Variable power optical system and optical device

Abstract

To provide a variable power optical system excellent in optical performance although small.SOLUTION: A variable power optical system ZL consists of a first lens group G1 having negative refractive power and a rear group GR having at least one lens group. An interval between adjacent lens groups changes during variable power; and at least one lens group of the rear group GR includes the final lens group GE arranged on the side closest to the image of the rear group GR and having positive refractive power satisfies the following conditional expression, 0.15<ft / fGE<0.60, where ft: the focal distance of the variable power optical system ZL in a telephoto end state, and fGE: the focal distance of the final lens group GE.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a zoom optical system and an optical apparatus.

Background Art

[0002] Conventionally, zoom optical systems suitable for photographic cameras, digital still cameras, video cameras, etc. have been proposed (see, for example, Patent Document 1). In such a zoom optical system, it is difficult to obtain good optical performance while making it small.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The zoom optical system according to the first aspect of the present invention includes a first lens group having a negative refractive power and a rear group having at least two lens groups, arranged in order from the object side along the optical axis. During zooming, the interval between adjacent lens groups changes. The at least two lens groups of the rear group include a final lens group having a positive refractive power arranged on the most image side of the rear group. The rear group includes at least one cemented lens of a positive lens and a negative lens, and the rear group includes a lens that moves during focusing, and satisfies the following conditional expression. 0.15 < ft / fGE < 0.60 However, ft: the focal length of the zoom optical system in the telephoto end state fGE: the focal length of the final lens group

[0005] The optical apparatus according to the present invention is configured to include the above-described zoom optical system.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0007] Hereinafter, preferred embodiments according to the present invention will be described. First, the zoom according to each embodiment A camera (optical device) equipped with an optical system will be described with reference to FIG. 11. As shown in FIG. 11, this camera 1 is composed of a main body 2 and a photographing lens 3 attached to the main body 2. The main body 2 includes an imaging element 4, a main body control unit (not shown) that controls the operation of the digital camera, and a liquid crystal screen 5. The photographing lens 3 includes a zoom optical system ZL composed of a plurality of lens groups and a lens position control mechanism (not shown) that controls the positions of the respective lens groups. The lens position control mechanism is composed of a sensor that detects the position of the lens group, a motor that moves the lens group back and forth along the optical axis, a control circuit that drives the motor, and the like.

[0008] Light from the subject is condensed by the zoom optical system ZL of the photographing lens 3 and reaches the image plane I of the imaging element 4. The light from the subject that has reached the image plane I is photoelectrically converted by the imaging element 4 and recorded in a memory (not shown) as digital image data. The digital image data recorded in the memory can be displayed on the liquid crystal screen 5 according to the user's operation. Note that this camera may be a mirrorless camera or a single-lens reflex type camera having a quick return mirror. Also, the zoom optical system ZL shown in FIG. 11 schematically shows the zoom optical system provided in the photographing lens 3, and the lens configuration of the zoom optical system ZL is not limited to this configuration.

[0009] Next, the zoom optical system according to the first embodiment will be described. As an example of the zoom optical system ZL (1) as the zoom optical system (zoom lens) ZL according to the first embodiment, as shown in FIG. 1, it is composed of a first lens group G1 having a negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis. During zooming, the interval between adjacent lens groups changes. At least one lens group of the rear group GR includes a final lens group GE having a positive refractive power arranged on the most image side of the rear group GR.

[0010] Under the above configuration, the zoom optical system ZL according to the first embodiment satisfies the following conditional expression (1). 0.15 < ft / fGE < 0.60 ···(1) However, ft: focal length of the zoom optical system ZL in the telephoto end state fGE: focal length of the final lens group GE

[0011] According to the first embodiment, it is possible to obtain a zoom optical system that is small in size and has good optical performance, and an optical apparatus including this zoom optical system. The zoom optical system ZL according to the first embodiment may be the zoom optical system ZL(2) shown in FIG. 3, the zoom optical system ZL(3) shown in FIG. 5, the zoom optical system ZL(4) shown in FIG. 7, or the zoom optical system ZL(5) shown in FIG. 9.

[0012] The conditional expression (1) defines an appropriate relationship between the focal length of the zoom optical system ZL in the telephoto end state and the focal length of the final lens group GE. By satisfying the conditional expression (1), it is possible to satisfactorily correct the field curvature while being small in size.

[0013] When the corresponding value of the conditional expression (1) exceeds the upper limit value, it becomes difficult to correct the field curvature. In addition, since the incident angle of the light beam with respect to the image plane (image sensor) increases, it becomes difficult to suppress shading. By setting the upper limit value of the conditional expression (1) to 0.55, 0.50, 0.47, 0.43, and further 0.40, the effects of the present embodiment can be made more certain.

[0014] When the corresponding value of the conditional expression (1) is below the lower limit value, it becomes difficult to correct the field curvature and coma aberration. By setting the lower limit value of the conditional expression (1) to 0.20, 0.24, 0.27, 0.30, and further 0.32, the effects of the present embodiment can be made more certain.

[0015] Next, the zoom optical system according to the second embodiment will be described. As an example of the zoom optical system (zoom lens) ZL according to the second embodiment, the zoom optical system ZL(1) is composed of a first lens group G1 having a negative refractive power and a rear group GR having at least one lens group, arranged in order from the object side along the optical axis as shown in FIG. 1. During zooming, the interval between adjacent lens groups changes.

[0016] Under the above configuration, the zoom optical system ZL according to the second embodiment satisfies the following conditional expressions (2) and (3). 2.00 < TLt / IHw < 3.00 ···(2) 1.00 < (-f1) / fRw < 1.50 ···(3) However, TLt: The overall length of the zoom optical system ZL in the telephoto end state IHw: The maximum image height of the zoom optical system ZL in the wide-angle end state f1: The focal length of the first lens group G1 fRw: The focal length of the rear group GR in the wide-angle end state

[0017] According to the second embodiment, it becomes possible to obtain a zoom optical system having good optical performance while being small, and an optical apparatus including this zoom optical system. The zoom optical system ZL according to the second embodiment may be the zoom optical system ZL(2) shown in FIG. 3, the zoom optical system ZL(3) shown in FIG. 5, the zoom optical system ZL(4) shown in FIG. 7, or the zoom optical system ZL(5) shown in FIG. 9.

[0018] Conditional expression (2) defines an appropriate relationship between the overall length of the zoom optical system ZL in the telephoto end state and the maximum image height of the zoom optical system ZL in the wide-angle end state. By satisfying conditional expression (2), a small zoom optical system can be obtained with respect to the size of the image plane (image sensor).

[0019] When the corresponding value of conditional expression (2) exceeds the upper limit value, the overall length of the zoom optical system ZL becomes large, making it difficult to obtain good optical performance while making the zoom optical system ZL small. By setting the upper limit value of conditional expression (2) to 2.90, 2.80, 2.70, 2.65, and further 2.60, the effects of the present embodiment can be made more certain.

[0020] When the corresponding value of conditional expression (2) is below the lower limit value, the overall length of the zoom optical system ZL is too small, making it difficult to correct coma aberration and field curvature. By setting the lower limit value of conditional expression (2) to 2.10, 2.20, 2.30, 2.40, and further 2.45, the effects of the present embodiment can be made more certain.

[0021] Conditional expression (3) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the rear group GR in the wide-angle end state. By satisfying conditional expression (3), it is possible to obtain good optical performance over the entire zoom range while being compact.

[0022] When the corresponding value of conditional expression (3) exceeds the upper limit value, it becomes difficult to correct spherical aberration and coma aberration. By setting the upper limit value of conditional expression (3) to 1.45, 1.40, 1.36, 1.33, and further to 1.30, the effects of the present embodiment can be made more certain.

[0023] When the corresponding value of conditional expression (3) is below the lower limit value, it becomes difficult to correct spherical aberration and field curvature. By setting the lower limit value of conditional expression (3) to 1.05, 1.10, 1.12, 1.15, and further to 1.18, the effects of the present embodiment can be made more certain.

[0024] In the zoom optical system ZL according to the second embodiment, it is desirable that at least one lens group of the rear group GR includes the final lens group GE having a positive refractive power disposed on the most image side of the rear group GR. Thereby, various aberrations can be corrected well.

[0025] Also, the zoom optical system ZL according to the first embodiment may satisfy the above-mentioned conditional expression (2). By satisfying conditional expression (2), similar to the second embodiment, a compact zoom optical system can be obtained with respect to the size of the image plane (imaging element). By setting the upper limit value of conditional expression (2) to 2.90, 2.80, 2.70, 2.65, and further to 2.60, the effects of the first embodiment can be made more certain. Also, by setting the lower limit value of conditional expression (2) to 2.10, 2.20, 2.30, 2.40, and further to 2.45, the effects of the first embodiment can be made more certain.

[0026] Also, the zoom optical system ZL according to the first embodiment may satisfy the above conditional expression (3). By satisfying the conditional expression (3), similar to the second embodiment, good optical performance can be obtained over the entire zoom range while being compact. By setting the upper limit value of the conditional expression (3) to 1.45, 1.40, 1.36, 1.33, and further 1.30, the effects of the first embodiment can be made more certain. Also, by setting the lower limit value of the conditional expression (3) to 1.05, 1.10, 1.12, 1.15, and further 1.18, the effects of the first embodiment can be made more certain.

[0027] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (4). 0.30 < Bfw / IHw < 0.60 ···(4) However, Bfw: Back focus of the zoom optical system ZL in the wide-angle end state IHw: Maximum image height of the zoom optical system ZL in the wide-angle end state

[0028] The conditional expression (4) defines an appropriate relationship between the back focus of the zoom optical system ZL in the wide-angle end state and the maximum image height of the zoom optical system ZL in the wide-angle end state. By satisfying the conditional expression (5), field curvature can be corrected well.

[0029] When the corresponding value of the conditional expression (4) exceeds the upper limit value, the back focus of the zoom optical system ZL is too long, so it becomes difficult to correct the field curvature while making the zoom optical system ZL compact. By setting the upper limit value of the conditional expression (4) to 0.56, 0.53, 0.50, 0.48, and further 0.46, the effects of each embodiment can be made more certain.

[0030] When the corresponding value of the conditional expression (4) is below the lower limit value, the back focus of the zoom optical system ZL is too short, so it interferes with the camera body (body) and is not suitable for practical use. By setting the lower limit value of the conditional expression (4) to 0.32, 0.35, 0.37, 0.40, and further 0.42, the effects of each embodiment can be made more certain.

[0031] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to satisfy the following conditional expression (5). 0.50 <YLE1 / IHw<1.00 ···(5) However, YLE1 is the effective radius of the lens surface on the object side of the lens located closest to the image side of the variable magnification optical system ZL. IHw: Maximum image height of the variable magnification optical system ZL in the wide-angle end state

[0032] Conditional formula (5) specifies the appropriate relationship between the effective radius of the object-side lens surface of the lens arranged closest to the image in the variable magnification optical system ZL and the maximum image height of the variable magnification optical system ZL in the wide-angle end state. Hereinafter, the lens arranged closest to the image in the variable magnification optical system ZL may be referred to as the final lens. By satisfying conditional formula (5), the amount of peripheral light can be ensured.

[0033] When the value of condition (5) exceeds the upper limit, the effectiveness of the lens surface on the object side of the final lens element becomes poor. Because the effective radius becomes large, it becomes difficult to obtain good optical performance while making the variable magnification optical system ZL small. By setting the upper limit value of conditional expression (5) to 0.95, 0.90, 0.85, 0.82, or further to 0.78, the effects of each embodiment can be made more certain.

[0034] When the corresponding value of conditional expression (5) falls below the lower limit, the effective diameter of the lens surface on the object side of the final lens becomes small, making it difficult to ensure the amount of peripheral light. By setting the lower limit of conditional expression (5) to 0.55, 0.60, 0.65, 0.68, or even 0.72, the effects of each embodiment can be made more certain.

[0035] It is desirable for the variable magnification optical system ZL according to the first and second embodiments to satisfy the following conditional expression (6). 0.80<(-f1) / fw<1.40 (6) where f1 is the focal length of the first lens group G1 fw: focal length of the variable magnification optical system ZL at the wide-angle end

[0036] Conditional expression (6) defines an appropriate relationship between the focal length of the first lens group G1 and the focal length of the zoom optical system ZL in the wide-angle end state. By satisfying conditional expression (6), various aberrations such as coma aberration can be corrected well while the size is small.

[0037] When the corresponding value of conditional expression (6) exceeds the upper limit value, the refractive power of the first lens group G1 is too weak, so it becomes difficult to correct various aberrations while making the zoom optical system ZL small. By setting the upper limit value of conditional expression (6) to 1.35, 1.30, 1.27, 1.24, and further 1.22, the effects of each embodiment can be made more reliable.

[0038] When the corresponding value of conditional expression (6) is less than the lower limit value, the refractive power of the first lens group G1 is too strong, so it becomes difficult to correct coma aberration. By setting the lower limit value of conditional expression (6) to 0.85, 0.90, 0.95, 1.00, and further 1.05, the effects of each embodiment can be made more reliable.

[0039] In the zoom optical system ZL according to the first embodiment and the second embodiment, at least one lens group of the rear group GR includes the second lens group G2 having a positive refractive power disposed on the most object side of the rear group GR, and it is desirable to satisfy the following conditional expression (7). 0.50 < f2 / fw < 1.00 ···(7) However, f2: the focal length of the second lens group G2 fw: the focal length of the zoom optical system ZL in the wide-angle end state

[0040] Conditional expression (7) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the zoom optical system ZL in the wide-angle end state. By satisfying conditional expression (7), various aberrations such as spherical aberration can be corrected well while the size is small.

[0041] When the corresponding value of conditional expression (7) exceeds the upper limit value, the refractive power of the second lens group G2 is too weak, making it difficult to correct various aberrations while miniaturizing the zoom optical system ZL. By setting the upper limit value of conditional expression (7) to 0.95, 0.90, 0.87, and further to 0.85, the effects of each embodiment can be made more certain.

[0042] When the corresponding value of conditional expression (7) is below the lower limit value, the refractive power of the second lens group G2 is too strong, making it difficult to correct spherical aberration. By setting the lower limit value of conditional expression (7) to 0.55, 0.60, 0.65, 0.70, and further to 0.73, the effects of each embodiment can be made more certain.

[0043] In the zoom optical system ZL according to the first and second embodiments, at least one lens group of the rear group GR includes the second lens group G2 having a positive refractive power disposed on the most object side of the rear group GR, and it is desirable to satisfy the following conditional expression (8). 0.60 < f2 / fRw < 1.20 ···(8) However, f2: the focal length of the second lens group G2 fRw: the focal length of the rear group GR in the wide-angle end state

[0044] Conditional expression (8) defines an appropriate relationship between the focal length of the second lens group G2 and the focal length of the rear group GR in the wide-angle end state. By satisfying conditional expression (8), various aberrations such as field curvature and spherical aberration can be corrected well while being small in size.

[0045] When the corresponding value of conditional expression (8) exceeds the upper limit value, the refractive power of the second lens group G2 is too weak, making it difficult to correct field curvature. By setting the upper limit value of conditional expression (8) to 1.15, 1.10, 1.05, 1.00, and further to 0.95, the effects of each embodiment can be made more certain.

[0046] When the corresponding value of conditional expression (8) is less than the lower limit value, the refractive power of the second lens group G2 is too strong, making it difficult to correct spherical aberration. By setting the lower limit value of conditional expression (8) to 0.65, 0.70, 0.75, 0.78, and further to 0.82, the effects of each embodiment can be made more certain.

[0047] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (9). 1.10 < ft / fw < 1.50 ···(9) However, ft: the focal length of the zoom optical system ZL in the telephoto end state fw: the focal length of the zoom optical system ZL in the wide-angle end state

[0048] Conditional expression (9) defines an appropriate range for the zoom ratio of the zoom optical system ZL. By satisfying conditional expression (9), various aberrations can be corrected well while being small in size.

[0049] When the corresponding value of conditional expression (9) exceeds the upper limit value, the zoom ratio of the zoom optical system ZL becomes large, making it difficult to correct various aberrations while making the zoom optical system ZL small. By setting the upper limit value of conditional expression (9) to 1.45, 1.40, 1.37, 1.33, and further to 1.30, the effects of each embodiment can be made more certain.

[0050] When the corresponding value of conditional expression (9) is less than the lower limit value, the zoom ratio of the zoom optical system ZL is too small, so it does not function as a zoom optical system (zoom lens). By setting the lower limit value of conditional expression (9) to 1.15, 1.18, 1.20, 1.22, and further to 1.25, the effects of each embodiment can be made more certain.

[0051] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (10). -1.50 < (L1r2 + L1r1) / (L1r2 - L1r1) < -0.60 ···(10) However, L1r1: the radius of curvature of the object-side lens surface of the lens disposed closest to the object side in the zoom optical system ZL L1r2: the radius of curvature of the image-side lens surface of the lens disposed closest to the object side in the zoom optical system ZL

[0052] The conditional expression (10) defines an appropriate range for the shape factor of the lens disposed closest to the object side in the zoom optical system ZL. By satisfying the conditional expression (10), it is possible to satisfactorily correct field curvature, distortion, spherical aberration, coma aberration, etc., while being compact.

[0053] When the corresponding value of the conditional expression (10) exceeds the upper limit value, it becomes difficult to correct field curvature and distortion. By setting the upper limit value of the conditional expression (10) to -0.65, -0.70, -0.75, and further -0.80, the effects of each embodiment can be made more certain.

[0054] When the corresponding value of the conditional expression (10) is below the lower limit value, it becomes difficult to correct spherical aberration and coma aberration. By setting the lower limit value of the conditional expression (10) to -1.45, -1.40, -1.35, -1.30, and further -1.25, the effects of each embodiment can be made more certain.

[0055] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (11). -0.50 < (LEr2 + LEr1) / (LEr2 - LEr1) < 0.60 ···(11) However, LEr1: the radius of curvature of the object-side lens surface of the lens disposed closest to the image side in the zoom optical system ZL LEr2: the radius of curvature of the image-side lens surface of the lens disposed closest to the image side in the zoom optical system ZL

[0056] The conditional expression (11) defines an appropriate range for the shape factor of the lens (the final lens) disposed on the most image side of the zoom optical system ZL. By satisfying the conditional expression (11), it is possible to satisfactorily correct coma aberration and field curvature while maintaining a compact size.

[0057] When the corresponding value of the conditional expression (11) exceeds the upper limit value, it becomes difficult to correct coma aberration. By setting the upper limit value of the conditional expression (11) to 0.55, 0.50, 0.45, 0.40, and further 0.38, the effects of each embodiment can be made more certain.

[0058] When the corresponding value of the conditional expression (11) is below the lower limit value, it becomes difficult to correct field curvature. By setting the lower limit value of the conditional expression (11) to -0.45, -0.40, -0.35, -0.30, and further -0.25, the effects of each embodiment can be made more certain.

[0059] The zoom optical system ZL according to the first and second embodiments preferably has a diaphragm disposed between the first lens group G1 and the rear group GR. Thereby, it becomes possible to suppress shading.

[0060] The zoom optical system ZL according to the first and second embodiments preferably satisfies the following conditional expression (12). 88.00° < 2ωw ···(12) However, 2ωw: the total angle of view of the zoom optical system ZL in the wide-angle end state

[0061] The conditional expression (12) defines an appropriate range for the total angle of view of the zoom optical system ZL in the wide-angle end state. By satisfying the conditional expression (12), a zoom optical system with a wide angle of view can be obtained, which is preferable. By setting the lower limit value of the conditional expression (12) to 90.00°, 92.00°, 94.00°, 96.00°, and further 98.00°, the effects of each embodiment can be made more certain. By setting the upper limit value of the conditional expression (12) to 114.00°, 110.00°, 107.00°, 104.00°, and further 102.00°, each imp The effects of the embodiment can be made more reliable.

[0062] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (13). 0.01 < D1 / TLw < 0.20 ···(13) However, D1: Thickness on the optical axis of the first lens group G1 TLw: Overall length of the zoom optical system ZL in the wide-angle end state

[0063] The conditional expression (13) defines an appropriate relationship between the thickness on the optical axis of the first lens group G1 and the overall length of the zoom optical system ZL in the wide-angle end state. By satisfying the conditional expression (13), various aberrations such as field curvature and spherical aberration can be favorably corrected while maintaining a small size.

[0064] When the corresponding value of the conditional expression (13) exceeds the upper limit value, it becomes difficult to correct various aberrations such as field curvature and spherical aberration while maintaining a small size. By setting the upper limit value of the conditional expression (13) to 0.19, 0.18, and further 0.17, the effects of each embodiment can be made more reliable.

[0065] When the corresponding value of the conditional expression (13) is below the lower limit value, it becomes difficult to correct various aberrations such as field curvature and spherical aberration. By setting the lower limit value of the conditional expression (13) to 0.03, 0.05, and further 0.10, the effects of each embodiment can be made more reliable.

[0066] The zoom optical system ZL according to the first embodiment and the second embodiment desirably satisfies the following conditional expression (14). 0.10 < Bfw / fw < 0.60 ···(14) However, Bfw: Back focus of the zoom optical system ZL in the wide-angle end state fw: Focal length of the zoom optical system ZL in the wide-angle end state

[0067] The conditional expression (14) defines the relationship between the back focus and the focal length of the zoom optical system ZL in the wide-angle end state. By setting the upper limit values of the conditional expression (14) to 0.58, 0.55, 0.53, and further to 0.50, the effects of each embodiment can be made more certain. Also, by setting the lower limit values of the conditional expression (14) to 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, and further to 0.45, the effects of each embodiment can be made more certain.

[0068] Subsequently, with reference to FIG. 12, a manufacturing method of the zoom optical system ZL according to the first embodiment will be outlined. First, a first lens group G1 having a negative refractive power and a rear group GR having at least one lens group are arranged in order from the object side along the optical axis (step ST1). Next, during zooming, the intervals between adjacent lens groups are configured to change (step ST2). Next, among at least one lens group of the rear group GR, the final lens group GE having a positive refractive power is arranged on the most image side of the rear group GR (step ST3). Then, each lens is arranged in the lens barrel so as to satisfy at least the above conditional expression (1) (step ST4). According to such a manufacturing method, it becomes possible to manufacture a zoom optical system that is small and has good optical performance.

[0069] Subsequently, with reference to FIG. 13, a manufacturing method of the zoom optical system ZL according to the second embodiment will be outlined. First, a first lens group G1 having a negative refractive power and a rear group GR having at least one lens group are arranged in order from the object side along the optical axis (step ST11). Next, during zooming, the intervals between adjacent lens groups are configured to change (step ST12). Then, each lens is arranged in the lens barrel so as to satisfy at least the above conditional expressions (2) and (3) (step ST13). According to such a manufacturing method, it is possible to manufacture a zoom optical system that is small and has good optical performance.

Example

[0070] Hereinafter, the zoom optical system ZL according to the examples of each embodiment will be described with reference to the drawings. FIGS. 1, 3, 5, 7, and 9 are cross-sectional views showing the configuration and refractive power distribution of the zoom optical systems ZL {ZL(1) to ZL(5)} according to the first to fifth embodiments. In the cross-sectional views of the zoom optical systems ZL(1) to ZL(5) according to the first to fifth embodiments, the moving direction along the optical axis of the focusing group when focusing from an infinite distance to a near-distance object is indicated by an arrow together with the word "focusing". In the cross-sectional views of the zoom optical systems ZL(1) to ZL(5) according to the first to fifth embodiments, the moving direction along the optical axis of each lens group when zooming from the wide-angle end state (W) to the telephoto end state (T) is indicated by an arrow.

[0071] In FIGS. 1, 3, 5, 7, and 9, each lens group is represented by a combination of the symbol G and a number, and each lens is represented by a combination of the symbol L and a number. In this case, in order to prevent the types and numbers of symbols and numbers from becoming large and complicated, the lens groups and the like are represented by using combinations of symbols and numbers independently for each embodiment. Therefore, even if the same combination of symbol and number is used between embodiments, it does not mean that they have the same configuration.

[0072] Tables 1 to 5 are shown below. Among these, Table 1 shows the specification data in the first embodiment, Table 2 shows the second embodiment, Table 3 shows the third embodiment, Table 4 shows the fourth embodiment, and Table 5 shows the fifth embodiment. In each embodiment, the d-line (wavelength λ = 587.6 nm) and the g-line (wavelength λ = 435.8 nm) are selected as the objects for calculating the aberration characteristics.

[0073] In the table of [Overall Specifications], f represents the focal length of the entire lens system, FNO represents the F-number, 2ω represents the angle of view (the unit is ° (degrees), where ω is the semi-angle of view), and Ymax represents the maximum image height. TL represents the distance obtained by adding BF to the distance from the frontmost surface of the lens to the rearmost surface of the lens on the optical axis when focused at infinity, and BF represents the distance from the rearmost surface of the lens to the image plane I on the optical axis when focused at infinity (back focus). Note that these values are shown for each of the zoom states of the wide-angle end (W) and the telephoto end (T).

[0074] In the table of [Overall Specifications], IHw indicates the maximum image height of the zoom optical system in the wide-angle end state. YLE1 indicates the effective radius of the object-side lens surface of the lens (final lens) arranged closest to the image side of the zoom optical system. fRw indicates the focal length of the rear group in the wide-angle end state. D1 indicates the thickness on the optical axis of the first lens group.

[0075] In the table of [Lens Specifications], the surface number indicates the order of the optical surfaces from the object side along the direction of light propagation. R is the radius of curvature of each optical surface (a surface with the center of curvature located on the image side is taken as a positive value). D is the surface interval, which is the distance on the optical axis from each optical surface to the next optical surface (or the image surface). nd is the refractive index of the material of the optical member with respect to the d-line, νd is the Abbe number based on the d-line of the material of the optical member, and ED indicates the effective diameter (effective aperture) of each optical surface. "∞" for the radius of curvature indicates a plane or an aperture, and (stop S) indicates the aperture stop S. The notation of the refractive index nd = 1.00000 of air is omitted. When the optical surface is an aspherical surface, an asterisk is attached to the surface number, and the paraxial radius of curvature is shown in the column of the radius of curvature R.

[0076] In the table of [Aspherical Data], for the aspherical surfaces shown in [Lens Specifications], the shape is represented by the following formula (A). X(y) is the distance along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y (sag amount). R is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and Ai is the i-th order aspherical coefficient. "E-n" indicates "×10 -n ". For example, 1.234E-05 = 1.234×10 -5 . Note that the second-order aspherical coefficient A2 is 0, and its description is omitted.

[0077] X(y)=(y 2 / R) / {1+(1-κ×y 2 / R 2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 …(A)

[0078] The table of [Variable Interval Data] indicates the surface interval at surface number i where the surface interval is (Di) in the table of [Lens Specifications]. The table of [Variable Interval Data] also indicates the surface interval in the infinite focus state, the surface interval in the intermediate distance focus state, and the surface interval in the closest distance focus state.

[0079] The table of [Lens Group Data] indicates the starting surface (the surface closest to the object) and the focal length of each lens group.

[0080] Hereinafter, in all specification values, the published focal length f, radius of curvature R, surface interval D, and other lengths, etc. generally use "mm" when not otherwise specified. However, since the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced, it is not limited to this.

[0081] The explanations of the tables so far are common to all embodiments, and duplicate explanations below are omitted.

[0082] (First Embodiment) The first embodiment will be described with reference to FIGS. 1 to 2 and Table 1. FIG. 1 is a diagram showing the lens configuration of the zoom optical system according to the first embodiment. The zoom optical system ZL(1) according to the first embodiment includes a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power, which are arranged in order from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, and the interval between adjacent lens groups changes. Also, during zooming, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the first lens group G1 is fixed with respect to the image plane I. The signs (+) or (-) attached to each lens group symbol indicate the refractive power of each lens group, and this is the same for all the following embodiments.

[0083] The first lens group G1 is composed of a biconcave negative lens L11 and a positive meniscus lens L12 with its convex surface facing the object side, arranged in order from the object side along the optical axis. The negative lens L11 has aspherical lens surfaces on both sides.

[0084] The second lens group G2 is composed of a biconvex positive lens L21, a positive meniscus lens L22 with its convex surface facing the object side, a positive meniscus lens L23 with its concave surface facing the object side, and a cemented lens of a negative meniscus lens L24 with its concave surface facing the object side, arranged in order from the object side along the optical axis. The positive meniscus lens L22 has aspherical lens surfaces on both sides. The negative meniscus lens L24 has an aspherical lens surface on the image side.

[0085] The third lens group G3 is composed of a negative meniscus lens L31 with its concave surface facing the object side. The negative meniscus lens L31 has aspherical lens surfaces on both sides.

[0086] The fourth lens group G4 is composed of a biconvex positive lens L41. An image plane I is arranged on the image side of the fourth lens group G4.

[0087] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 constitute a rear group GR having a positive refractive power as a whole. And the fourth lens group G4 corresponds to the final lens group GE arranged on the most image side of the rear group GR. Also, the positive lens L41 of the fourth lens group G4 corresponds to the final lens. When focusing from an infinite object to a near object, the third lens group G3 moves toward the image side along the optical axis.

[0088] The following Table 1 lists the values of the specifications of the zoom optical system according to the first embodiment. Note that the fifth surface is a virtual surface.

[0089] (Table 1) [Overall specifications] Zoom ratio = 1.272 IHw = 19.629 YLE1 = 14.900 fRw = 17.133 D1 = 6.256 WT f 18.400 23.400 FNO 5.720 5.720 2ω 100.18 85.74 Ymax 19.629 21.050 TL 49.452 49.452 Bf 8.581 13.436 [Lens specifications] Surface number R D nd νd ED 1* -357.725 1.200 1.693430 53.30 2* 6.954 2.756 3 12.294 2.300 1.900430 37.38 4 28.572 (D4) 5 ∞ 1.000 6 ∞ 0.700 (Aperture S) 7 7.133 2.598 1.497000 81.61 8 -41.896 0.221 9* 12.222 1.449 1.531100 55.91 10* 12.544 0.852 11 -32.130 2.220 1.497000 81.61 12 -6.730 0.900 1.860999 37.10 13* -21.076 (D13) 14* -10.583 1.200 1.882020 37.23 15* -14.489 (D15) 16 111.344 3.056 1.953750 32.33 29.810 17 -162.063 Bf 30.550 [Aspherical data] First surface κ = 2.000, A4 = 1.5424E-06, A6 = -8.3988E-08, A8 = -3.0649E-10, A10 = 4.4239E-12 Second surface κ = 0.636, A4 = -6.4400E-05, A6 = -8.2111E-07, A8 = -7.4721E-09, A10 = -4.0071E-10 The 9th surface κ = 1.000, A4 = -1.7502E-04, A6 = -4.9201E-07, A8 = 5.4360E-07, A10 = -4.5297E-11 The 10th surface κ = 1.000, A4 = -2.7091E-04, A6 = 3.9890E-08, A8 = 4.1729E-07, A10 = 4.0626E-08 The 13th surface κ = 1.000, A4 = 4.6801E-04, A6 = 1.0244E-05, A8 = 1.2203E-07, A10 = -1.5857E-10 The 14th surface κ = 0.986, A4 = 3.5436E-04, A6 = -2.4094E-06, A8 = 7.1549E-09, A10 = -6.6462E-11 The 15th surface κ = 0.854, A4 = 3.2250E-04, A6 = -1.9429E-06, A8 = 7.6924E-10, A10 = 1.5871E-11 [Variable interval data] Infinity focus state WMT Focal length 18.400 20.000 23.400 Object distance ∞ ∞ ∞ D4 8.153 6.692 3.985 D13 7.266 6.981 7.067 D15 5.000 5.263 4.512 Bf 8.581 10.063 13.436 Intermediate distance focus state WMT Magnification -0.025 -0.025 -0.025 Object distance 730.527 795.834 934.488 D4 8.153 6.692 3.985 D13 7.978 7.693 7.823 D15 4.289 4.552 3.756 Bf 8.581 10.063 13.436 To the closest focusing state W M T Magnification -0.052 -0.056 -0.067 Object distance 350.002 350.003 350.003 D4 8.153 6.692 3.985 D13 8.775 8.631 9.142 D15 3.491 3.614 2.437 Bf 8.581 10.063 13.436 [Lens group data] Group Starting surface Focal length G1 1 -20.575 G2 7 14.938 G3 14 -52.001 G4 16 69.580

[0090] Fig. 2(A) is a diagram of various aberrations at infinity focus in the wide-angle end state of the zoom optical system according to the first embodiment. Fig. 2(B) is a diagram of various aberrations at infinity focus in the telephoto end state of the zoom optical system according to the first embodiment. In each aberration diagram, FNO indicates the F-number and Y indicates the image height. In the spherical aberration diagram, the value of the F-number corresponding to the maximum aperture is shown. In the astigmatism diagram and the distortion aberration diagram, the maximum value of the image height is shown respectively. In the coma aberration diagram, the value of each image height is shown. d indicates the d-line (wavelength λ = 587.6 nm) and g indicates the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane and the dashed line indicates the meridional image plane. In the aberration diagrams of each of the following embodiments, the same reference numerals as in this embodiment are used and repeated explanations are omitted.

[0091] From each of the various aberration diagrams, it can be seen that the zoom optical system according to the first embodiment corrects various aberrations well from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0092] (Second embodiment) The second embodiment will be described with reference to FIGS. 3 to 4 and Table 2. FIG. 3 is a diagram showing the lens configuration of the zoom optical system according to the second embodiment. The zoom optical system ZL(2) according to the second embodiment includes a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power, which are arranged in order from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, and the interval between adjacent lens groups changes. Also, during zooming, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the first lens group G1 is fixed with respect to the image plane I. The first lens group G1 is composed of a biconcave negative lens L11 and a positive meniscus lens L12 with its convex surface facing the object side, which are arranged in order from the object side along the optical axis. The negative lens L11 is a hybrid lens in which a resin layer is provided on the image side surface of the glass lens body. The image side surface of the resin layer is an aspherical surface, and the negative lens L11 is a composite aspherical lens. In the [Lens Data] described later, surface number 1 is the object side surface of the lens body, surface number 2 is the image side surface of the lens body and the object side surface of the resin layer (the surface where the two are joined), and surface number 3 is the image side surface of the resin layer.

[0093] The second lens group G2 is composed of a biconvex positive lens L21, a positive meniscus lens L22 with its convex surface facing the object side, a positive meniscus lens L23 with its concave surface facing the object side, and a cemented lens of a negative meniscus lens L24 with its concave surface facing the object side, which are arranged in order from the object side along the optical axis. The positive meniscus lens L22 has aspherical surfaces on both lens surfaces. The negative meniscus lens L24 has an aspherical surface on its image side lens surface.

[0094] The third lens group G3 is composed of a negative meniscus lens L31 with its concave surface facing the object side. The negative meniscus lens L31 has aspherical surfaces on both lens surfaces.

[0095] The fourth lens group G4 is composed of a positive meniscus lens L41 with its convex surface facing the object side and a biconvex positive lens L42, which are arranged in order from the object side along the optical axis. The positive meniscus lens L41 has an aspherical surface on its object side lens surface.

[0096] The fourth lens group G4 is composed of a biconvex positive lens L41. An image plane I is disposed on the image side of the fourth lens group G4.

[0097] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 constitute a rear group GR having a positive refractive power as a whole. And the fourth lens group G4 corresponds to the final lens group GE disposed on the most image side of the rear group GR. Further, the positive lens L41 of the fourth lens group G4 corresponds to the final lens. When focusing from an infinite object to a close object, the third lens group G3 moves toward the image side along the optical axis.

[0098] The following Table 2 lists the values of the specifications of the zoom optical system according to the second embodiment. Note that the sixth surface is a virtual surface.

[0099] (Table 2) [Overall specifications] Zoom ratio = 1.272 IHw = 19.683 YLE1 = 14.870 fRw = 17.483 D1 = 3.588 W T f 18.400 23.400 FNO 5.713 5.705 2ω 98.96 85.62 Ymax 19.683 21.120 TL 49.358 49.358 Bf 8.579 12.361 [Lens specifications] Surface number R D nd νd ED 1 -129.182 1.000 1.741000 52.76 2 9.532 0.050 1.560930 36.64 3* 6.858 2.538 4 13.334 2.300 1.902650 35.72 5 47.321 (D5) 6 ∞ 1.000 7 ∞ 0.700 (Diaphragm S) 8 6.988 2.376 1.496997 81.61 9 -53.107 0.374 10* 15.475 1.767 1.531131 55.75 11* 16.211 0.690 12 -29.593 2.194 1.496997 81.61 13 -6.685 0.900 1.882023 37.22 14* -20.145 (D14) 15* -10.562 1.200 1.882023 37.22 16* -14.452 (D16) 17 113.759 3.010 1.953750 32.33 29.730 18 -168.330 Bf 30.470 [Aspherical Data] The 3rd surface κ = 0.481, A4 = -1.0183E-04, A6 = -1.2459E-06, A8 = 3.6115E-09, A10 = -1.9727E-10 The 10th surface κ = 1.000, A4 = -3.4705E-04, A6 = 1.3896E-06, A8 = -2.7121E-08, A10 = 2.4890E-08 The 11th surface κ = 1.000, A4 = -6.4815E-04, A6 = -6.7139E-06, A8 = 9.0303E-08, A10 = 5.7656E-08 The 14th surface κ = 1.000, A4 = 5.7814E-04, A6 = 1.3551E-05, A8 = 2.3393E-07, A10 = -5.2514E-09 The 15th surface κ = 0.741, A4 = 3.4284E-04, A6 = -2.9692E-06, A8 = 9.9964E-09, A10 = -1.3394E-10 The 16th surface κ = 1.217, A4 = 3.4208E-04, A6 = -2.1674E-06, A8 = 1.4380E-09, A10 = 2.0020E-11 [Variable interval data] Infinity focus state WMT Focal length 18.400 20.000 23.400 Object distance ∞ ∞ ∞ D5 8.735 7.230 4.467 D14 7.509 6.994 7.015 D16 4.438 5.034 5.418 Bf 8.579 10.003 12.361 Intermediate distance focus state WMT Magnification -0.025 -0.025 -0.025 Object distance 730.410 795.845 934.378 D5 8.735 7.230 4.467 D14 8.242 7.713 7.763 D16 3.705 4.315 4.670 Bf 8.579 10.003 12.361 Closest distance focus state WMT Magnification -0.052 -0.056 -0.066 Object distance 350.097 350.096 350.097 D5 8.735 7.230 4.467 D14 9.066 8.661 9.071 D16 2.881 3.367 3.362 Bf 8.579 10.003 12.361 [Lens group data] Group Starting surface Focal length G1 1 -22.079 G2 8 15.408 G3 15 -52.012 G4 17 71.547

[0100] FIG. 4(A) is a diagram of various aberrations at infinity focus in the wide-angle end state of the zoom optical system according to the second embodiment. FIG. 4(B) is a diagram of various aberrations at infinity focus in the telephoto end state of the zoom optical system according to the second embodiment. From each diagram of various aberrations, it can be seen that the zoom optical system according to the second embodiment has good correction of various aberrations from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0101] (Third Embodiment) The third embodiment will be described with reference to FIGS. 5 to 6 and Table 3. FIG. 5 is a diagram showing the lens configuration of the zoom optical system according to the third embodiment. The zoom optical system ZL(3) according to the third embodiment is composed of a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power, which are arranged in order from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, and the intervals between adjacent lens groups change. Also, during zooming, the aperture stop S moves along the optical axis together with the second lens group G2, and the position of the first lens group G1 is fixed with respect to the image plane I.

[0102] The first lens group G1 is composed of a cemented lens including a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The negative meniscus lens L11 has aspherical lens surfaces on both sides.

[0103] The second lens group G2 is composed of a cemented lens including a positive meniscus lens L21 with a convex surface facing the object side, a positive meniscus lens L22 with a convex surface facing the object side, a biconvex positive lens L23, and a negative meniscus lens L24 with a concave surface facing the object side, which are arranged in order from the object side along the optical axis. The negative meniscus lens L24 has an aspherical lens surface on the image side.

[0104] The third lens group G3 is composed of a negative meniscus lens L31 with a concave surface facing the object side. The negative meniscus lens L31 has aspherical lens surfaces on both sides.

[0105] The fourth lens group G4 is composed of a biconvex positive lens L41. An image plane I is arranged on the image side of the fourth lens group G4.

[0106] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 together form a rear group GR having a positive refractive power as a whole. And the fourth lens group G4 corresponds to the final lens group GE arranged on the most image side of the rear group GR. Also, the positive lens L41 of the fourth lens group G4 corresponds to the final lens. When focusing from an infinite object to a near-distance object, the third lens group G3 moves toward the image side along the optical axis.

[0107] The following Table 3 lists the values of the specifications of the variable magnification optical system according to the third embodiment. Note that the sixth surface is a virtual surface.

[0108] (Table 3) [Overall specifications] Zoom ratio = 1.272 IHw = 19.477 YLE1 = 14.420 fRw = 16.595 D1 = 7.964 W T f 18.400 23.400 FNO 5.713 5.717 2ω 100.44 85.97 Ymax 19.477 20.710 TL 49.532 49.532 Bf 8.647 13.482 [Lens specifications] Surface number R D nd νd ED 1* 130.766 1.200 1.727926 49.17 2* 7.203 2.864 3 14.601 0.900 1.497820 82.57 4 8.389 3.000 1.749341 42.57 5 27.175 (D5) 6 ∞ 0.700 7 ∞ 0.500 (Aperture S) 8 8.814 1.749 1.496997 81.61 9 112.334 0.442 10 10.063 1.308 1.531131 55.75 11 10.297 0.500 12 33.074 3.477 1.496997 81.61 13 -7.477 0.900 1.619518 36.33 14* -32.358 (D14) 15* -9.518 1.200 1.882023 37.22 16* -15.063 (D16) 17 126.420 3.455 1.900430 37.37 28.830 18 -100.736 Bf 29.800 [Aspherical Data] First Surface κ = 2.000, A4 = 1.0197E-06, A6 = -8.9402E-08, A8 = -2.7648E-10, A10 = 3.7893E-12 Second Surface κ = 1.000, A4 = -2.6735E-05, A6 = -6.0936E-07, A8 = 1.6250E-09, A10 = -4.0421E-10 Fourteenth Surface κ = 1.000, A4 = 3.1906E-04, A6 = 4.8473E-06, A8 = 7.4277E-08, A10 = 3.2640E-09 Fifteenth Surface κ = 1.000, A4 = 2.4482E-04, A6 = -2.4107E-06, A8 = 1.3351E-09, A10 = -4.9608E-12 Sixteenth Surface κ = 1.333, A4 = 2.7878E-04, A6 = -1.9504E-06, A8 = 8.1780E-09, A10 = -8.9157E-12 [Variable interval data] Infinity focus state W M T Focal length 18.400 20.000 23.400 Object distance ∞ ∞ ∞ D5 6.596 5.184 2.575 D14 7.308 7.148 7.233 D16 4.787 4.837 4.049 Bf 8.647 10.169 13.482 Intermediate distance focus state W M T Magnification -0.026 -0.026 -0.026 Object distance 700.012 749.998 890.028 D5 6.596 5.184 2.575 D14 7.760 7.609 7.712 D16 4.335 4.376 3.570 Bf 8.647 10.169 13.482 Closest distance focus state W M T Magnification -0.052 -0.056 -0.066 Object distance 350.026 350.087 350.216 D5 6.596 5.184 2.575 D14 8.218 8.144 8.467 D16 3.878 3.841 2.816 Bf 8.647 10.169 13.482 [Lens group data] Group Starting surface Focal length G1 1 -20.271 G2 8 14.114 G3 15 -32.619 G4 17 62.714

[0109] Fig. 6(A) is a diagram of various aberrations at infinity focus in the wide-angle end state of the zoom optical system according to the third embodiment. Fig. 6(B) is a diagram of various aberrations at infinity focus in the telephoto end state of the zoom optical system according to the third embodiment. From each diagram of various aberrations, it can be seen that the zoom optical system according to the third embodiment has good correction of various aberrations from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0110] (Fourth Embodiment) The fourth embodiment will be described with reference to Figs. 7 to 8 and Table 4. Fig. 7 is a diagram showing the lens configuration of the zoom optical system according to the fourth embodiment. The zoom optical system ZL(4) according to the fourth embodiment is composed of a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power, which are arranged in order from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1 first moves toward the image side along the optical axis and then moves toward the object side, and the second lens group G2 and the third lens group G3 move toward the object side along the optical axis, and the interval between adjacent lens groups changes. Also, during zooming, the aperture stop S moves along the optical axis together with the second lens group G2.

[0111] The first lens group G1 is composed of a cemented lens of a negative meniscus lens L11 with a convex surface facing the object side, a negative meniscus lens L12 with a convex surface facing the object side, and a positive meniscus lens L13 with a convex surface facing the object side, which are arranged in order from the object side along the optical axis. The negative meniscus lens L11 has aspherical lens surfaces on both sides.

[0112] The second lens group G2 is composed of a biconvex positive lens L21, a negative meniscus lens L22 with a convex surface facing the object side, a cemented lens of a positive meniscus lens L23 with a convex surface facing the object side, a cemented lens of a biconvex positive lens L24 and a negative meniscus lens L25 with a concave surface facing the object side, a positive meniscus lens L26 with a concave surface facing the object side, and a negative meniscus lens L27 with a concave surface facing the object side, arranged in order from the object side along the optical axis. The positive meniscus lens L26 has aspherical surfaces on both sides. The negative meniscus lens L27 has aspherical surfaces on both sides.

[0113] The third lens group G3 is composed of a biconvex positive lens L31. An image plane I is arranged on the image side of the third lens group G3.

[0114] In this embodiment, the second lens group G2 and the third lens group G3 constitute a rear group GR having a positive refractive power as a whole. And the third lens group G3 corresponds to the final lens group GE arranged on the most image side of the rear group GR. Also, the positive lens L31 of the third lens group G3 corresponds to the final lens. When focusing from an infinite object to a near object, the first lens group G1 and the second lens group G2 move along the optical axis toward the object side with different trajectories (amounts of movement).

[0115] The following Table 4 lists the values of the specifications of the zoom optical system according to the fourth embodiment.

[0116] (Table 4) [Overall specifications] Zoom ratio = 1.272 IHw = 19.626 YLE1 = 14.790 fRw = 16.390 D1 = 7.881 W T f 18.400 23.400 FNO 5.709 5.715 2ω 100.57 95.34 Ymax 19.626 21.600 TL 49.499 49.462 Bf 8.607 12.538 [Lens Specifications] Surface No. R D nd νd ED 1* 71.036 1.200 1.693430 53.30 2* 7.423 3.005 3 13.478 1.000 1.497820 82.57 4 8.024 2.676 1.741855 43.59 5 19.000 (D5) 6 ∞ 0.500 (Aperture S) 7 15.280 1.627 1.496997 81.61 8 -33.660 0.200 9 14.812 0.900 1.850000 27.03 10 8.658 1.596 1.900430 37.37 11 17.168 1.207 12 41.240 2.803 1.496997 81.61 13 -7.645 0.900 1.587634 41.38 14 -37.583 0.500 15* -447.785 1.941 1.531131 55.75 16* -166.952 3.156 17* -10.496 1.200 1.882023 37.22 18* -18.856 (D18) 19 162.352 3.705 1.900430 37.37 29.570 20 -78.975 Bf 30.540 [Aspherical Data] First Surface κ = 2.000, A4 = -5.3759E-06, A6 = -3.2180E-07, A8 = 1.9522E-09, A10 = -3.2146E-12 Second Surface κ = 0.692, A4 = 2.4610E-05, A6 = -2.1145E-07, A8 = -1.0420E-08, A10 = -1.1155E-10 Page 15 κ = 1.000, A4 = 2.4812E-04, A6 = -1.1561E-05, A8 = 6.9825E-07, A10 = -8.7384E-09 Page 16 κ = 1.000, A4 = 3.2250E-04, A6 = -1.5148E-05, A8 = 3.7657E-07, A10 = -3.0591E-10 Page 17 κ = 2.000, A4 = 2.4715E-04, A6 = -1.5123E-05, A8 = 1.3715E-07, A10 = -3.6625E-09 Page 18 κ = 2.000, A4 = 2.5191E-04, A6 = -8.2472E-06, A8 = 1.1360E-07, A10 = -3.9580E-10 [Variable interval data] Infinity focus state W M T Focal length 18.400 20.000 23.400 Object distance ∞ ∞ ∞ D5 6.923 5.437 2.955 D18 5.855 5.855 5.855 Bf 8.607 9.865 12.538 Intermediate distance focus state W M T Magnification -0.026 -0.026 -0.026 Object distance 699.337 749.569 889.517 D5 7.105 5.793 3.440 D18 6.329 6.142 5.838 Bf 8.607 9.865 12.538 Closest distance focus state W M T Magnification -0.123 -0.129 -0.139 Object distance 147.150 147.227 147.589 D5 7.948 7.042 5.553 D18 7.766 7.293 5.814 Bf 8.607 9.865 12.538 [Lens group data] Group starting surface Focal length G1 1 -20.847 G2 7 15.067 G3 19 59.438

[0117] Figure 8(A) is a diagram of various aberrations at infinity focus in the wide-angle end state of the zoom optical system according to the fourth embodiment. Figure 8(B) is a diagram of various aberrations at infinity focus in the telephoto end state of the zoom optical system according to the fourth embodiment. From each diagram of various aberrations, it can be seen that the zoom optical system according to the fourth embodiment has good correction of various aberrations from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0118] (Fifth Embodiment) The fifth embodiment will be described with reference to FIGS. 9 to 10 and Table 5. FIG. 9 is a diagram showing the lens configuration of the zoom optical system according to the fifth embodiment. The zoom optical system ZL(5) according to the fifth embodiment includes a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power, which are arranged in order from the object side along the optical axis. When zooming from the wide-angle end state (W) to the telephoto end state (T), the first lens group G1, the second lens group G2, the third lens group G3, and the fourth lens group G4 move toward the object side along the optical axis, and the interval between adjacent lens groups changes. Also, during zooming, the aperture stop S moves along the optical axis together with the second lens group G2.

[0119] The first lens group G1 is composed of a biconcave negative lens L11 and a positive meniscus lens L12 with its convex surface facing the object side, arranged in order from the object side along the optical axis. The negative lens L11 is a hybrid lens formed by providing a resin layer on the image side surface of a glass lens body. The image side surface of the resin layer is an aspherical surface, and the negative lens L11 is a composite aspherical lens. In the [Lens Specifications] described later, surface number 1 is the object side surface of the lens body, surface number 2 is the image side surface of the lens body and the object side surface of the resin layer (the surface where the two are joined), and surface number 3 is the image side surface of the resin layer.

[0120] The second lens group G2 is composed of a biconvex positive lens L21, a positive meniscus lens L22 with its convex surface facing the object side, a positive meniscus lens L23 with its concave surface facing the object side, and a cemented lens of a negative meniscus lens L24 with its concave surface facing the object side, arranged in order from the object side along the optical axis. The positive meniscus lens L22 has aspherical surfaces on both lens surfaces. The negative meniscus lens L24 has an aspherical surface on its image side lens surface.

[0121] The third lens group G3 is composed of a negative meniscus lens L31 with its concave surface facing the object side. The negative meniscus lens L31 has aspherical surfaces on both lens surfaces.

[0122] The fourth lens group G4 is composed of a biconvex positive lens L41. An image plane I is arranged on the image side of the fourth lens group G4.

[0123] In this embodiment, the second lens group G2, the third lens group G3, and the fourth lens group G4 together form a rear group GR having a positive refractive power as a whole. And the fourth lens group G4 corresponds to the final lens group GE arranged on the most image side of the rear group GR. Also, the positive lens L41 of the fourth lens group G4 corresponds to the final lens. When focusing from an infinite object to a near object, the third lens group G3 moves toward the image side along the optical axis.

[0124] The following Table 5 lists the values of the specifications of the zoom optical system according to the fifth embodiment. Note that the sixth surface is a virtual surface.

[0125] (Table 5) [Overall Specifications] Magnification Ratio = 1.272 IHw = 19.701 YLE1 = 14.910 fRw = 17.165 D1 = 6.219 W T f 18.400 23.400 FNO 5.710 5.708 2ω 99.996 85.06 Ymax 19.701 21.020 TL 49.709 50.616 Bf 8.603 12.351 [Lens Specifications] Surface No. R D nd νd ED 1 -281.384 1.000 1.729160 54.61 2 9.554 0.050 1.560930 36.64 3* 6.796 2.869 4 13.179 2.300 1.902650 35.72 5 35.513 (D5) 6 ∞ 1.000 7 ∞ 0.700 (Aperture S) 8 6.899 3.043 1.496997 81.61 9 -42.666 0.476 10* 15.768 1.421 1.531131 55.75 11* 16.691 0.700 12 -25.255 2.160 1.496997 81.61 13 -6.778 0.900 1.882023 37.22 14* -20.575 (D14) 15* -10.893 1.200 1.882023 37.22 16* -15.024 (D16) 17 111.885 2.987 1.953750 32.33 29.840 18 - 182.140 Bf 30.530 [Aspherical Data] Third Surface κ = 0.480, A4 = -7.8376E-05, A6 = -1.0021E-06, A8 = 4.2191E-09, A10 = -2.0788E-10 Tenth Surface κ = 1.000, A4 = -5.5094E-04, A6 = -3.0360E-06, A8 = 6.0886E-08, A10 = 3.2465E-08 Eleventh Surface κ = 1.000, A4 = -8.3560E-04, A6 = -8.8381E-06, A8 = 1.6661E-07, A10 = 7.8627E-08 Fourteenth Surface κ = 1.000, A4 = 5.8322E-04, A6 = 1.2048E-05, A8 = 2.4869E-07, A10 = -1.0244E-08 Fifteenth Surface κ = 1.000, A4 = 3.4821E-04, A6 = -2.5826E-06, A8 = 1.3777E-08, A10 = -1.0716E-10 Sixteenth Surface κ = 1.000, A4 = 3.0694E-04, A6 = -2.1817E-06, A8 = 4.7344E-09, A10 = -5.5702E-12 [Variable Interval Data] Infinity Focus State W M T Focal Length 18.400 20.000 23.400 Object Distance ∞ ∞ ∞ D5 8.428 7.074 4.640 D14 7.745 7.030 6.721 D16 4.127 4.903 6.098 Bf 8.603 10.160 12.351 Intermediate Distance Focus State W M T Magnification -0.025 -0.025 -0.025 Object Distance 730.163 795.653 934.123 D5 8.428 7.074 4.640 D14 8.494 7.749 7.444 D16 3.378 4.183 5.374 Bf 8.603 10.160 12.351 To the close focusing state W M T Magnification -0.052 -0.056 -0.066 Object distance 349.746 349.482 348.839 D5 8.428 7.074 4.640 D14 9.338 8.701 8.711 D16 2.534 3.232 4.107 Bf 8.603 10.160 12.351 [Lens group data] Group Starting surface Focal length G1 1 -21.059 G2 8 15.289 G3 15 -52.000 G4 17 73.033

[0126] FIG. 10(A) is a diagram of various aberrations at infinity focus in the wide-angle end state of the zoom optical system according to the fifth embodiment. FIG. 10(B) is a diagram of various aberrations at infinity focus in the telephoto end state of the zoom optical system according to the fifth embodiment. From each diagram of various aberrations, it can be seen that the zoom optical system according to the fifth embodiment has good correction of various aberrations from the wide-angle end state to the telephoto end state and has excellent imaging performance.

[0127] Next, a table of [conditional expression corresponding values] is shown below. This table collectively shows the values corresponding to each conditional expression (1) to (14) for all the embodiments (the first to the fifth embodiments). Conditional expression (1) 0.15 < ft / fGE < 0.60 Conditional expression (2) 2.00 < TLt / IHw < 3.00 Conditional expression (3) 1.00 < (-f1) / fRw < 1.50 Conditional expression (4) 0.30 < Bfw / IHw < 0.60 Conditional expression (5) 0.50 < YLE1 / IHw < 1.00 Conditional expression (6) 0.80 < (-f1) / fw < 1.40 Conditional expression (7) 0.50 < f2 / fw < 1.00 Conditional expression (8) 0.60 < f2 / fRw < 1.20 Conditional expression (9) 1.10 < ft / fw < 1.50 Conditional expression (10) -1.50 < (L1r2 + L1r1) / (L1r2 - L1r1) < -0.60 Conditional expression (11) -0.50 < (LEr2 + LEr1) / (LEr2 - LEr1) < 0.60 Conditional expression (12) 88.00° < 2ωw Conditional expression (13) 0.01 < D1 / TLw < 0.20 Conditional expression (14) 0.10 < Bfw / fw < 0.60

[0128] [Corresponding values of conditional expressions] (First to third embodiments) Conditional expression First embodiment Second embodiment Third embodiment (1) 0.336 0.327 0.373 (2) 2.519 2.508 2.543 (3) 1.201 1.263 1.222 (4) 0.442 0.436 0.444 (5) 0.759 0.755 0.740 (6) 1.118 1.200 1.102 (7) 0.812 0.837 0.767 (8) 0.872 0.881 0.850 (9) 1.272 1.272 1.272 (10) -0.962 -0.863 -1.117 (11) -0.186 -0.193 0.113 (12) 100.18 98.96 100.44 (13) 0.127 0.073 0.161 (14) 0.472 0.466 0.470 [Conditional response values] (4th to 5th embodiments) Conditional expression 4th embodiment 5th embodiment (1) 0.394 0.320 (2) 2.520 2.569 (3) 1.272 1.227 (4) 0.439 0.437 (5) 0.754 0.757 (6) 1.133 1.145 (7) 0.819 0.831 (8) 0.919 0.891 (9) 1.272 1.272 (10) -1.233 -0.934 (11) 0.345 -0.239 (12) 100.57 100.00 (13) 0.159 0.125 (14) 0.468 0.468

[0129] According to each of the above embodiments, it is possible to realize a zoom optical system that is small in size and has bright and good optical performance.

[0130] Each of the above embodiments shows a specific example of the present invention, and the present invention is not limited thereto.

[0131] The following content can be appropriately adopted within a range that does not impair the optical performance of the zoom optical system of the present embodiment.

[0132] Examples of the zoom optical system of the present embodiment have shown those having a three-group configuration and a four-group configuration, but the present application is not limited thereto, and it is also possible to configure a zoom optical system having other group configurations (for example, five groups, six groups, etc.). Specifically, a configuration in which a lens or a lens group is added to the most object side or the most image plane side of the zoom optical system of the present embodiment may be used. Note that the lens group refers to a portion having at least one lens separated by an air interval that changes during zooming.

[0133] It may also be used as a focusing lens group that moves a single or multiple lens groups, or partial lens groups, in the optical axis direction to focus from an infinite object to a close - up object. The focusing lens group can also be applied to autofocus and is suitable for motor drive (using an ultrasonic motor or the like) for autofocus.

[0134] It may also be used as an anti - shake lens group that moves a lens group or partial lens group so as to have a component in a direction perpendicular to the optical axis, or rotates (swings) in a plane direction including the optical axis to correct image blur caused by camera shake.

[0135] The lens surface may be formed as a spherical surface, a planar surface, or an aspherical surface. When the lens surface is a spherical surface or a planar surface, it is preferable because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented. Also, it is preferable because deterioration of the imaging performance is small even when the image plane is shifted.

[0136] When the lens surface is an aspherical surface, the aspherical surface may be any of an aspherical surface formed by grinding, a glass - molded aspherical surface formed by shaping glass into an aspherical shape using a mold, and a composite aspherical surface formed by forming a resin on the surface of glass into an aspherical shape. Also, the lens surface may be a diffractive surface, and the lens may be a gradient - index lens (GRIN lens) or a plastic lens.

[0137] The aperture stop is preferably arranged between the first lens group and the second lens group, but the role of the aperture stop may be substituted by the frame of the lens without providing a member as the aperture stop.

[0138] An antireflection film having a high transmittance in a wide wavelength range may be applied to each lens surface to reduce flare and ghost and achieve high - contrast optical performance.

Explanation of symbols

[0139] G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group I Image plane S Aperture stop

Claims

1. It consists of a first lens group having a negative refractive power and arranged in order from the object side along the optical axis, and a rear group having at least two lens groups. During zooming, the distance between adjacent lens groups changes. The at least two lens groups of the rear group include a final lens group having a positive refractive power arranged on the most image side of the rear group. The rear group includes at least one cemented lens of a positive lens and a negative lens. The rear group includes a lens that moves during focusing. A zoom optical system that satisfies the following conditional expression. 0.15 < ft / fGE < 0.60 However, ft: The focal length of the zoom optical system in the telephoto end state fGE: The focal length of the final lens group

2. The zoom optical system according to claim 1, wherein the lens that moves during focusing consists of one lens.

3. The zoom optical system according to claim 1 that satisfies the following conditional expression. 2.00 < TLt / IHw < 3.00 However, TLt: The overall length of the zoom optical system in the telephoto end state IHw: The maximum image height of the zoom optical system in the wide-angle end state

4. The zoom optical system according to claim 1 or 3 that satisfies the following conditional expression. 1.00 < (-f1) / fRw < 1.50 However, f1: The focal length of the first lens group fRw: The focal length of the rear group in the wide-angle end state

5. The zoom optical system according to any one of claims 1 to 4 that satisfies the following conditional expression. 0.30 < Bfw / IHw < 0.60 However, Bfw: The back focus of the zoom optical system in the wide-angle end state IHw: The maximum image height of the zoom optical system in the wide-angle end state

6. The zoom optical system according to any one of claims 1 to 5 that satisfies the following conditional expression. 0.50 < YLE1 / IHw < 1.00 However, YLE1: The effective radius of the lens surface on the object side of the lens arranged on the most image side of the zoom optical system IHw: The maximum image height of the zoom optical system in the wide-angle end state

7. The zoom optical system according to any one of claims 1 to 6 that satisfies the following conditional expression. 0.80 < (-f1) / fw < 1.40 However, f1: The focal length of the first lens group fw: The focal length of the zoom optical system in the wide-angle end state

8. The at least two lens groups of the rear group include a second lens group having a positive refractive power arranged on the most object side of the rear group. The zoom optical system according to any one of claims 1 to 7 that satisfies the following conditional expression. 0.50 < f2 / fw < 1.00 However, f2: The focal length of the second lens group fw: Focal length of the zoom optical system in the wide-angle end state

9. The at least two lens groups of the rear group include a second lens group having a positive refractive power disposed on the most object side of the rear group, The zoom optical system according to any one of Claims 1 to 8, satisfying the following conditional expression. 0.60 < f2 / fRw < 1.20 However, f2: Focal length of the second lens group fRw: Focal length of the rear group in the wide-angle end state

10. The zoom optical system according to any one of Claims 1 to 9, satisfying the following conditional expression. 1.10 < ft / fw < 1.50 However, ft: Focal length of the zoom optical system in the telephoto end state fw: Focal length of the zoom optical system in the wide-angle end state

11. The zoom optical system according to any one of Claims 1 to 10, satisfying the following conditional expression. -1.50 < (L1r2 + L1r1) / (L1r2 - L1r1) < -0.60 However, L1r1: Curvature radius of the object-side lens surface of the lens disposed on the most object side of the zoom optical system L1r2: Curvature radius of the image-side lens surface of the lens disposed on the most object side of the zoom optical system

12. The zoom optical system according to any one of Claims 1 to 11, satisfying the following conditional expression. -0.50 < (LEr2 + LEr1) / (LEr2 - LEr1) < 0.60 However, LEr1: Curvature radius of the object-side lens surface of the lens disposed on the most image side of the zoom optical system LEr2: Curvature radius of the image-side lens surface of the lens disposed on the most image side of the zoom optical system

13. The zoom optical system according to any one of Claims 1 to 12, having a diaphragm disposed between the first lens group and the rear group.

14. The zoom optical system according to any one of Claims 1 to 13, satisfying the following conditional expression. 88.00° < 2ωw However, 2ωw: Total field angle of the zoom optical system in the wide-angle end state

15. The zoom optical system according to any one of Claims 1 to 14, satisfying the following conditional expression. 0.01 < D1 / TLw < 0.20 However, D1: Thickness on the optical axis of the first lens group TLw: Total length of the zoom optical system in the wide-angle end state

16. The zoom optical system according to any one of Claims 1 to 15, satisfying the following conditional expression. 0.10 < Bfw / fw < 0.60 However, Bfw: Back focus of the zoom optical system in the wide-angle end state fw: Focal length of the zoom optical system in the wide-angle end state

17. ​ An optical apparatus comprising the zoom optical system according to any one of claims 1 to 16.

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