Optical system, and imaging device provided with optical system

Abstract

Provided is an optical system and an imaging device having the optical system, the optical system including, in order from an object side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having negative refractive power, wherein, at the time of focusing, the second lens group moves along an optical axis, and the first lens group and the third lens group are fixed with respect to an imaging surface, and wherein, when a distance from an object-side surface of the second lens group to an image-side surface thereof is set as OAL2, and a distance from an object-side surface of the entire optical system to the imaging surface is set as OAL, 0.06 ≤ OAL2 / OAL is satisfied.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical system having a plurality of lens groups, and an imaging device having the optical system. BACKGROUND

[0002] In the past, as an optical system having a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group arranged in order from an object side to an image side, and in which only the second lens group moves along an optical axis at the time of focusing, optical systems described in Patent Literature 1 (Japanese Patent No. 5749629) and Patent Literature 2 (Japanese Patent Application Laid-Open No. 2021-173847) are known.

[0003] However, the optical system described in Patent Literature 1 is insufficient for close-up photography, and in the optical system described in Patent Literature 2, the optical system is large compared to the total length of the focal length, and is insufficient in terms of miniaturization.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent No. 5749629

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2021-173847 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Therefore, an object of the present application is to provide an optical system that is small and can perform close-up photography, and an imaging device having the above-described optical system.

[0010] SOLUTION TO PROBLEM

[0011] The optical system of the present application has:

[0012] a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having negative refractive power, arranged in order from an object side to an image side,

[0013] at the time of focusing,

[0014] the above-described second lens group moves along the optical axis,

[0015] the above-described first lens group and the above-described third lens group are fixed in position in the optical axis direction with respect to an imaging surface,

[0016] when a distance from the most object side surface of the above-described second lens group to the most image side surface is set as OAL2, and a distance from the most object side surface of the entire optical system to the imaging surface is set as OAL, the following is satisfied:

[0017] 0.06 ≤ OAL2 / OAL.

[0018] In the optical system described above, also,

[0019] The second lens group described above has:

[0020] at least one lens having positive refractive power; and

[0021] at least one lens having negative refractive power,

[0022] In the second lens group described above, the lens having the strongest positive refractive power is located at a position closer to the image side than the lens having the strongest negative refractive power.

[0023] Also, in the optical system described above, also,

[0024] When the focal length at the time of focusing on infinity of the entire optical system is set to f, the following is satisfied:

[0025] OAL / f ≤ 2.00.

[0026] Also, in the optical system described above, also,

[0027] When the maximum lateral magnification of the entire optical system is set to B, the following is satisfied:

[0028] 0.50 ≤ |B|.

[0029] Also, in the optical system described above, also,

[0030] When the lateral magnification at the time of focusing on infinity of the second lens group described above is set to b2, and the lateral magnification at the time of focusing on infinity of the third lens group described above is set to b3, the following is satisfied:

[0031] -10.00 ≤ (1-b2 2 ) x b3 2 ≤ -2.00.

[0032] Also, in the optical system described above, also,

[0033] When the focal length at the time of focusing on infinity of the entire optical system is set to f, and the focal length of the second lens group described above is set to f2, the following is satisfied:

[0034] -0.70 ≤ f2 / f ≤ -0.10.

[0035] Also, the photographic device of the present application is provided with:

[0036] the optical system described above; and

[0037] A photographing element configured on an image plane side of the optical system converts an optical image formed by the optical system into an electric signal. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic view showing a configuration of a photographing apparatus of the present embodiment.

[0039] Figure 2 is a lens configuration diagram of the optical system of Example 1 in an infinite focus state.

[0040] Figure 3 is a lens configuration diagram of the optical system of Example 1 in a closest focus state.

[0041] Figure 4 is a longitudinal aberration diagram of the optical system of Example 1 in the infinite focus state.

[0042] Figure 5 is a longitudinal aberration diagram of the optical system of Example 1 in a "-0.5 times" magnification.

[0043] Figure 6 is a longitudinal aberration diagram of the optical system of Example 1 in a "-1.0 times" magnification.

[0044] Figure 7 is a lens configuration diagram of the optical system of Example 2 in the infinite focus state.

[0045] Figure 8 is a lens configuration diagram of the optical system of Example 2 in the closest focus state.

[0046] Figure 9 is a longitudinal aberration diagram of the optical system of Example 2 in the infinite focus state.

[0047] Figure 10 is a longitudinal aberration diagram of the optical system of Example 2 in a "-0.5 times" magnification.

[0048] Figure 11 is a longitudinal aberration diagram of the optical system of Example 2 in a "-1.0 times" magnification.

[0049] Figure 12 is a lens configuration diagram of the optical system of Example 3 in the infinite focus state.

[0050] Figure 13 is a lens configuration diagram of the optical system of Example 3 in the closest focus state.

[0051] Figure 14 is a longitudinal aberration diagram of the optical system of Example 3 in the infinite focus state.

[0052] Figure 15 is a longitudinal aberration diagram of the optical system of Example 3 at a " -0.5 times" magnification.

[0053] Figure 16 is a longitudinal aberration diagram of the optical system of Example 3 at a " -1.0 times" magnification.

[0054] Figure 17 is a lens configuration diagram of the optical system of Example 4 in an infinite focus state.

[0055] Figure 18 is a lens configuration diagram of the optical system of Example 4 in a closest focus state.

[0056] Figure 19 is a longitudinal aberration diagram of the optical system of Example 4 in an infinite focus state.

[0057] Figure 20 is a longitudinal aberration diagram of the optical system of Example 4 at a " -0.5 times" magnification.

[0058] Figure 21 is a longitudinal aberration diagram of the optical system of Example 4 at a " -1.0 times" magnification. DETAILED DESCRIPTION

[0059] Hereinafter, one embodiment of the present application will be described with reference to the drawings.

[0060] As shown in Figure 1 , the photographing apparatus 1 of the present embodiment is provided with an optical system 2, a photographing element 3 disposed at an imaging position of the optical system 2, and a liquid crystal screen 4 that displays photographing (image) data transmitted from the photographing element 3. In addition, the photographing apparatus 1 is provided with a driving section (omitted from illustration) that drives the optical system 2. The driving section is an actuator such as a VCM (voice coil motor) that drives a prescribed lens or lens group and the like included in the optical system 2 in a direction (optical axis direction) that is substantially perpendicular to a light receiving surface of the photographing element 3. In addition, the photographing element 3 is an element that converts an optical image formed by the optical system 2 into an electric signal (photographing data), and the photographing element 3 of the present embodiment is a CMOS image sensor.

[0061] The optical system 2 is a so-called inner focus optical system, and the optical system 2 of the present embodiment is a so-called periscope tele lens that bends an optical axis (optical path) C by a reflecting optical element such as a prism or a mirror. Specifically, the optical system 2 is provided with, in order from the object side to the image side along the optical axis C, a prism 20 that bends the optical axis C, and a plurality of lens groups G arranged on the optical axis C. In addition, the optical system 2 is provided with an aperture stop 24, a filter 25 disposed between the plurality of lens groups G and the photographing element 3, and a lens barrel 26 that holds the plurality of lens groups G.

[0062] The plurality of lens groups G include, in order from the object side to the image side along the optical axis C, at least the first lens group 21, the second lens group 22, and the third lens group 23. Each of the lens groups 21, 22, 23 includes at least one lens (optical element).

[0063] In addition, in the optical system 2 of the present embodiment, the lens groups 21 to 23 are names 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, 23 each have at least one optical element of a lens, etc. In addition, in the optical system 2, the optical element (lens, etc.) whose position on the optical axis C is fixed at the time of focusing is separated from the moving optical element, and the above-described fixed at least one optical element in the separated region is taken as one lens group, and the above-described moving at least one optical element in the separated region is taken as another lens group.

[0064] In the above-described optical system 2, at the time of focusing, the second lens group 22 moves along the optical axis C, and the first lens group 21 and the third lens group 23 are fixed in position with respect to the position of the imaging element 3 (imaging surface of the optical system 2) in the direction of the optical axis C. That is, in the optical system 2 of the present embodiment, among the lens groups 21, 22, 23, the second lens group 22 constitutes a focusing lens group F.

[0065] Hereinafter, each of the lens groups 21 to 23 in the optical system 2 will be described in detail.

[0066] The first lens group 21 includes a plurality of (four in the example of the present embodiment) lenses and has positive refractive power. In addition, the second lens group 22 includes a plurality of (two in the example of the present embodiment) lenses and has negative curvature. In addition, the third lens group 23 includes a plurality of (two in the example of the present embodiment) lenses and has negative refractive power.

[0067] Here, when the distance from the most object side surface to the most image side surface of the second lens group 22 is set as OAL2, and the distance from the most object side surface of the entire optical system 2 to the imaging surface is set as OAL, the optical system 2 satisfies the following formula (1).

[0068] 0.06 ≤ OAL2 / OAL • • • (1)

[0069] In the optical system 2 described above, among the plurality of lens groups G arranged along the optical axis C, the first lens group 21 having positive refractive power is arranged on the most object side, the second lens group 22 having negative refractive power is arranged on the image side of the first lens group 21, and the third lens group 23 having negative refractive power is arranged on the most image side. Thereby, in the optical system 2, a long-telephoto power arrangement is easily obtained, and thus the focal length of the first lens group 21 can be shortened, as a result of which the optical system 2 can be miniaturized (in detail, miniaturized in the direction of the optical axis C).

[0070] Further, by making the second lens group movable at the time of focusing, the balance of aberration variation with the front and rear lens groups 21, 23 is adjusted, and compared with the overall push type, the variation in curvature of field at the time of close-range shooting can be suppressed, and thus the close-range shooting distance can be further shortened.

[0071] Furthermore, by fixing the first lens group 21 and the third lens group 23 with respect to the imaging plane, and making only the second lens group 22 a movable lens group, the load on the mechanism or actuator can be reduced, and thus the entire photographing apparatus 1 including the optical system 2 can be miniaturized.

[0072] In addition, the above-described formula (1) defines the ratio (OAL2 / OAL) of the distance from the most object side surface of the second lens group 22 to the most image side surface to the distance from the most object side surface of the entire optical system 2 to the imaging plane, and when this ratio (OAL2 / OAL) is lower than the lower limit value (0.06), the aberration correction in the entire focusing range becomes insufficient, and the imaging performance becomes insufficient. Therefore, in the optical system 2 of the present embodiment, by setting the ratio (OAL2 / OAL) of the distance from the most object side surface of the second lens group 22 to the most image side surface to the distance from the most object side surface of the entire optical system 2 to the imaging plane within the range of formula (1), sufficient aberration correction can be performed in the entire focusing range, and thus sufficient imaging performance is ensured.

[0073] In addition, in the optical system 2 of the present embodiment, the above-described ratio (OAL2 / OAL) is preferably satisfied as follows:

[0074] 0.11 ≤ OAL2 / OAL ≤ 0.30,

[0075] More preferably, the following is satisfied:

[0076] 0.15 ≤ OAL2 / OAL ≤ 0.22.

[0077] Further, in the optical system 2, the second lens group 22 has at least one lens having positive refractive power and at least one lens having negative refractive power, and in the second lens group 22, the lens 221 having the strongest positive refractive power is disposed at a position closer to the image side than the lens 222 having the strongest negative refractive power.

[0078] According to this configuration, it is possible to achieve aberration correction in the entire focusing range from infinity to close-range shooting by moving only the second lens group 22. Details are as follows.

[0079] In order to achieve aberration correction in the entire focusing range from infinity to close-range shooting by moving only the second lens group 22, the on-axis light beam that is strongly convergent by the first lens group 21 on the object side of the second lens group 22 is made to be a properly convergent light beam, and a negative optical power is required to jump up the peripheral light beam and guide it to the image side of the second lens group 22. Further, on the image side of the second lens group 22, a positive optical power is required for convergence to obtain a desired F number.

[0080] Therefore, in the optical system 2 of the present embodiment, as in the above-described configuration, the second lens group 22 has at least one lens having positive refractive power and at least one lens having negative refractive power, and by adopting a configuration in which, in the second lens group 22, the lens 221 having the strongest positive refractive power is disposed at a position closer to the image side than the lens 222 having the strongest negative refractive power, it is possible to achieve proper aberration correction in the entire focusing range from infinity to close-range shooting by moving only the second lens group 22.

[0081] Further, in the optical system 2, when the focal length at the time of infinity focusing of the entire optical system is set to f, the optical system 2 can also satisfy the following expression (2).

[0082] OAL / f ≤ 2.00 • • • (2)

[0083] The above-described expression (2) specifies the ratio (OAL / f) of the distance from the most object-ward surface of the entire optical system to the image plane to the focal length, and when this ratio (OAL / f) exceeds the upper limit value (2.00), it cannot be said that the total optical length is sufficiently shortened, and not only the optical system 2 but also the entire photographing apparatus 1 provided with the optical system 2 cannot be miniaturized. Therefore, in the optical system 2 of the present embodiment, by setting the ratio (OAL / f) of the distance from the most object-ward surface of the entire optical system to the image plane to the focal length within the range of expression (2), the total optical length can be sufficiently shortened, and thus not only the optical system 2 but also the entire photographing apparatus 1 provided with the optical system 2 can be miniaturized.

[0084] Further, in the optical system 2 of the present embodiment, the above-described ratio (OAL / f) is preferably satisfied as follows:

[0085] 0.80 ≤ OAL / f ≤ 1.50,

[0086] More preferably, the following is satisfied:

[0087] 0.90 ≤ OAL / f ≤ 1.00.

[0088] In addition, in the optical system 2, when the maximum lateral magnification of the entire optical system is set as B, the optical system 2 can also satisfy the following equation (3).

[0089] 0.50 ≤ |B| • • • (3)

[0090] The above equation (3) defines the maximum lateral magnification of the entire optical system, and when the value is lower than the lower limit value (0.50), it cannot be said that close-up shooting is sufficiently achieved, and the photographable object distance cannot be shortened. Therefore, in the optical system 2 of the present embodiment, by setting the maximum lateral magnification of the entire optical system within the range of equation (3), the photographable object distance can be shortened, and thus, a small optical system 2 that can perform close-up shooting, and a photographing apparatus 1 provided with the optical system 2 can be achieved.

[0091] Here, the maximum lateral magnification is a value indicating the degree of close-up shooting, and is the ratio of the height of the image of the photographing surface to the height of the object of the subject. For example, when |B| is 1.00 at the time of close-up shooting, the size of the subject and the photographing surface are equal. In addition, at the time of long-distance shooting, |B| approaches 0.00.

[0092] In addition, in the optical system 2 of the present embodiment, the maximum lateral magnification of the entire optical system preferably satisfies:

[0093] 0.75 ≤ |B|,

[0094] More preferably, the following is satisfied:

[0095] 1.00 ≤ |B|.

[0096] In addition, in the optical system 2, when the lateral magnification at the time of infinity focus of the second lens group is set as b2, and the lateral magnification at the time of infinity focus of the third lens group is set as b3, the optical system 2 can also satisfy the following equation (4).

[0097] -10.00 ≤ (1-b2 2 ) x b3 2 ≤ -2.00 • • • (4)

[0098] The above equation (4) defines the ratio of the movement amount of the imaging surface to the movement amount of the second lens group 22 in the optical axis C direction ((1-b2 2 ) x b3 2), the value corresponding to the formula is 1 in the entire optical system, but in the inner focusing optical system of the optical system 2 of the present embodiment, by making the ratio larger in the negative direction, close-up shooting can be achieved with a small movement amount, and miniaturization of the entire optical system 2 is achieved. When the ratio ((1 - b2 2 ) x b3 2 ) is less than the lower limit value (-10.00), the movement amount of the imaging plane becomes too large with respect to the movement amount of the second lens group 22 in the direction of the optical axis C, and it is difficult to improve the precision of the stop position of the second lens group 22 by a driving device such as an actuator. When the ratio ((1 - b2 2 ) x b3 2 ) exceeds the upper limit value (-2.00), the movement amount of the second lens group 22 for close-up shooting becomes large, and thus, it is difficult to achieve miniaturization of the entire optical system 2. Therefore, in the optical system 2 of the present embodiment, by setting the ratio 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 ((1 - b2 2 ) x b3 2 ) within the range of the above formula (4), it is possible to achieve a balance between improving the precision of the stop position of the second lens group 22 by an actuator or the like at the time of focusing and miniaturization of the entire optical system 2.

[0099] In addition, in the optical system 2 of the present embodiment, the above ratio ((1 - b2 2 ) x b3 2 ) is preferably satisfied as follows:

[0100] -9.00 ≤ (1 - b2 2 ) x b3 2 ≤ -2.50,

[0101] More preferably, it is satisfied as follows:

[0102] -8.00 ≤ (1 - b2 2 ) x b3 2 ≤ -5.00.

[0103] In addition, in the optical system 2, when the focal length of the entire optical system at the time of infinity focusing is set to f, and the focal length of the above second lens group is set to f2, the optical system 2 can also satisfy the following formula (5).

[0104] -0.70 ≤ f2 / f ≤ -0.10 • • • (5)

[0105] The above-described formula (5) defines the ratio of the focal length of the second lens group 22 to the focal length of the entire optical system 2 at the time of focusing on infinity (f2 / f), and when this ratio (f2 / f) is lower than the lower limit value (-0.70), the power of the second lens group 22 becomes weak, and the moving amount of the second lens group 22 for close-up shooting becomes large, and thus, it is difficult to achieve the miniaturization of the entire optical system 2. When this ratio (f2 / f) exceeds the upper limit value (-0.10), the moving amount of the imaging surface becomes excessively large with respect to the moving amount of the second lens group 22 in the direction of the optical axis C, and it is difficult to improve the precision 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 of the focal length of the second lens group 22 to the focal length of the entire optical system 2 at the time of focusing on infinity (f2 / f) within the range of the above-described formula (5), it is possible to achieve a balance between the miniaturization of the entire optical system 2 and the improvement of the precision of the stop position of the second lens group 22 by an actuator or the like at the time of focusing.

[0106] In addition, in the optical system 2 of the present embodiment, the above-described ratio (f2 / f) is preferably satisfied as follows:

[0107] -0.65 ≤ f2 / f ≤ -0.15,

[0108] More preferably, the following is satisfied:

[0109] -0.60 ≤ f2 / f ≤ -0.20.

[0110] According to the optical system 2 configured as described above, and the photographing device 1 provided with the optical system 2, it is possible to achieve a small size and close-up shooting. That is, in the optical system 2 of the present embodiment in which the first lens group 21 has positive refractive power, the second lens group 22 has negative refractive power, and the third lens group 23 has negative refractive power, and the second lens group 22 is movable at the time of focusing from infinity to a close-up, by appropriately selecting the configuration, magnification, lens material, and the like of each lens group 21 to 23, it is possible to achieve a small size as a whole, and to sufficiently achieve the performance at the time of close-up shooting and the correction of chromatic aberration.

[0111] In addition, in the optical system 2 of the present embodiment, and the photographing device 1 provided with the optical system 2, even in the case of a so-called inner focusing optical system, it is possible to achieve the miniaturization of the optical system 2, and the photographing device 1 provided with the optical system 2, and the like. Details are as follows.

[0112] As a focusing method of a conventional lens, a whole-advance optical system is known. The above whole-advance optical system adopts a method of advancing the whole optical system to the object side at the time of focusing from infinity to a close range, and the whole optical system is fixed as one without being divided into subgroups, so that it is relatively easy to improve the optical performance at the time of design. However, when focusing is performed on the whole lens, the position through which the lens system of a peripheral high beam passes differs between infinity and the close range, the variation of the curvature of the image surface becomes large, and it is difficult to correct the aberration thereof. In addition, the distance by which the whole lens is moved at the time of focusing increases in proportion to the square of the focal length. Therefore, particularly in a long focal length telephoto lens, in order to achieve close-range shooting, the amount of movement at the time of focusing becomes long, as a result of which it is difficult to achieve the miniaturization of the optical system and the shooting device.

[0113] On the other hand, an inner-focusing optical system adopts a method of making a partial lens group in the optical system movable to the object side or the image side at the time of focusing from infinity to a close range, and since the aberration correction corresponding to each object distance is distributed to each group, the aberration correction in the focusing range is relatively easy. In addition, it is possible to improve the sensitivity of the distance by which the focusing group is moved at the time of focusing, and easily shorten the amount of movement.

[0114] Therefore, in the shooting device 1 of the present embodiment, even if an inner-focusing optical system is adopted as the optical system 2, it is possible to achieve an optical system which is overall miniaturized and sufficiently achieves the performance at the time of close-range shooting and the correction of chromatic aberration.

[0115] Next, Embodiments 1 to 4 of the optical system of the present application will be described. In each of the following embodiments, the same reference numerals are used for the configurations corresponding to each configuration of the optical system 2 of the above-described embodiment. In addition, in the table of each of the following embodiments, r is the radius of curvature, d is the lens thickness or the lens interval, nd is the refractive index of the d line, and vd indicates the Abbe number with the d line as a reference. In addition, the aspheric surface is defined by the following formula.

[0116] z = ch 2 / [1 + {1 - (1 + k) c 2 h 2} 1 / 2 ] + A4h 4 + A6h 6 + A8h 8 + A10h 10 •••

[0117] (where c is the curvature (1 / r), h is the height from the optical axis, k is the conic coefficient, and A4, A6, A8, A10 ••• are the aspheric coefficients of each order)

[0118] In addition, each longitudinal aberration diagram indicates, from the left side, a spherical aberration (SA (mm)), a coma (AST (mm)), and a distortion (DIS (%)). In the spherical aberration diagram, the vertical axis indicates an F number (indicated by FNO in the drawing), the solid line indicates a characteristic of a d-line, the short-dashed line indicates a characteristic of an F-line, and the long-dashed line indicates a characteristic of a C-line. In the coma diagram, the vertical axis indicates a maximum image height (indicated by Y in the drawing), the solid line indicates a characteristic of a sagittal plane (indicated by S in the drawing), and the dashed line indicates a characteristic of a tangential plane (indicated by M in the drawing). In the distortion diagram, the vertical axis indicates a maximum image height (indicated by Y in the drawing).

[0119] [Example 1]

[0120] Figure 2 and Figure 3 is a lens configuration diagram of the optical system of Example 1, Figure 2 shows an infinite focus state, Figure 3 shows a closest focus state. In addition, the reference numerals of each configuration of the optical system are the same as those of the corresponding configuration of the optical system 2 of the above-described embodiment. In addition, in this optical system, the positions of the first lens group 21 and the third lens group 23 on the optical axis C with respect to the imaging element (image plane) 3 are fixed at the time of focusing.

[0121] Figure 4 is a longitudinal aberration diagram in the infinite focus state, Figure 5 is a longitudinal aberration diagram in the "-0.5 times" magnification, Figure 6 is a longitudinal aberration diagram in the "-1.0 times" magnification. In addition, Table 1 below shows surface data of each lens, Table 2 shows aspherical surface data, Table 3 shows various data, Table 4 shows lens group data, and Table 5 shows single lens data.

[0122] Table 1

[0123]

[0124] Table 2

[0125]

[0126] Table 3

[0127]

[0128] The focal length is 21.999, and the maximum image height is 4.000.

[0129] Table 4

[0130]

[0131] Table 5

[0132]

[0133] [Example 2]

[0134] Figure 7 and Figure 8 is a lens configuration diagram of the optical system of this Example 2, Figure 7 shows an infinite focus state, Figure 8 shows a closest focus state. In addition, the reference numerals of the respective configurations of the optical system are the same as those of the corresponding configurations of the optical system 2 of the above-described embodiment. In addition, in this optical system as well, the positions of the first lens group 21 and the third lens group 23 on the optical axis C relative to the imaging element (image plane) 3 are fixed at the time of focusing.

[0135] Figure 9 is a longitudinal aberration diagram in the infinite focus state, Figure 10 is a longitudinal aberration diagram in the "-0.5 times" magnification, Figure 11 is a longitudinal aberration diagram in the "-1.0 times" magnification. In addition, Table 6 below shows the surface data of each lens, Table 7 shows the aspherical surface data, Table 8 shows various data, Table 9 shows the lens group data, and Table 10 shows the single lens data.

[0136] Table 6

[0137]

[0138] Table 7

[0139]

[0140] Table 8

[0141]

[0142] The focal length is 11.600, and the maximum image height is 2.060.

[0143] Table 9

[0144]

[0145] Table 10

[0146]

[0147] [Example 3]

[0148] Figure 12 and Figure 13 is a lens configuration diagram of the optical system of this Example 3, Figure 12 shows an infinite focus state, Figure 13shows the closest focus state. In addition, the reference numerals of the respective components of the optical system are the same as those of the corresponding components of the optical system 2 of the above-described embodiment. In this optical system as well, the positions of the first lens group 21 and the third lens group 23 on the optical axis C relative to the imaging element (image plane) 3 are fixed at the time of focusing.

[0149] Figure 14 is a longitudinal aberration diagram at the time of infinite focus, Figure 15 is a longitudinal aberration diagram at the time of " -0.5 times" magnification, Figure 16 is a longitudinal aberration diagram at the time of " -1.0 times" magnification. In addition, Table 11 below shows the surface data of each lens, Table 12 shows the aspheric surface data, Table 13 shows various data, Table 14 shows the lens group data, and Table 15 shows the single lens data.

[0150] Table 11

[0151]

[0152] Table 12

[0153]

[0154] Table 13

[0155]

[0156] The focal length is 11.598, and the maximum image height is 2.060.

[0157] Table 14

[0158]

[0159] Table 15

[0160]

[0161] [Embodiment 4]

[0162] Figure 17 and Figure 18 is a lens configuration diagram of the optical system of this Embodiment 4, Figure 17 shows the infinite focus state, Figure 18 shows the closest focus state. In addition, the reference numerals of the respective components of the optical system are the same as those of the corresponding components of the optical system 2 of the above-described embodiment. In this optical system as well, the positions of the first lens group 21 and the third lens group 23 on the optical axis C relative to the imaging element (image plane) 3 are fixed at the time of focusing.

[0163] Figure 19 is a longitudinal aberration diagram at the time of infinite focus,Figure 20 is a longitudinal aberration diagram at a magnification of "-0.5 times", Figure 21 is a longitudinal aberration diagram at a magnification of "-1.0 times". In addition, Table 16 below shows surface data of each lens, Table 17 shows aspherical surface data, Table 18 shows various data, Table 19 shows lens group data, and Table 20 shows single lens data.

[0164] Table 16

[0165]

[0166] Table 17

[0167]

[0168] Table 18

[0169]

[0170] The focal length is 21.999, and the maximum image height is 4.000.

[0171] Table 19

[0172]

[0173] Table 20

[0174]

[0175] In the above Embodiments 1 to 4, values corresponding to each condition of the above-described embodiments are shown in Table 21 below. In Table 21, the condition formula (1) is OAL2 / OAL, the condition formula (2) is OAL / f, the condition formula (3) is |B|, the condition formula (4) is (1 - b2 2 ) x b3 2 , and the condition formula (5) is f2 / f.

[0176] Table 21

[0177]

[0178] In order to describe the present application, the present application has been adequately and sufficiently explained by the embodiments while referring to the accompanying drawings, but it should be recognized by those skilled in the art that the above-described embodiments can be easily changed and / or modified. Therefore, as long as the changed or modified embodiments by those skilled in the art do not depart from the scope of the claims recited in the claims, the changed or modified embodiments are interpreted as being included in the scope of the claims.

[0179] Explanation of Reference Numerals:

[0180] 1…image pickup 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…image pickup element, 4…liquid crystal screen, C…optical axis, F…focusing lens group, G…lens group.

Claims

1. An optical system characterized by comprising, in order from an object side to an image side, a first lens group having positive refractive power, a second lens group having negative refractive power, and a third lens group having negative refractive power, at the time of focusing, the second lens group moves along an optical axis, the first lens group and the third lens group are fixed in position in the direction of the optical axis with respect to an image plane, 0.06 ≤ OAL2 / OAL, -10.00 < (1 - b2 2 ) x b3 2 ≤ -2.

0. at the time of infinity focus of the second lens group, a lateral magnification is b2, and at the time of infinity focus of the third lens group, a lateral magnification is b3, and 2. The optical system according to claim 1, wherein the second lens group has at least one lens having positive refractive power, and at least one lens having negative refractive power, in the second lens group, a lens having the strongest positive refractive power is located at a position further toward the image side than a lens having the strongest negative refractive power.

3. The optical system according to claim 1 or 2, wherein OAL / f ≤ 2.

00.

4. The optical system according to claim 1 or 2, wherein 5. The optical system according to claim 1 or 2, wherein 0.50≤｜B｜。 -0.70 ≤ f2 / f ≤ -0.

10. comprises the optical system according to any one of claims 1 to 5, and 6. An imaging device, characterized by comprising: a photoelectric conversion element disposed on the image side of the optical system and configured to convert an optical image formed by the optical system into an electric signal. ​ ​

Images