9.74 18.55
FNO. 3.50 5.70 6.99
Angle of view 2ω 81.47 45.58 24.22

d6 11.44 4.77 0.40
d12 1.54 11.94 24.09
d14 2.94 1.65 0.41

fb (in air) 1.73 1.73 1.73
Total length (in air) 40.28 42.67 49.22

Group focal length
f1 = -14.47 f2 = 13.19 f3 = 11.32 f4 = 3550.96

Numerical Example 3
Unit: mm

Surface data Surface number rd nd υd
Object ∞ ∞
1 * -7.723 0.97 1.53110 55.91
2 * 13.321 1.80
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * -103.204 1.50 1.63493 23.90
6 * -22.075 variable
7 (Aperture) ∞ 0.70
8 * 6.017 2.45 1.58313 59.46
9 * -14.331 0.10
10 17.521 3.22 1.67790 55.34
11 -18.644 0.52 1.80000 29.84
12 4.514 Variable
13 13.564 3.35 1.51633 64.06
14 * -9.459 variable
15 ∞ 0.30 1.51633 64.14
16 ∞ 0.50
17 ∞ 0.50 1.51633 64.14
18 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 2.01100e-03, A6 = -3.17633e-05, A8 = 3.40021e-07
Second side
k = 4.850
A4 = 8.04082e-04, A6 = 1.24917e-05, A8 = -7.81066e-07
5th page
k = 0.000
A4 = -7.28518e-04, A6 = 2.32616e-05
6th page
k = 0.000
A4 = -6.16676e-04, A6 = 1.63810e-05
8th page
k = 0.000
A4 = -5.63612e-04, A6 = -1.78863e-06
9th page
k = 0.000
A4 = 4.35888e-04
14th page
k = 0.000
A4 = 8.10896e-04, A6 = -6.04860e-06

Zoom data
Wide angle Medium Telephoto height 3.65 4.04 4.04
Focal length 4.93 9.67 18.57
FNO. 3.50 5.80 7.00
Angle of view 2ω 81.34 45.46 24.23

d6 11.25 5.38 0.40
d12 1.37 12.01 24.28
d14 3.72 2.11 1.25

fb (in air) 5.15 3.48 2.63
Total length (in air) 39.67 42.78 49.23

Group focal length
f1 = -14.48 f2 = 13.14 f3 = 11.36

Numerical Example 4
Unit: mm
Surface data Surface number rd nd υd
Object ∞ ∞
1 * -8.064 0.97 1.53110 55.91
2 * 7.911 2.31
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * 38.761 1.42 1.63493 23.90
6 * -17.817 0.10
7 115.199 0.50 1.73800 32.26
8 19.007 Variable
9 (Aperture) ∞ 0.70
10 * 7.442 3.50 1.49700 81.54
11 * -16.608 0.10
12 12.189 2.25 1.55880 62.55
13 -38.244 0.50 1.72825 28.46
14 10.486 Variable
15 -7.127 0.50 1.48749 70.23
16 * 117.173 Variable
17 -12.335 0.96 1.53110 55.91
18 * -6.212 variable
19 * 22.356 2.69 1.53110 55.91
20 * -15.107 0.35
21 ∞ 0.30 1.51633 64.14
22 ∞ 0.50
23 ∞ 0.50 1.51633 64.14
24 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 1.92254e-03, A6 = -3.05452e-05, A8 = 2.95162e-07, A10 = -1.96811e-10
Second side
k = 0.000
A4 = 3.00358e-04, A6 = 5.85037e-05, A8 = -2.09886e-06, A10 = 1.94417e-08
5th page
k = 0.000
A4 = -7.55038e-04, A6 = 6.27574e-06
6th page
k = 0.000
A4 = -5.69667e-04, A6 = 7.47124e-07
10th page
k = 0.000
A4 = -1.16640e-04, A6 = -5.81051e-06, A8 = 8.88556e-07, A10 = 6.10606e-09
11th page
k = 0.000
A4 = 3.62002e-04, A6 = -1.98208e-06, A8 = 6.94737e-07, A10 = 3.69823e-08
16th page
k = 0.000
A4 = 7.91854e-04, A6 = -1.78713e-05, A8 = 1.37930e-06
18th page
k = 0.000
A4 = 1.35150e-03, A6 = 5.19416e-05, A8 = -1.13501e-06
19th page
k = 0.000
A4 = -1.99872e-04, A6 = 8.28693e-06
20th page
k = 0.000
A4 = -2.69595e-03, A6 = 7.85161e-05, A8 = -5.57333e-07

Zoom data
Wide angle Medium Telephoto height 3.94 3.94 3.94
Focal length 4.89 10.80 23.40
FNO. 3.50 5.76 6.97
Angle of view 2ω 88.08 38.53 18.33

d8 19.30 9.24 0.71
d14 6.18 7.09 14.92
d16 1.16 10.47 13.24
d18 2.54 2.35 0.40

fb (in air) 1.72 1.72 1.72
Total length (in air) 54.73 54.73 54.73

Group focal length
f1 = -10.14 f2 = 11.75 f3 = -13.76 f4 = 22.34 f5 = 17.41

Numerical Example 5
Unit: mm
Surface data Surface number rd nd υd
Object ∞ ∞
1 * -7.732 0.97 1.53110 55.91
2 * 12.844 1.86
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * -177.135 1.50 1.63493 23.90
6 * -23.553 variable
7 (Aperture) ∞ 0.70
8 * 6.100 2.45 1.58313 59.46
9 * -13.726 0.10
10 18.057 3.22 1.67790 55.34
11 -17.834 0.52 1.80000 29.84
12 4.573 Variable
13 13.533 3.35 1.51633 64.06
14 * -9.332 variable
15 * -18.206 0.61 1.53110 55.91
16 -18.631 0.35
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 2.03975e-03, A6 = -3.13927e-05, A8 = 3.28916e-07
Second side
k = 4.165
A4 = 8.58770e-04, A6 = 1.54895e-05, A8 = -7.16243e-07
5th page
k = 0.000
A4 = -8.33560e-04, A6 = 2.40172e-05
6th page
k = 0.000
A4 = -7.15440e-04, A6 = 1.68215e-05
8th page
k = 0.000
A4 = -5.51470e-04, A6 = -6.20584e-07
9th page
k = 0.000
A4 = 4.69307e-04
14th page
k = 0.000
A4 = 5.20020e-04, A6 = -2.65063e-06
15th page
k = 0.000
A4 = -4.62715e-04, A6 = 5.83109e-06

Zoom data
Wide angle Medium Telephoto height 4.04 4.04 4.04
Focal length 4.93 9.99 18.55
FNO. 3.50 5.79 6.99
Angle of view 2ω 89.07 44.36 24.21

d6 11.45 4.47 0.40
d12 1.58 12.34 24.08
d14 2.93 1.66 0.42

fb (in air) 1.74 1.74 1.74
Total length (in air) 40.32 42.77 49.22

Group focal length
f1 = -14.46 f2 = 13.19 f3 = 11.26 f4 = -2999.97

Numerical Example 6
Unit: mm
Surface data Surface number rd nd υd
Object ∞ ∞
1 * -7.831 0.95 1.53110 55.91
2 * 12.001 1.92
3 ∞ 7.00 1.88300 40.80
4 ∞ 0.30
5 * -287.847 1.51 1.63493 23.90
6 * -23.890 variable
7 (Aperture) ∞ 0.70
8 * 6.094 2.45 1.58313 59.46
9 * -13.769 0.10
10 18.727 3.22 1.72000 46.02
11 -11.693 0.52 1.80000 29.84
12 4.561 Variable
13 13.324 3.33 1.51633 64.06
14 * -10.020 variable
15 * -12.560 0.60 1.53110 55.91
16 -12.973 0.35
17 ∞ 0.30 1.51633 64.14
18 ∞ 0.50
19 ∞ 0.50 1.51633 64.14
20 ∞ 0.37
Image plane (imaging plane) ∞

Aspheric data first surface
k = 0.000
A4 = 2.07313e-03, A6 = -3.15508e-05, A8 = 3.16680e-07
Second side
k = 3.578
A4 = 8.36072e-04, A6 = 2.19679e-05, A8 = -8.04809e-07
5th page
k = 0.000
A4 = -8.89903e-04, A6 = 2.56386e-05
6th page
k = 0.000
A4 = -7.55491e-04, A6 = 1.73458e-05
8th page
k = 0.000
A4 = -5.31694e-04, A6 = -5.99689e-07
9th page
k = 0.000
A4 = 4.86196e-04
14th page
k = 0.000
A4 = 4.43386e-04, A6 = -2.67304e-06
15th page
k = 0.000
A4 = -3.08363e-04, A6 = 4.65425e-06

Zoom data
Wide angle Medium Telephoto height 4.04 4.04 4.04
Focal length 4.93 10.45 18.55
FNO. 3.50 5.95 6.99
Angle of view 2ω 88.75 42.90 24.41

d6 11.82 4.17 0.40
d12 1.61 13.08 24.07
d14 3.03 1.65 0.42

fb (in air) 1.74 1.74 1.74
Total length (in air) 40.83 43.23 49.22

Group focal length
f1 = -14.46 f2 = 13.29 f3 = 11.64 f4 = -1499.44

  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) is the wide-angle end, (b) is the intermediate focal length state, (c) is the spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration at the telephoto end. (CC) is shown. In each figure, “FIY” indicates the maximum image height.

Next, the values of the conditional expressions in each example are listed. A hyphen (-) indicates that there is no corresponding value.
Example 1 Example 2 Example 3 Example 4
(1) N _1FN -N _1RP -0.104 -0.104 -0.104 -0.104
_{(2) ν 1FN -ν 1RP 32.008} 32.008 32.008 32.008
(3) α _FN 5.840E-05 5.840E-05 5.840E-05 5.840E-05
(4) α _RP 6.500E-05 6.500E-05 6.500E-05 6.500E-05
(5) | α _FN −α _RP | 6.600E-06 6.600E-06 6.600E-06 6.600E-06
(6) ΔASP _FNO / f _FN -0.00085 -0.00069 -0.00067 -0.00198
(7) ΔASP _FNI / f _FN -0.00047 -0.00047 -0.00045 -0.00060
(8) (r _1FNO + r _1FNI ) / (r _1FNO −r _1FNI ) -0.239 -0.251 -0.266 0.010
(9) D _1FNon / D _1FNoff 0.203 0.184 0.202 0.168
(10) D _1RP / D _1G 0.130 0.129 0.130 0.113
_{(11) f 1FN / f 1G} 0.549 0.619 0.626 0.726
_{(12) f 1RP / f 1G} -2.133 -2.957 -3.034 -1.914
(13) (r _1RPI + r1 _RNO ) / (r _1RPI −r _1RNO )----0.732
(14) f _1RN / f _{1G ---} 3.048

Example 5 Example 6
_{(1) N 1FN -N 1RP -0.10383} -0.10383
_{(2) ν 1FN -ν 1RP 32.008} 32.008
(3) α _FN 5.840E-05 5.840E-05
(4) α _RP 6.500E-05 6.500E-05
(5) | α _FN −α _R P | 6.600E-06 6.600E-06
(6) ΔASP _FNO / f _FN -0.00069 -0.00071
(7) ΔASP _FNI / f _FN -0.00048 -0.00048
(8) (r _1FNO + r _1FNI ) / (r _1FNO −r _1FNI ) -0.248 -0.210
(9) D _1FNon / D _1FNoff 0.187 0.178
(10) D _1RP / D _1G 0.129 0.129
_{(11) f 1FN / f 1G} 0.618 0.607
_{(12) f 1RP / f 1G} -2.948 -2.832
(13) (r _1RPI + r _1RNO ) / (r _1RPI −r _1RNO )--
_{(14) f 1RN / f 1G} - -

(Optical path folding digital camera)
The zoom lens of the present invention as described above forms an object image, and the image can be received by an electronic image sensor such as a CCD. The embodiment is illustrated below.

  FIG. 13 to FIG. 15 are conceptual diagrams of structures in which the zoom lens according to the present invention is incorporated in the photographing optical system 141 of the digital camera. 13 is a front perspective view showing the appearance of the digital camera 140, FIG. 14 is a rear perspective view thereof, and FIG. 15 is a cross-sectional view showing the configuration of the digital camera 140. 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 145, a flash 146, a liquid crystal display monitor 147, and the like. When the shutter 145 disposed in the position is pressed, photographing is performed through the photographing optical system 141, for example, the optical path bending zoom lens according to the first embodiment in conjunction therewith. An object image formed by the photographing optical system 141 is formed on the imaging surface of the CCD 149 through a near-infrared cut filter and an optical low-pass filter F. 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 object image formed by the finder objective optical system 153 is formed on the field frame 157 of the Porro prism 155 that is an image erecting member. Behind this polyprism 155, an eyepiece optical system 159 for guiding an erect image to the observer eyeball E is disposed. Cover members 150 are disposed on the incident side of the photographing optical system 141 and the finder objective optical system 153 and on the exit side of the eyepiece optical system 159, respectively.

  The digital camera 140 configured in this manner is a zoom lens having a high zoom ratio and a high optical performance of the photographing optical system 141, which is about 5 times. Can be realized.

  In addition, in the example of FIG. 15, although a parallel plane board is arrange | positioned as the cover member 150, you may omit.

(Internal circuit configuration)
FIG. 16 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. 16, 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 and converts the light amount of each pixel of the object image into an electric 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.

  As described above, the zoom lens according to the present invention is useful for maintaining high optical performance and reducing costs, and is particularly suitable for an optical system of an image pickup apparatus including an electronic image pickup device such as a CCD or a CMOS.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Aperture stop F ... Low pass filter C ... Cover glass P ... Prism I ... Image plane 112 ... Operation part 113 ... Control Section 114 ... Bus 115 ... Bus 116 ... Imaging drive circuit 117 ... Temporary storage memory 118 ... Image processing section 119 ... Storage medium section 120 ... Display section 121 ... Setting information storage memory section 122 ... Bus 124 ... CDS / ADC section 140 ... Digital Camera 141 ... Shooting optical system 142 ... Shooting optical path 143 ... Viewfinder optical system 144 ... Viewfinder optical path 145 ... Shutter button 146 ... Flash 147 ... Liquid crystal display 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

In the zoom lens according to the present invention, it is preferable that, in the above-described configuration, the biconcave single lens in the front sub lens group satisfies the following conditional expression (9).
0.03 < _D1FNon / _D1FNoff <0.31 (9)
However,
D _1FNon is the thickness on the optical axis of the biconcave single lens of the front sub-lens group,
D _1FNoff is the thickness in the direction along the optical axis at the position of the maximum effective diameter of the biconcave single lens of the front sub-lens group,
It is.

Claims (18)

In order from the object side to the image side, at least a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a lens,
The distance between the first lens group and the second lens group is narrower at the telephoto end than at the wide-angle end,
During zooming from the wide angle end to the telephoto end, the distance between the second lens group and the third lens group changes,
The first lens group includes, in order from the object side, a front sub lens group having a negative refractive power, an optical path bending member, and a rear sub lens group having a positive refractive power,
The front sub-lens group includes a negative lens;
The rear sub-lens group includes a positive lens;
The zoom lens according to claim 1, wherein the negative lens and the positive lens are plastic lenses. The at least one of the negative lens of the front sub-lens group and the positive lens of the rear sub-lens group satisfies the following conditional expressions (1) and (2). Zoom lens.
-0.3 <N _1FN -N _1RP <0.2 (1)
_{10.5 <ν 1FN -ν 1RP <50} (2)
However,
N _1FN is the refractive index at the d-line of the negative lens of the front sub-lens group,
N _1RP is the refractive index at the d-line of the positive lens in the rear sub-lens group,
ν _1FN is the Abbe number of the negative lens of the front sub-lens group,
ν _1RP is the Abbe number of the positive lens in the rear sub-lens group,
It is. The front sub-lens group consists of one negative lens,
The rear sub-lens group consists of at most two lenses,
3. The zoom lens according to claim 1, wherein the number of positive lenses in the rear sub lens group is only one. The negative lens of the front sub lens group and the positive lens of the rear sub lens group satisfy the following conditional expressions (3) to (5), respectively: The zoom lens according to claim 1.
150E-7 / ° C <α _FN <1000E-7 / ° C (3)
150E-7 / ° C <α _RP <1000E-7 / ° C (4)
0 / ° C ≤ | α _FN -α _RP | ≤200E-7 / ° C (5)
However,
α _FN is an average linear expansion coefficient of the negative lens of the front sub-lens group,
α _RP is the average linear expansion coefficient of the positive lens of the rear sub-lens group,
Here, E-7 is “× 10 ⁻⁷ ”,
It is.   The zoom lens according to any one of claims 1 to 4, wherein the negative lens of the front sub lens group is a biconcave single lens.   The zoom lens according to claim 5, wherein the biconcave single lens of the front sub lens group is a double-sided aspheric lens. The object-side surface shape of the biconcave single lens of the front sub-lens group is an aspherical shape with a negative curvature that decreases as the distance from the optical axis increases.
The zoom lens according to claim 6, wherein the image-side surface shape of the biconcave single lens is an aspherical shape in which a positive curvature increases as the distance from the optical axis increases. The zoom lens according to claim 6 or 7, wherein the aspheric shape of the object side surface and the image side surface of the biconcave single lens satisfies the following conditional expressions (6) and (7).
−0.1 <ΔASP _FNO / f _FN <0 (6)
−0.1 <ΔASP _FNI / f _FN <0 (7)
However,
f _FNO is the focal length of the biconcave single lens,
ΔASP _FNO is the amount of aspherical deviation at the axial marginal ray height at the telephoto end on the object side surface of the biconcave single lens,
ΔASP _FNI is an aspherical deviation amount at the axial marginal ray height at the telephoto end on the object side surface of the biconcave single lens,
And
The aspherical deviation amount is a distance in the optical axis direction from the reference spherical surface to the aspherical surface with the aspherical surface apex being the apex and the radius of curvature being the paraxial curvature radius of the aspherical surface. The case where the aspherical surface is on the image side is a positive sign,
It is. 9. The zoom lens according to claim 5, wherein the biconcave single lens of the front sub-lens group satisfies the following conditional expression (8).
−1 <(r _1FNO + r _1FNI ) / (r _1FNO −r _1FNI ) <0.7 (8)
However,
r _1FNO is the paraxial radius of curvature of the object side surface of the biconcave single lens of the front sub-lens group,
r _1FNI is the paraxial radius of curvature of the image side surface of the biconcave single lens in the front sub lens group. 10. The zoom lens according to claim 5, wherein the biconcave single lens of the front sub lens group satisfies the following conditional expression (9): 10.
0.03 < _D1FNon / _D1FNoff <0.31 (9)
However,
D _1FNoff is the thickness of the front sub lens group on the optical axis of the biconcave single lens,
D _1FNon is the thickness in the direction along the optical axis at the maximum effective diameter position of the biconcave single lens of the front sub-lens group,
It is. The zoom lens according to any one of claims 5 to 10, wherein the following conditional expressions (10) and (11) are satisfied.
0.1 <f _1FN / f _1G <10 (10)
−16 <f _1RP / f _1G <−1.2 (11)
However,
f _1G is the focal length of the first lens group,
f _1FN is the focal length of the biconcave lens of the front sub-lens group,
f _1RP is the focal length of the positive lens of the rear sub-lens group,
It is. The zoom lens according to any one of claims 1 to 11, wherein the positive lens of the rear sub-lens group satisfies the following conditional expression (12).
0.02 <D _1RP / D _1G <0.3 (12)
However,
D _1RP is the thickness on the optical axis measured along the optical axis of the positive lens of the rear sub-lens group,
D _1G is the thickness on the optical axis measured along the optical axis of the first lens group,
It is.   The zoom lens according to any one of claims 1 to 12, wherein the positive lens of the rear sub-lens group is a double-sided aspheric lens.   The zoom lens according to any one of claims 1 to 13, wherein the rear side sub lens group includes only one positive lens. The rear sub-lens group consists of only one positive lens and one negative lens,
The zoom lens according to claim 1, wherein the negative lens is disposed on the image side of the positive lens. The air layer sandwiched between the positive lens and the negative lens of the rear sub lens group has a positive refractive power,
The zoom lens according to claim 15, wherein the positive lens and the negative lens of the rear sub-lens group satisfy the following conditional expression (13).
-1 <( _r1RPI + _r1RNO ) / ( _{r1RPI- r1RNO} ) <1 (13)
However,
r _1RPI is the paraxial radius of curvature of the image side surface of the positive lens of the rear sub-lens group,
r _1RNO is the paraxial radius of curvature of the object side surface of the negative lens of the rear sub-lens group,
It is. The zoom lens according to claim 15 or 16, wherein the negative lens of the rear sub-lens group satisfies the following conditional expression (14).
0.1 <f _1RN / f _1G <10 (14)
However,
f _1RN is the focal length of the negative lens of the rear sub-lens group,
f _1G is the focal length of the first lens group,
It is. A zoom lens,
An image sensor disposed on the image side of the zoom lens;
An image processing unit for processing a signal from the image sensor;
The zoom lens according to claim 1, wherein the zoom lens is the zoom lens according to claim 1.

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