JP6976225B2 - Zoom lens and image pickup device - Google Patents

Description

The present invention relates to a zoom lens and an image pickup device, and in particular, uses a solid-state image pickup device that receives an optical image such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) and converts it into an electrical image signal. The present invention relates to a zoom lens and an image pickup device suitable for an image pickup device.

Conventionally, solid-state image pickup devices such as CCDs and CMOSs are provided with an on-chip microlens or the like on each pixel in order to efficiently receive incident light from an image pickup lens or the like. When the angle of inclination of the incident light with respect to the optical axis becomes large, vignetting occurs and the light collection rate by the on-chip microlens decreases. Therefore, conventionally, there is a restriction that the tilt angle of the incident light with respect to the optical axis must be reduced, and it has been required to increase the exit pupil diameter of the image pickup lens to a certain level or more to ensure image-side telecentricity.

However, in recent years, the effective aperture ratio of the on-chip microlens has been remarkably improved, and even when light rays are obliquely incident on the light receiving surface of the solid-state image sensor, vignetting is less likely to occur and limb darkening (shading) is less noticeable. I came. Therefore, in the past, a positive lens was arranged on the image side of the image pickup lens in order to ensure telecentricity on the image side, but in recent years, restrictions on the exit pupil diameter of the image pickup lens have become smaller, and the image side of the image pickup lens has become smaller. It has become possible to place negative lenses. Therefore, in recent years, it has become possible to reduce the size of an image pickup lens by arranging a negative lens on the image side of the image pickup lens.

As such an image pickup lens, a zoom lens having a four-group configuration having negative, positive, and negative refractive power arrangements in order from the object side is known (see, for example, Patent Documents 1 to 3). In these zoom lenses, by arranging the negative lens group on the image side most, the total optical length is shortened especially at the wide-angle end. By the way, in a zoom lens, the focal length is changed by changing the distance on the optical axis between each lens group at the time of scaling, and aberration correction is performed for each focal length. At this time, it is preferable that all the lens groups are movable groups because it becomes easy to increase the magnification ratio and at the same time, it becomes easy to correct aberrations at each focal length.

Japanese Unexamined Patent Publication No. 63-032513 Japanese Unexamined Patent Publication No. 2012-226307 Japanese Unexamined Patent Publication No. 2016-90746

However, in the zoom lens disclosed in Patent Document 1, since the first group and the fourth group are fixed on the optical axis at the time of scaling, it is difficult to increase the scaling ratio, and it is also possible to correct aberrations. It is disadvantageous. Further, in the zoom lens having a negative positive / negative negative four group configuration disclosed in Patent Document 1 (Numerical Example 1, Numerical Example 2, Numerical Example 5), since the fourth group is a fixed group, the image plane is curved. The optical configuration is disadvantageous for correcting distortion. Further, since the fourth group is composed of one concave lens, it is difficult to satisfactorily correct curvature of field and distortion at this point as well.

Further, in the zoom lens having a negative positive / negative negative four group configuration disclosed in Patent Document 2 (Examples 7 and 8), although the fourth lens group is composed of a plurality of lenses, it is also the first at the time of scaling. Since the four lens groups are fixed on the optical axis, it is difficult to correct curvature of field and distortion.

Further, in the zoom lens disclosed in Patent Document 3, since the fourth lens group moves along the optical axis at the time of scaling, a large scaling ratio is obtained as compared with the zoom lens disclosed in Patent Document 1 and Patent Document 2. It is easy to realize and is advantageous in terms of aberration correction. However, in the zoom lens disclosed in Patent Document 3, the fourth lens group is composed of one negative lens, and it is difficult to satisfactorily correct curvature of field and distortion. Further, in the zoom lens disclosed in Patent Document 3, the third lens group is composed of a lens having a relatively large diameter, and the miniaturization of the zoom lens is not sufficient.

An object of the present invention is to provide a compact and high-performance zoom lens and an image pickup apparatus.

In order to solve the above problems, the zoom lens according to the present invention has a first lens group having a negative refractive force, a second lens group having a positive refractive force, and a negative refractive force in order from the object side. It is substantially composed of a third lens group and a fourth lens group having a negative refractive force, and each lens group moves in the optical axis direction so that the distance between adjacent lens groups changes at the time of scaling. The fourth lens group includes at least one positive lens and one negative lens, respectively, and is characterized by satisfying the following conditions.
0.40 ≤ f3 / f1 ≤ 1.15 ... (2)
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group

Further, in order to solve the above problems, the image pickup device according to the present invention is characterized by including the zoom lens and an image pickup element that receives an optical image formed by the zoom lens and converts it into an electrical image signal. do.

According to the present invention, it is possible to provide a zoom lens and an image pickup device which are small in size and have high performance.

It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 1 of this invention. FIG. 3 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the wide-angle end of the zoom lens of the first embodiment. FIG. 3 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at an intermediate focal length position of the zoom lens of the first embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the first embodiment. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 2 of this invention. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the second embodiment. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of the second embodiment. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the second embodiment. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 3 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at infinity focusing at the wide-angle end of the zoom lens of Example 3. FIG. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at infinity focusing at the intermediate focal length position of the zoom lens of Example 3. FIG. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of Example 3. FIG. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 4 of this invention. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the fourth embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of Example 4. FIG. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the fourth embodiment. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 5 of this invention. 5 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the wide-angle end of the zoom lens of Example 5. FIG. 5 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at an intermediate focal length position of the zoom lens of the fifth embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of Example 5. FIG. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 6 of this invention. 6 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the wide-angle end of the zoom lens of the sixth embodiment. 6 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at an intermediate focal length position of the zoom lens of the sixth embodiment. 6 is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at infinity focusing at the telephoto end of the zoom lens of the sixth embodiment. It is sectional drawing which shows the lens composition example at the time of infinity focusing at a wide-angle end (upper stage), an intermediate focal length position (middle stage), and a telephoto end (lower stage) of the zoom lens of Example 7 of this invention. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the seventh embodiment. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length position of the zoom lens of the seventh embodiment. It is a spherical aberration diagram, an astigmatism diagram, and a distortion diagram at the time of infinity focusing at the telephoto end of the zoom lens of the seventh embodiment.

Hereinafter, embodiments of the zoom lens and the image pickup apparatus according to the present invention will be described. However, the zoom lens and the image pickup apparatus described below are one aspect of the zoom lens and the image pickup apparatus according to the present invention, and the zoom lens and the image pickup apparatus according to the present invention are not limited to the following aspects.

1. 1. Zoom lens 1-1. Optical Configuration of Zoom Lens First, an embodiment of the zoom lens according to the present invention will be described. The zoom lens of the present embodiment has a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a second lens group having a negative refractive power in order from the object side. It is substantially composed of three lens groups and a fourth lens group having a negative refractive power. Here, "substantially configured" means that the lens groups substantially constituting the zoom lens are the four lens groups of the first lens group to the fourth lens group, but other than that, they are substantially configured. It means that it is permissible to provide a lens group having no power, an optical element other than a lens such as an aperture and a cover glass, and the like. It should be noted that each lens group includes at least one lens.

In the zoom lens, the first lens group and the second lens group are defined as an object side group having a positive refractive power as a whole, and the third lens group and the fourth lens group are regarded as an image side group having a negative refractive power as a whole. Therefore, a telephoto type refractive power arrangement can be realized, and the total optical length of the zoom lens at the telephoto end can be shortened with respect to the focal distance. Further, since the third lens group and the fourth lens group each have a negative refractive power, it is relatively easy to reduce the diameter of the lenses constituting the image side group with respect to the size of the image pickup element. .. From these things, it becomes easy to realize a small zoom lens. Hereinafter, the optical configuration of each lens group will be described in more detail.

(1) First lens group The first lens group is a lens group having a negative refractive power. By arranging a negative refractive power in the first lens group arranged on the object side of the zoom lens, it is advantageous in reducing the size of the zoom lens while widening the angle at the wide-angle end.

The first lens group includes at least one negative lens. In particular, if the first lens group is configured by using a plurality of negative lenses, various aberrations (various aberrations) can be obtained by distributing the refractive power to each negative lens while arranging an appropriate negative refractive power in the first lens group. Spherical aberration, image plane curvature, etc.) can be suppressed, and it becomes easy to realize a zoom lens with high optical performance, which is preferable. Further, it is preferable that the first lens group includes at least one positive lens in order to perform aberration correction (spherical aberration, curvature of field, chromatic aberration, etc.) satisfactorily.

(2) Second lens group The second lens group includes at least one positive lens. Among the zoom lenses, the lens group having a positive refractive power is only the second lens group. Therefore, by arranging a strong positive refractive power in the second lens group, a strong positive refractive power can be arranged in the object side group, and a strong refractive power arrangement with a strong telephoto tendency can be realized. Here, the second lens group preferably includes at least two positive lenses. By constructing the second lens group using a plurality of positive lenses, a strong positive refractive power is distributed to the second lens group, and the refractive power is distributed to each positive lens to generate spherical aberration. The total optical length at the telephoto end is short, the size is small, and it becomes easy to realize a high-performance zoom lens. Further, it is preferable that the second lens group includes at least one negative lens in order to perform aberration correction satisfactorily.

(3) Third lens group The third lens group includes at least one negative lens. For example, it is preferable that the third lens group includes at least one positive lens and one negative lens, because spherical aberration and chromatic aberration can be satisfactorily corrected. Here, it is preferable that the third lens group is composed of two lenses, a positive lens and a negative lens, so that the third lens group can be compactly configured while achieving good optical performance. In particular, as will be described later, when the third lens group is used as the focus group, the focus group can be made smaller and lighter by constituting the third lens group with two lenses, a positive lens and a negative lens. Can be done.

(4) Fourth lens group The fourth lens group includes at least one negative lens. Here, among the negative lenses included in the fourth lens group, the object side surface of the negative lens arranged on the object side is preferably a concave surface. By making the side surface of the object of the negative lens concave, astigmatism can be satisfactorily corrected.

Further, it is preferable that the fourth lens group includes at least one positive lens and at least one negative lens. By configuring the fourth lens group to include not only a negative lens but also at least one positive lens, distortion and curvature of field can be satisfactorily corrected.

Here, if the positive lens is arranged on the most image side of the fourth lens group, that is, on the most image side of the zoom lens, it becomes easy to correct the pincushion type distortion (positive distortion). Further, if the positive lens is arranged on the most image side of the fourth lens group, it is possible to suppress the angle of incidence of the main ray on the image plane from becoming too large, so that the focusing rate of the on-chip microlens can be improved. Can be done. In order to obtain this effect, it is preferable that the positive lens arranged on the image side of the fourth lens group has a biconvex shape.

Further, if the fourth lens group is composed of two lenses, a positive lens and a negative lens, the fourth lens group can be compactly configured while achieving good optical performance, which is preferable.

(5) Aperture diaphragm The arrangement of the aperture diaphragm is not particularly limited in the zoom lens according to the present invention. The aperture diaphragm referred to here refers to an aperture diaphragm that defines the luminous flux diameter of the zoom lens, that is, an aperture diaphragm that defines the Fno of the zoom lens.

Placing the aperture diaphragm between the object side of the second lens group and the image side of the third lens group effectively cuts the light rays before and after it to improve the performance of the zoom lens. preferable. Further, it is more preferable that the aperture stop is arranged on the object side rather than the focus group. By arranging the aperture diaphragm closer to the object than the focus group, it is possible to suppress fluctuations in the angle of view during wobbling. In the zoom lens, for example, when the third lens group is the focus group, it is preferable to arrange the aperture diaphragm on the object side of the third lens group, and in particular, arrange the aperture diaphragm on the object side of the second lens group. If this is done, the diameter of the front lens can be further reduced, which is more preferable.

1-2. Operation (1) Operation at magnification change In the zoom lens, each lens group moves in the optical axis direction so that the distance between adjacent lens groups changes when the magnification is changed from the wide-angle end to the telephoto end. In this way, by making all the lens groups (first lens group to fourth lens group) constituting the zoom lens a movable group at the time of scaling, it becomes easy to increase the scaling ratio, and at the same time, at the same time. Aberration correction at each focal length becomes easy. In particular, by making the fourth lens group a movable group, it becomes easy to correct curvature of field and distortion in the entire variable magnification range, and a high-performance zoom lens can be realized in the entire variable magnification range. The amount of movement and the direction of movement of each lens group at the time of scaling are not particularly limited as long as a desired scaling ratio can be achieved. In particular, the distance between the first lens group and the second lens group is small, the distance between the second lens group and the third lens group is large, the distance between the third lens group and the fourth lens group changes, and the fourth lens It is preferable to move each lens group so that the distance between the group and the image plane becomes large in order to realize a high-performance zoom lens in the entire variable magnification range.

(2) Operation during focusing In the zoom lens, one of the first lens group to the fourth lens group is used as the focus group when focusing from infinity to a close object, and the focus group is used. Is moved in the direction of the optical axis to focus. In particular, in the zoom lens, it is preferable that the third lens group is the focus group. The zoom lens employs a four-group configuration of negative, positive, negative, and negative in order from the object side. A light flux converged by the second lens group is incident on the third lens group. Therefore, the third lens group is composed of a lens having a smaller diameter as compared with the lenses constituting the other lens groups. Further, since the third lens group has a negative refractive power, it is easy to reduce the weight as compared with the lens group having a positive refractive power. From these facts, it is possible to realize a rapid autofocus operation by setting the third lens group as the focus group. Further, by reducing the size and weight of the focus group, it is possible to reduce the load on the focus drive mechanism for moving the focus group along the optical axis. Therefore, the focus drive mechanism can be made smaller and lighter, and the entire zoom lens unit including the lens barrel portion can be made smaller and lighter.

Further, on the image side of the third lens group, a fourth lens group having a negative refractive power like the third lens group is arranged. Therefore, the image magnification of the focus group can be easily increased, and the amount of movement of the focus group at the time of focusing can be reduced. As a result, a faster autofocus operation can be realized, and the optical total length of the zoom lens can be shortened.

For example, when wobbling is performed at the time of moving image imaging in the contrast AF method using the zoom lens, in a zoom lens having a negative positive / negative refractive power arrangement, the third lens group arranged on the image side of the aperture stop is the focus group. By doing so, rapid wobbling becomes possible, and fluctuations in the angle of view during wobbling can be suppressed. Therefore, even when the zoom lens is used for moving image imaging, it is possible to prevent the image displayed on the liquid crystal monitor of the image pickup apparatus from causing a sense of discomfort. Note that wobbling refers to an operation of maintaining a focused state by moving the focus group back and forth along the optical axis at a high speed by a small amount at the time of image pickup in the contrast AF method.

1-3. Conditional expression Next, it is preferable that the zoom lens satisfies one or more conditional expressions described below.

1-3-1. Conditional expression (1)
3.00 ≤ | (1-β _3t ² ) x β _4t ² | ≤ 15.00 ... (1)
However,
β _3t : Lateral magnification of the 3rd lens group at the telephoto end at infinity focus β _4t : Lateral magnification of the 4th lens group at the telephoto end at infinity focus

The conditional expression (1) is an expression that defines the so-called focus sensitivity of the third lens group when the third lens group is used as the focus group. By satisfying the conditional expression (1), the focus sensitivity of the third lens group when the third lens group is used as the focus group is within an appropriate range. Therefore, since the amount of movement of the third lens group at the time of focusing can be reduced, rapid wobbling can be performed and the optical total length of the zoom lens can be shortened. In addition, the aberration fluctuation during focusing is small, and a high-performance zoom lens can be realized in the entire focusing range regardless of the object distance.

On the other hand, when the numerical value of the conditional expression (1) is less than the lower limit value, the focus sensitivity of the third lens group becomes smaller when the third lens group is used as the focus group. Therefore, the amount of movement of the third lens group at the time of focusing becomes large, and the total optical length of the zoom lens becomes long. On the other hand, when the numerical value of the conditional expression (1) exceeds the upper limit value, the focus sensitivity of the third lens group becomes large when the third lens group is used as the focus group. In this case, since the amount of movement of the third lens group at the time of focusing can be reduced, it is preferable in terms of realizing quick wobbling and shortening the optical total length of the zoom lens. However, if the focus sensitivity becomes too large, the aberration fluctuation at the time of focusing becomes large. Therefore, in order to obtain good imaging performance in the entire focusing region, a large number of lenses are required for aberration correction, and it becomes difficult to miniaturize the zoom lens, which is not preferable.

In order to obtain these effects, the lower limit of the conditional expression (1) is more preferably 3.60, further preferably 4.20, and even more preferably 4.60. The upper limit of the conditional expression (1) is more preferably 14.00, further preferably 13.00, and even more preferably 12.50.

1-3-2. Conditional expression (2)
0.40 ≤ f3 / f1 ≤ 3.00 ... (2)
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group

The conditional expression (2) is an expression that defines the ratio between the focal length of the third lens group and the focal length of the first lens group. By satisfying the conditional expression (2), the refractive power of the third lens group with respect to the first lens group is within an appropriate range, and a higher performance zoom lens is realized while reducing the size of the third lens group. be able to. Further, if the third lens group is the focus group, rapid wobbling becomes possible by satisfying the conditional expression (2).

On the other hand, when the numerical value of the conditional expression (2) is less than the lower limit value, the refractive power of the third lens group with respect to the first lens group becomes stronger, which is preferable in order to reduce the size of the third lens group. , It becomes difficult to correct spherical aberration. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (2) exceeds the upper limit value, the refractive power of the third lens group with respect to the first lens group is weak, and it is necessary to increase the diameter of the lens constituting the third lens group. Further, in this case, in order to realize a desired magnification ratio, it is necessary to increase the amount of movement of the third lens group at the time of magnification change, and the optical total length of the zoom lens is also lengthened. For these reasons, it is not preferable to reduce the size of the zoom lens.

In order to obtain these effects, the lower limit of the conditional expression (2) is more preferably 0.43, and even more preferably 0.47. Further, the upper limit of the conditional expression (2) is more preferably 2.00, further preferably 1.30, further preferably 1.15, and more preferably 0.90. It is even more preferably 0.80, even more preferably 0.72.

1-3-3. Conditional expression (3)
1.50 ≤ β _3t ≤ 3.50 ・ ・ ・ (3)
However,
β _3t : Lateral magnification at infinity focusing of the 3rd lens group at the telephoto end

The conditional expression (3) is an expression that defines the lateral magnification of the third lens group at the telephoto end when it is in focus at infinity. By satisfying the conditional expression (3), the refractive power of the third lens group is within an appropriate range, the total optical length of the zoom lens at the telephoto end can be shortened, and a smaller and higher performance zoom can be obtained. A lens can be realized.

On the other hand, when the numerical value of the conditional expression (3) exceeds the upper limit value, the lateral magnification at the telephoto end of the third lens group becomes large, and it becomes difficult to correct the curvature of field. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (3) is less than the lower limit value, the lateral magnification at the telephoto end of the third lens group becomes small, so that the amount of movement at the time of scaling becomes large in order to realize the desired magnification ratio. , It is not preferable because the total optical length becomes long. Further, when the third lens group is used as the focus group, the amount of movement during focusing becomes large, and this is also not preferable because the total optical length becomes long.

In order to obtain these effects, the lower limit of the conditional expression (3) is more preferably 1.80, further preferably 2.00, and even more preferably 2.20. It is even more preferable to be 30. Further, the upper limit value of the conditional expression (3) is more preferably 3.40, further preferably 3.30, further preferably 3.20, and more preferably 3.10. More preferred.

1-3-4. Conditional expression (4)
0.30 ≤ f2 / | f1 | ≤ 0.90 ... (4)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group

The conditional expression (4) is an expression that defines the ratio between the focal length of the second lens group and the focal length of the first lens group. By satisfying the conditional expression (4), the refractive power of the second lens group with respect to the first lens group is within an appropriate range, the total optical length can be shortened, and a smaller and higher performance zoom lens can be obtained. It can be realized.

On the other hand, when the numerical value of the conditional expression (4) is less than the lower limit value, the refractive power of the second lens group with respect to the first lens group becomes stronger, and it becomes difficult to correct the spherical aberration. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (4) exceeds the upper limit value, the refractive power of the second lens group with respect to the first lens group becomes weak and the optical total length becomes long, which is not preferable.

In order to obtain these effects, the lower limit of the conditional expression (4) is more preferably 0.34, further preferably 0.38, further preferably 0.40, and 0. It is even more preferably 44, and even more preferably 0.48. Further, the upper limit of the conditional expression (4) is more preferably 0.80, further preferably 0.75, further preferably 0.68, and even more preferably 0.64. It is even more preferable, and even more preferably 0.60.

1-3-5. Conditional expression (5)
3.00 ≤ f4 / f1 ≤ 500.00 ... (5)
However,
f1: Focal length of the first lens group f4: Focal length of the fourth lens group

The conditional expression (5) is an expression that defines the ratio between the focal length of the fourth lens group and the focal length of the first lens group. By satisfying the conditional expression (5), the refractive power of the fourth lens group with respect to the first lens group is within an appropriate range, and a higher performance zoom lens is realized while reducing the size of the fourth lens group. be able to.

On the other hand, when the numerical value of the conditional expression (5) is less than the lower limit value, the refractive power of the fourth lens group with respect to the first lens group becomes stronger, and it becomes difficult to correct the curvature of field. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (5) exceeds the upper limit value, the refractive power of the fourth lens group with respect to the first lens group becomes weak, and it is necessary to configure the fourth lens group with a lens having a large diameter, which is not preferable. ..

In order to obtain these effects, the lower limit of the conditional expression (5) is more preferably 3.5, further preferably 4.0, and even more preferably 4.5. 0 is even more preferred, 5.50 is even more preferred, 6.00 is even more preferred, 7.00 is even more preferred, and 9.00. Is the most preferable. The upper limit of the conditional expression (5) is more preferably 100.00 and even more preferably 50.00.

1-3-6. Conditional expression (6)
0.80 ≤ | f3 | / f2 ≤ 2.00 ... (6)
However,
f2: Focal length of the 2nd lens group f3: Focal length of the 3rd lens group

The conditional expression (6) is an expression that defines the ratio between the focal length of the third lens group and the focal length of the second lens group. By satisfying the conditional expression (6), the refractive power of the third lens group with respect to the second lens group is within an appropriate range, the optical total length of the zoom lens can be shortened, and the size is smaller and the performance is higher. A wide zoom lens can be realized.

On the other hand, when the numerical value of the conditional expression (6) is less than the lower limit value, the refractive power of the third lens group with respect to the second lens group becomes strong, and it becomes difficult to correct the spherical aberration. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (6) exceeds the upper limit value, the refractive power of the third lens group with respect to the second lens group becomes weak. Therefore, in order to realize the desired magnification ratio, the amount of movement at the time of scaling becomes large and the total optical length becomes long, which is not preferable. Further, when the third lens group is used as the focus group, the amount of movement during focusing becomes large, and this is also not preferable because the total optical length becomes long.

In order to obtain these effects, the lower limit of the conditional expression (6) is more preferably 0.90 and further preferably 1.00. The upper limit of the conditional expression (6) is more preferably 1.80 and even more preferably 1.60.

1-3-7. Conditional expression (7)
nd_max ≧ 1.85 ・ ・ ・ (7)
However,
nd_max: Refractive index of a lens made of a glass material having the highest refractive index among the lenses constituting the zoom lens with respect to the d line.

The conditional expression (7) is an expression that defines the refractive index of a lens made of a glass material having the highest refractive index among the lenses constituting the zoom lens with respect to the d-line. When the conditional expression (7) is satisfied, the refractive index of the lens made of the glass material having the highest refractive index among the zoom lenses is high with respect to the d-line. The desired refractive power can be placed. Therefore, it is possible to suppress the occurrence of spherical aberration and curvature of field and realize a zoom lens with higher performance.

On the other hand, when the numerical value of the conditional expression (7) is less than the lower limit value, the refractive index of the lens constituting the zoom lens is lowered as a whole. Therefore, if an attempt is made to place a strong refractive power on a lens made of a glass material having the highest refractive index, the curvature of the lens becomes too large, and it becomes difficult to correct spherical aberration and curvature of field, which is not preferable.

In order to obtain these effects, the lower limit of the conditional expression (7) is more preferably 1.88, further preferably 1.89, and even more preferably 1.90. Since the larger the numerical value of the conditional expression (7) is, the more preferable it is. Therefore, it is not necessary to specify the upper limit value of the conditional expression (7), but if the upper limit value is provided, it is preferably 2.30.

1-3-8. Conditional expression (8)
0.08 ≤ R4n / f4n ≤ 1.00 ... (8)
However,
R4n: Radius of curvature of the object side surface of the negative lens arranged on the object side most among the negative lenses included in the 4th lens group f4n: Among the negative lenses included in the 4th lens group, arranged on the object side most Focal length of negative lens

Conditional expression (8) is for defining the ratio between the radius of curvature of the object side surface of the negative lens arranged on the object side of the negative lenses included in the fourth lens group and the focal length of the negative lens. It is an expression. Here, the "negative lens arranged on the object side most among the negative lenses included in the fourth lens group" is arranged on the object side most when viewed among the negative lenses included in the fourth lens group. Means a negative lens that is made. Therefore, in the fourth lens group, the lens arranged closest to the object side may be a positive lens.

By satisfying the conditional equation (8), among the negative lenses included in the fourth lens group, the radius of curvature of the surface of the negative lens arranged on the object side on the object side is relative to the focal length of the negative lens. The value is within an appropriate range, astigmatism can be satisfactorily corrected, and a higher-performance zoom lens can be realized.

On the other hand, when the numerical value of the conditional expression (8) is less than the lower limit value, the radius of curvature of the surface of the negative lens on the object side becomes too small, and it becomes difficult to correct astigmatism. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable. On the other hand, when the numerical value of the conditional expression (8) exceeds the upper limit value, the radius of curvature of the surface of the negative lens on the object side becomes too large, and it becomes difficult to correct astigmatism in this case as well. Therefore, it becomes difficult to realize a high-performance zoom lens, which is not preferable.

In order to obtain these effects, the lower limit of the conditional expression (8) is more preferably 0.12 and further preferably 0.15. Further, the upper limit of the conditional expression (8) is more preferably 0.90, further preferably 0.80, further preferably 0.70, and more preferably 0.65. More preferred.

2. 2. Imaging Device Next, an embodiment of the imaging device according to the present invention will be described. The image pickup apparatus of the present embodiment is characterized by comprising the zoom lens and an image pickup element that converts an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens.

Here, the image pickup device is not particularly limited, and a solid-state image pickup device such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can also be used. The image pickup device according to the present invention is suitable for an image pickup device using these solid-state image pickup elements such as a digital camera and a video camera. Further, the image pickup device may be a lens-fixed image pickup device in which the lens is fixed to a housing, or may be an interchangeable lens type image pickup device such as a single-lens reflex camera or a mirrorless camera. Of course. In particular, since the zoom lens according to the present invention can shorten the back focus, it is not equipped with an optical viewfinder such as a mirrorless camera or a reflex mirror for branching light to these, and is compact (thin). It is particularly suitable for an image pickup device.

Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. The zoom lens of each embodiment listed below can be applied to an image pickup device (optical device) such as a digital camera, a video camera, and a silver halide film camera. Further, in each lens cross-sectional view, the left side is the object side and the right side is the image side when facing the drawing.

(1) Optical Configuration of Zoom Lens FIG. 1 shows the lens configuration of the zoom lens of the first embodiment according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of the first embodiment includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 1 shows the surface data of the zoom lens. In Table 1, "plane number" is the order of the lens surfaces counted from the object side, "R" is the radius of curvature of the lens surface, "D" is the distance on the optical axis of the lens surface, and "Nd" is the d line (wavelength). Refractive index with respect to λ = 587.56 nm), “ABV” indicates the Abbe number with respect to the d line. Further, "ASPH" displayed in the next column of the surface number indicates that the lens surface is an aspherical surface, and "STOP" indicates an aperture diaphragm. Further, "D (10)", "D (18)", etc. are shown in the column of the distance on the optical axis of the lens surface, which changes when the distance on the optical axis of the lens surface changes. It means that the interval is variable. The unit of length in each table is "mm". Further, "0.0000" in the column of radius of curvature means a plane.

Table 2 is a specification table of the zoom lens. The specification table shows the focal length "f", the F number "Fno", and the half angle of view "W" of the zoom lens at the time of focusing at infinity. However, Table 2 shows the respective values at the wide-angle end, the intermediate focal length position, and the telephoto end in order from the left side. The unit of length in each table is "mm", and the unit of angle of view is "°".

Table 3 shows the variable spacing on the optical axis of the zoom lens when focusing at infinity. In Table 3, the values at the wide-angle end, the intermediate focal length position, and the telephoto end are shown in order from the left side.

Table 4 shows the aspherical coefficients of each aspherical surface. The aspherical coefficient is a value when each aspherical shape is defined by the following equation.

However, in the above equation, Z is the amount of displacement from the reference plane in the optical axis direction, "h" is the height from the optical axis, "r" is the radius of curvature of the lens surface, k is the conical constant (conic coefficient), and An. Is the nth-order aspherical coefficient. Further, in Table 4, " ^Ea " indicates "x10-a".

Further, Table 29 shows the values of the conditional expressions (1) to (8). Further, Table 30 shows the focal lengths of each lens group constituting the zoom lens. Since the matters related to these tables are the same in each table shown in other examples, the description thereof will be omitted below.

[Table 1]
Surface number RD Nd ABV
1 262.4016 2.5145 1.64850 53.02
2 -94.5059 0.1500
3 23.8754 1.0000 1.49700 81.61
4 12.3169 4.6871
5ASPH 116.4202 1.1000 1.59201 67.02
6ASPH 30.4547 1.3000
7 19.9091 2.0157 1.85025 30.05
8 34.5261 2.2342
9 -22.4772 0.8000 1.83481 42.72
10 -48.7562 D (10)
11STOP 0.0000 5.7000
12ASPH 14.6415 3.4440 1.59201 67.02
13ASPH -47.6062 3.8656
14 -23.6702 1.3189 1.48749 70.44
15 -16.8463 0.1500
16 46.0017 0.6500 1.90525 35.04
17 9.8673 3.6391 1.49700 81.61
18 -26.1762 D (18)
19 41.1281 2.7696 1.85478 24.80
20 -39.2129 0.6000 1.87070 40.73
21 14.6661 D (21)
22 -14.0244 0.8000 1.48749 70.44
23 69.6142 0.1500
24 38.1984 4.6287 1.62004 36.30
25 -30.7530 D (25)
26 0.0000 3.5600 1.51680 64.20
27 0.0000 1.0000

[Table 2]
Wide-angle intermediate telephoto
f 30.3983 37.4089 57.2344
Fno 4.1273 4.5238 5.7955
W 24.3778 20.2503 13.6039

[Table 3]
Wide-angle intermediate telephoto
D (10) 18.7785 11.5253 1.0000
D (18) 1.9897 2.4990 3.4144
D (21) 8.4546 7.8756 7.2090
D (25) 10.5000 14.1236 24.0992

[Table 4]
Surface number K A4 A6 A8 A10
5 -1.00000E + 00 1.60208E-05 -3.03538E-07 9.00607E-10
6 -4.68179E-01 5.05372E-06 -4.15836E-07 8.23239E-10
12 -8.20957E-01 -1.58005E-06 3.48510E-07 -3.70322E-09 -2.45693E-11
13 6.81681E-01 6.05224E-05 3.68740E-07 -6.33976E-09

Further, FIGS. 2 to 4 show longitudinal aberration diagrams at infinity focusing at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens of the first embodiment, respectively. The longitudinal aberration diagrams shown in each figure are spherical aberration (mm), astigmatism (mm), and distortion (%), respectively, in order from the left side when facing the drawing.

In the spherical aberration diagram, the vertical axis represents the F number (indicated by Fno in the figure), the solid line is the spherical aberration at the d line (wavelength 587.56 nm), and the short broken line is the spherical aberration at the C line (wavelength 656.28 nm). The long broken line indicates spherical aberration at the F line (wavelength 486.13 nm).

In the astigmatism diagram, the vertical axis is the image height (y), the solid line is the sagittal image plane (S) with respect to the d line (wavelength 587.56 nm), and the four-dot chain line is the meridional (tangential) image plane (T). It shows astigmatism.

In the distortion diagram, the vertical axis is the image height (y), and the solid line shows the distortion at the d line (wavelength 587.56 nm).

Since the matters related to these longitudinal aberration diagrams are the same in the longitudinal aberration diagrams shown in other examples, the description thereof will be omitted below.

(1) Optical Configuration of Zoom Lens FIG. 5 shows the lens configuration of the zoom lens of the second embodiment according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of the second embodiment includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 5 to 8 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 6 to 8 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 5]
Surface number RD Nd ABV
1 350.0000 2.2482 1.72342 37.99
2 -117.6537 0.1500
3 27.6575 1.0000 1.51680 64.20
4 13.4303 4.6982
5ASPH 155.4605 1.1000 1.59201 67.02
6ASPH 32.6330 1.0000
7 20.8844 2.3305 1.85026 32.27
8 40.9642 2.4954
9 -24.0997 0.8000 1.80610 40.73
10 -48.1650 D (10)
11STOP 0.0000 5.7000
12ASPH 14.7016 3.5017 1.59201 67.02
13ASPH -42.3991 3.9613
14 -19.0813 1.2963 1.48749 70.44
15 -14.6832 0.1500
16 72.8286 0.6500 1.90525 35.04
17 10.0353 3.6030 1.49700 81.61
18 -23.3847 D (18)
19 92.5254 5.1549 1.85478 24.80
20 -14.7070 0.8364 1.85135 40.10
21ASPH 15.8645 D (21)
22 -19.2912 0.8000 1.49700 81.61
23 103.3723 0.1500
24 29.3994 3.8368 1.60342 38.01
25 -71.9577 D (25)
26 0.0000 3.5600 1.51680 64.20
27 0.0000 1.0000

[Table 6]
Wide-angle intermediate telephoto
f 30.3973 37.4029 57.2229
Fno 4.0207 4.4021 5.5619
W 24.3518 20.1852 13.5450

[Table 7]
Wide-angle intermediate telephoto
D (10) 21.6346 13.6684 1.1000
D (18) 1.9911 2.2231 3.0250
D (21) 5.8516 5.5586 5.5740
D (25) 10.5000 13.9758 22.0540

[Table 8]
Surface number K A4 A6 A8 A10
5 -1.00000E + 00 3.16444E-05 -2.55840E-07 9.60504E-10
6 1.10196E + 00 1.92735E-05 -3.25232E-07 8.57182E-10
12 -8.39058E-01 1.26405E-08 2.90315E-07 -2.20897E-10 -6.11827E-12
13 8.67267E-01 6.27003E-05 3.10662E-07 -5.17925E-10
21 0.00000E + 00 2.77791E-05 -1.97028E-07 5.84657E-09 -1.06205E-10

(1) Optical Configuration of Zoom Lens FIG. 9 shows the lens configuration of the zoom lens of the third embodiment of the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of Example 3 includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 9 to 12 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 10 to 12 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 9]
Surface number RD Nd ABV
1ASPH 30.7652 1.3000 1.85135 40.10
2ASPH 13.4310 6.1372
3 116.6805 1.1000 1.90366 31.31
4 33.3493 0.3000
5 22.2064 3.6619 1.84666 23.78
6 150.8137 2.3612
7 -25.5712 0.8000 1.49700 81.61
8 -75.4261 D (8)
9STOP 0.0000 1.5000
10ASPH 14.6696 3.6605 1.58313 59.46
11ASPH -83.8000 3.2893
12 22.7815 0.6500 1.90366 31.31
13 9.5309 5.0570 1.49700 81.61
14 -17.3877 D (14)
15 272.5525 3.5674 1.90366 31.31
16 -8.7685 0.7000 1.85135 40.10
17ASPH 14.3382 D (17)
18 -12.1349 0.8000 1.49700 81.61
19 259.7001 0.1500
20 32.1025 5.1159 1.48749 70.44
21 -20.8039 D (21)
22 0.0000 3.5600 1.51680 64.20
23 0.0000 1.0000

[Table 10]
Wide-angle intermediate telephoto
f 18.5452 30.0017 53.3331
Fno 3.5704 4.2677 5.7338
W 38.3105 25.5570 14.7739

[Table 11]
Wide-angle intermediate telephoto
D (8) 28.3047 12.4399 1.1000
D (14) 1.9972 2.5641 3.4057
D (17) 4.4882 4.5051 4.9492
D (21) 10.5000 17.9396 32.4735

[Table 12]
Surface number K A4 A6 A8 A10
1 1.00000E + 00 9.00806E-07 3.33627E-08 -6.11915E-11 -4.91726E-14
2 -6.37073E-01 2.86583E-05 1.28732E-07 4.32501E-10 2.69315E-12
10 -6.84699E-01 3.92664E-06 -1.61411E-08 7.33736E-09 -1.27761E-10
11 1.00000E + 00 5.65666E-05 5.07996E-08 5.13741E-09 -1.31065E-10
17 0.00000E + 00 7.00805E-05 3.62899E-07 -7.75680E-10 -3.44972E-11

(1) Optical Configuration of Zoom Lens FIG. 13 shows the lens configuration of the zoom lens of the fourth embodiment according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of Example 4 includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 13 to 16 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 14 to 16 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 13]
Surface number RD Nd ABV
1ASPH 27.7946 1.3000 1.85135 40.10
2ASPH 12.7938 6.3351
3 898.2679 1.1000 1.90366 31.31
4 43.9533 0.3000
5 23.9993 3.4582 1.84666 23.78
6 326.4429 2.1221
7 -24.6780 0.8000 1.49700 81.61
8 -75.4261 D (8)
9STOP 0.0000 1.5000
10ASPH 15.5129 6.3391 1.58313 59.46
11ASPH -80.7335 1.5540
12 21.5568 0.6500 1.90366 31.31
13 10.0025 5.4392 1.49700 81.61
14 -15.5857 D (14)
15 -1595.3445 3.3993 1.90366 31.31
16 -9.0127 0.7000 1.85135 40.10
17ASPH 14.0142 D (17)
18 -12.0182 0.8000 1.49700 81.61
19 -19.5564 0.1500
20 -33.5367 1.0000 1.62041 60.34
21 128.9094 0.1500
22 32.3955 4.5256 1.51680 64.20
23 -27.1529 D (23)
24 0.0000 3.5600 1.51680 64.20
25 0.0000 1.0000

[Table 14]
Wide-angle intermediate telephoto
f 18.5451 30.0045 53.3400
Fno 3.6048 4.2940 5.7503
W 38.3084 25.5299 14.7931

[Table 15]
Wide-angle intermediate telephoto
D (8) 26.9097 11.7376 1.1000
D (14) 1.9977 2.4211 2.9317
D (17) 4.4104 4.4116 5.1764
D (23) 10.5000 18.3892 33.9123

[Table 16]
Surface number K A4 A6 A8 A10
1 3.89163E-01 -3.57105E-06 6.80585E-08 -2.49971E-10 4.22826E-13
2 -2.14434E-01 -1.31373E-06 4.58609E-08 4.08509E-10 -1.31445E-12
10 -8.29497E-01 -1.67924E-06 -4.43070E-08 2.21955E-09 -7.29102E-11
11 -9.12967E-01 6.87447E-05 4.94342E-08 4.52688E-10 -9.19049E-11
17 0.00000E + 00 5.48071E-05 4.31057E-07 -7.55733E-09 1.79733E-11

(1) Optical Configuration of Zoom Lens FIG. 17 shows the lens configuration of the zoom lens of Example 5 according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of Example 5 includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 17 to 20 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 17 to 20 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 17]
Surface number RD Nd ABV
1ASPH 32.4551 1.3000 1.85135 40.10
2ASPH 14.1446 6.0938
3 69.5786 1.1000 1.90366 31.31
4 28.6192 0.3000
5 21.1352 3.8223 1.84666 23.78
6 104.3321 2.6839
7 -24.9500 0.8000 1.49700 81.61
8 -75.4261 D (8)
9STOP 0.0000 1.5000
10ASPH 15.6093 4.6179 1.58313 59.46
11ASPH -88.9268 1.6387
12 22.8427 0.6500 1.90366 31.31
13 10.5111 5.3718 1.49700 81.61
14 -14.3709 D (14)
15 -4026.6611 3.5404 1.90366 31.31
16 -8.6183 0.7000 1.85135 40.10
17ASPH 13.6109 D (17)
18 -12.3968 0.8000 1.49700 81.61
19 72.1891 0.1500
20 31.6824 2.0755 1.49700 81.61
21 399.6726 0.1500
22 82.7803 3.4794 1.49700 81.61
23 -22.9201 D (23)
24 0.0000 3.5600 1.51680 64.20
25 0.0000 1.0000

[Table 18]
Wide-angle intermediate telephoto
f 18.5475 30.0028 53.3285
Fno 3.5106 4.1380 5.6863
W 38.3098 25.6276 14.8217

[Table 19]
Wide-angle intermediate telephoto
D (8) 27.8534 12.0446 1.1000
D (14) 1.9967 2.2712 2.5309
D (17) 4.3171 4.3914 4.9747
D (23) 10.5000 18.3736 34.6287

[Table 20]
Surface number K A4 A6 A8 A10
1 1.00000E + 00 2.27125E-07 9.47300E-08 -2.75903E-10 3.06117E-13
2 -2.05691E-01 5.03071E-06 1.15643E-07 4.26019E-10 7.16928E-13
10 -9.00982E-01 -3.79475E-06 -1.92094E-07 7.35737E-09 -2.00692E-10
11 -1.00000E + 00 7.10411E-05 8.69306E-08 3.47955E-09 -2.00612E-10
17 0.00000E + 00 8.24825E-05 5.99386E-07 -2.75720E-09 -4.12739E-12

(1) Optical Configuration of Zoom Lens FIG. 21 shows the lens configuration of the zoom lens of the sixth embodiment according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of Example 6 includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 21 to 24 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 22 to 24 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 21]
Surface number RD Nd ABV
1ASPH 26.1943 1.3000 1.85135 40.10
2ASPH 12.4196 6.4346
3 541.5568 1.1000 1.91082 35.25
4 41.0493 0.3000
5 23.2087 3.3402 1.84666 23.78
6 206.7894 2.7356
7 -22.4424 0.8000 1.49700 81.61
8 -75.4261 D (8)
9STOP 0.0000 1.5000
10ASPH 14.8328 4.2290 1.58313 59.46
11ASPH -67.5735 3.3986
12 26.9739 0.6500 1.90366 31.31
13 9.9105 6.1783 1.49700 81.61
14 -18.5175 D (14)
15 113.4654 3.6022 1.90366 31.31
16 -9.6048 0.7000 1.85135 40.10
17ASPH 15.6829 D (17)
18 -13.7085 0.8000 1.49700 81.61
19 902.0785 0.1500
20 32.1243 4.8153 1.48749 70.44
21 -26.3845 D (21)
22 0.0000 3.5600 1.51680 64.20
23 0.0000 1.0000

[Table 22]
Wide-angle intermediate telephoto
f 18.5414 29.9967 53.3413
Fno 3.6626 4.4089 5.7268
W 38.3161 25.6600 14.8010

[Table 23]
Wide-angle intermediate telephoto
D (8) 25.4015 11.5251 1.1000
D (14) 1.9990 3.0457 5.0971
D (17) 5.5059 5.0451 5.0700
D (21) 10.5000 18.5992 32.1392

[Table 24]
Surface number K A4 A6 A8 A10
1 1.00000E + 00 1.41767E-07 -2.47665E-08 5.01015E-11 1.72262E-13
2 -9.07102E-02 -1.27328E-06 -5.68344E-08 -1.43488E-10 -2.60341E-13
10 -6.74637E-01 3.97113E-06 1.54442E-07 1.38179E-09 -1.95114E-11
11 -1.00000E + 00 5.44635E-05 1.30005E-07 7.80457E-10 -2.44607E-11
17 0.00000E + 00 4.77862E-05 1.63370E-07 -7.71061E-10 -6.36119E-12

(1) Optical Configuration of Zoom Lens FIG. 25 shows the lens configuration of the zoom lens of the seventh embodiment according to the present invention in the wide-angle end state (WIDE), the intermediate focal length position state (MID), and the telephoto end state (TELE). .. In the figure, the trajectory of the movement of each lens group at the time of scaling is indicated by an arrow.

The zoom lens of Example 7 includes a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power in order from the object side. It is composed of a fourth lens group G4 having a negative refractive power. The specific lens configuration is as shown in FIG.

When scaling from the wide-angle end to the telephoto end, each lens group from the first lens group to the fourth lens group moves in the optical axis direction. Specifically, the first lens group G1 once moves to the image side and then moves to the object side, and the second lens group G2, the third lens group G3, and the fourth lens group G4 move to the object side, respectively. Scales from the wide-angle end to the telephoto end.

Further, by moving the third lens group G3 to the image side, the object at infinity is focused on the object at close range.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Tables 25 to 28 show the surface data of the zoom lens, the specifications of the zoom lens, the variable spacing on the optical axis of the zoom lens at the time of infinity focusing, and the aspherical coefficient of each aspherical surface. Further, Table 29 shows the numerical values of the above conditional expressions (1) to (8) of the optical system, and Table 30 shows the focal length of each lens group constituting the zoom lens. Further, FIGS. 26 to 28 show longitudinal aberrations at the wide-angle end, the intermediate focal length position, and the telephoto end of the zoom lens at infinity focusing.

[Table 25]
Surface number RD Nd ABV
1ASPH 24.4482 1.3000 1.85135 40.10
2ASPH 11.9836 6.3913
3 357.9398 1.1000 1.91082 35.25
4 38.4649 0.3000
5 22.6467 3.2695 1.84666 23.78
6 208.6969 2.3703
7 -20.9973 0.8000 1.49700 81.61
8 -75.4261 D (8)
9STOP 0.0000 1.5000
10ASPH 14.7763 4.4776 1.58313 59.46
11ASPH -61.6084 3.3681
12 29.1210 0.6500 1.90366 31.31
13 10.0630 6.3907 1.49700 81.61
14 -18.6731 D (14)
15 113.6097 3.5172 1.90366 31.31
16 -9.9117 0.7000 1.85135 40.10
17ASPH 16.7061 D (17)
18 -13.8736 0.8000 1.49700 81.61
19 386.4347 0.1500
20 34.0322 4.9099 1.48749 70.44
21 -25.0310 D (21)
22 0.0000 3.5600 1.51680 64.20
23 0.0000 1.0000

[Table 26]
Wide-angle intermediate telephoto
f 18.5411 29.9970 53.3434
Fno 3.6626 4.4089 5.7271
W 38.3179 25.6582 14.7772

[Table 27]
Wide-angle intermediate telephoto
D (8) 25.0912 11.5655 1.1000
D (14) 1.9991 3.2491 6.0746
D (17) 5.8552 5.3271 5.2002
D (21) 10.5000 18.6451 31.0705

[Table 28]
Surface number K A4 A6 A8 A10
1 1.00000E + 00 -8.43847E-06 4.79157E-08 -3.98054E-10 1.47201E-12
2 -4.40134E-02 -1.57075E-05 -2.48918E-08 -5.59461E-10 -2.48948E-12
10 -6.73795E-01 4.52180E-06 1.87648E-07 4.50753E-10 3.00784E-12
11 -9.99876E-01 5.63719E-05 1.47794E-07 1.86609E-10 2.35236E-14
17 0.00000E + 00 4.30328E-05 9.77008E-08 8.71723E-10 -1.98188E-11

[Table 29]
Example 1 Example 2 Example 3 Example 4 Example 4 Example 5 Example 6 Example 7
(1) | (1-β3t ² ) × β4t ² | 4.90 4.89 8.99 11.54 11.99 6.49 5.63
(2) f3 / f1 0.68 0.50 0.70 0.64 0.59 1.00 1.12
(3) β3t 2.12 2.30 2.78 3.08 3.09 2.46 2.32
(4) f2 / | f1 | 0.47 0.42 0.56 0.55 0.50 0.70 0.74
(5) f4 / f1 7.94 21.30 34.69 27.47 27.42 37.78 39.13
(6) | f3 | / f2 1.46 1.20 1.24 1.16 1.18 1.43 1.52
(7) nd_max 1.91 1.91 1.90 1.90 1.90 1.91 1.91
(8) R4n / f4n 0.59 0.59 0.52 0.18 0.58 0.50 0.52

[Table 30]
Example 1 Example 2 Example 3 Example 4 Example 4 Example 5 Example 6 Example 7
f1 -40.18 -46.96 -28.83 -28.18 -29.95 -25.08 -24.21
f2 18.69 19.56 16.27 15.49 14.97 17.58 17.87
f3 -27.21 -23.48 -20.18 -18.04 -17.67 -25.08 -27.17
f4 -318.91 -1000.00 -1000.00 -774.20 -821.20 -947.60 -947.60

According to the present invention, it is possible to provide a zoom lens and an image pickup device which are small in size and have high performance.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group

Claims (12)

From the object side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, the third lens group having a negative refractive power, and the fourth lens having a negative refractive power. It is a zoom lens that is substantially composed of a group and each lens group moves in the optical axis direction so that the distance between adjacent lens groups changes at the time of scaling.
The fourth lens group includes at least one positive lens and one negative lens, respectively.
A zoom lens characterized by satisfying the following conditions.
0.40 ≤ f3 / f1 ≤ 1.15 ... (2)
However,
f1: Focal length of the first lens group f3: Focal length of the third lens group The zoom lens according to claim 1, wherein the third lens group is moved along the optical axis to focus. The zoom lens according to claim 2, which satisfies the following conditions.
3.00 ≤ | (1-β _3t ² ) x β _4t ² | ≤ 15.00 ... (1)
However,
β _3t : Lateral magnification of the third lens group at infinity _{at the telephoto end β 4t} : Lateral magnification of the fourth lens group at infinity at the telephoto end The zoom lens according to any one of claims 1 to 3, which satisfies the following conditions.
1.50 ≤ β _3t ≤ 3.50 ・ ・ ・ (3)
However,
β _3t : Lateral magnification at infinity focusing of the third lens group at the telephoto end The zoom lens according to any one of claims 1 to 4, which satisfies the following conditions.
0.30 ≤ f2 / | f1 | ≤ 0.90 ... (4)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group The zoom lens according to any one of claims 1 to 5, which satisfies the following conditions.
3.00 ≤ f4 / f1 ≤ 500.00 ... (5)
However,
f1: Focal length of the first lens group f4: Focal length of the fourth lens group The zoom lens according to any one of claims 1 to 6, which satisfies the following conditions.
0.80 ≤ | f3 | / f2 ≤ 2.00 ... (6)
However,
f2: Focal length of the second lens group f3: Focal length of the third lens group The zoom lens according to any one of claims 1 to 7, which satisfies the following conditions.
nd_max ≧ 1.85 ・ ・ ・ (7)
However,
nd_max: Refractive index of a lens made of a glass material having the highest refractive index among the lenses constituting the zoom lens with respect to the d line. The zoom lens according to any one of claims 1 to 8, which satisfies the following conditions.
0.08 ≤ R4n / f4n ≤ 1.00 ... (8)
However,
R4n: Radius of curvature of the object side surface of the negative lens arranged on the object side most among the negative lenses included in the fourth lens group f4n: Arranged on the object side most among the negative lenses included in the fourth lens group Focal length of negative lens The zoom lens according to any one of claims 1 to 9, wherein the second lens group includes at least two positive lenses. The zoom lens according to any one of claims 1 to 10, wherein the third lens group includes at least one positive lens and at least one negative lens. An image pickup apparatus comprising the zoom lens according to any one of claims 1 to 11 and an image pickup element that receives an optical image formed by the zoom lens and converts it into an electrical image signal. ..

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