JP6826941B2 - Zoom lens and imaging device - Google Patents

Description

The present invention relates to a zoom lens suitable as an imaging optical system such as a film camera, a video camera, and a digital still camera, and an imaging device provided with the zoom lens.

Image pickup devices using solid-state image sensors such as digital cameras and video cameras have become widespread. Further, in recent years, with the miniaturization of the optical system in the lens interchangeable system, the market for interchangeable lens image pickup devices such as single-lens reflex cameras (hereinafter referred to as single-lens reflex cameras) and mirrorless single-lens cameras has expanded remarkably, and a wide range of users. Has come to use interchangeable lens image pickup devices. With the expansion of the user base, in the lens interchangeable system, not only high performance and miniaturization of the optical system but also cost reduction are required.

Under such circumstances, for example, Patent Document 1 describes a zoom lens that achieves good optical performance by using a glass lens having positive anomalous dispersibility as the positive lens constituting the first lens group. Proposed.

Japanese Patent No. 4678194

However, the glass material having the above-mentioned anomalous dispersibility is expensive and has low processability. In the optical system of a zoom lens, the lens constituting the first lens group generally has a larger outer diameter than the lens constituting the other lens group. Therefore, when the positive lens constituting the first lens group is made of a glass material having the above-mentioned anomalous dispersibility like the zoom lens described in Patent Document 1, it is difficult to reduce the cost of the zoom lens. It was.

Therefore, an object of the present invention is to provide a zoom lens capable of achieving high performance and low cost, and an imaging device provided with the zoom lens.

In order to solve the above problems, the zoom lens according to the present invention includes a first lens group having a positive refractive force, a second lens group having a negative refractive force, and at least one lens group in order from the object side. The first lens group is provided with an aperture aperture after the first lens group, and the first lens group is provided with the following conditional expression (1) and conditional expression. When (2) is satisfied and the lens group having a positive refractive power included in the rear group is the i-th lens group (however, i is a natural number of 3 or more), at least one of the i-lens groups. Is characterized by including at least one negative lens Gni that satisfies the following conditional expression (3) and also satisfies the following conditional expression (4) and the following conditional expression (5).

(1) 1.45 <Ndp1ave <1.65
(2) 50.00 <Vdp1ave <71.00
(3) 0.50 <Hi_t / Hstop_t <1.60
(4) 1.79 <Ndni <2.10
(5) 26.00 <Vdni <37.00
However,
Ndp1ave: Average value of the refractive index of the positive lens included in the first lens group with respect to the d line Vdp1ave: Average value of the number of abbes with respect to the d line of the positive lens included in the first lens group Hi_t: Telescopic end of the zoom lens Hstop_t: Maximum height from the optical axis when the axial light beam passes through the surface of the i-th lens group on the most object side: When the axial light beam passes through the aperture aperture at the telephoto end of the zoom lens. Maximum height from the optical axis Ndni: Refractive coefficient of the negative lens Gni included in the i-lens group with respect to the d-line Vdni: Abbe number of the negative lens Gni included in the i-lens group with respect to the d-line.

In order to solve the above problems, the image pickup device according to the present invention includes the zoom lens and an image pickup device provided on the image side of the zoom lens to convert an optical image formed by the zoom lens into an electrical signal. It is characterized by having and.

According to the present invention, it is possible to provide a zoom lens capable of achieving high performance and low cost, and an imaging device provided with the zoom lens.

It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 1 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of Example 1. It is a spherical aberration diagram, astigmatism diagram and distortion diagram at the time of infinity focusing at the intermediate focal length of the zoom lens of Example 1. 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 1. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 2 of this invention. It is a spherical aberration diagram, astigmatism diagram, and 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, astigmatism diagram, and distortion diagram at the time of infinity focusing at the intermediate focal length of the zoom lens of the second 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 second embodiment. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 3 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of the third embodiment. It is a spherical aberration diagram, astigmatism diagram and distortion diagram at the time of infinity focusing at the intermediate focal length 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 structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 4 of this invention. It is a spherical aberration diagram, astigmatism diagram, and 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 of the zoom lens of Example 4. 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 4. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 5 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of Example 5. It is a spherical aberration diagram, astigmatism diagram and distortion diagram at the time of infinity focusing at the intermediate focal length of the zoom lens of Example 5. 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. It is sectional drawing which shows the lens structure example at the time of infinity focusing at the wide-angle end of the zoom lens of Example 6 of this invention. It is a spherical aberration diagram, astigmatism diagram, and distortion diagram at the time of infinity focusing at the wide-angle end of the zoom lens of Example 6. It is a spherical aberration diagram, astigmatism diagram and distortion diagram at the time of infinity focusing at the intermediate focal length of the zoom lens of Example 6. 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 6.

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

1. 1. Zoom lens 1-1. 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 includes a first lens group having a positive refractive force, a second lens group having a negative refractive force, and a rear group including at least one lens group in order from the object side. , The magnification is changed by changing the distance between each lens group, the first lens group and subsequent lens groups are provided with an aperture aperture, and the first lens group satisfies the condition formulas (1) and (2) described later, and is used as the rear group. When the included lens group having a positive refractive power is the i-th lens group (however, i is a natural number of 3 or more), at least one of the i-th lens groups satisfies the conditional expression (3) described later. Moreover, it is characterized by including at least one negative lens Gni satisfying the conditional formula (4) and the conditional formula (5) described later. Hereinafter, matters relating to the configuration of the zoom lens will be described first, and then matters relating to the conditional expression will be described.

(1) Lens group configuration The specific lens group configuration of the zoom lens is not particularly limited as long as the above configuration and the like are satisfied. For example, the number of lens groups included in the rear group may be one or two or more. If the number of lens groups constituting the zoom lens is large, it is advantageous to realize a high magnification ratio and high optical performance. However, when the number of lens groups constituting the zoom lens is large, it becomes difficult to reduce the size, weight, and cost of the zoom lens. In addition, a moving mechanism for moving the lens group along the optical axis at the time of scaling becomes complicated. Therefore, from the viewpoint of miniaturization and cost reduction by simplifying the configuration of the zoom lens, the number of lens groups included in the rear group is preferably two or less, and is preferably one. More preferred. By reducing the number of lens groups included in the rear group to two or less, more preferably one, the zoom lens can be made smaller and lighter, and a moving mechanism for moving the lens group can be maintained while maintaining sufficient optical performance. It becomes easier to realize cost reduction by simplifying such as. Here, the rear group may have a positive refractive power as a whole or a negative refractive power, but it is preferable that the rear group has a positive refractive power. In the telephoto zoom lens as shown in this embodiment, the combined focal lengths of the first lens group and the second lens group have a negative value at the wide-angle end. In order to form a subject image on the image plane, it is necessary to arrange a positive refractive power in the rear group. Therefore, in the telephoto zoom lens as in this embodiment, it is preferable that the rear group has a positive refractive power as a whole.

(2) I-th lens group In the present invention, the rear group includes the i-th lens group. As described above, the i-th lens group is a lens group having a positive refractive power included in the rear group. It is preferable that the third lens group arranged on the object side of the second lens group is a lens group having a positive refractive power, and the third lens group is the i-th lens group referred to in the present invention. However, the i-th lens group does not necessarily have to be the third lens group. That is, it is sufficient that the i-th lens group having the negative lens Gni satisfying the conditional equation (3) and satisfying the conditional equations (4) and (5) is arranged in the rear group, and the third lens group is negatively refracted. Similarly, the effect of the present invention can be obtained when a lens group having a force is used and a lens group having a positive refractive power (i-th lens group) is arranged on the image side of the third lens group. When the rear group includes two or more i-th lens groups, at least one of the i-th lens groups satisfies the conditional expression (3) and the negative lens Gni satisfying the conditional expressions (4) and (5). A plurality of i-th lens groups may satisfy each of the above conditional expressions. The number of the i-th lens groups included in the rear group is preferably two or less, and preferably one, for the same reason as described above.

Among the i-th lens groups, the lens group satisfying the conditional expression (3) described later includes at least one negative lens Gni, and the conditional expression (9) and the conditional expression (10) described later are on the object side of the negative lens Gni. It is preferable to include a positive lens Gpi that satisfies the above conditions. The negative lens Gni and the positive lens Gpi will be described later together with the matters related to the conditional expression.

(3) Aperture diaphragm The zoom lens includes an aperture diaphragm after the first lens group. Here, the provision of the aperture diaphragm after the first lens group means that the aperture diaphragm is arranged in the first lens group or on the image side of the first lens group. The position of the aperture diaphragm in the optical system of the zoom lens is not particularly limited as long as the conditional expression (3) described later is satisfied in relation to the i-th lens group. For example, in the examples described later, an example in which the aperture diaphragm is arranged on the object side of the i-th lens group or in the i-th lens group is given, but in the zoom lens according to the present invention, the aperture diaphragm is an image of the first lens group. It can be appropriately arranged at an appropriate position depending on the size of the image pickup element, the angle of view range of the zoom lens, and the like, such as the side and the image side of the second lens group.

1-2. Conditional expression Next, the conditions that the zoom lens should satisfy or the conditions that are preferable to satisfy will be described.

In the zoom lens, as described above, the first lens group satisfies the following conditional expression (1) and the following conditional expression (2), and at least one of the i-th lens groups satisfies the following conditional expression (3). The i-th lens group is characterized by including at least one negative lens Gni that satisfies the following conditional equations (4) and (5).

(1) 1.45 <Ndp1ave <1.65
(2) 50.00 <Vdp1ave <71.00
(3) 0.50 <Hi_t / Hstop_t <1.60
(4) 1.79 <Ndni <2.10
(5) 26.00 <Vdni <37.00

However,
Ndp1ave: Average value of the refractive index of the positive lens included in the first lens group with respect to the d line Vdp1ave: Average value of the number of abbes with respect to the d line of the positive lens included in the first lens group Hi_t: At the telephoto end of the zoom lens Maximum height from the optical axis when the axial light beam passes through the surface of the i-th lens group on the most object side Hstop_t: The optical axis when the axial light beam passes through the aperture aperture at the telephoto end of the zoom lens. Maximum height from Ndni: Refractive coefficient of negative lens Gni included in the i-th lens group with respect to d-line Vdni: Abbe number of negative lens Gni included in i-th lens group with respect to d-line

1-2-1. Conditional expression (1)
The conditional expression (1) defines the average value of the refractive index of the positive lens included in the first lens group with respect to the d-line. Since the first lens group has a positive refractive power, it includes at least one positive lens. Ndp1ave in the conditional expression (1) is a value obtained by dividing the total refractive index of each positive lens included in the first lens group with respect to the d line by the total number of positive lenses included in the first lens group. By satisfying the conditional expression (1), the average value of the refractive indexes of the positive lenses included in the first lens group with respect to the d-line is within an appropriate range. That is, the positive refractive power arranged in the first lens group is within an appropriate range, the aberration generated in the first lens group can be reduced, and the aberration can be satisfactorily corrected with a small number of lenses. .. Therefore, aberration correction can be performed satisfactorily over the entire zoom range, and a compact and high-performance zoom lens can be realized.

On the other hand, when the numerical value of the conditional expression (1) exceeds the upper limit value, the average value of the refractive indexes of the positive lenses included in the first lens group is larger than the appropriate range, and the positive lens group is arranged in the first lens group. The refractive power of the lens becomes stronger. Therefore, in order to cancel the spherical aberration and coma aberration generated in the first lens group, it is necessary to increase the negative refractive power arranged after the second lens group. Further, in this case, in order to ensure good optical performance over the entire zoom range, the number of lenses required for aberration correction increases, and it becomes difficult to configure the zoom lens with a small number of lenses. It becomes difficult to reduce the cost. Further, as the number of lenses constituting each lens group increases, each lens group becomes heavier, so that the load on the drive mechanism for moving each lens group at the time of scaling increases, and the drive mechanism itself also becomes larger. Therefore, it is difficult to reduce the size and cost of the entire zoom lens unit, which is not preferable.

On the other hand, when the numerical value of the conditional expression (1) becomes equal to or less than the lower limit value, the average value of the refractive indexes of the positive lenses included in the first lens group is smaller than the appropriate range, and the positive refractive power arranged in the first lens group Becomes smaller. Therefore, when trying to achieve a predetermined zoom ratio, the amount of movement of each lens group increases, and it becomes difficult to reduce the size of the zoom lens at the telephoto end. Further, in a zoom lens, one or more inner cylinders are generally housed in a lens barrel (outermost cylinder) in a nested manner. The inner cylinder is extended to the object side according to the variable magnification. When the difference in the total optical length between the wide-angle end and the telephoto end becomes large, a plurality of inner cylinders are accommodated in the outermost cylinder in order to shorten the total length of the lens barrel when the inner cylinder is accommodated. In that case, the outer diameter of the lens barrel becomes larger by the thickness of the inner cylinder, and the cam mechanism for feeding out the inner cylinder becomes complicated. For these reasons, it is difficult to reduce the size and cost of the entire zoom lens unit, which is not preferable.

In order to obtain these effects, the lower limit of the conditional expression (1) is preferably 1.46. The upper limit of the conditional expression (1) is preferably 1.60, more preferably 1.56, and even more preferably 1.52. Regarding these preferable numerical values, the inequality sign described in the conditional expression (1) may be replaced with an inequality sign with an equal sign. The same applies to other conditional expressions described later.

1-2-2. Conditional expression (2)
The conditional expression (2) defines the average value of the Abbe numbers with respect to the d-line of the positive lens included in the first lens group. Vdp1ave in the conditional expression (2) is a value obtained by dividing the sum of the Abbe numbers for the d-line of each positive lens included in the first lens group by the total number of positive lenses included in the first lens group. By satisfying the conditional expression (2), the average value of the Abbe numbers with respect to the d-line of the positive lens included in the first lens group is within an appropriate range. Therefore, axial chromatic aberration and chromatic aberration of magnification can be satisfactorily corrected with a small number of lenses, and a compact zoom lens having good chromatic aberration over the entire zoom range can be realized.

On the other hand, when the numerical value of the conditional expression (2) exceeds the upper limit value, the average value of the Abbe numbers of the positive lenses included in the first lens group is larger than the appropriate range, and the conditional expression (2) is satisfied. In comparison with the above, the positive lens included in the first lens group includes a positive lens made of a low-dispersion glass material or a positive lens made of a glass material having anomalous dispersibility. A low-dispersion glass material and a glass material having anomalous dispersibility are generally more expensive than other glass materials. Further, the glass material having anomalous dispersibility has low processability. Therefore, it is difficult to reduce the cost of the zoom lens because the glass material cost and the processing cost are required.

On the other hand, when the numerical value of the conditional expression (2) is equal to or less than the lower limit value, the average value of the Abbe numbers of the positive lenses included in the first lens group is smaller than the appropriate range, which is compared with the case where the conditional expression (2) is satisfied. Therefore, the positive lens included in the first lens group includes a positive lens made of a highly dispersed glass material. In that case, it becomes difficult to correct the axial chromatic aberration and the chromatic aberration of magnification generated in the first lens group, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

In order to obtain these effects, the lower limit of the conditional expression (2) is preferably 55.00, more preferably 60.00.

1-2-3. Conditional expression (3)
Conditional expression (3) is the maximum height from the optical axis when the axial light beam passes through the most object-side surface of the i-lens group with respect to the i-lens group at the telephoto end of the zoom lens, and on the axis. Specifies the ratio of the light beam to the maximum height from the optical axis as it passes through the aperture stop. By satisfying the conditional expression (3), the height of the outermost light beam of the axial light beam when passing through the surface of the i-th lens group on the most object side becomes within an appropriate range, and the i-th lens group It is possible to suppress the occurrence of spherical aberration and coma aberration in the lens. Therefore, it becomes easy to realize a high-performance zoom lens with a small number of lenses, and it is possible to reduce the size and cost of the zoom lens.

On the other hand, when the numerical value of the conditional expression (3) exceeds the upper limit value, the height of the outermost light beam of the axial luminous flux when passing through the surface of the i-th lens group on the most object side exceeds the appropriate range. Will be expensive. In this case, spherical aberration and coma generated in the i-th lens group become large, and the number of lenses required for aberration correction increases, so that it becomes difficult to reduce the size and cost of the zoom lens.

On the other hand, when the numerical value of the conditional expression (3) is equal to or less than the lower limit value, the height of the maximum light beam of the axial luminous flux when passing through the surface of the i-th lens group on the most object side becomes lower than the appropriate range. In this case, the height of the outermost light beam of the axial light beam passing through the negative lens Gni included in the i-th lens group from the optical axis becomes low, and the correction effect of chromatic aberration by the negative lens Gni becomes weak. Chromatic aberration is insufficiently corrected when viewed with the entire lens system. Therefore, it becomes difficult to realize high optical performance over the entire zoom range.

In order to obtain these effects, the lower limit of the conditional expression (3) is preferably 0.75, more preferably 0.85. Further, the upper limit value is preferably 1.40, more preferably 1.30, and further preferably 1.20 (this is referred to as conditional expression (3-1)) .

1-2-4. Conditional expression (4)
The conditional expression (4) defines the refractive index of the negative lens Gni included in the i-th lens group with respect to the d-line. When the conditional equation (4) is satisfied, spherical aberration and coma aberration generated by the negative lens Gni can be suppressed, so that these aberrations can be easily corrected with a small number of lenses. Therefore, a compact zoom lens with high performance over the entire zoom range can be realized at low cost.

On the other hand, when the numerical value of the conditional expression (4) becomes equal to or higher than the upper limit value, the refractive index of the negative lens Gni with respect to the d line is larger than the appropriate range, and the spherical aberration and coma aberration generated by the negative lens Gni are large. Become. Therefore, it becomes difficult to correct these aberrations with a small number of lenses, and it becomes difficult to realize a high-performance compact zoom lens over the entire zoom range at low cost.

On the other hand, when the numerical value of the conditional expression (4) becomes less than the lower limit value, the refractive index of the negative lens Gni with respect to the d line becomes smaller than the appropriate range, and spherical aberration generated in the positive lens included in the i-th lens group or It becomes difficult to cancel the coma aberration with the negative lens Gni, and the correction becomes insufficient. Therefore, it becomes difficult to realize a high-performance compact zoom lens over the entire zoom range at low cost with a small number of lenses.

In order to obtain these effects, the lower limit of the conditional expression (4) is preferably 1.82 (this is referred to as the conditional expression (4-1)), and more preferably 1.86. .. The upper limit is preferably 1.99, more preferably 1.95.

1-2-5. Conditional expression (5)
The conditional expression (5) defines the Abbe number of the negative lens Gni included in the i-th lens group with respect to the d-line. When the conditional expression (5) is satisfied, axial chromatic aberration and chromatic aberration of magnification generated in the positive lens included in the i-th lens group can be satisfactorily corrected, and a compact zoom lens having good chromatic aberration over the entire zoom range is realized. can do.

On the other hand, when the numerical value of the conditional expression (5) becomes equal to or larger than the upper limit value, the Abbe number of the negative lens Gni is larger than the appropriate range, and the negative lens is compared with the case where the conditional expression (5) is satisfied. Gni means that it is composed of a low-dispersion glass material. In this case, the axial chromatic aberration and the chromatic aberration of magnification generated by the positive lens included in the i-th lens group are insufficiently corrected, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

On the other hand, when the numerical value of the conditional expression (5) is equal to or less than the lower limit value, the Abbe number of the negative lens Gni is smaller than the appropriate range, and the negative lens Gni is higher than the case where the conditional expression (5) is satisfied. It means that it consists of dispersed glass material. In that case, the axial chromatic aberration and the magnification chromatic aberration generated in the first lens group are overcorrected, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

In order to obtain these effects, the lower limit of the conditional expression (5) is preferably 28.00, more preferably 30.00. The upper limit is more preferably 35.00.

In the zoom lens, the i-th lens group includes at least one negative lens Gni that satisfies the above conditional expression (4) and conditional expression (5). The i-th lens group may include a plurality of negative lenses Gni, but one negative lens Gni is sufficient for reducing the size and cost of the zoom lens.

1-2-6. Conditional expression (6) and conditional expression (7)
In the zoom lens, the first lens group preferably includes at least one negative lens satisfying the following conditional equations (6) and (7).

(6) 1.70 <Ndn1 <2.10
(7) 15.00 <Vdn1 <37.00
However,
Ndn1: Refractive index of the negative lens included in the first lens group with respect to the d-line Vdn1: Abbe number of the negative lens included in the first lens group with respect to the d-line

The conditional expression (6) defines the refractive index of the negative lens included in the first lens group with respect to the d-line. When the first lens group includes a negative lens satisfying the conditional equation (6), the negative lens can satisfactorily correct spherical aberration and coma generated by the positive lens included in the first lens group. Therefore, a compact zoom lens with high performance over the entire zoom range can be realized at low cost.

On the other hand, when the numerical value of the conditional expression (6) becomes equal to or more than the upper limit value, the refractive index of the negative lens becomes larger than the appropriate range, so that spherical aberration and coma aberration generated in the negative lens become large. Therefore, the correction by the negative lens is overcorrection for the spherical aberration and the coma aberration generated in the positive lens included in the first lens group. On the other hand, when the numerical value of the conditional expression (6) is equal to or less than the lower limit value, the refractive index of the negative lens becomes smaller than the appropriate range, so that spherical aberration and coma aberration generated in the negative lens become smaller. Therefore, the correction by the negative lens is insufficient for the spherical aberration and the coma aberration generated in the positive lens included in the first lens group. From these facts, if the numerical value of the conditional expression (6) is out of the range, it becomes difficult to realize good optical performance in the entire zoom range, and at the same time, the size and cost of the zoom lens should be reduced. Becomes difficult.

In order to obtain these effects, the lower limit of the conditional expression (6) is more preferably 1.72 and even more preferably 1.75. Further, the upper limit value is more preferably 1.99, and even more preferably 1.95.

Next, the conditional expression (7) will be described. The conditional expression (7) defines the Abbe number for the d-line of the negative lens included in the first lens group. When the first lens group includes a negative lens satisfying the conditional expression (7), the negative lens can satisfactorily correct axial chromatic aberration and lateral chromatic aberration generated by the positive lens included in the first lens group. A zoom lens with good chromatic aberration can be realized over the entire zoom range.

On the other hand, when the numerical value of the conditional expression (7) becomes equal to or larger than the upper limit value, the Abbe number of the negative lens is larger than the appropriate range, and the negative lens becomes larger than the case where the conditional expression (7) is satisfied. It means that it is made of low-dispersion glass material. In this case, the axial chromatic aberration and the chromatic aberration of magnification generated by the positive lens included in the first lens group are insufficiently corrected, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

On the other hand, when the numerical value of the conditional expression (7) is equal to or less than the lower limit value, the Abbe number of the negative lens is smaller than the appropriate range, and the negative lens has a higher dispersion than the case where the conditional expression (7) is satisfied. It means that it is made of glass material. In that case, the axial chromatic aberration and the magnification chromatic aberration generated in the first lens group are overcorrected, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

In order to obtain these effects, the lower limit of the conditional expression (7) is more preferably 20.00 and even more preferably 25.00. Further, the upper limit value is more preferably 35.00.

In the zoom lens, the first lens group includes at least one negative lens satisfying the above conditional equation (6) and conditional equation (7). The first lens group may include a plurality of negative lenses of the conditional expression (6) and the conditional expression (7), but in order to reduce the size and cost of the zoom lens, one negative lens may be used. Is enough.

1-2-7. Conditional expression (8)
The zoom lens preferably satisfies the following conditional expression (8).

(8) 0.10 <f1 / ft <1.00
However,
f1: Focal length of the first lens group ft: Focal length of the entire zoom lens system at the telephoto end

Conditional expression (8) defines the ratio between the focal length of the first lens group and the focal length of the entire zoom lens system at the telephoto end. By satisfying the conditional expression (8), the focal length of the first lens group with respect to the focal length of the entire zoom lens system at the telephoto end becomes within an appropriate range, the optical performance becomes better, and at the same time, the zoom It becomes easier to reduce the size and cost of the lens.

On the other hand, when the numerical value of the conditional expression (8) becomes equal to or more than the upper limit value, the focal length of the first lens group with respect to the focal length of the entire zoom lens system at the telephoto end becomes longer than an appropriate range, and the first The refractive power of the lens group becomes weak. In this case, when trying to achieve a predetermined zoom ratio, the amount of movement of each lens group at the time of scaling increases. Therefore, it becomes difficult to reduce the size of the zoom lens at the telephoto end. Further, if the difference in the total optical length between the wide-angle end and the telephoto end becomes large, it becomes difficult to reduce the size and cost of the entire zoom lens unit for the same reason as described above, which is not preferable.

On the other hand, when the numerical value of the conditional expression (8) becomes less than the lower limit value, the focal length of the first lens group with respect to the focal length of the entire zoom lens system at the telephoto end becomes shorter than the appropriate range, and the refraction of the first lens group The power becomes stronger. In this case, in order to cancel the spherical aberration and coma aberration generated in the first lens group, it is necessary to increase the refractive power arranged after the second lens group. Further, in this case, in order to ensure good optical performance over the entire zoom range, the number of lenses required for aberration correction increases, and it becomes difficult to configure the zoom lens with a small number of lenses. It becomes difficult to reduce the cost.

In order to obtain these effects, the lower limit of the conditional expression (8) is more preferably 0.20 and even more preferably 0.30. The upper limit is more preferably 0.70, and even more preferably 0.60.

1-2-8. Conditional expression (9) and conditional expression (10)
In the zoom lens, it is preferable that a positive lens Gpi satisfying the following conditional equations (9) and (10) is arranged adjacent to the object side of the negative lens Gni included in the i-th lens group.

(9) 1.45 <Ndpi <1.75
(10) 50.00 <Vdpi <80.00
However,
Ndpi: Refractive index of the positive lens Gpi with respect to the d-line Vdpi: Abbe number of the positive lens Gpi with respect to the d-line

The conditional expression (9) defines the refractive index of the positive lens Gpi with respect to the d-line. By satisfying the conditional expression (9), the refractive index of the positive lens Gpi with respect to the d-line is within an appropriate range, spherical aberration and coma generated by the positive lens Gpi can be suppressed, and a small number of lenses can be used. Aberration correction can be performed satisfactorily. Therefore, aberration correction can be performed satisfactorily over the entire zoom range, and a compact and high-performance zoom lens can be realized.

On the other hand, when the numerical value of the conditional expression (9) becomes equal to or more than the upper limit value, the refractive index of the positive lens Gpi is larger than the appropriate range, and the refractive power of the positive lens Gpi becomes stronger. Therefore, in order to cancel the spherical aberration and coma generated by the positive lens Gpi, it is necessary to arrange a negative lens having a strong refractive power, and in order to secure good optical performance over the entire zoom range, the aberration correction Since the number of lenses required for this is large and it becomes difficult to configure the zoom lens with a small number of lenses, it becomes difficult to reduce the cost of the zoom lens.

On the other hand, when the numerical value of the conditional expression (9) is equal to or less than the lower limit value, the refractive index of the positive lens Gpi becomes smaller than the appropriate range, and the refractive power of the positive lens Gpi becomes smaller. Therefore, when trying to achieve a predetermined zoom ratio, the amount of movement of the i-th lens group increases. Therefore, it becomes difficult to reduce the size of the zoom lens at the telephoto end. Further, if the difference in the total optical length between the wide-angle end and the telephoto end becomes large, it becomes difficult to reduce the size and cost of the entire zoom lens unit for the same reason as described above, which is not preferable.

In order to obtain these effects, the lower limit value is more preferably 1.47 in the conditional expression (9). The upper limit is more preferably 1.72, further preferably 1.69, further preferably 1.61, and even more preferably 1.57.

Next, the conditional expression (10) will be described. The conditional expression (10) defines the Abbe number for the d-line of the positive lens Gpi. By satisfying the conditional expression (10), the Abbe number of the positive lens Gpi is within an appropriate range, axial chromatic aberration and chromatic aberration of magnification can be satisfactorily corrected with a small number of lenses, and chromatic aberration is good over the entire zoom range. It is possible to realize a compact zoom lens.

On the other hand, when the numerical value of the conditional expression (10) becomes equal to or larger than the upper limit value, the Abbe number of the positive lens Gpi is larger than the appropriate range, and the positive lens Gpi is compared with the case where the conditional expression (10) is satisfied. Means that it is made of a low-dispersion glass material or a glass material having anomalous dispersibility. Therefore, for the same reason as described above, the glass material cost and the processing cost are required, and it becomes difficult to reduce the cost of the zoom lens.

On the other hand, when the numerical value of the conditional expression (10) is equal to or less than the lower limit value, the Abbe number of the positive lens Gpi is smaller than the appropriate range, and the positive lens Gpi is higher than the case where the conditional expression (10) is satisfied. It means that it consists of dispersed glass material. In that case, it becomes difficult to correct the axial chromatic aberration and the chromatic aberration of magnification generated by the positive lens Gpi, and it becomes difficult to realize a zoom lens having good chromatic aberration over the entire zoom range.

In order to obtain these effects, the lower limit of the conditional expression (10) is more preferably 55.00, further preferably 60.0, and even more preferably 63.00. Further, the upper limit value is more preferably 75.00.

Here, with respect to the negative lens Gni included in the i-th lens, the positive lens Gpi may be arranged on the object side, and the presence or absence of an air gap between the negative lens Gni and the positive lens Gpi is particularly limited. It's not something. However, it is more preferable that the positive lens Gpi and the negative lens Gni are bonded and included in the i-th lens group as a bonded lens composed of the positive lens Gpi and the negative lens Gni. By arranging the positive lens Gpi and the negative lens Gni without air spacing, it is possible to suppress the occurrence of eccentric coma caused by assembly errors, and realize good optical performance with reduced manufacturing errors. It will be easier to do.

1-2-9. Conditional expression (11)
When the lens group after the second lens group is the j-th lens group (where j is a natural number of 2 or more) in the zoom lens, it is preferable that each j-lens group satisfies the following equation.

(11) 1.00 ≤ Bj_t / Bj_w ≤ 50.0
Bj_t: Lateral magnification of the j-th lens group at the telephoto end of the zoom lens Bj_w: Lateral magnification of the j-th lens group at the wide-angle end of the zoom lens

Conditional expression (11) shows the rate of change in the lateral magnification of each lens group when the magnification is changed from the wide-angle end to the telephoto end for each lens group arranged after the second lens group in the zoom lens. At this time, the j-th lens group indicates each lens group from the second lens group to the final lens group. For example, when the zoom lens has a three-group configuration of a first lens group to a third lens group, the j lens group corresponds to each of the second lens group and the third lens group. Therefore, when the zoom lens has a three-group configuration, the second lens is the second lens when the lateral magnification of the second lens group at the telephoto end is B2_t and the lateral magnification of the second lens group at the wide-angle end of the zoom lens is B2_w. The value of B2_t / B2_w indicating the rate of change in the lateral magnification of the group satisfies the above conditional expression (11). Further, in the case of the third lens group as well, when the lateral magnification of the third lens group at the telephoto end of the zoom lens is B3_t and the lateral magnification of the third lens group at the wide angle end of the zoom lens is B3_w, the third lens group is obtained. The value of B3_t / B3_w, which indicates the rate of change in the lateral magnification of the three lens groups, also satisfies the above conditional expression (11). Similarly, when the zoom lens includes the fourth lens group, the fifth lens group, and the like, the values of Bj_t / Bj_w indicating the rate of change in the lateral magnification of each lens group are the above-mentioned conditional expressions (11). ) Is satisfied.

When the numerical value of the conditional expression (11) for each lens group after the second lens group included in the zoom lens is within the above range, the rate of change in lateral magnification is in each lens group after the second lens group. Since it is 1 or more, the lateral magnification is not reduced in any of the lens groups at the time of variable magnification. Therefore, the amount of movement of each lens group is within an appropriate range in order to obtain a predetermined zoom ratio, and the entire zoom lens unit can be miniaturized and reduced in cost.

On the other hand, if the zoom lens includes a lens group in which the numerical value of the conditional expression (11) is equal to or less than the lower limit value, the lateral magnification is reduced by the lens group when the magnification is changed from the wide-angle end to the telephoto end. The lens. That is, the lens group that does not satisfy the conditional expression (11) acts in the direction of shortening the focal length of the zoom lens at the telephoto end. Therefore, in order to obtain a predetermined zoom ratio, it is necessary to secure the magnification ratio by increasing the amount of movement of the other lens group at the time of magnification change or by strengthening the refractive power of the other lens group. In this case, it is difficult to reduce the size and cost of the entire zoom lens unit. In addition, it becomes difficult to achieve good optical performance over the entire zoom range because the correction of spherical aberration and coma is insufficient.

On the other hand, if the zoom lens includes a lens group in which the numerical value of the conditional expression (11) is equal to or larger than the upper limit value, the lateral magnification is greatly increased by the lens group when the magnification is changed from the wide-angle end to the telephoto end. In that case, an extremely large refractive power is distributed to the lens group, or a larger amount of movement than usual is required at the time of scaling, which makes it difficult to ensure good optical performance over the entire zoom range, and also zooms. This is not desirable because it leads to an increase in the size of the entire lens unit and increases the cost.

In order to obtain these effects, it is preferable that "≧" is ">" in the conditional expression (11). That is, in the zoom lens, the rate of change in the lateral magnification at the time of scaling from the wide-angle end to the telephoto end of the lens group arranged after the second lens group is preferably larger than 1. Further, the upper limit value is more preferably 25.00, further preferably 15.00, and even more preferably 10.00.

The negative lens Gni included in the i-th lens may have a negative refractive power, and the shape is not particularly limited. However, in order to obtain an appropriate refractive power capable of performing aberration correction satisfactorily, the negative lens Gni preferably has a biconcave shape. Further, the positive lens Gpi included in the i-th lens may have a positive refractive power, and the shape is not particularly limited. However, in order to obtain an appropriate refractive power capable of satisfactorily correcting aberrations, the positive lens Gpi preferably has a biconvex shape.

2. 2. Imaging Device Next, the imaging device according to the present invention will be described. The image pickup apparatus according to the present invention includes the zoom lens according to the present invention and an image pickup element provided on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal. It is characterized by that. Here, the image sensor is not particularly limited, and a solid-state image sensor such as a CCD sensor or a CMOS 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 a 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 single-lens camera. Of course.

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples. The optical system of each example listed below is a photographing optical system used in an imaging device (optical device) such as a digital camera, a video camera, and a silver salt 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 viewed from the drawing.

(1) Configuration of Optical System FIG. 1 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a first embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. This is a zoom lens that changes the magnification by changing the distance between each lens group.

In the zoom lens of Example 1, the third lens group is the i-lens group referred to in the present invention. The lens with the L9 code is the negative lens Gni according to the present invention, and the lens with the L8 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L1 code most arranged on the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

Further, "S" shown in the figure is an aperture diaphragm, and "I" shown on the image side of the zoom lens is an image plane. Specifically, an imaging plane of a solid-state image sensor such as a CCD sensor or a CMOS sensor. Alternatively, the film surface of the silver salt film or the like is shown. The specific lens configuration of each lens group is as shown in FIG. Since these reference numerals are the same in the drawings shown in Examples 2 to 6, the description thereof will be omitted below.

A vibration isolation group that corrects image blur by moving the zoom lens in a direction perpendicular to the optical axis, and a focus group that moves along the optical axis when focusing from an infinity object to a short-distance object. May be provided. In this case, any of the first lens group to the third lens group shown in FIG. 1 (or a partial lens group composed of at least one lens constituting the lens group) is referred to as an anti-vibration group and a focus group. However, for example, it is preferable that the second lens group is the vibration isolation group and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 1 to which a specific numerical value of the zoom lens is applied will be described. Table 1 shows the lens data of the zoom lens. In Table 1, "No." 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). The refractive index for λ = 587.5600 nm) and “νd” indicate the Abbe number for the d line (wavelength λ = 587.600 nm). Further, the aperture diaphragm (aperture S) is indicated by adding "STOP" next to the surface number. Further, when the lens surface is aspherical, "ASPH" is added next to the surface number, the column of radius of curvature R indicates the paraxial radius of curvature, and "inf." Indicates ∞.

Table 2 shows the aspherical coefficient and the conical constant when the shape of the aspherical surface is expressed by the following equation. The aspherical surface shall be defined by the following equation.

z = ch ² / [1 + {1- (1 + k) c ² h ² } ^1/2 ] + A4h ⁴ + A6h ⁶ + A8h ⁸ + A10h ¹⁰
However, c is the curvature (1 / r), h is the height from the optical axis, k is the conical coefficient, and A4, A6, A8, and A10 are the aspherical coefficients of each order.

Table 3 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of scaling at each focal length (F) of the zoom lens.

Since the matters related to these tables are the same in each of the tables shown in Examples 2 to 6, the description thereof will be omitted below.

FIGS. 2 to 4 show longitudinal aberration diagrams at the wide-angle end, the intermediate focal length, and the telephoto end of the zoom lens when the zoom lens is in focus at infinity. Each longitudinal aberration diagram shows spherical aberration, astigmatism, and distortion in order from the left. In the figure showing spherical aberration, the vertical axis represents the ratio to the open F value, the horizontal axis represents the defocus, the solid line represents the d line (587.5600 nm), and the broken line represents the g line (435.8400 nm). In the figure showing astigmatism, the vertical axis represents the angle of view and the horizontal axis represents the defocus, the solid line represents the sagittal direction (X) of the d line, and the broken line represents the meridional direction (Y) of the d line. In the diagram showing distortion, the vertical axis represents the angle of view and the horizontal axis represents%. It should be noted that the order and arrangement in which these aberrations are displayed, and those shown by solid lines, wavy lines, etc. in each figure are the same in each of the figures shown in Examples 2 to 6, and thus the description thereof will be omitted below.

Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3) of each lens group. Here, in this embodiment, since the third lens group is the i-th lens group, Table 19 shows the value of “H3_t / Hstop_t” as the value of the conditional expression (3). H3_t is the maximum height from the optical axis when the axial luminous flux passes through the surface of the third lens group on the most object side at the telephoto end of the zoom lens. Regarding the conditional expression (11), "B2_t / B2_w" shown in Table 19 is the value of the conditional expression (11) for the second lens group, and "B3_t / B3_w" is the conditional expression (11) for the third lens group. "B4_t / B4_w" is the value of the conditional expression (11) relating to the fourth lens group. Since the zoom lens of Example 1 does not have a fourth lens group, [-] is shown in Table 19. The notation relating to the conditional expression (3) and the conditional expression (11) is the same in the other embodiments. Table 1 can be referred to for the numerical values of the conditional expression (4) to the conditional expression (7), the conditional expression (9), and the conditional expression (10).

(1) Configuration of Optical System FIG. 5 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a second embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. This is a zoom lens that changes the magnification by changing the distance between each lens group.

In the zoom lens of the second embodiment, the third lens group is the i-lens group referred to in the present invention. The lens with the L8 code is the negative lens Gni according to the present invention, and the lens with the L7 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L1 code most arranged on the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

The zoom lens may be provided with a vibration isolation group and a focus group. In this case, any of the first lens group to the third lens group shown in FIG. 5 (or a partial lens group) can be set as the vibration isolation group or the focus group. For example, the second lens group. Is preferably the vibration isolation group, and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 2 to which a specific numerical value of the zoom lens is applied will be described. Table 4 shows the lens data of the zoom lens. Table 5 shows the aspherical coefficient and the conical constant for the aspherical surface. Table 6 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of scaling at each focal length (F) of the zoom lens. Further, FIGS. 5 to 8 show a longitudinal aberration diagram of the zoom lens when it is in focus at infinity. Further, Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3) of each lens group. Table 4 can be referred to for the numerical values of the conditional expressions (4) to (7), the conditional expression (9), and the conditional expression (10).

(1) Configuration of Optical System FIG. 9 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a third embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. This is a zoom lens that changes the magnification by changing the distance between each lens group.

In the zoom lens of Example 3, the third lens group is the i-lens group referred to in the present invention. The lens with the L8 code is the negative lens Gni according to the present invention, and the lens with the L7 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L1 code most arranged on the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

The zoom lens may be provided with a vibration isolation group and a focus group. In this case, any of the first lens group to the third lens group shown in FIG. 9 (or a partial lens group) can be set as the vibration isolation group or the focus group. For example, the second lens group. Is preferably the vibration isolation group, and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 3 to which a specific numerical value of the zoom lens is applied will be described. Table 7 shows the lens data of the zoom lens. Table 8 shows the aspherical coefficient and the conical constant for the aspherical surface. Table 9 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of scaling at each focal length (F) of the zoom lens. Further, FIGS. 10 to 12 show a longitudinal aberration diagram of the zoom lens when it is in focus at infinity. Further, Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3) of each lens group. Table 7 can be referred to for the numerical values of the conditional expressions (4) to (7), the conditional expression (9), and the conditional expression (10).

(1) Configuration of Optical System FIG. 13 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a fourth embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. This is a zoom lens that changes the magnification by changing the distance between each lens group.

In the zoom lens of Example 4, the third lens group is the i-lens group referred to in the present invention. The lens with the L9 code is the negative lens Gni according to the present invention, and the lens with the L8 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L2 reference numeral arranged second from the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

The zoom lens may be provided with a vibration isolation group and a focus group. In this case, any of the first lens group to the third lens group shown in FIG. 13 (or a partial lens group) can be set as the vibration isolation group or the focus group. For example, the second lens group. Is preferably the vibration isolation group, and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 4 to which a specific numerical value of the zoom lens is applied will be described. Table 10 shows the lens data of the zoom lens. Table 11 shows the aspherical coefficient and the conical constant for the aspherical surface. Table 12 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of magnification change at each focal length (F) of the zoom lens. Further, FIGS. 14 to 16 show longitudinal aberration diagrams of the zoom lens at infinity focusing. Further, Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3) of each lens group. For the numerical values of the conditional expressions (4) to (7), the conditional expression (9), and the conditional expression (10), Table 10 can be referred to.

(1) Configuration of Optical System FIG. 17 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a fifth embodiment of the present invention. The zoom lens has a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. It is a zoom lens that is composed of a fourth lens group G4 having an optical power of the above, and changes the magnification by changing the interval of each lens group.

In the zoom lens of Example 5, the third lens group is the i-lens group referred to in the present invention. The lens with the L9 code is the negative lens Gni according to the present invention, and the lens with the L8 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L1 code most arranged on the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

The zoom lens may be provided with a vibration isolation group and a focus group. In this case, any of the first lens group to the fourth lens group shown in FIG. 17 (or a partial lens group) can be set as the vibration isolation group or the focus group. For example, the second lens group. Is preferably the vibration isolation group, and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 5 to which a specific numerical value of the zoom lens is applied will be described. Table 13 shows the lens data of the zoom lens. Table 14 shows the aspherical coefficient and the conical constant for the aspherical surface. Table 15 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of scaling at each focal length (F) of the zoom lens. Further, FIGS. 18 to 20 show longitudinal aberration diagrams of the zoom lens at infinity focusing. Further, Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3, f4) of each lens group. For the numerical values of the conditional expressions (4) to (7), the conditional expression (9), and the conditional expression (10), Table 13 can be referred to.

(1) Configuration of Optical System FIG. 21 is a cross-sectional view of a lens showing a configuration of a zoom lens according to a sixth embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power in order from the object side. This is a zoom lens that changes the magnification by changing the distance between each lens group.

In the zoom lens of Example 6, the third lens group is the i-lens group referred to in the present invention. The lens with the L98 code is the negative lens Gni according to the present invention, and the lens with the L7 code arranged on the object side of the negative lens Gni is the positive lens Gpi according to the present invention. The negative lens Gni and the positive lens Gpi are bonded to each other to form a bonded lens. Further, the lens with the L1 code most arranged on the object side in the first lens group is a negative lens satisfying the conditional equation (6) and the conditional equation (7).

The zoom lens may be provided with a vibration isolation group and a focus group. In this case, any of the first lens group to the third lens group shown in FIG. 21 (or a partial lens group) can be set as the vibration isolation group or the focus group. For example, the second lens group. Is preferably the vibration isolation group, and the first lens group is the focus group.

(2) Numerical Example Next, Numerical Example 6 to which a specific numerical value of the zoom lens is applied will be described. Table 16 shows the lens data of the zoom lens. Table 17 shows the aspherical coefficient and the conical constant for the aspherical surface. Table 18 shows the F number (Fno), the half angle of view (W), and the lens spacing on the image side of each lens group (movable group) that moves at the time of scaling at each focal length (F) of the zoom lens. Further, FIGS. 22 to 24 show longitudinal aberration diagrams of the zoom lens at infinity focusing. Further, Table 19 shows the numerical values of the conditional expressions (1) to (3), the conditional expressions (8) and the conditional expression (11), and the combined focal lengths (f1, f2, f3) of each lens group. Table 1 can be referred to for the numerical values of the conditional expressions (4) to (7), the conditional expression (9), and the conditional expression (10).

According to the present invention, the subject of the present invention is to provide a zoom lens capable of achieving high performance and low cost, and an image pickup device provided with the zoom lens.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Aperture diaphragm I ... Image plane

Claims (7)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a rear group including at least one lens group are provided.
The magnification is changed by changing the distance between each lens group.
An aperture diaphragm is provided after the first lens group.
The first lens group satisfies the following conditional expression (1) and conditional expression (2).
When the lens group having a positive refractive power included in the rear group is the i-th lens group (where i is a natural number of 3 or more), at least one of the i-th lens groups has the following conditional expression (however, i is a natural number of 3 or more). 3) meet, at least one saw including a negative lens Gni satisfying the following conditional expression (4-1) and conditional expression (5), and, to satisfy the following conditional expression (8),
A zoom lens featuring.
(1) 1.45 <Ndp1ave < 1.56
(2) 50.00 <Vdp1ave <71.00
(3) 0.50 <Hi_t / Hstop_t <1.60
(4-1) 1.82 <Ndni <2.10
(5) 26.00 <Vdni <37.00
(8) 0.10 <f1 / ft <0.70
However,
Ndp1ave: Average value of the refractive index of the positive lens included in the first lens group with respect to the d line Vdp1ave: Average value of the number of abbes with respect to the d line of the positive lens included in the first lens group Hi_t: Telescopic end of the zoom lens Hstop_t: Maximum height from the optical axis when the axial light beam passes through the most object-side surface of the i-th lens group: At the telephoto end of the zoom lens, the outermost light beam of the axial light beam is the aperture aperture. Maximum height from the optical axis passing through Ndni: Refractive coefficient of the negative lens Gni included in the i-lens group with respect to the d-line Vdni: Abbe number of the negative lens Gni included in the i-lens group with respect to the d-line.
f1: Focal length of the first lens group
ft: Focal length of the entire zoom lens system at the telephoto end In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a rear group including at least one lens group are provided.
The magnification is changed by changing the distance between each lens group.
An aperture diaphragm is provided after the first lens group.
The first lens group satisfies the following conditional expression (1) and conditional expression (2).
When the lens group having a positive refractive power included in the rear group is the i-th lens group (where i is a natural number of 3 or more), at least one of the i-th lens groups has the following conditional expression (however, i is a natural number of 3 or more). Satisfying 3-1), including at least one negative lens Gni satisfying the following conditional expression (4) and the following conditional expression (5), and satisfying the following conditional expression (8).
A zoom lens featuring.
(1) 1.45 <Ndp1ave <1.56
(2) 50.00 <Vdp1ave <71.00
(3-1) 0.50 <Hi_t / Hstop_t <1.20
(4) 1.79 <Ndni <2.10
(5) 26.00 <Vdni <37.00
(8) 0.10 <f1 / ft <0.70
However,
Ndp1ave: The average value of the refractive index of the positive lens included in the first lens group with respect to the d line.
Vdp1ave: The average value of the Abbe numbers with respect to the d-line of the positive lens included in the first lens group.
Hi_t: At the telephoto end of the zoom lens, the maximum height from the optical axis when the axial luminous flux passes through the surface of the i-th lens group on the most object side.
Hstop_t: At the telephoto end of the zoom lens, the maximum height from the optical axis through which the outermost light beam of the axial luminous flux passes through the aperture diaphragm.
Ndni: Refractive index of the negative lens Gni included in the i-th lens group with respect to the d-line.
Vdni: Abbe number of the negative lens Gni included in the i-th lens group with respect to the d-line.
f1: Focal length of the first lens group
ft: Focal length of the entire zoom lens system at the telephoto end The zoom lens according to claim 1 or 2 , wherein the first lens group includes at least one negative lens satisfying the following conditional formula (6) and conditional formula (7).
(6) 1.70 <Ndn1 <2.10
(7) 15.00 <Vdn1 <37.00
However,
Ndn1: Refractive index of the negative lens included in the first lens group with respect to the d line Vdn1: Abbe number of the negative lens included in the first lens group with respect to the d line The zoom lens according to any one of claims 1 to 3, wherein a positive lens Gpi satisfying the following conditional equations (9) and (10) is adjacent to the object side of the negative lens Gni. ..
(9) 1.45 <Ndpi <1.75
(10) 50.00 <Vdpi <80.00
However,
Ndpi: Refractive index of the positive lens Gpi with respect to the d-line Vdpi: Abbe number of the positive lens Gpi with respect to the d-line The zoom lens according to claim 4, wherein the i-th lens group includes a junction lens including the negative lens Gni and the positive lens Gpi. The claim that each j lens group satisfies the following conditional expression (11) when the lens group after the second lens group is the j lens group (where j is a natural number of 2 or more) in the zoom lens. The zoom lens according to any one of claims 1 to 5.
(11) 1.0 ≤ Bj_t / Bj_w ≤ 50.0
Bj_t: Lateral magnification of the j-th lens group at the telephoto end of the zoom lens Bj_w: Lateral magnification of the j-th lens group at the wide-angle end of the zoom lens The zoom lens according to any one of claims 1 to 6 and an image pickup device provided on the image side of the zoom lens that converts an optical image formed by the zoom lens into an electrical signal. An image sensor characterized by being equipped.

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