OPTICAL SYSTEM AND PHOTOGRAPHING DEVICE HAVING OPTICAL SYSTEM

Abstract

An optical system includes: a first lens group having a positive refractive power, a second lens group having a negative refractive power and a third lens group having a positive or negative refractive power, arranged from an object side to an image side; when focusing, the second lens group moves along an optical axis, positions of the first and third lens groups relative to an imaging plane along the optical axis are fixed; when a lateral magnification of the third lens group at infinity is b3, a distance from a face closest to the object side of the entire optical system to the imaging plane is OAL, a focal length of the entire optical system focusing at infinity is f, and a maximum lateral magnification of the entire optical system is B, it is satisfied that: (0.80b3), (OAL/f2.00), (0.50|B|).

Claims

1. An optical system, comprising a first lens group having a positive refractive power, a second lens group having a negative refractive power and a third lens group having a positive or negative refractive power, sequentially arranged from an object side to an image side; when focusing, the second lens group moves along an optical axis, positions of the first lens group and the third lens group relative to an imaging plane in a direction of the optical axis are fixed, where a lateral magnification of the third lens group focusing at infinity is b3, a distance from a face closest to the object side of the entire optical system to the imaging plane is OAL, a focal length of the entire optical system focusing at infinity is f, and a maximum lateral magnification of the entire optical system is B, it is satisfied that: $0.8b3\underset{\_}{,}$ $\mathrm{OAL}/f2.\underset{\_}{,\mathrm{and}}$ $0.5.Math.B.Math..$

2. An optical system, comprising: a first lens group having a positive refractive power, a second lens group having a negative refractive power and a third lens group having a positive or negative refractive power, sequentially arranged from an object side to an image side, when focusing, the second lens group moves along an optical axis, positions of the first lens group and the third lens group relative to an imaging plane in a direction of the optical axis are fixed, the second lens group has at least one lens having a positive refractive power, when a refractive index of the lens having a positive refractive power based on a d-line is nd2p, an Abbe number of the lens having a positive refractive power based on the d-line is vd2p, and a variable is A, it is satisfied that: $\mathrm{nd}2p=-0.01\mathrm{vd}2p+A$ $1.55\mathrm{nd}2p1.72\underset{\_}{,\mathrm{and}}$ $1.82A1.94.$

3. The optical system according to claim 1, wherein, the second lens group having: at least one lens having a positive refractive power; and at least one lens having a negative refractive power, in the second lens group, a lens having the strongest positive refractive power is located closer to the image side than a lens having the strongest negative refractive power.

4. The optical system according to claim 1, wherein, when a lateral magnification of the second lens group focusing at infinity is b2 and the lateral magnification of the third lens group focusing at infinity is b3, it is satisfied that: $-10.\left(1-b{2}^2\right)b{3}^2-2..$

5. The optical system according to claim 1, wherein, when the focal length of the entire optical system focusing at infinity is f, and a focal length of the second lens group is f2, it is satisfied that: $-0.70\mathrm{f2}/f-0.10.$

6. A photographing device, comprising: an optical system according to claim 1; and a photographing element arranged at a side of the imaging plane of the optical system and configured to convert an optical image formed by the optical system into an electrical signal.

7. The optical system according to claim 1, wherein, it is satisfied that:
0.90b32.00.

8. The optical system according to claim 7, wherein it is satisfied that:
1.00b31.20.

9. The optical system according to claim 1, wherein it is satisfied that: $0.8\mathrm{OAL}/f1.5.$

10. The optical system according to claim 9, wherein it is satisfied that: $0.9\mathrm{OAL}/f1..$

11. The optical system according to claim 1, wherein it is satisfied that: $0.75.Math.B.Math..$

12. The optical system according to claim 11, wherein it is satisfied that: $1..Math.B.Math..$

13. The optical system according to claim 2, wherein wherein, the second lens group having: at least one lens having a positive refractive power; and at least one lens having a negative refractive power, in the second lens group, a lens having the strongest positive refractive power is located closer to the image side than a lens having the strongest negative refractive power.

14. The optical system according to claim 2, wherein, a lateral magnification of the second lens group focusing at infinity is b2, the lateral magnification of the third lens group focusing at infinity is b3, and it is satisfied that: $-10.00\left(1-b{2}^2\right)b{3}^2-2.00.$

15. The optical system according to claim 2, wherein, the focal length of the optical system focusing at infinity is f, a focal length of the second lens group is f2, and it is satisfied that: $-0.70f2/f-0.10.$

16. The optical system according to claim 2, wherein it is satisfied that:
1.57nd2p1.70.

17. The optical system according to claim 16, wherein it is satisfied that:
1.59nd2p1.68.

18. The optical system according to claim 2, wherein it is satisfied that:
1.84A1.92.

19. The optical system according to claim 18, wherein it is satisfied that:
1.86A1.90.

20. A photographing device, comprising: an optical system according to claim 2; and a photographing element arranged at a side of the imaging plane of the optical system and configured to convert an optical image formed by the optical system into an electrical signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a schematic diagram showing a configuration of a photographing device according to an embodiment.

[0007] FIG. 2 is a lens configuration diagram of an optical system according to embodiment 1 in an infinity focus state.

[0008] FIG. 3 is a lens configuration diagram of an optical system according to embodiment 1 in a closest focus state.

[0009] FIG. 4 is a longitudinal aberration diagram of an optical system according to embodiment 1 in an infinity focus state.

[0010] FIG. 5 is a longitudinal aberration diagram of an optical system according to embodiment 1 at a magnification of 0.5.

[0011] FIG. 6 is a longitudinal aberration diagram of an optical system according to embodiment 1 at a magnification of 1.0.

[0012] FIG. 7 is a lens configuration diagram of an optical system according to embodiment 2 in an infinity focus state.

[0013] FIG. 8 is a lens configuration diagram of an optical system according to embodiment 2 in a closest focus state.

[0014] FIG. 9 is a longitudinal aberration diagram of an optical system according to embodiment 2 in an infinity focus state.

[0015] FIG. 10 is a longitudinal aberration diagram of an optical system according to embodiment 2 at a magnification of 0.5.

[0016] FIG. 11 is a longitudinal aberration diagram of an optical system according to embodiment 2 at a magnification of 1.0.

[0017] FIG. 12 is a lens configuration diagram of an optical system according to embodiment 3 in an infinity focus state.

[0018] FIG. 13 is a lens configuration diagram of an optical system according to embodiment 3 in a closest focus state.

[0019] FIG. 14 is a longitudinal aberration diagram of an optical system according to embodiment 3 in an infinity focus state.

[0020] FIG. 15 is a longitudinal aberration diagram of an optical system according to embodiment 3 at a magnification of 0.5.

[0021] FIG. 16 is a longitudinal aberration diagram of an optical system according to embodiment 3 at a magnification of 1.0.

[0022] FIG. 17 is a lens configuration diagram of an optical system according to embodiment 4 in an infinity focus state.

[0023] FIG. 18 is a lens configuration diagram of an optical system according to embodiment 4 in a closest focus state.

[0024] FIG. 19 is a longitudinal aberration diagram of an optical system according to embodiment 4 in an infinity focus state.

[0025] FIG. 20 is a longitudinal aberration diagram of an optical system according to embodiment 4 at a magnification of 0.5.

[0026] FIG. 21 is a longitudinal aberration diagram of an optical system according to embodiment 4 at a magnification of 1.0.

[0027] FIG. 22 is a lens configuration diagram of an optical system according to embodiment 5 in an infinity focus state.

[0028] FIG. 23 is a lens configuration diagram of an optical system according to embodiment 5 in a closest focused state.

[0029] FIG. 24 is a longitudinal aberration diagram of an optical system according to embodiment 5 in an infinity focus state.

[0030] FIG. 25 is a longitudinal aberration diagram of an optical system according to embodiment 5 at a magnification of 0.5.

[0031] FIG. 26 is a longitudinal aberration diagram of an optical system according to embodiment 5 at a magnification of 1.0.

DETAILED DESCRIPTION

[0032] In related art, the optical system described in Japanese patent communiqu No.5749629 is not sufficient for close range photographing, and the optical system described in patent Japanese special publication communiqu No. 2021-173847 is not sufficiently miniaturized because a ratio of a total length of the optical system to a total lens of a focal length is large.

[0033] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0034] As shown in FIG. 1, a photographing device 1 according to the present embodiment includes an optical system 2, a photographing element 3 arranged at a position of an imaging plane of the optical system 2, and a liquid crystal screen 4 for displaying photographing (image) data transmitted from a photographing element 3. The photographing device 1 includes a driving part (not shown in the figures) for driving the optical system 2. The driving part is an actuator such as a VCM (Voice Coil Motor), to drive a predetermined lens or lens group and the like included in the optical system 2 in a direction substantially perpendicular to a light receiving surface of the photographing element 3 (a direction of an optical axis). In addition, the photographing element 3 is an element that converts an optical image formed by the optical system 2 into an electrical signal (photographing data), and the photographing element 3 of the present embodiment is a CMOS image sensor.

[0035] The optical system 2 is a so-called internal focus optical system, and the optical system 2 of the present embodiment is a so-called periscope telephoto lens in which an optical axis (optical path) C is bent by a reflective optical element such as a prism or a mirror. Specifically, the optical system 2 includes a prism 20 that bends the optical axis C and a plurality of lens groups G arranged on the optical axis C, sequentially from an object side to an image side along the optical axis C. In addition, the optical system 2 includes an aperture diaphragm 24, an optical filter 25 arranged between the plurality of lens groups G and the photographing element 3, and a lens barrel 26 holding the plurality of lens groups G.

[0036] The plurality of lens groups G at least include a first lens group 21, a second lens group 22, and a third lens group 23 sequentially from the object side to the image side along the optical axis C. Each of the lens groups 21, 22 and 23 includes at least one lens (optical element).

[0037] In addition, in the optical system 2 of the present embodiment, the lens groups 21 to 23 are named for convenience, and include a lens group composed of only one optical element (lens, etc.). That is, the first to third lens groups 21, 22 and 23 each have at least one optical element such as a lens. In addition, in the optical system 2, the optical elements (lenses, etc.) whose positions are fixed on the optical axis C during focusing are separated from the moving optical elements, and the at least one fixed optical element in a separated area is regarded as one lens group, and the at least one moving optical element in a separated area is regarded as another lens group.

[0038] In the above-mentioned optical system 2, during focusing, the second lens group 22 moves along the optical axis C, and positions of the first lens group 21 and the third lens group 23 in the direction of the optical axis C are fixed relative to the photographing element 3 (the imaging plane of the optical system 2). That is, in the optical system 2 of the present embodiment, among the lens groups 21, 22 and 23, the second lens group 22 constitutes a focusing lens group F.

[0039] The lens groups 21 to 23 in the optical system 2 will be described in detail below.

[0040] The first lens group 21 includes a plurality of lenses (four lenses in an example of the present embodiment) having a positive refractive power. In addition, the second lens group 22 includes a plurality of lenses (two lenses in the example of the present embodiment) having a negative refractive power. In addition, the third lens group 23 includes a plurality of lenses (two lenses in the example of the present embodiment) having a positive or negative refractive power.

[0041] When a lateral magnification of the third lens group 23 focusing at infinity is b3, a distance from a face closest to the object side of the entire optical system to the imaging plane is OAL, a focal length of the entire optical system focusing at infinity is f, and a maximum lateral magnification of the entire optical system is B, the optical system 2 satisfies the following formula (1), (2), (3).

[00001]$\begin{array}{cc}0.8b3& \left(1\right)\end{array}$$\begin{array}{cc}\mathrm{OAL}/f2.& \left(2\right)\end{array}$$\begin{array}{cc}0.5.Math.B.Math.& \left(3\right)\end{array}$

[0042] In the above optical system 2, among the plurality of lens groups G arranged along the optical axis C, the first lens group 21 having a positive refractive power is arranged at closest to the object side, the second lens group 22 having a negative refractive power is arranged at an image side of the first lens group 21, and the third lens group 23 having a positive or negative refractive power is arranged closest to the image side. As a result, it is easy to obtain a focal power arrangement of telephoto in the optical system 2, and therefore a focal length of the first lens group 21 may be shortened, resulting in that miniaturization of the optical system 2 (specifically, miniaturation in the direction of the optical axis C) may be realized.

[0043] Moreover, by moving the second lens group during focusing, the aberration variation balance with the front and rear lens groups 21, 23 may be adjusted. Bending variation of the imaging plane during a close range photographing may be suppressed compared with a whole extension mode, so that the close range photographing distance may be further shortened.

[0044] Furthermore, by fixing the first lens group 21 and the third lens group 23 relative to the imaging plane, only the second lens group 22 is set as a movable lens group, so that a load on a mechanism or actuator may be reduced, and therefore, the overall miniaturization of the photographing device 1 including the optical system 2 may be realized.

[0045] The above formula (1) specifies the lateral magnification (b3) of the third lens group 23 focusing at infinity. When the lateral magnification (b3) is lower than a lower limit (0.80), the lateral magnification of the lens group (third lens group) 23 closest to the image side among the plurality of lens groups 21, 22 and 23 becomes smaller, so that the focal length of the second lens group 22 becomes longer, and the miniaturization of the entire optical system 2 is insufficient.

[0046] In addition, the above formula (2) represents the distance (OAL) from the face closest to the object side of the entire optical system 2 to the imaging plane relative to the focal length. When the distance (OAL) exceeds an upper limit (2.00), it cannot be said that the total optical length may be sufficiently shortened, and not only the optical system 2 but also the entire photographing device 1 cannot be miniaturized.

[0047] In addition, the above formula (3) specifies the maximum lateral magnification of the entire optical system 2, that is, a ratio (B) of a height of an image on the imaging plane to a height of an object of a subject. When the absolute value of this numerical value is lower than a lower limit (0.50), it cannot be said that a close-range photographing may be fully realized and a distance from the object that may be photographed cannot be shortened.

[0048] Therefore, in the optical system 2 of the present embodiment, the above three formulas (formula (1), formula (2), and formula (3)) are satisfied at the same time, thereby realizing an optical system 2 that has a small overall size and capable of photographing at a close range.

[0049] The maximum lateral magnification (B) of the entire optical system 2 is a numerical value indicating a degree of a close range photographing, and as mentioned above, it is expressed by a ratio of a height of the image on the photographing surface to a height of the object of the subject. For example, when photographing at a close range and |B| is 1.00, sizes of the subject and the photographing surface are equal, and when photographing at a long distance, |B| becomes close to 0.00.

[0050] In addition, in some examples, in the optical system 2 of the present embodiment, the lateral magnification (b3) satisfies the following formula. 0.90b32.00.

[0051] In some examples, the following formula is satisfied. 1.00b31.20.

[0052] In addition, in some examples, in the optical system 2 of the present embodiment,

[0053] the distance (OAL) satisfies the following formula.

[00002]$0.8\mathrm{OAL}/f1.5.$

[0054] In some examples, the following formula is satisfied.

[00003]$0.9\mathrm{OAL}/f1..$

[0055] In addition, in some examples, in the optical system 2 of the present embodiment, the maximum lateral magnification (B) satisfies the following formula (3).

[00004]$0.75.Math.B.Math..$

[0056] In some examples, the following formula is satisfied.

[00005]$1..Math.B.Math..$

[0057] In addition, in the optical system 2 of the photographing device 1, when a refractive index of a lens having a positive refractive power based on a d-line is nd2p, an Abbe number of the lens having a positive refractive power based on the d-line is vd2p, and a variable is A, the optical system 2 may satisfy the following formulas (4), (5) and (6).

[00006]$\begin{array}{cc}\mathrm{nd}2p=-0.01\mathrm{vd}2p+A& \left(4\right)\end{array}$$\begin{array}{cc}1.55\mathrm{nd}2p1.72& \left(5\right)\end{array}$$\begin{array}{cc}1.82A1.94& \left(6\right)\end{array}$

[0058] In the optical system 2 that satisfies the above formulas (4), (5), and (6), similarly, among the plurality of lens groups G arranged along the optical axis C, the first lens group 21 having a positive refractive power is arranged closest to the object side, the second lens group 22 having a negative refractive power is arranged at an image side of the first lens group 21, and the third lens group 23 having a positive or negative refractive power is arranged closest to the image side. Thus, the optical power arrangement of telephoto may be easily obtained in the optical system 2, and therefore, the focal length of the first lens group 21 may be shortened, resulting in that miniaturization of the optical system 2 (specifically, miniaturization in the direction of the optical axis C) may be realized.

[0059] Moreover, in the optical system 2 satisfying the formulas (4), (5) and (6), similarly, by moving the second lens group when focusing, the aberration variation balance with the front and rear lens groups 21 and 23 may be adjusted, bending variation of the imaging plane during a close range photographing may be suppressed compared with a whole extension mode, and therefore the close range photographing distance may be further shortened.

[0060] Furthermore, in the optical system 2 satisfying the formulas (4), (5) and (6), similarly, by fixing the first lens group 21 and the third lens group 23 relative to the imaging plane, only the second lens group 22 is set as a movable lens group, so that a load on a mechanism or actuator may be reduced, and therefore, the overall miniaturization of the photographing device 1 including the optical system 2 may be realized.

[0061] The above formula (5) specifies a range of the refractive index (nd2p) of the lens having a positive refractive power based on the d-line. When the refractive index (nd2p) is lower than a lower limit (1.55), a positive focal power in the second lens group 22 becomes weak, and it is difficult to correct spherical aberration, imaging plane bending and other aberrations in the whole focus area. On the other hand, when the refractive index (nd2p) exceeds an upper limit (1.72), the positive focal power of the second lens group 22 becomes strong, and it is difficult to improve the negative focal power of the entire second lens group 22. As a result, a movement amount for the focusing becomes large, and therefore it is difficult to miniaturize the optical system 2.

[0062] In addition, the above-mentioned formula (6) specifies a range of the variable A in the above-mentioned formula (4), thereby determining a range of the Abbe number (vd2p) of the lens having a positive refractive power based on the d-line. If a lens material outside the range of the Abbe number (vd2p) is used, it will be difficult to perform good chromatic aberration correction in the entire focus area, or the number and weight of the lenses of the second lens group 22 will increase, resulting in an increase in the size of actuators and other driving devices.

[0063] Therefore, in the above optical system 2, the above three formulas (formula (4), formula (5) and formula (6)) are satisfied at the same time, so that an optical system 2 that has a small overall size and is capable of photographing at a close range may be realized.

[0064] In addition, in some examples, in the optical system 2 satisfying the above-mentioned formulas (4), (5) and (6), the above refractive index (nd2p) satisfies:

1.57nd2p1.70.

[0065] In some examples, the following formula is satisfied:

1.59nd2p1.68.

[0066] In addition, in some examples, in this optical system 2, the above variable (A) satisfies:

1.84A1.92.

[0067] In some examples, the following formula is satisfied:

1.86A1.90.

[0068] In addition, in the optical system 2, the second lens group 22 has at least one lens having a positive refractive power and at least one lens having a negative refractive power. In the second lens group 22, a lens 221 having the strongest positive refractive power may be arranged at a position closer to the image side than a lens 222 having the strongest negative refractive power.

[0069] According to this configuration, the aberration correction may be achieved in the entire focus area from infinity to close range photographing just by moving the second lens group 22. The details are as follows.

[0070] In order to realize the aberration correction in the whole focus area from infinity to close range photographing just by moving the second lens group 22, an on-axis light beam that is strongly converged by the first lens group 21 on the object side of the second lens group 22 is regarded as a properly converged light beam and, in embodiments, a peripheral light beam needs a negative focal power to jump up and be guided to the image side of the second lens group 22. In addition, on the image side of the second lens group 22, a positive focal power is required for convergence to obtain a desired F number.

[0071] Therefore, in the optical system 2 of the present embodiment, as the configuration described above, the second lens group 22 has at least one lens having a positive refractive power and at least one lens having a negative refractive power. By adopting a configuration in which the lens 221 having the strongest positive refractive power is located at the position closer to the image side than the lens 222 having the strongest negative refractive power in the second lens group 22, a proper aberration correction in the whole focus area from infinity to close range photographing may be achieved just by moving the second lens group 22.

[0072] In addition, in the optical system 2, when the lateral magnification of the second lens group focusing at infinity is b2 and the lateral magnification of the third lens group focusing at infinity is b3, the optical system 2 may satisfy the following formula (7).

[00007]$\begin{array}{cc}-10.\left(1-b{2}^2\right)b{3}^2-2.& \left(7\right)\end{array}$

[0073] The above formula (7) specifies a ratio ((1b2.sup.2)b3.sup.2) of a movement amount of the

[0074] imaging plane to a movement amount of the second lens group 22 in the direction of the optical axis C. In the optical system with the whole extension mode, a numerical value corresponding to this formula is 1. However, in the internal focus optical system of the optical system 2 of the present embodiment, by increasing this ratio with a negative value, a close range photographing may be realized with a small movement amount, and the miniaturization of the entire optical system 2 is realized. When the ratio ((1b2.sup.2)b3.sup.2) is less than a lower limit (10.00), the movement amount of the imaging plane relative to the movement amount of the second lens group 22 in the direction of the optical axis C becomes too large to improve accuracy of the stop position of the second lens group 22 by a driving device such as an actuator. However, when the ratio ((1b2.sup.2)b3.sup.2) exceeds an upper limit (2.00), the movement amount of the second lens group 22 for a close range photographing increases, so it is difficult to realize the miniaturization of the entire optical system 2. Therefore, in the optical system 2 of the present embodiment, by setting the ratio ((1b2.sup.2)b3.sup.2) of the movement amount of the imaging plane to the movement amount of the second lens group 22 in the direction of the optical axis C within the above-mentioned formula (7), it is possible to achieve a balance between improving the accuracy of the stop position of the second lens group 22 by an actuator or the like during focusing and the miniaturization of the entire optical system 2.

[0075] In addition, in some examples, in the optical system 2 of the present embodiment, the above ratio ((1b2.sup.2)b3.sup.2) satisfies the following formula.

[00008]$-9.\left(1-b{2}^2\right)b{3}^2-2.5$

[0076] In some examples, the following formula is satisfied the following formula.

[00009]$-8.\left(1-b{2}^2\right)b{3}^2-5.$

[0077] In addition, in the optical system 2, when the focal length of the entire optical system focusing at infinity is f and the focal length of the above-mentioned second lens group is f2, the optical system 2 may satisfy the following formula (8).

[00010]$\begin{array}{cc}-0.7f2/f-0.1& \left(8\right)\end{array}$

[0078] The above formula (8) specifies a ratio (f2/f) of the focal length of the second lens group 22 to the focal length of the entire optical system 2 focusing at infinity. When this ratio (f2/f) is lower than a lower limit (0.70), the focal power of the second lens group 22 becomes weak, and the movement amount of the second lens group 22 for a close range photographing becomes large, so it is difficult to realize the miniaturization of the entire optical system 2. On the other hand, when the ratio (f2/f) exceeds an upper limit (0.10), the movement amount of the imaging plane relative to the movement amount of the second lens group 22 in the direction of the optical axis C becomes too large to improve the accuracy of the stop position of the second lens group 22 by a driving device such as an actuator. Therefore, in the optical system 2 of the present embodiment, by setting the ratio (f2/f) of the focal length of the second lens group 22 to the focal length of the entire optical system 2 focusing at infinity within the above-mentioned formula (8), it is possible to achieve a balance between the miniaturization of the entire optical system 2 and improvement of the accuracy of the stop position of the second lens group 22 by an actuator or the like during focusing.

[0079] In addition, in some examples, in the optical system 2 of the present embodiment, the above ratio (f2/f) satisfies the following formula.

[00011]$-0.65f2/f-0.15$

[0080] In some examples, the following formula is satisfied the following formula.

[00012]$-0.6f2/f-0.02$

[0081] According to the optical system 2 configured as above and the photographing device 1 having the optical system 2, the miniaturation and the close range photographing may be realized. That is, in the optical system 2 of the present embodiment in which the first lens group 21 has a positive refractive power, the second lens group 22 has a negative refractive power, and the third lens group 23 has a positive or negative refractive power, and the second lens group 22 is movable when focusing from infinity to close range, by appropriately selecting the configurations, magnifications, lens materials, etc. of the lens groups 21 to 23, an optical system, which has a small overall size, and fully realizes the performance and chromatic aberration correction at a close range photographing, may be realized.

[0082] In addition, in the optical system 2 and the photographing device 1 having the optical system 2 according to the present embodiment, even in the so-called internal focus optical system, the miniaturization and the like of the optical system 2 and the photographing device 1 having the optical system 2 may be realized. The details are as follows.

[0083] As a conventional focusing method of a lens, an optical system with a whole extension mode is known. The optical system with a whole extension mode adopts a way of extending the entire optical system to the object side when focusing from infinity to close range, and the entire optical system is fixed as one without being divided into subgroups, so it is relatively easy to improve the optical performance when designing. However, when the entire lens is focused, there is a difference between the positions where the lens system of a peripheral image high beam passes between infinity and close range focus, and the variation of imaging plane bending becomes larger, and its aberration is difficult to correct. In addition, a movement distance of the entire lens during focusing increases in proportion to the square of the focal length. Therefore, especially for a telephoto lens with a long focal length, in order to achieve the close range photographing, the movement amount of focusing becomes longer, and as a result, it is difficult to realize the miniaturization of the optical system and the photographing device.

[0084] On the other hand, the internal focus optical system, when focusing from infinity to close range, adopts a way of moving some lens groups in the optical system to the object side or the image side. Because the aberration correction corresponding to the object distance is distributed to respective groups, it is easier to correct the aberration in the focusing range. In addition, the sensitivity of the movement distance of the focus group during focusing may be improved, and the movement amount may be easily shortened.

[0085] Therefore, in the photographing device 1 of the present embodiment, even when the internal focus optical system is adopted as the optical system 2, it is possible to realize an optical system that has a small overall size and can fully realize the performance and chromatic aberration correction during the close range photographing.

[0086] Embodiments 1 to 5 of the optical system of the present disclosure will be described. In the following embodiments, the same reference numerals are used for the components corresponding to the components of the optical system 2 of the above embodiments. In addition, in the tables of the following embodiments, r is a radius of curvature, d is a lens thickness or lens spacing, nd is a refractive index of the d-line, and vd represents an Abbe number based on the d-line. In addition, aspheric surface is defined by the following formula.

[00013]$z={\mathrm{ch}}^2/\left[1+{\left\{1-\left(1+k\right)c^2{h}^2\right\}}^{1/2}\right]+A4h^4+A6h^6+A8h^8+A10h^{10}.Math..Math.$

[0087] (Where, c is a curvature (l/r), h is a height from the optical axis, k is a conic coefficient, and A4, A6, A8 and A10 . . . are aspheric coefficients of each order).

[0088] In addition, each longitudinal aberration diagrams shows spherical aberration (SA (mm)), astigmatism (AST (mm)) and distortion (DIS (%)) in turn from the left. In the spherical aberration diagram, the vertical axis represents the F number (represented by FNO in the diagram), the solid-line represents the characteristics of the d-line, the short dashed-line represents the characteristics of a F-line, and the long dashed-line represents the characteristics of a C-line. In the astigmatism diagram, the vertical axis represents the maximum image height (represented by Y in the diagram), the solid-line represents the characteristics of the sagittal plane (represented by S in the diagram), and the dashed-line represents the characteristics of the meridian plane (represented by M in the diagram). In the distortion diagram, the vertical axis represents the maximum image height (represented by Y in the diagram).

Embodiment 1

[0089] FIGS. 2 and 3 are lens configuration diagrams of an optical system according to

[0090] Embodiment 1, with FIG. 2 showing an infinity focus state and FIG. 3 showing a closest focus state. In addition, the reference numerals indicating the configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above embodiments. In addition, in this optical system, when focusing, the positions of the first lens group 21 and the third lens group 23 on the optical axis C are fixed relative to the photographing element (imaging plane) 3.

[0091] FIG. 4 is a longitudinal aberration diagram in an infinity focus state, FIG. 5 is a longitudinal aberration diagram at a magnification of 0.5, and FIG. 6 is a longitudinal aberration diagram at a magnification of 1.0. In addition, Table 1 below shows surface data of each lens, Table 2 shows aspheric surface data, Table 3 shows various data, Table 4 shows lens group data, and Table 5 shows individual lens data.

TABLE-US-00001 TABLE 1 Surface data Surface number r d nd vd 1* 10.837 0.889 1.5731 37.65 2* 20.302 1.869 3* 11.842 0.400 1.6422 22.40 4* 8.631 0.400 5* 7.439 0.701 1.5445 55.96 6* 1016.183 0.459 7* 244.855 1.007 1.5445 55.96 8* 4.791 d8 (Aperture diaphragm) 9* 23.884 0.400 1.5445 55.96 10* 3.953 2.049 11* 7.996 0.959 1.6714 19.27 12* 20.258 d12 13* 26.885 0.600 1.6714 19.27 14* 127.054 1.443 15* 14.148 1.060 1.5731 37.65 16* 18.241 1.822 17 0.210 1.5168 64.20 18 0.390 *for aspheric surface

TABLE-US-00002 TABLE 2 Aspheric surface data (the aspheric coefficient not shown is 0.00.) Surface number k A4 A6 A8 A10 1 0.0000E+00 1.1639E05 6.0054E05 8.6396E06 2.2041E07 2 0.0000E+00 5.8633E04 7.3252E05 7.4744E06 5.8661E07 3 0.0000E+00 7.0037E04 1.9898E04 1.8774E05 2.9685E07 4 0.0000E+00 1.1742E03 1.9847E04 2.4243E05 5.3635E06 5 0.0000E+00 1.2877E03 9.0202E05 2.2704E06 9.5701E07 6 0.0000E+00 1.0370E03 1.7134E05 2.3536E06 1.7400E06 7 0.0000E+00 5.1023E04 4.7470E08 9.8188E06 3.7361E07 8 0.0000E+00 2.8113E04 5.1933E05 6.3363E06 3.6540E07 9 0.0000E+00 8.8416E03 1.4970E03 1.9667E04 1.3207E05 10 0.0000E+00 7.6667E03 7.8779E04 1.2420E04 4.5422E06 11 0.0000E+00 6.0882E03 3.6197E04 4.1107E05 2.7115E06 12 0.0000E+00 6.6253E03 2.4105E04 3.3557E05 1.3859E06 13 0.0000E+00 2.0583E04 2.7586E04 2.5465E05 2.7532E07 14 0.0000E+00 1.4314E03 3.1864E04 8.5224E06 1.1200E06 15 0.0000E+00 4.2498E04 1.1331E04 1.8972E05 8.9180E07 16 0.0000E+00 1.8677E03 9.7671E08 1.7520E07 2.0773E07

TABLE-US-00003 TABLE 3 Various data object distance 44.617 21.900 lateral magnification 0.5 times 1.0 times F number 4.100 4.604 4.983 lens total length 21.680 21.680 21.680 d8 1.000 3.112 6.036 d12 6.022 3.910 0.986

[0092] The focal length is 21.999, and the maximum image height is 4.000.

TABLE-US-00004 TABLE 4 Lens group data Lens Lens Starting Focal configuration movement Group surface length length amount Magnification 1 1 8.242 5.725 0.000 2 9 10.613 3.408 5.036 2.331 3 13 35.740 3.103 0.000 1.145

TABLE-US-00005 TABLE 5 Individual lens data Starting Focal Lens surface length 1 1 12.458 2 3 7.715 3 5 13.566 4 7 8.981 5 9 6.197 6 11 19.077 7 13 50.915 8 15 121.484

Embodiment 2

[0093] FIGS. 7 and 8 are lens configuration diagrams of an optical system according to Embodiment 2, with FIG. 7 showing an infinity focus state and FIG. 8 showing a closest focus state. In addition, the reference numerals indicating the configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above embodiment. In addition, in this optical system, similarly, when focusing, the positions of the first lens group 21 and the third lens group 23 on the optical axis C are fixed relative to the photographing element (imaging plane) 3.

[0094] FIG. 9 is a longitudinal aberration diagram in an infinity focus state, FIG. 10 is a longitudinal aberration diagram at a magnification of 0.5, and FIG. 11 is a longitudinal aberration diagram at a magnification of 1.0. In addition, Table 6 below shows surface data of each lens, Table 7 shows aspheric surface data, Table 8 shows various data, Table 9 shows lens group data, and Table 10 shows individual lens data.

TABLE-US-00006 TABLE 6 Surface data Surface number r d nd vd 1* 5.000 0.893 1.5731 37.65 2* 10.734 0.966 3* 8.150 0.300 1.6714 19.27 4* 5.654 0.300 5* 4.317 0.907 1.5445 55.96 6* 2.867 d6 (Aperture diaphragm) 7* 5.422 0.300 1.6445 55.96 8* 2.824 0.685 9* 27.713 0.405 1.6714 19.27 10* 8.501 0.300 11* 10.352 0.300 1.5445 55.96 12* 24.347 d12 13* 13.515 0.600 1.5445 55.96 14* 25.363 0.368 15* 6.612 0.407 1.6714 19.27 16* 6.720 0.500 17 0.105 1.5168 64.20 18 0.195 *for aspheric surface

TABLE-US-00007 TABLE 7 Aspheric surface data (the aspheric coefficient not shown is 0.00.) Surface number k A4 A6 A8 A10 1 0.0000E+00 2.3666E03 2.0426E05 6.8914E04 6.1516E05 2 0.0000E+00 1.6713E03 8.7447E04 7.9219E04 1.5080E04 3 0.0000E+00 1.9033E03 1.1546E03 4.6620E04 4.3690E04 4 0.0000E+00 3.2511E03 3.0497E03 6.7443E04 1.5675E04 5 0.0000E+00 1.1837E02 2.7722E03 7.9428E04 4.8106E04 6 0.0000E+00 4.1623E04 4.6327E04 1.2627E03 3.9072E04 7 0.0000E+00 1.4546E01 1.0408E01 4.7577E02 9.9469E03 8 0.0000E+00 1.6352E01 6.6907E02 2.2009E02 1.6217E04 9 0.0000E+00 9.3001E03 3.1386E02 3.5351E03 2.5583E03 10 0.0000E+00 4.5596E03 1.5161E02 2.1792E02 1.1358E02 11 0.0000E+00 1.2992E01 2.1642E02 2.9409E02 2.0420E02 12 0.0000E+00 1.3818E01 3.8975E02 5.9382E03 4.1109E03 13 0.0000E+00 2.9073E02 8.7898E03 2.5602E04 1.9794E05 14 0.0000E+00 2.6118E02 6.2895E03 9.2413E04 6.0528E05 15 0.0000E+00 1.7191E02 9.6305E03 3.2638E04 1.8985E04 16 0.0000E+00 1.7921E02 6.5500E03 1.1147E03 3.4194E04

TABLE-US-00008 TABLE 8 Various data object distance 23.135 10.954 lateral magnification 0.5 times 1.0 times F number 3.400 3.744 3.931 lens total length 10.800 10.800 10.800 d6 0.500 1.492 2.978 d12 2.968 1.976 0.490

[0095] The focal length is 11.600 and the maximum image height is 2.060.

TABLE-US-00009 TABLE 9 Lens group data Lens Lens Starting Focal configuration movement Group surface length length amount Magnification 1 1 4.167 3.167 0.000 2 7 3.745 1.990 2.478 2.613 3 13 58.120 1.376 0.000 1.065

TABLE-US-00010 TABLE 10 Individual lens data Starting Focal Lens surface length 1 1 6.049 2 3 4.929 3 5 3.311 4 7 3.367 5 9 9.733 6 11 13.299 7 13 54.100 8 15 1192.695

Embodiment 3

[0096] FIGS. 12 and 13 are lens configuration diagrams of the optical system according to Embodiment 3, with FIG. 12 showing an infinity focus state and FIG. 13 showing a closest focus state. In addition, the reference numerals indicating the configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above embodiment. In addition, in this optical system, similarly, when focusing, the positions of the first lens group 21 and the third lens group 23 on the optical axis C are fixed relative to the photographing element (imaging plane) 3.

[0097] FIG. 14 is a longitudinal aberration diagram in an infinity focus state, FIG. 15 is a longitudinal aberration diagram at a magnification of 0.5, and FIG. 16 is a longitudinal aberration diagram at a magnification of 1.0. In addition, Table 11 below shows surface data of each lens, Table 12 shows aspheric surface data, Table 13 shows various data, Table 14 shows lens group data, and Table 15 shows individual lens data

TABLE-US-00011 TABLE 11 Surface data Surface number r d nd vd 1* 5.000 0.706 1.5731 37.65 2* 10.173 0.993 3* 8.056 0.300 1.6714 19.27 4* 6.129 0.300 5* 4.306 0.860 1.5445 55.96 6* 2.901 d6 (Aperture diaphragm) 7* 4.269 0.388 1.5445 55.96 8* 2.842 1.255 9* 33.107 0.481 1.6714 19.27 10* 20.856 d10 11* 8.636 0.800 1.6714 19.27 12* 5.869 0.397 13* 2.388 0.432 1.5445 55.96 14* 3.516 0.500 15 0.105 1.5168 64.20 16 0.195 *for aspheric surface

TABLE-US-00012 TABLE 12 Aspheric surface data (the aspheric coefficient not shown is 0.00.) Surface number k A4 A6 A8 A10 1 0.0000E+00 1.9112E03 1.5546E05 6.7772E04 6.1390E05 2 0.0000E+00 1.8475E03 7.8046E04 7.4538E04 1.4350E04 3 0.0000E+00 2.4046E03 1.4414E03 5.4986E04 4.4954E04 4 0.0000E+00 3.2006E03 3.1773E03 7.5880E04 1.7843E04 5 0.0000E+00 1.2499E02 2.9279E03 8.2432E04 5.1155E04 6 0.0000E+00 2.6964E04 7.1603E04 1.2165E03 3.9514E04 7 0.0000E+00 1.4553E01 1.0374E01 5.0877E02 1.1549E02 8 0.0000E+00 1.6999E01 7.855SE02 3.6428E02 3.2533E03 9 0.0000E+00 3.2310E02 7.0395E03 3.1606E03 9.0266E04 10 0.0000E+00 4.4445E02 4.4951E03 2.4390E03 1.8147E04 11 0.0000E+00 2.7469E02 6.6085E03 2.3747E04 3.3901E04 12 0.0000E+00 2.1601E02 8.6923E04 5.7099E04 1.0567E05 13 0.0000E+00 3.5570E02 6.5430E03 7.4509E04 6.9896E05 14 0.0000E+00 2.5797E02 3.5508E03 2.0065E03 3.3999E04

TABLE-US-00013 TABLE 13 Various data object distance 23.360 11.411 lateral magnification 0.5 times 1.0 times F number 3.400 3.797 4.101 lens total length 10.800 10.800 10.800 d6 0.500 1.433 2.700 d10 2.787 1.854 0.587

[0098] The focal length is 11.598, and the maximum image height is 2.060.

TABLE-US-00014 TABLE 14 Lens group data Group Starting surface Focal length Lens configuration length Lens movement amount Magnification 1 1 4.076 3.159 0.000 2 7 4.044 2.124 2.200 2.622 3 11 38.871 1.429 0.000 1.085

TABLE-US-00015 TABLE 15 Individual lens data Lens Starting surface Focal length 1 1 5.950 2 3 5.141 3 5 3.323 4 7 3.074 5 9 19.127 6 11 25.097 7 13 15.804

Embodiment 4

[0099] FIGS. 17 and 18 are lens configuration diagrams of the optical system according to Embodiment 4, with FIG. 17 showing an infinity focus state and FIG. 18 showing a closest focus state. In addition, the reference numerals indicating the configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above embodiment. In addition, in this optical system, similarly, when focusing, the positions of the first lens group 21 and the third lens group 23 on the optical axis C are fixed relative to the photographing element (imaging plane) 3.

[0100] FIG. 19 is a longitudinal aberration diagram in an infinity focus state, FIG. 20 is a longitudinal aberration diagram at a magnification of 0.5, and FIG. 21 is a longitudinal aberration diagram at a magnification of 1.0. In addition, Table 16 below shows surface data of each lens, Table 17 shows aspheric surface data, Table 18 shows various data, Table 19 shows lens group data, and Table 20 shows individual lens data.

TABLE-US-00016 TABLE 16 Surface data Surface number r d nd vd 1* 11.363 0.891 1.5445 55.96 2* 16.648 2.105 3* 11.791 0.483 1.6161 25.78 4* 8.889 0.508 5* 9.425 1.316 1.5445 55.96 6* 4.732 d6 (Aperture diaphragm) 7* 18.298 0.400 1.5445 55.96 8* 4.125 1.654 9* 9.133 1.296 1.6560 21.25 10* 54.302 d10 11* 24.402 0.600 1.6714 19.27 12* 292.433 0.788 13* 38.540 0.790 1.5880 28.42 14* 52.998 2.870 15 0.210 1.5168 64.20 16 0.390 *for aspheric surface

TABLE-US-00017 TABLE 17 Aspheric surface data (the aspheric coefficient not shown is 0.00.) Surface number k A4 A6 A8 A10 1 0.0000E+00 2.4234E04 6.7694E05 9.5189E06 3.2738E07 2 0.0000E+00 7.4728E04 8,5317E05 7.9662E06 8.4874E07 3 0.0000E+00 1.0455E03 2.7135E04 2.4506E05 1.2958E06 4 0.0000E+00 1.4090E03 2.8033E04 3.6940E05 4.6898E06 5 0.0000E+00 3.9939E03 1.4629E04 1.7838E05 2.6301E06 6 0.0000E+00 2.8018E04 9.8170E08 5.4890E06 3.8947E07 7 0.0000E+00 9.8294E03 1.4827E03 1.6449E04 9.6737E06 8 0.0000E+00 7.9215E03 4.7219E04 4.8074E05 2.5181E06 9 0.0000E+00 6.0098E03 4.9475E04 5.6628E05 4.1063E06 10 0.0000E+00 6.0192E03 2.4361E04 3.5619E05 1.5327E06 11 0.0000E+00 1.7119E03 1.3443E04 3.2076E05 5.3290E07 12 0.0000E+00 4.0167E03 1.8733E04 5.3277E06 1.3317E06 13 0.0000E+00 8.6012E04 2.3103E04 1.6139E05 1.2058E06 14 0.0000E+00 3.3438E03 2.4644E04 1.505SE05 7.3173E07

TABLE-US-00018 TABLE 18 Various data object distance 45.139 22.397 lateral magnification 0.5 times 1.0 times F number 4.100 4.608 4.987 lens total length 21.680 21.680 21.680 d6 1.000 3.249 8.396 d10 6.380 4.131 0.984

[0101] The focal length is 21.999, and the maximum image height is 4.000.

TABLE-US-00019 TABLE 19 Lens group data Group Starting surface Focal length Lens configuration length Lens movement amount Magnification 1 1 8.437 5.301 0.000 2 7 11.495 3.350 5.396 2.269 3 11 34.345 2.178 0.000 1.149

TABLE-US-00020 TABLE 20 Individual lens data Lens Stating surface Focal length 1 1 12.544 2 3 8.154 3 5 5.982 4 7 6.143 5 9 16.548 6 11 39.691 7 13 270.708

Embodiment 5

[0102] FIGS. 22 and 23 are lens configuration diagrams of the optical system according to Embodiment 5, with FIG. 22 showing an infinity focus state and FIG. 23 showing a recent focus state. In addition, the reference numerals indicating the configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above embodiment. In addition, in this optical system, similarly, when focusing, the positions of the first lens group 21 and the third lens group 23 on the optical axis C are fixed relative to the photographing element (imaging plane) 3.

[0103] FIG. 24 is a longitudinal aberration diagram in an infinity focus state, FIG. 25 is a longitudinal aberration diagram at a magnification of 0.5, and FIG. 26 is a longitudinal aberration diagram at a magnification of 1.0. In addition, Table 21 below shows surface data of each lens, Table 22 shows aspheric surface data, Table 23 shows various data, Table 24 shows lens group data, and Table 25 shows individual lens data.

TABLE-US-00021 TABLE 21 Surface data Surface number r d nd vd 1* 5.000 0.704 1.5731 37.65 2* 10.134 0.918 3* 8.745 0.300 1.6714 19.27 4* 5.062 0.300 5* 4.203 0.943 1.5445 55.96 6* 2.710 d6 (Aperture diaphragm) 7* 4.355 0.300 1.5445 85.96 8* 2.680 0.539 9* 7.651 0.393 1.6714 19.27 10* 35.784 0.648 11* 9.963 0.303 1.5445 55.96 12* 68.840 d12 13* 15.998 0.600 1.5445 55.96 14* 17.581 0.400 15* 3.703 0.426 1.6397 23.49 16* 3.566 0.500 17 0.105 1.5168 64.20 18 0.195 *for aspheric surface

TABLE-US-00022 TABLE 22 Aspheric surface data (the aspheric coefficient not shown is 0.00.) Surface number k A4 A6 A8 A10 1 0.0000E+00 2.0137E03 6.1164E04 5.5341E04 5.0798E05 2 0.0000E+00 2.8040E03 1.3283E03 5.7280E04 1.3893E04 3 0.0000E+00 4.6433E03 3.4295E03 5.6554E04 3.7552E04 4 0.0000E+00 8.3886E03 4.4996E03 1.2698E03 4.6198E04 5 0.0000E+00 1.3497E02 2.1801E03 9.8512E04 4.2974E04 6 0.0000E+00 4.6798E04 3.8477E04 8.2789E04 2.2079E04 7 0.0000E+00 1.4642E01 1.0687E01 4.7813E02 9.5268E03 8 0.0000E+00 1.5113E01 5.0849E02 8.3324E03 2.6763E03 9 0.0000E+00 7.9018E03 8.6001E02 1.7887E02 2.1887E03 10 0.0000E+00 1.5248E02 4.0273E02 1.8810E02 1.5587E02 11 0.0000E+00 9.2058E02 2.2545E02 1.9782E02 1.5821E02 12 0.0000E+00 1.0625E01 2.6879E02 6.5986E04 4.7834E03 13 0.0000E+00 3.3818E02 1.6708E03 2.0335E03 2.9540E04 14 0.0000E+00 1.9122E02 3.0555E03 1.3109E03 2.4628E04 15 0.0000E+00 4.0458E02 1.0220E02 3.0396E03 4.4084E04 18 0.0000E+00 3.1649E02 9.5572E03 4.1256E03 5.8904E04

TABLE-US-00023 TABLE 23 Various data object distance 44.617 21.900 lateral magnification 0.5 times 1.0 times F number 3.400 3.718 3.899 lens total length 10.800 10.800 10.800 d6 0.500 1.413 2.733 d12 2.725 1.812 0.492
The focal length is 11.601, and the maximum image height is 2.060.

TABLE-US-00024 TABLE 24 Lens group data Group Starting surface Focal length Lens confirmation length Lens movement amount Magnification 1 1 4.043 3.166 0.000 2 7 3.431 2.183 2.233 2.729 3 13 79.998 1.426 0.000 1.051

TABLE-US-00025 TABLE 25 Individual lens data Lens Starting surface Focal length 1 1 5.943 2 3 4.734 3 5 3.179 4 7 3.002 5 9 9.423 6 11 15.963 7 13 376.637 8 15 68.077

[0104] In the above embodiments 1 to 5, the values corresponding to the conditions of the above embodiments are shown in the following Table 26. In addition, in Table 26, conditional formula (1) is b3, conditional formula (2) is OAL/f, conditional formula (3) is |B|, and conditional formula (5) is nd2p, conditional formula (6) is A, conditional formula (7) is (1b2.sup.2)b3.sup.2, conditional formula (8) is f2/f.

TABLE-US-00026 TABLE 26 Corresponding values of conditional formulas Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Conditional formula (1) 1.145 1.065 1.085 1.149 1.051 Conditional formula (2) 0.986 0.931 0.931 0.985 0.931 Conditional formula (3) 1.000 1.000 1.000 1.000 1.000 Conditional formula (4) 1.671 1.671 1.671 1.656 1.671 Conditional formula (5) 1.864 1.864 1.864 1.869 1.864 Conditional formula (7) 5.813 6.610 8.916 5.477 7.122 Conditional formula (8) 0.482 0.323 0.349 0.523 0.296 b3 1.145 1.065 1.085 1.149 1.051 OAL 21.680 10.800 10.800 21.680 10.800 f 21.999 11.600 11.598 21.999 11.601 | B | 1.000 1.000 1.000 1.000 1.000 nd2p 1.671 1.671 1.671 1.656 1.671 vd2p 19.270 19.270 19.270 21.250 19.270 A 1.864 1.884 1.864 1.869 1.864 b2 2.331 2.613 2.622 2.269 2.729 f2 10.613 3.745 4.044 11.495 3.431

[0105] In order to indicate the present disclosure, while referring to the attached drawings, the present disclosure has been properly and fully explained through the embodiments, but those skilled in the art should realize that the above embodiments may be easily changed and/or improved. Therefore, as long as the alteration or improvement carried out by a person skilled in the art does not deviate from the scope of the claims recorded in the claims, the alteration or improvement shall be interpreted as being included in the scope of the rights of the claims.

Description of Reference Numerals

[0106] 1 . . . photographing device, 2 . . . optical system, 20 . . . prism (reflective optical element), 21 . . . first lens group, 22 . . . second lens group, 221 . . . lens having the strongest positive refractive power in the second lens group 22, 222 . . . lens having the strongest negative refractive power in the second lens group 22, 23 . . . third lens group, 25 . . . filter, 26 . . . lens barrel, 3 . . . photographing element, 4 . . . liquid crystal screen, C . . . optical axis, F . . . focusing lens group, G . . . lens group.