Variable magnification optical systems and optical instruments

Abstract

The present invention provides a variable magnification optical system in which various aberrations, such as spherical aberration, are well corrected. [Solution] The variable magnification optical system ZL consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a subsequent lens group GR, arranged in order from the object side. When magnification is applied, the spacing between adjacent lens groups changes, the first lens group G1 is fixed relative to the image plane, the third lens group G3 moves when magnification is applied from the wide-angle end to the telephoto end, and the subsequent lens group GR consists of a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, and a final lens group. When focusing, the fifth lens group G5 and the sixth lens group G6 move, satisfying the following conditional equation. 0.30 <f3 / (-fE)<3.50 2.90

Description

[Technical Field]

[0001] This invention relates to a variable magnification optical system and an optical instrument using the same. [Background technology]

[0002] Conventionally, variable magnification optical systems suitable for photographic cameras, electronic still cameras, video cameras, etc., have been proposed (see, for example, Patent Document 1). In variable magnification optical systems, there is a need to correct aberrations well. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-139125 [Overview of the Initiative]

[0004] The variable magnification optical system according to the present invention consists of a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and a subsequent lens group, arranged in order from the object side. When magnification is applied, the spacing between adjacent lens groups changes, the first lens group is fixed with respect to the image plane, the third lens group moves when magnification is applied from the wide-angle end to the telephoto end, and the subsequent lens group consists of a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, a sixth lens group having positive refractive power, and a final lens group. When focusing is achieved, the fifth and sixth lens groups move, satisfying the following conditional equation. 0.30 <f3 / (-fE)<3.50 2.90 <f1 / (-f2)<5.00 However, f3: focal length of the third lens group fE: Focal length of the final lens group f1: Focal length of the first lens group f2: Focal length of the second lens group

[0005] The optical device according to the third embodiment is configured to be equipped with the above-mentioned variable magnification optical system. [Brief explanation of the drawing]

[0006] [Figure 1] This figure shows the movement of the lens when the variable magnification optical system according to the first embodiment changes from the wide-angle end state to the telephoto end state. [Figure 2] Figures 2(A), 2(B), and 2(C) show aberration diagrams of the variable magnification optical system according to the first embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. [Figure 3] This figure shows the movement of the lens when the variable magnification optical system according to the second embodiment changes from the wide-angle end state to the telephoto end state. [Figure 4] Figures 4(A), 4(B), and 4(C) show the aberration diagrams of the variable magnification optical system according to the second embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. [Figure 5] This figure shows the movement of the lens when the variable magnification optical system according to the third embodiment changes from the wide-angle end state to the telephoto end state. [Figure 6] Figures 6(A), 6(B), and 6(C) show the aberration diagrams of the variable magnification optical system according to the third embodiment in the wide-angle end state, intermediate focal length state, and telephoto end state, respectively. [Figure 7] This figure shows the movement of the lens when the variable magnification optical system according to the fourth embodiment changes from the wide-angle end state to the telephoto end state. [Figure 8] Figures 8(A), 8(B), and 8(C) show the aberration diagrams of the variable magnification optical system according to the fourth embodiment in the wide-angle end state, intermediate focal length state, and telephoto end state, respectively. [Figure 9] This figure shows the movement of the lens when the variable magnification optical system according to the fifth embodiment changes from the wide-angle end state to the telephoto end state. [Figure 10] Figures 10(A), 10(B), and 10(C) show the aberrations of the variable magnification optical system according to the fifth embodiment in the wide-angle end state, intermediate focal length state, and telephoto end state, respectively. [Figure 11]This figure shows the movement of the lens when the variable magnification optical system according to the sixth embodiment changes from the wide-angle end state to the telephoto end state. [Figure 12] Figures 12(A), 12(B), and 12(C) show the aberration diagrams of the variable magnification optical system according to the sixth embodiment in the wide-angle end state, intermediate focal length state, and telephoto end state, respectively. [Figure 13] This figure shows the movement of the lens when the variable magnification optical system according to the seventh embodiment changes from the wide-angle end state to the telephoto end state. [Figure 14] Figures 14(A), 14(B), and 14(C) show the aberration diagrams of the variable magnification optical system according to the seventh embodiment in the wide-angle end state, intermediate focal length state, and telephoto end state, respectively. [Figure 15] This figure shows the configuration of a camera equipped with a variable magnification optical system according to this embodiment. [Figure 16] This flowchart shows the method for manufacturing the variable magnification optical system according to this embodiment. [Modes for carrying out the invention]

[0007] The variable magnification optical system and optical equipment according to this embodiment will be described below with reference to the figures. First, a camera (optical equipment) equipped with the variable magnification optical system according to this embodiment will be described based on Figure 15. As shown in Figure 15, this camera 1 is a digital camera equipped with the variable magnification optical system according to this embodiment as the photographic lens 2. In camera 1, light from an object (subject) not shown is focused by the photographic lens 2 and reaches the image sensor 3. As a result, the light from the subject is captured by the image sensor 3 and recorded as a subject image in memory not shown. In this way, the photographer can take a photograph of the subject with camera 1. Note that this camera may be a mirrorless camera or a single-lens reflex type camera with a quick-return mirror.

[0008] Next, the zoom optical system (imaging lens) according to the present 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 present embodiment, as shown in FIG. 1, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a subsequent lens group GR arranged in order from the object side. During zooming, the distance between adjacent lens groups changes. Note that the first lens group G1 is fixed with respect to the image plane during zooming. When zooming from the wide-angle end state to the telephoto end state, the third lens group G3 moves toward the image side along the optical axis. The subsequent lens group GR has a final lens group arranged on the most image side.

[0009] Under the above configuration, the zoom optical system ZL according to the present embodiment satisfies the following conditional expression (1).

[0010] -10.00 < f3 / (-fE) < 3.50 ···(1) However, f3: focal length of the third lens group G3 fE: focal length of the final lens group

[0011] According to the present embodiment, it is possible to obtain a zoom optical system in which various aberrations such as spherical aberration are well corrected, and an optical device provided with this zoom optical system. The zoom optical system ZL according to the present embodiment may be the zoom optical system ZL (2) shown in FIG. 3, may be the zoom optical system ZL (3) shown in FIG. 5, or may be the zoom optical system ZL (4) shown in FIG. 7. Further, the zoom optical system ZL according to the present embodiment may be the zoom optical system ZL (5) shown in FIG. 9, may be the zoom optical system ZL (6) shown in FIG. 11, or may be the zoom optical system ZL (7) shown in FIG. 13.

[0012] The conditional expression (1) defines the ratio between the focal length of the third lens group G3 and the focal length of the final lens group. By satisfying the conditional expression (1), spherical aberration, coma aberration, and field curvature can be well corrected.

[0013] If the corresponding value in conditional equation (1) exceeds the upper limit, the refractive power of the third lens group G3 weakens, making it difficult to adequately correct spherical aberration and coma aberration. Furthermore, the negative refractive power of the final lens group becomes stronger, making it difficult to adequately correct coma aberration and field curvature. Setting the upper limit of conditional equation (1) to 3.40 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the upper limit of conditional equation (1) may be set to 3.30, 3.20, 3.10, 3.00, 2.90, 2.85, 2.75, 2.70, and even 2.65.

[0014] If the corresponding value in conditional equation (1) falls below the lower limit, the refractive power of the third lens group G3 increases, making it difficult to adequately correct spherical aberration and coma aberration. Also, the refractive power of the final lens group decreases, making it difficult to adequately correct coma aberration and field curvature. Setting the lower limit of conditional equation (1) to -8.00 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the lower limit of conditional equation (1) may be set to -5.00, -3.00, -1.00, -0.50, 0.30, 0.40, and even 0.45.

[0015] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (2).

[0016] -10.00 <f1 / (-fE)<3.50 ···(2) However, f1: Focal length of the first lens group G1

[0017] Condition (2) specifies the ratio of the focal length of the first lens group G1 to the focal length of the final lens group. By satisfying condition (2), spherical aberration, field curvature, and coma aberration can be effectively corrected.

[0018] If the corresponding value in conditional equation (2) exceeds the upper limit, the refractive power of the first lens group G1 weakens, making it difficult to adequately correct spherical aberration near the telephoto end and field curvature near the wide-angle end. Furthermore, the negative refractive power of the final lens group becomes stronger, making it difficult to adequately correct coma aberration and field curvature. Setting the upper limit of conditional equation (2) to 3.40 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the upper limit of conditional equation (2) may be set to 3.30, 3.20, 3.10, 3.00, 2.95, 2.90, 2.85, 2.80, and even 2.75.

[0019] If the corresponding value in conditional equation (2) falls below the lower limit, the refractive power of the first lens group G1 increases, making it difficult to adequately correct spherical aberration near the telephoto end and field curvature near the wide-angle end. Furthermore, the refractive power of the final lens group decreases, making it difficult to adequately correct coma aberration and field curvature. Note that setting the lower limit of conditional equation (2) to -8.00 can make the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the lower limit of conditional equation (2) may be set to -5.00, -3.00, -1.00, -0.50, 0.30, 0.50, 0.75, 0.90, and even 1.00.

[0020] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (3).

[0021] -10.00 <f2 / fE<1.50 ···(3) However, f2: Focal length of the second lens group G2

[0022] Condition (3) specifies the ratio of the focal length of the second lens group G2 to the focal length of the final lens group. By satisfying condition (3), spherical aberration and coma aberration can be effectively corrected.

[0023] If the corresponding value in conditional equation (3) exceeds the upper limit, the refractive power of the second lens group G2 weakens, making it difficult to adequately correct spherical aberration and coma aberration. Furthermore, the negative refractive power of the final lens group becomes stronger, making it difficult to adequately correct coma aberration and field curvature. Setting the upper limit of conditional equation (3) to 1.40 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the upper limit of conditional equation (3) may be set to 1.30, 1.20, 1.10, 1.00, 0.90, or even 0.80.

[0024] If the corresponding value in conditional equation (3) falls below the lower limit, the refractive power of the second lens group G2 increases, making it difficult to adequately correct spherical aberration and coma aberration. Also, the refractive power of the final lens group decreases, making it difficult to adequately correct coma aberration and field curvature. Setting the lower limit of conditional equation (3) to -8.00 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the lower limit of conditional equation (3) may be set to -5.00, -3.00, -1.00, -0.50, 0.10, 0.20, 0.30, and even 0.35.

[0025] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (4).

[0026] 1.50 <f1 / (-f2)<5.00 ···(4) However, f1: Focal length of the first lens group G1 f2: Focal length of the second lens group G2

[0027] Conditional equation (4) defines the ratio of the focal length of the first lens group G1 to the focal length of the second lens group G2. By satisfying conditional equation (4), coma aberration and spherical aberration can be well corrected, and a magnification ratio that satisfies this embodiment can be ensured.

[0028] If the corresponding value in conditional equation (4) exceeds the upper limit, the refractive power of the second lens group G2 becomes stronger, making it difficult to correct coma aberration and spherical aberration. Setting the upper limit of conditional equation (4) to 4.80 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (4) may be set to 4.50, 4.30, 4.00, 3.90, 3.80, or even 3.75.

[0029] If the corresponding value in conditional equation (4) falls below the lower limit, the refractive power of the first lens group G1 becomes stronger, making it difficult to correct coma aberration and spherical aberration. Setting the lower limit of conditional equation (4) to 1.75 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (4) may be set to 1.90, 2.00, 2.25, 2.40, 2.50, 2.70, 2.80, 2.90, and even 3.00.

[0030] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (5).

[0031] 0.80 <f1 / f3<2.50 ···(5) However, f1: Focal length of the first lens group G1

[0032] Condition (5) specifies the ratio of the focal length of the first lens group G1 to the focal length of the third lens group G3. By satisfying condition (5), spherical aberration and coma aberration can be effectively corrected.

[0033] If the corresponding value in conditional equation (5) exceeds the upper limit, the refractive power of the third lens group G3 becomes stronger, making it difficult to correct spherical aberration and coma aberration. Setting the upper limit of conditional equation (5) to 2.45 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (5) may be set to 2.40, 2.20, 2.00, 1.90, 1.80, 1.70, 1.60, and even 1.50.

[0034] If the corresponding value in conditional equation (5) falls below the lower limit, the refractive power of the first lens group G1 becomes stronger, making it difficult to correct spherical aberration and coma aberration. Setting the lower limit of conditional equation (5) to 0.82 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (5) may be set to 0.85, 0.87, 0.90, 0.92, 0.95, 0.98, or even 1.00.

[0035] In the variable magnification optical system ZL according to this embodiment, the subsequent lens group GR preferably has a fourth lens group G4 and satisfies the following condition (6).

[0036] -2.00 <f1 / f4<4.00 ···(6) However, f1: Focal length of the first lens group G1 f4: Focal length of lens group G4

[0037] Condition (6) specifies the ratio of the focal length of the first lens group G1 to the focal length of the fourth lens group G4. By satisfying condition (6), spherical aberration and coma aberration can be effectively corrected.

[0038] If the corresponding value in conditional equation (6) exceeds the upper limit, the refractive power of the fourth lens group G4 becomes stronger, making it difficult to correct spherical aberration and coma aberration. Setting the upper limit of conditional equation (6) to 3.80 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (6) may be set to 3.60, 3.50, 3.20, 3.00, 2.80, 2.60, 2.50, 2.40, and even 2.30.

[0039] If the corresponding value in conditional equation (6) falls below the lower limit, the refractive power of the first lens group G1 becomes stronger, making it difficult to correct spherical aberration and coma aberration. Setting the lower limit of conditional equation (6) to -1.50 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (6) may be set to 0.50, 0.80, 1.00, 1.20, 1.40, 1.50, and even 1.55.

[0040] In the variable magnification optical system ZL according to this embodiment, it is desirable that the final lens group be fixed to the image plane during magnification. This simplifies the drive mechanism of the lens group in this embodiment and allows for miniaturization of the lens barrel.

[0041] In the variable magnification optical system ZL according to this embodiment, it is desirable that at least one lens group among the lens groups positioned closer to the image than the third lens group G3 be fixed to the image plane during magnification. This is preferable because it simplifies the drive mechanism of the lens group in this embodiment, allows for miniaturization of the lens barrel, and reduces aberration fluctuations during magnification.

[0042] In the variable magnification optical system ZL according to this embodiment, the subsequent lens group GR has a first focusing lens group having a negative refractive power that moves when focusing, and a second focusing lens group having a positive refractive power that moves when focusing, arranged in order from the object side, and it is desirable that the following condition (7) is satisfied.

[0043] 0.80<(-fF1) / fF2<5.00 (7) However, fF1: Focal length of the first focusing lens group fF2: Focal length of the second focusing lens group

[0044] Condition (7) specifies the ratio of the focal length of the first focusing lens group to the focal length of the second focusing lens group. By satisfying condition (7), fluctuations in various aberrations, including spherical aberration, when focusing from an object at infinity to an object at a close distance can be suppressed.

[0045] If the corresponding value in conditional equation (7) exceeds the upper limit, the refractive power of the second focusing lens group becomes stronger, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. Setting the upper limit of conditional equation (7) to 4.75 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (7) may be set to 4.50, 4.25, 4.00, 3.75, 3.50, 3.25, 3.00, 2.75, 2.50, 2.25, and even 2.00.

[0046] If the corresponding value in conditional equation (7) falls below the lower limit, the negative refractive power of the first focusing lens group becomes stronger, making it difficult to suppress fluctuations in various aberrations, including spherical aberration, during focusing. Setting the lower limit of conditional equation (7) to 0.85 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (7) may be set to 0.90, 1.00, 1.10, 1.20, 1.25, 1.28, and even 1.30.

[0047] In the variable magnification optical system ZL according to this embodiment, it is desirable that the second lens group G2 has a positive lens that satisfies the following conditions (8) to (10).

[0048] 18.0 < νdP < 35.0 ···(8) 1.83 <ndP+(0.01425×νdP)<2.12 ···(9) 0.702<θgFP+(0.00316×νdP) (10) However, νdP: Abbe number based on the d line of the positive lens. ndP: Refractive index of a positive lens with respect to the d line θgFP is the partial dispersion ratio of a positive lens, and is defined by the following equation, where ngP is the refractive index of the positive lens with respect to the g line, nFP is the refractive index of the positive lens with respect to the f line, and nCP is the refractive index of the positive lens with respect to the c line. θgFP = (ngP - nFP) / (nFP - nCP) The Abbe number νdP, with respect to the d-line of the positive lens, is defined by the following equation. νdP=(ndP-1) / (nFP-nCP)

[0049] Conditional equation (8) defines an appropriate range for the Abbe number with respect to the d line of the positive lens in the second lens group G2. By satisfying conditional equation (8), good correction of reference aberrations such as spherical aberration and coma aberration, as well as correction (achromatic correction) of first-order chromatic aberration, can be achieved.

[0050] If the corresponding value in conditional equation (8) exceeds the upper limit, it becomes difficult to correct axial chromatic aberration, which is undesirable. Setting the upper limit of conditional equation (8) to 32.5 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (8) to 31.5.

[0051] If the corresponding value in conditional equation (8) falls below the lower limit, it becomes difficult to correct axial chromatic aberration, which is undesirable. Setting the lower limit of conditional equation (8) to 20.00 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 22.00, 23.00, 23.50, 24.00, 25.00, and even 26.00.

[0052] Conditional equation (9) defines an appropriate relationship between the refractive index of the positive lens in the second lens group G2 with respect to the d line and the Abbe number with respect to the d line. By satisfying conditional equation (9), good correction of reference aberrations such as spherical aberration and coma aberration, as well as correction (achromatic correction) of first-order chromatic aberration can be achieved.

[0053] If the corresponding value of conditional expression (9) falls outside the above range, for example, the Petzval sum becomes smaller, making it difficult to correct the field curvature, which is undesirable. Setting the upper limit of conditional expression (9) to 2.10 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (9) to 2.08, and even further to 2.06. Furthermore, setting the lower limit of conditional expression (9) to 1.84 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (9) to 1.85.

[0054] Conditional equation (10) appropriately defines the anomalous dispersion of the positive lens in the second lens group G2. By satisfying conditional equation (10), in addition to correcting the first-order aberration, the second-order spectrum can be corrected effectively.

[0055] If the corresponding value in conditional equation (10) falls below the lower limit, the anomalous dispersion of the positive lens decreases, making it difficult to correct chromatic aberration. Setting the lower limit of conditional equation (10) to 0.704 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (10) to 0.708, 0.710, and even 0.715.

[0056] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (11).

[0057] 25.00°<2ωw<50.00° ···(11) However, 2ωw: the entire field of view of the variable magnification optical system ZL at the wide-angle end.

[0058] Conditional equation (11) defines the total angle of view of the variable magnification optical system ZL at the wide-angle end. By satisfying conditional equation (11), it is possible to have a wide angle of view that satisfies this embodiment while effectively correcting various aberrations such as coma aberration, distortion aberration, and field curvature. Setting the lower limit of conditional equation (11) to 27.00° makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (11) may be set to 29.00°, 30.00°, 32.00°, and even 33.00°. Furthermore, setting the upper limit of conditional equation (11) to 48.00° makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (11) may be set to 45.00°, 42.00°, 40.00°, 38.00°, 36.00°, and even 35.00°.

[0059] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (12).

[0060] 5.00°<2ωt<20.00° (12) However, 2ωt: the entire field of view of the variable magnification optical system ZL at the telephoto end.

[0061] Conditional equation (12) defines the entire field of view of the variable magnification optical system ZL at the telephoto end. By satisfying conditional equation (12), various aberrations such as coma aberration, distortion aberration, and field curvature can be well corrected. Setting the upper limit of conditional equation (12) to 18.00° makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (12) may be set to 16.00°, 15.00°, 14.00°, and even 13.00°. On the other hand, setting the lower limit of conditional equation (12) to 7.00° makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the lower limit of conditional equation (12) may be set to 8.00°, 10.00°, 11.00°, and even 12.00°.

[0062] The variable magnification optical system ZL according to this embodiment preferably satisfies the following condition (13).

[0063] 0.20 <BFw / fw<0.85 ···(13) However, BFw: Back focus of the variable magnification optical system ZL at the wide-angle end. fw: Focal length of the variable magnification optical system ZL at the wide-angle end.

[0064] Conditional equation (13) defines the ratio of the back focus of the variable magnification optical system ZL at the wide-angle end to the focal length of the variable magnification optical system ZL at the wide-angle end. By satisfying conditional equation (13), various aberrations, including coma aberration, can be effectively corrected at the wide-angle end.

[0065] If the corresponding value in conditional equation (13) exceeds the upper limit, the back focus becomes too large relative to the focal length of the variable magnification optical system ZL at the wide-angle end, making it difficult to correct aberrations, including coma aberration, at the wide-angle end. Setting the upper limit of conditional equation (13) to 0.80 makes the effect of this embodiment more reliable. To further ensure the effect of this embodiment, the upper limit of conditional equation (13) may be set to 0.75, 0.70, 0.65, 0.60, or even 0.55.

[0066] If the corresponding value in conditional equation (13) falls below the lower limit, the back focus becomes too small relative to the focal length of the variable magnification optical system ZL at the wide-angle end, making it difficult to correct aberrations, including coma aberration, at the wide-angle end. Furthermore, it becomes difficult to arrange the mechanical components of the lens barrel. Setting the lower limit of conditional equation (13) to 0.25 makes the effects of this embodiment more reliable. To further ensure the effects of this embodiment, the lower limit of conditional equation (13) may be set to 0.30, 0.35, 0.40, or even 0.42.

[0067] Next, with reference to Figure 16, the manufacturing method of the variable magnification optical system ZL according to this embodiment will be outlined. First, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a subsequent lens group GR are arranged in order from the object side (step ST1). Then, the spacing between adjacent lens groups is configured to change during magnification (step ST2). During magnification, the first lens group G1 is fixed with respect to the image plane. When magnification changes from the wide-angle end to the telephoto end, the third lens group G3 moves towards the image side along the optical axis. In addition, the final lens group is placed on the image side of the subsequent lens group GR (step ST3). Furthermore, each lens is arranged in the lens barrel so as to satisfy at least the above condition (1) (step ST4). With such a manufacturing method, it is possible to manufacture a variable magnification optical system in which various aberrations such as spherical aberration are well corrected. [Examples]

[0068] The variable magnification optical system ZL according to an embodiment of this model will be described below with reference to the drawings. Figures 1, 3, 5, 7, 9, 11, and 13 show the movement of the lenses when the variable magnification optical system ZL{ZL(1) to ZL(7)} according to the first to seventh embodiments changes from the wide-angle end state to the telephoto end state. In each figure, the direction of movement of the lens group along the optical axis when magnification changes from the wide-angle end state to the telephoto end state is indicated by an arrow. Furthermore, the direction of movement of the focusing lens group when focusing from infinity to a nearby object is indicated by an arrow along with the word "Focused".

[0069] In these figures (Figures 1, 3, 5, 7, 9, 11, and 13), 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 number and types of symbols and numbers from becoming too large and complicated, each embodiment independently represents the lens groups, etc., using a combination of symbols and numbers. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that they have the same configuration.

[0070] Tables 1 to 7 are shown below. Table 1 shows the specifications for the first example, Table 2 for the second example, Table 3 for the third example, Table 4 for the fourth example, Table 5 for the fifth example, Table 6 for the sixth example, and Table 7 for the seventh example. In each example, the d-line (wavelength λ=587.6nm) and the g-line (wavelength λ=435.8nm) were selected as the targets for calculating the aberration characteristics.

[0071] In the [Overall Specifications] table, FNO is the F-number, 2ω is the angle of view (in degrees, where ω is half the angle of view), and Y is the image height. TL is the distance from the frontmost lens element to the final lens element on the optical axis when focused at infinity, plus BF, and BF is the air-equivalent distance (back focus) from the final lens element on the optical axis to the image plane I when focused at infinity. These values ​​are shown for each magnification state: wide-angle (W), intermediate focal length (M), and telephoto (T). Also, in the [Overall Specifications] table, θgFP is the partial dispersion ratio of the positive lens in the second lens group.

[0072] In the [Lens Specifications] table, 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 positive value is given for surfaces where the center of curvature is located on the image side), D is the interplanar spacing, which is the distance along the optical axis from each optical surface to the next optical surface (or image plane), nd is the refractive index of the optical material with respect to the d line, νd is the Abbe number of the optical material with respect to the d line, and θgF is the partial dispersion ratio of the optical material. "∞" for the radius of curvature indicates a plane or aperture, and (S) indicates an aperture diaphragm. The refractive index of air nd = 1.00000 is omitted. If the lens surface is aspherical, an asterisk (*) is added to the surface number and the paraxial radius of curvature is shown in the radius of curvature R column.

[0073] Let ng be the refractive index of the optical component material with respect to the g-line (wavelength λ = 435.8 nm), nF be the refractive index of the optical component material with respect to the F-line (wavelength λ = 486.1 nm), and nC be the refractive index of the optical component material with respect to the C-line (wavelength λ = 656.3 nm). Then, the partial dispersion ratio θgF of the optical component material is defined by the following equation (A).

[0074] θgF = (ng - nF) / (nF - nC) …(A)

[0075] In the table of [Aspherical Data], for the aspherical surface shown in [Lens Specifications], its shape is expressed by the following formula (B). X(y) is the distance along the optical axis (sag amount) from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, 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.

[0076] 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 + A12 × y 12 ···(B)

[0077] In the table of [Lens Group Data], the starting surface (the most object-side surface) and the focal length of each lens group are shown.

[0078] In the table of [Variable Interval Data], the surface intervals at the surface numbers where the surface intervals are "variable" in the table showing [Lens Specifications] are shown. Here, for each of the cases of focusing at infinity and close distance, the surface intervals in each zoom state of the wide-angle end (W), the intermediate focal length (M), and the telephoto end (T) are shown. In [Variable Interval Data], f represents the focal length of the entire lens system and β represents the shooting magnification.

[0079] In the table of [Condition Formula Corresponding Values], the values corresponding to each condition formula are shown.

[0080] In all specifications listed below, the focal length f, radius of curvature R, interplanar spacing D, and other lengths are generally expressed in "mm" unless otherwise specified. However, since optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced, this is not the only way to express them.

[0081] The explanations in the table above are common to all examples, and any redundant explanations below will be omitted.

[0082] (First embodiment) The first embodiment will be described using Figures 1 and 2 and Table 1. Figure 1 is a diagram showing the movement of the lenses when the variable magnification optical system according to the first embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(1) according to the first embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, an eighth lens group G8 having positive refractive power, and a ninth lens group G9 having negative refractive power, all arranged in order from the object side. When changing magnification from the wide-angle end to the telephoto end, the second lens group G2, the third lens group G3, the fifth lens group G5, the seventh lens group G7, and the eighth lens group G8 move separately in the direction indicated by the arrows in Figure 1, changing the spacing between adjacent lens groups. During magnification, the first lens group G1, the fourth lens group G4, the sixth lens group G6, and the ninth lens group G9 remain fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 corresponds to the subsequent lens group GR. The sign (+) or (-) attached to each lens group symbol indicates the refractive power of each lens group, and this is the same in all the following embodiments.

[0083] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a plano-convex positive lens L12 with its convex surface facing the object, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0084] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a biconcave negative lens L24, arranged in order from the object side.

[0085] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0086] The fourth lens group G4 consists of a biconvex positive lens L41 and a negative meniscus lens L42 with its convex surface facing the object, arranged in order from the object side.

[0087] The fifth lens group G5 is composed of a cemented lens consisting of a biconcave negative lens L51 and a biconvex positive lens L52. An aperture diaphragm S is positioned closest to the object in the fifth lens group G5 and moves together with the fifth lens group G5 during magnification.

[0088] The sixth lens group G6 consists of, arranged in order from the object side, a negative meniscus lens L61 with its convex surface facing the object, a cemented lens formed by a biconvex positive lens L62 and a negative meniscus lens L63 with its concave surface facing the object, and a positive meniscus lens L64 with its convex surface facing the object. The lens surface of the positive lens L62 facing the object is aspherical.

[0089] The seventh lens group G7 consists of a positive meniscus lens L71 with its concave surface facing the object and a negative meniscus lens L72 with its convex surface facing the object, arranged in order from the object side.

[0090] The eighth lens group G8 consists of a biconvex positive lens L81.

[0091] The ninth lens group G9 consists of two negative meniscus lenses, L91 and L92, arranged in order from the object side, with the concave surface facing the object. The negative meniscus lens L91 has an aspherical lens surface on the object side. The image plane I is positioned on the image side of the ninth lens group G9. In other words, the ninth lens group G9 is the final lens group.

[0092] In this embodiment, focusing is achieved from a distant object to a near object (from an object at infinity to an object at a finite distance) by moving the seventh lens group G7 toward the image plane I and the eighth lens group G8 toward the object. In other words, the seventh lens group G7 corresponds to the first focusing lens group, and the eighth lens group G8 corresponds to the second focusing lens group.

[0093] Table 1 below lists the specifications of the variable magnification optical system according to the first embodiment.

[0094] (Table 1) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.88277 2.8637 2.87906 2ω 33.79332 17.81742 12.27158 Y 21.70 21.70 21.70 TL 199.88619 199.88619 199.88619 BF 32.5469 32.5469 32.5469 [Lens Specifications] Face number RD nd νd θgF 1 116.34563 2.80 2.00100 29.12 2 85.133 9.70 1.49782 82.57 3 ∞ 0.10 4 92.01324 7.70 1.43385 95.25 5 696.98757 D5 (Variable) 6 58.77 1.90 1.60300 65.44 7 31.87745 10.30 8 -186.53352 1.60 1.49782 82.57 9 105.34866 0.80 10 41.08366 3.70 1.66382 27.35 0.6319 11 64.00891 5.50 12 -71.62319 1.90 1.49782 82.57 13 88.67881 D13 (Variable) 14 69.46271 3.20 1.94595 17.98 15 201.8299 D15 (Variable) 16 126.26563 4.70 1.49782 82.57 17 -126.26563 0.10 18 47.66354 3.85 1.49782 82.57 19 122.86616 D19 (Variable) 20 ∞ 3.50 (Aperture S) 21 -84.82141 1.80 1.92286 20.88 22 52.171 5.00 1.49782 82.57 23 -170.93248 D23 (Variable) 24 111.64091 1.70 1.85026 32.35 25 60.55636 2.00 26* 58.68256 7.70 1.59306 66.97 27 -55.839 1.70 1.62004 36.4 28 -95.85894 1.30 29 58.0393 2.70 1.80100 34.92 30 135.30037 D30 (Variable) 31 -369.28597 2.00 1.94595 17.98 32 -98.65201 0.80 33 1344.92022 1.25 1.71300 53.96 34 37.13115 D34 (Variable) 35 119.39985 3.85 1.90265 35.77 36 -119.39985 D36 (Variable) 37* -83.23047 1.90 1.51696 64.14 38 -335.27926 4.10 39 -54.71091 1.90 1.56384 60.71 40 -276.64763 BF [Aspherical Data] The 26th surface κ = 0.00, A4 = -2.00E-06, A6 = 8.31E-10 A8 = -6.83E-12, A10 = 2.63E-14, A12 = -3.55E-17 The 37th surface κ = 0.00, A4 = 1.18E-06, A6 = 1.63E-09 A8 = -7.32E-12, A10 = 2.41E-14, A12 = -2.65E-17 [Lens Group Data] Group Starting Surface Focal Length G1 1 147.97696 G2 6 -40.5909 G3 14 110.66613 G4 16 69.76371 G5 20 -62.56946 G6 24 56.88582 G7 31 -87.28124 G8 35 66.64828 G9 37 -76.28082 [Variable Interval Data] W M T W M T Infinity Infinity Infinity Close Distance Close Distance Close Distance f 71.50119 135 196 ― ― ― β ― ― ― -0.08318 -0.14416 -0.19832 D5 1.59716 33.49859 49.53103 1.59716 33.49859 49.53103 D13 37.80333 11.65214 1.60516 37.80333 11.65214 1.60516 D15 14.09965 8.34942 2.36395 14.09965 8.34942 2.36395 D19 4.24982 7.0795 8.12305 4.24982 7.0795 8.12305 D23 5.35666 2.52698 1.48342 5.35666 2.52698 1.48342 D30 3.81632 6.22894 4.10722 5.10137 11.89468 15.63265 D34 28.12371 22.59291 27.70989 24.58984 10.97816 4.65903 D36 3.7896 6.90778 3.91252 6.03843 12.8568 15.43795 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=1.45 Conditional expression (2) f1 / (-fE)=1.94 Conditional expression (3) f2 / fE=0.53 Conditional expression (4) f1 / (-f2)=3.65 Conditional expression (5) f1 / f3=1.34 Conditional expression (6) f1 / f4=2.12 Conditional expression (7) (-fF1) / fF2=1.31 Condition (8) νdP = 27.35 Conditional expression (9) ndP+(0.01425×νdP)=2.0536 Conditional expression (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=33.79° Conditional expression (12) 2ωt=12.27° Conditional expression (13) BFw / fw=0.46

[0095] Figures 2(A), 2(B), and 2(C) are aberration diagrams of the variable magnification optical system according to the first embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. In each aberration diagram, FNO indicates the F-number and Y indicates the image height. The spherical aberration diagram shows the F-number value corresponding to the maximum aperture, the astigmatism and distortion diagrams show the maximum image height, respectively, and the transverse aberration diagrams show the values ​​of each image height. d indicates the d-line (wavelength λ=587.6nm), and g indicates the g-line (wavelength λ=435.8nm). In the astigmatism diagram, the solid line indicates the sagittal image plane and the dashed line indicates the meridional image plane. Note that the same reference numerals as in this embodiment are used in the aberration diagrams of the embodiments shown below, and redundant explanations are omitted.

[0096] From the various aberration diagrams, it can be seen that the variable magnification optical system according to the first embodiment has good correction of aberrations and possesses excellent imaging performance.

[0097] (Second example) The second embodiment will be described using Figures 3-4 and Table 2. Figure 3 is a diagram showing the movement of the lenses when the variable magnification optical system according to the second embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(2) according to the second embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having negative refractive power, arranged in order from the object side. When magnification changes from the wide-angle end state to the telephoto end state, the second lens group G2, the third lens group G3, the fifth lens group G5, and the sixth lens group G6 move separately in the direction indicated by the arrows in Figure 3, and the spacing between adjacent lens groups changes. During magnification, the first lens group G1, the fourth lens group G4, and the seventh lens group G7 are fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7 corresponds to the subsequent lens group GR.

[0098] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0099] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a negative meniscus lens L24 with its concave surface facing the object, arranged in order from the object side.

[0100] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0101] The fourth lens group G4 consists of, arranged in order from the object side, a positive meniscus lens L41 with its convex surface facing the object, a positive meniscus lens L42 with its convex surface facing the object, a cemented lens of a biconcave negative lens L43 and a biconvex positive lens L44, a negative meniscus lens L45 with its convex surface facing the object, a cemented lens of a biconvex positive lens L46 and a negative meniscus lens L47 with its concave surface facing the object, and a positive meniscus lens L48 with its convex surface facing the object. An aperture diaphragm S is positioned between the positive meniscus lens L42 and the negative lens L43 in the fourth lens group G4, and moves together with the fourth lens group G4 during magnification. The lens surface of the positive lens L46 facing the object is aspherical.

[0102] The fifth lens group G5 consists of a positive meniscus lens L51 with its concave surface facing the object, and a negative lens L52 with a biconcave shape, arranged in order from the object side.

[0103] The sixth lens group G6 consists of a biconvex positive lens L61.

[0104] The seventh lens group G7 consists of a biconcave negative lens L71. The negative lens L71 has an aspherical surface on the object side. The image plane I is located on the image side of the seventh lens group G7. In other words, the seventh lens group G7 is the final lens group.

[0105] In this embodiment, focusing is achieved from a distant object to a near object (from an object at infinity to an object at a finite distance) by moving the fifth lens group G5 toward the image plane I and the sixth lens group G6 toward the object. That is, the fifth lens group G5 corresponds to the first focusing lens group, and the sixth lens group G6 corresponds to the second focusing lens group.

[0106] Table 2 below lists the specifications of the variable magnification optical system according to the second embodiment.

[0107] (Table 2) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.87938 2.83556 2.81768 2ω 33.81302 17.80714 12.26884 Y 21.70 21.70 21.70 TL 196.12284 196.12284 196.12284 BF 36.61267 36.61267 36.61267 [Lens Specifications] Face number RD nd νd θgF 1 108.74314 2.8 1.95000 31.13 2 80.29769 9.7 1.49782 82.57 3 -691.77549 0.1 4 93.78423 7.7 1.43385 95.23 5 338.64045 D5 (Variable) 6 71.48912 1.9 1.59349 67.89 7 30.17301 9.4 8 -137.03151 1.6 1.49782 82.57 9 93.66474 0.8 10 44.41047 3.94815 1.66382 27.35 0.6319 11 87.61105 5.59008 12 -54.89519 1.9 1.49782 82.57 13 -689.02421 D13 (Variable) 14 75.42635 4.5 1.94595 30.42 15 490.04562 D15 (Variable) 16 94.04866 4 1.49782 59.34 17 1181.8169 0.1 18 56.70631 4 1.49782 69.79 19 243.15543 4.5 20 ∞ 3.5 (Aperture S) 21 -180.79776 1.8 1.92286 29.82 22 38.61345 4.2 1.49782 67.44 23 -792.77195 4.35979 24 479.73489 1.7 1.80518 22.51 25 75.80342 2 26* 58.49695 7.7 1.59306 67 27 -63.34766 1.7 1.60342 46.96 28 -90.09789 1.3 29 66.31481 2.5 1.80400 44.63 30 153.3585 D30 (Variable) 31 -130.80634 2.2 1.94594 17.98 32 -67.89935 0.8 33 -163.52036 1.25 1.56883 31.71 34 37.07534 D34 (Variable) 35 66.52215 4.75 1.80100 48.75 36 -175.782 D36 (Variable) 37* -73.66538 1.9 1.71999 82.57 38 282.5465 BF [Aspherical Data] 26th Surface κ = 0.00, A4 = -2.17E-06, A6 = 1.23E-09 A8 = -8.20E-12, A10 = 2.53E-14, A12 = -2.96E-17 37th Surface κ = 0.00, A4 = 9.91E-08, A6 = 2.50E-09 A8 = -1.38E-11, A10 = 4.59E-14, A12 = -5.72E-17 [Lens Group Data] Group Start Surface Focal Length G1 1 139.63445 G2 6 -43.68068 G3 14 93.7469 G4 16 86.63044 G5 31 -83.20858 G6 35 60.77856 G7 37 -80.9748 [Variable Interval Data] W M T W M T Infinity Infinity Infinity Close Distance Close Distance Close Distance f 71.49616 135 196.00002 ― ― ― β ― ― ― -0.08386 -0.14611 -0.20261 D5 1.98083 33.88478 49.73838 1.98083 33.88478 49.73838 D13 47.67943 16.00066 1.60866 47.67943 16.00066 1.60866 D15 2.53884 2.31366 0.85206 2.53884 2.31366 0.85206 D30 6.84927 7.75031 3.99572 8.37353 13.43196 15.53626 D34 26.8749 21.64199 27.84545 23.36912 9.9946 4.76438 D36 6.00155 10.33343 7.88455 7.98308 16.29916 19.42509 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=1.16 Conditional expression (2) f1 / (-fE)=1.72 Conditional expression (3) f2 / fE=0.54 Conditional expression (4) f1 / (-f2)=3.20 Conditional expression (5) f1 / f3=1.49 Conditional expression (6) f1 / f4=1.61 Conditional expression (7) (-fF1) / fF2=1.37 Condition (8) νdP = 27.35 Conditional expression (9) ndP+(0.01425×νdP)=2.0536 Conditional expression (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=33.81° Conditional expression (12) 2ωt=12.27° Conditional expression (13) BFw / fw=0.51

[0108] Figures 4(A), 4(B), and 4(C) show aberration diagrams of the variable magnification optical system according to the second embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From each aberration diagram, it can be seen that the variable magnification optical system according to the second embodiment has good aberration correction and excellent imaging performance.

[0109] (Third embodiment) The third embodiment will be explained using Figures 5 to 6 and Table 3. Figure 5 is a diagram showing the movement of the lenses when the variable magnification optical system according to the third embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(3) according to the third embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, an eighth lens group G8 having positive refractive power, a ninth lens group G9 having positive refractive power, and a tenth lens group G10 having negative refractive power, all arranged in order from the object side. When changing magnification from the wide-angle end to the telephoto end, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 move separately in the direction indicated by the arrows in Figure 5, changing the spacing between adjacent lens groups. During magnification, the first lens group G1, the sixth lens group G6, and the tenth lens group G10 remain fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, the ninth lens group G9, and the tenth lens group G10 corresponds to the subsequent lens group GR.

[0110] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0111] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a biconcave negative lens L24, arranged in order from the object side.

[0112] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0113] The fourth lens group G4 consists of a biconvex positive lens L41 and a positive meniscus lens L42 with its convex surface facing the object, arranged in order from the object side.

[0114] The fifth lens group G5 is composed of a cemented lens consisting of a biconcave negative lens L51 and a biconvex positive lens L52. An aperture diaphragm S is positioned closest to the object in the fifth lens group G5 and moves together with the fifth lens group G5 during magnification.

[0115] The sixth lens group G6 consists of, arranged in order from the object side, a negative meniscus lens L61 with its convex surface facing the object, a cemented lens formed by a biconvex positive lens L62 and a negative meniscus lens L63 with its concave surface facing the object, and a positive meniscus lens L64 with its convex surface facing the object. The lens surface of the positive lens L62 facing the object is aspherical.

[0116] The seventh lens group G7 consists of a biconvex positive lens L71 and a negative meniscus lens L72 with its convex surface facing the object, arranged in order from the object side.

[0117] The eighth lens group G8 consists of a positive meniscus lens L81 with its convex surface facing the object.

[0118] The ninth lens group G9 consists of a positive meniscus lens L91 with its concave surface facing the object. The positive meniscus lens L91 has an aspherical lens surface facing the object.

[0119] The tenth lens group G10 consists of a biconcave negative lens L101. The image plane I is positioned on the image side of the tenth lens group G10. In other words, the tenth lens group G10 corresponds to the final lens group.

[0120] In this embodiment, focusing is achieved from a distant object to a near object (from an object at infinity to an object at a finite distance) by moving the seventh lens group G7 toward the image plane I and the eighth lens group G8 toward the object. In other words, the seventh lens group G7 corresponds to the first focusing lens group, and the eighth lens group G8 corresponds to the second focusing lens group.

[0121] Table 3 below lists the specifications of the variable magnification optical system according to the third embodiment.

[0122] (Table 3) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.8471 2.86934 2.91965 2ω 33.70556 17.86124 12.26972 Y 21.70 21.70 21.70 TL 207.00792 207.00792 207.00792 Bf 32.57205 32.57205 32.57205 [Lens Specifications] Face number RD nd νd θgF 1 101.99194 2.80 2.00100 29.12 2 78.37407 9.70 1.49782 82.57 3 -1022.4124 0.10 4 75.80458 7.70 1.43385 95.23 5 278.09823 D5 (Variable) 6 67.03073 1.90 1.60300 65.44 7 29.65154 7.20 8 -4189.1769 1.60 1.49782 82.57 9 72.21235 2.92 10 41.05723 3.70 1.66382 27.35 0.6319 11 51.79281 6.99 12 -47.57525 1.90 1.49782 82.57 13 876.17776 D13 (Variable) 14 75.45331 3.20 1.94594 17.98 15 263.87074 D15 (Variable) 16 99.38463 4.70 1.49782 82.57 17 -385.66566 0.10 18 69.30883 3.85 1.49782 82.57 19 1544.1877 D19 (variable) 20 ∞ 3.50 (Aperture S) 21 -84.39308 1.80 1.92286 20.88 22 76.70869 5.00 1.49782 82.57 23 -157.06149 D23 (Variable) 24 168.47838 1.70 1.85026 32.35 25 77.42169 2.00 26* 59.12213 7.70 1.59349 67 27 -51.6115 1.70 1.62004 36.4 28 -89.79626 1.30 29 87.29534 2.70 1.80100 34.92 30 136.2385 D30 (Variable) 31 627.77024 2.00 1.94594 17.98 32 -206.69697 0.80 33 386.92798 1.25 1.71300 53.96 34 42.23229 D34 (Variable) 35 66.92449 4.00 1.90265 35.77 36 418.69787 D36 (Variable) 37* -553.02647 3.00 1.55518 71.49 38 -77.65664 D38 (Variable) 39 -70.45081 1.90 1.56384 60.71 40 88.47517 BF [Aspherical data] Page 26 κ = 0.00, A4 = -2.06E-06, A6 = 3.72E-10 A8 = -2.74E-12, A10 = 1.30E-14, A12 = -1.97E-17 Page 37 κ = 0.00, A4 = -5.43E-07, A6 = 5.65E-10 A8 = -1.54E-12, A10 = 4.63E-15, A12 = -5.42E-18 [Lens Group Data] Group Starting Surface Focal Length G1 1 124.35572 G2 6 -34.94136 G3 14 110.79292 G4 16 76.69466 G5 20 -76.01113 G6 24 72.09875 G7 31 -114.02434 G8 35 87.7742 G9 37 162.36222 G10 39 -69.26098 [Variable Interval Data] W M T W M T Infinity Infinity Infinity Close Distance Close Distance Close Distance f 71.48828 135 196 ― ― ― β ― ― ― -0.08481 -0.15088 -0.20696 D5 3.14675 27.96403 40.90704 3.14675 27.96403 40.90704 D13 29.53764 8.15958 1.60832 29.53764 8.15958 1.60832 D15 19.15996 9.78302 1.19195 19.15996 9.78302 1.19195 D19 4.5 8.45422 8.9974 4.5 8.45422 8.9974 D23 1.47462 3.45814 5.11428 1.47462 3.45814 5.11428 D30 3.7091 6.11122 3.97416 5.8438 13.08039 18.03258 D34 35.19368 27.95231 37.56575 29.85694 10.52937 3.82554 D36 3.33819 8.98173 3.81873 6.54023 19.4355 23.50052 D38 8.23679 7.4325 5.11912 8.23679 7.4325 5.11912 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=1.60 Conditional expression (2) f1 / (-fE)=1.80 Conditional expression (3) f2 / fE=0.50 Conditional expression (4) f1 / (-f2)=3.56 Conditional expression (5) f1 / f3=1.12 Conditional expression (6) f1 / f4=1.62 Conditional expression (7) (-fF1) / fF2=1.30 Condition (8) νdP = 27.35 Conditional expression (9) ndP+(0.01425×νdP)=2.0536 Conditional expression (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=33.71° Conditional expression (12) 2ωt=12.27° Conditional expression (13) BFw / fw=0.46

[0123] Figures 6(A), 6(A), and 6(C) show aberration diagrams of the variable magnification optical system according to the third embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From these aberration diagrams, it can be seen that the variable magnification optical system according to the third embodiment has good aberration correction and excellent imaging performance.

[0124] (Fourth embodiment) The fourth embodiment will be described using Figures 7-8 and Table 4. Figure 7 is a diagram showing the movement of the lenses when the variable magnification optical system according to the fourth embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(4) according to the fourth embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive refractive power, a sixth lens group G6 having negative refractive power, a seventh lens group G7 having positive refractive power, and an eighth lens group G8 having negative refractive power, all arranged in order from the object side. When changing magnification from the wide-angle end to the telephoto end, the second lens group G2, the third lens group G3, the fourth lens group G4, the sixth lens group G6, and the seventh lens group G7 move independently in the direction indicated by the arrows in Figure 7, changing the spacing between adjacent lens groups. During magnification, the first lens group G1, the fifth lens group G5, and the eighth lens group G8 remain fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, and the eighth lens group G8 corresponds to the subsequent lens group GR.

[0125] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0126] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a biconcave negative lens L24, arranged in order from the object side.

[0127] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0128] The fourth lens group G4 consists of a biconvex positive lens L41 and a positive meniscus lens L42 with its convex surface facing the object, arranged in order from the object side.

[0129] The fifth lens group G5 consists of a cemented lens formed from a biconcave negative lens L51 and a biconvex positive lens L52, arranged in order from the object side, a negative meniscus lens L53 with its convex surface facing the object side, a cemented lens formed from a biconvex positive lens L54 and a negative meniscus lens L55 with its concave surface facing the object side, and a positive meniscus lens L56 with its convex surface facing the object side. An aperture diaphragm S is positioned closest to the object side of the fifth lens group G5 and is fixed to the image plane I together with the fifth lens group G5 during magnification. The lens surface of the positive lens L54 on the object side is aspherical.

[0130] The sixth lens group G6 consists of a positive meniscus lens L61 with its concave surface facing the object and a negative meniscus lens L62 with its convex surface facing the object, arranged in order from the object side.

[0131] The seventh lens group G7 consists of a biconvex positive lens L71.

[0132] The eighth lens group G8 consists of a negative meniscus lens L81 with its convex surface facing the object and a negative meniscus lens L82 with its concave surface facing the object, arranged in order from the object side. The negative meniscus lens L81 has an aspherical lens surface on the object side. The image plane I is positioned on the image side of the eighth lens group G8. In other words, the eighth lens group G8 is the final lens group.

[0133] In this embodiment, focusing is achieved from a distant object to a nearby object (from an infinity-far object to a finite-distance object) by moving the sixth lens group G6 toward the image plane I and the seventh lens group G7 toward the object. That is, the sixth lens group G6 corresponds to the first focusing lens group, and the seventh lens group G7 corresponds to the second focusing lens group.

[0134] Table 4 below lists the specifications of the variable magnification optical system according to the fourth embodiment.

[0135] (Table 4) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.88923 2.87811 2.87676 2ω 33.62692 17.8017 12.26826 Y 21.70 21.70 21.70 TL 207.00795 207.00795 207.00795 BF 32.57205 32.57205 32.57205 [Lens Specifications] Face number RD nd νd θgF 1 104.96946 2.80 2.00100 29.12 2 81.23029 9.70 1.49782 82.57 3 -5013.309 0.10 4 98.76892 7.70 1.43385 95.23 5 349.12389 D5 (Variable) 6 62.87568 1.90 1.60300 65.44 7 32.61551 8.00 8 -1223.4377 1.60 1.49782 82.57 9 88.74378 2.77 10 43.50207 3.70 1.66382 27.35 0.6319 11 56.12991 7.85 12 -59.98159 1.90 1.49782 82.57 13 180.55889 D13 (Variable) 14 72.53962 3.20 1.94594 17.98 15 224.56923 D15 (Variable) 16 107.03817 4.70 1.49782 82.57 17 -183.81713 0.10 18 54.21049 3.85 1.49782 82.57 19 173.7794 D19 (Variable) 20 ∞ 3.50 (Aperture S) 21 -89.65067 1.80 1.92286 20.88 22 53.92556 5.00 1.49782 82.57 23 -180.67725 1.50 24 151.38095 1.70 1.85026 32.35 25 72.515 2.00 26* 60.75581 7.70 1.59349 67 27 -54.39087 1.70 1.62004 36.4 28 -94.7071 1.30 29 58.34653 2.70 1.80100 34.92 30 116.10532 D30 (Variable) 31 -642.22297 2.00 1.94594 17.98 32 -108.81859 0.80 33 1100.6245 1.25 1.71300 53.96 34 36.03135 D34 (Variable) 35 70.63159 3.85 1.90265 35.77 36 -359.66973 D36 (Variable) 37* 1093.756 1.90 1.53793 55.01 38 73.85081 8.76 39 -68.15582 1.90 1.56384 60.71 40 -183.66574 BF [Aspherical data] Page 26 κ=0.00,A4=-1.87E-06,A6=-4.52E-10 A8=3.30E-12,A10=-9.39E-15,A12=1.05E-17 Page 37 κ=0.00,A4=-5.10E-07,A6=2.18E-09 A8=-1.11E-11,A10=3.84E-14,A12=-5.02E-17 [Lens group data] Group starting plane focal length G1 1 151.31596 G2 6 -40.77182 G3 14 112.1271 G4 16 73.19762 G5 20 204.39955 G6 31 -85.38342 G7 35 65.68378 G8 37 -81.7079 [Variable interval data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance f 71.48789 135 196.00001 ― ― ― β ― ― ― -0.08409 -0.14666 -0.20387 D5 1.85197 33.16708 49.31235 1.85197 33.16708 49.31235 D13 39.7348 11.81928 1.60349 39.7348 11.81928 1.60349 D15 16.28719 9.45385 1.9819 16.28719 9.45385 1.9819 D19 4.5 7.93374 9.47621 4.5 7.93374 9.47621 D30 3.7 5.7618 4.22253 4.95966 10.39125 14.39741 D34 29.10973 22.62707 26.97381 25.70866 11.51639 4.5890 D36 2.5956 7.01646 4.209 4.73702 13.49769 16.41886 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=1.37 Conditional expression (2) f1 / (-fE)=1.85 Conditional expression (3) f2 / fE=0.50 Conditional expression (4) f1 / (-f2)=3.71 Conditional expression (5) f1 / f3=1.35 Conditional expression (6) f1 / f4=2.07 Conditional expression (7) (-fF1) / fF2=1.30 Condition (8) νdP = 27.35 Conditional expression (9) ndP+(0.01425×νdP)=2.0536 Conditional expression (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=33.63° Conditional expression (12) 2ωt=12.27° Conditional expression (13) BFw / fw=0.456

[0136] Figures 8(A), 8(B), and 8(C) show the aberration diagrams of the variable magnification optical system according to the fourth embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From each aberration diagram, it can be seen that the variable magnification optical system according to the fourth embodiment has good aberration correction and excellent imaging performance.

[0137] (Fifth example) The fifth embodiment will be described using Figures 9 to 10 and Table 5. Figure 9 is a diagram showing the movement of the lenses when the variable magnification optical system according to the fifth embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(5) according to the fifth embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, an eighth lens group G8 having positive refractive power, and a ninth lens group G9 having negative refractive power, all arranged in order from the object side. When changing magnification from the wide-angle end to the telephoto end, the second lens group G2, the third lens group G3, the fifth lens group G5, the seventh lens group G7, and the eighth lens group G8 move separately in the direction indicated by the arrows in Figure 9, changing the spacing between adjacent lens groups. During magnification, the first lens group G1, the fourth lens group G4, the sixth lens group G6, and the ninth lens group G9 remain fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 corresponds to the subsequent lens group GR.

[0138] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0139] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconvex positive lens L22, a biconcave negative lens L23, and a negative meniscus lens L24 with its concave surface facing the object, arranged in order from the object side.

[0140] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0141] The fourth lens group G4 consists of a positive meniscus lens L41 with its convex surface facing the object, and a biconvex positive lens L42, arranged in order from the object side.

[0142] The fifth lens group G5 is composed of a cemented lens of a biconcave negative lens L51 and a positive meniscus lens L52 with its convex surface facing the object side. An aperture stop S is disposed on the most object side of the fifth lens group G5 and moves together with the fifth lens group G5 during zooming.

[0143] The sixth lens group G6 is composed of a negative meniscus lens L61 with its convex surface facing the object side, a biconvex positive lens L62, and a positive meniscus lens L63 with its convex surface facing the object side, arranged in order from the object side. The positive lens L62 has an aspherical lens surface on the image side.

[0144] The seventh lens group G7 is composed of a positive meniscus lens L71 with its concave surface facing the object side and a biconcave negative lens L72, arranged in order from the object side.

[0145] The eighth lens group G8 is composed of a biconvex positive lens L81.

[0146] The ninth lens group G9 is composed of a biconcave negative lens L91. An image plane I is disposed on the image side of the ninth lens group G9. That is, the ninth lens group G9 corresponds to the final lens group.

[0147] In this embodiment, by moving the seventh lens group G7 toward the image plane I side and moving the eighth lens group G8 toward the object side, focusing from a distant object to a near object (from an infinite object to a finite distance object) is performed. That is, the seventh lens group G7 corresponds to the first focusing lens group, and the eighth lens group G8 corresponds to the second focusing lens group.

[0148] Table 5 below shows the values of the specifications of the zoom optical system according to the fifth embodiment.

[0149] (Table 5) [Overall specifications] Zoom ratio 2.74 θgFP = 0.625146 W M T FNO 2.79867 2.84973 2.88046 2ω 33.269 17.64798 12.20244 Y 21.70 21.70 21.70 TL 194.00000 194.00000 194.00000 BF 32.56419 32.56419 32.56419 [Lens Specifications] Face number RD nd νd θgF 1 142.398 2.80 1.85000 27.03 2 89.22539 11.50 1.49782 82.57 3 -475.12414 0.20 4 78.29293 7.00 1.43385 95.23 5 169.60505 D5 (Variable) 6 2649.01093 2.00 1.55705 45.85 7 40.96873 5.00 8 91.52844 7.00 1.80809 22.74 9 -108.37528 0.10 10 -300.55351 1.60 1.49782 82.57 11 49.61316 9.00 12 -50.05975 2.00 1.66046 27.57 0.625146 13 -282.49474 D13 (Variable) 14 62.00807 3.50 1.92286 20.88 15 104.61485 D15 (Variable) 16 71.46374 5.00 1.49782 82.57 17 705.70649 0.10 18 54.57663 6.50 1.60300 65.44 19 -278.60199 D19 (Variable) 20 ∞ 3.00 (Aperture S) 21 -104.70389 1.80 1.90499 26.68 22 30.2441 5.00 1.51188 68.34 23 130.63306 D23 (Variable) 24 39.55621 1.80 1.79124 28.25 25 31.45913 1.00 26 35.35387 7.00 1.55332 71.68 27* -111.74355 1.00 28 58.49751 2.50 1.81057 40.15 29 105.99178 D29 (Variable) 30 -286.5457 2.00 1.94594 17.98 31 -84.48026 0.80 32 -270.24499 1.25 1.59349 67 33 32.39702 D33 (Variable) 34 77.85755 4.80 1.80100 34.92 35 -88.13641 D35 (Variable) 36 -75.46523 2.00 1.72200 34.56 37 104.96677 BF [Aspherical Data] The 27th Surface κ = 0.00, A4 = 2.11E-06, A6 = -1.20E-09 A8 = -2.82E-13, A10 = -3.58E-15, A12 = 0.00E+00 [Lens Group Data] Group Starting Surface Focal Length G1 1 164.12723 G2 6 -47.62588 G3 14 158.7209 G4 16 52.56296 G5 20 -38.49179 G6 24 46.69749 G7 30 -80.39666 G8 34 52.28209 G9 36 -60.52463 [Variable interval data] WMTWMT Infinity Infinity Infinity Close distance Close distance Close distance f 71.5 135 196 — — — β ― ― ― -0.0839 -0.14665 -0.20273 D5 3.50002 37.12414 54.5663 3.50002 37.12414 54.5663 D13 37.00636 10.01061 2 37.00636 10.01061 2 D15 18.05993 11.43157 2 18.05993 11.43157 2 D19 3.82591 6.93485 8.82776 3.82591 6.93485 8.82776 D23 7.16459 4.05564 2.16276 7.16459 4.05564 2.16276 D29 4.89453 5.25712 2.03164 6.68467 11.36918 13.66092 D33 16.59265 15.71825 22.606 13.60117 5.68565 3 D35 5.706 6.21782 2.55555 6.90733 10.13836 10.53228 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=2.62 Conditional expression (2) f1 / (-fE)=2.71 Conditional expression (3) f2 / fE=0.79 Conditional expression (4) f1 / (-f2)=3.45 Conditional expression (5) f1 / f3=1.03 Conditional expression (6) f1 / f4=3.12 Conditional expression (7) (-fF1) / fF2=1.54 Condition (8) νdP = 27.57 Conditional expression (9) ndP+(0.01425×νdP)=2.0533 Conditional expression (10) θgFP+(0.00316×νdP)=0.7123 Conditional expression (11) 2ωw=33.27° Conditional expression (12) 2ωt=12.20° Conditional expression (13) BFw / fw=0.46

[0150] Figures 10(A), 10(B), and 10(C) show the aberration diagrams of the variable magnification optical system according to the fifth embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From each aberration diagram, it can be seen that the variable magnification optical system according to the fifth embodiment has good aberration correction and excellent imaging performance.

[0151] (Sixth embodiment) The sixth embodiment will be described using Figures 11 to 12 and Table 6. Figure 11 is a diagram showing the movement of the lenses when the variable magnification optical system according to the sixth embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(6) according to the sixth embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having negative refractive power, a sixth lens group G6 having positive refractive power, a seventh lens group G7 having negative refractive power, an eighth lens group G8 having positive refractive power, and a ninth lens group G9 having negative refractive power, all arranged in order from the object side. When changing magnification from the wide-angle end to the telephoto end, the second lens group G2, the third lens group G3, the fifth lens group G5, the seventh lens group G7, and the eighth lens group G8 move independently in the direction indicated by the arrows in Figure 11, changing the spacing between adjacent lens groups. During magnification, the first lens group G1, the fourth lens group G4, the sixth lens group G6, and the ninth lens group G9 remain fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, the seventh lens group G7, the eighth lens group G8, and the ninth lens group G9 corresponds to the subsequent lens group GR.

[0152] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0153] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a biconcave negative lens L24, arranged in order from the object side.

[0154] The third lens group G3 consists of a positive meniscus lens L31 with its convex surface facing the object.

[0155] The fourth lens group G4 consists of a biconvex positive lens L41. The object-facing lens surface of the positive lens L41 is aspherical.

[0156] The fifth lens group G5 is composed of a cemented lens consisting of a biconcave negative lens L51 and a biconvex positive lens L52. An aperture diaphragm S is positioned closest to the object in the fifth lens group G5 and moves together with the fifth lens group G5 during magnification.

[0157] The sixth lens group G6 consists of, arranged in order from the object side, a negative meniscus lens L61 with its convex surface facing the object, a cemented lens formed by a biconvex positive lens L62 and a negative meniscus lens L63 with its concave surface facing the object, and a positive meniscus lens L64 with its convex surface facing the object. The lens surface of the positive lens L62 facing the object is aspherical.

[0158] The seventh lens group G7 consists of a biconvex positive lens L71 and a biconcave negative lens L72, arranged in order from the object side.

[0159] The eighth lens group G8 consists of a biconvex positive lens L81.

[0160] The ninth lens group G9 consists of two negative lenses, L91, which are biconcave in shape, and L92, a negative meniscus lens, which has its concave surface facing the object, arranged in order from the object side. The negative lens L91 has an aspherical surface on the object side. The image plane I is positioned on the image side of the ninth lens group G9. In other words, the ninth lens group G9 is the final lens group.

[0161] In this embodiment, focusing is achieved from a distant object to a near object (from an object at infinity to an object at a finite distance) by moving the seventh lens group G7 toward the image plane I and the eighth lens group G8 toward the object. In other words, the seventh lens group G7 corresponds to the first focusing lens group, and the eighth lens group G8 corresponds to the second focusing lens group.

[0162] Table 6 below lists the specifications of the variable magnification optical system according to the sixth embodiment.

[0163] (Table 6) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.83129 2.85335 2.87996 2ω 33.76242 17.81528 12.26938 Y 21.70 21.70 21.70 TL 191.79997 191.79997 191.79997 BF 32.65404 32.65404 32.65404 [Lens Specifications] Face number RD nd νd θgF 1 113.29192 2.8 2.001 29.12 2 81.40925 10.5 1.49782 82.57 3 -795.64249 0.1 4 74.88525 8.2 1.433848 95.23 5 376.798 D5 (Variable) 6 82.73428 1.9 1.59349 67 7 31.04017 9.35 8 -168.77759 1.6 1.49782 82.57 9 115.02437 0.8 10 41.14809 3.8 1.663819 27.35 0.6319 11 73.00001 5.6 12 -61.06953 1.9 1.49782 82.57 13 98.51376 D13 (Variable) 14 86.14679 3.4 1.94595 17.98 15 694.90071 D15 (Variable) 16* 52.81421 8 1.553319 71.68 17 -117.98245 D17 (Variable) 18∞ 3.7 (Aperture S) 19 -65.12937 1.8 1.92286 20.88 20 57.80344 5.30 1.49782 82.57 21 -111.65652 D21 (Variable) 22 92.32113 1.7 1.935421 18.16 23 60.00966 2 24* 58.92406 7.60 1.59201 66.89 25 -55 1.7 1.62004 36.4 26 -91.54022 1.3 27 59.23711 2.8 1.746869 23.4 28 126.70086 D28 (Variable) 29 448.34721 2.4 1.94595 17.98 30 -94.32707 0.8 31 -205.67313 1.25 1.794772 36.19 32 38.13601 D32 (Variable) 33 112.2489 3.85 1.90265 35.72 34 -112.24891 D34 (Variable) 35* -72.74439 1.9 1.49782 82.57 36 498.35011 4.9 37 -37.82283 1.90 1.716676 52.08 38 -51.98812 BF [Aspherical Data] Surface 16 κ = 0.00, A4 = 2.07E-07, A6 = 1.58E-10 A8 = -2.50E-13, A10 = 2.86E-16, A12 = 0.00E+00 Surface 24 κ = 0.00, A4 = -1.36E-06, A6 = 6.98E-10 A8 = -4.57E-12, A10 = 1.66E-14, A12 = -2.22E-17 Surface 35 κ = 0.00, A4 = 1.84E-07, A6 = 3.48E-09 A8 = -1.61E-11, A10 = 6.41E-14, A12 = -9.19E-17 [Lens Group Data] Group Starting Surface Focal Length G1 1 126.73821 G2 6 -35.76434 G3 14 103.67509 G4 16 67.05334 G5 18 -59.65998 G6 22 57.09316 G7 29 -82.17953 G8 33 62.68745 G9 35 -77.91319 [Variable Interval Data] W M T W M T Infinity Infinity Infinity Close Distance Close Distance Close Distance f 71.49323 135 196 ― ― ― β ― ― ― -0.08339 -0.14602 -0.1994 D5 1.6 28.92133 42.60181 1.6 28.92133 42.60181 D13 30.28784 9.66169 1.59632 30.28784 9.66169 1.59632 D15 13.82513 7.12995 1.51484 13.82513 7.12995 1.51484 D17 4.5 6.8522 7.51331 4.50 6.85 7.51 D21 4.51511 2.16291 1.5018 4.51511 2.16291 1.5018 D28 4.04215 6.41537 4.00083 5.37286 11.89757 14.49678 D32 22.88318 19.60826 26.72334 19.55641 8.36976 4.68183 D34 7.29656 8.19826 3.49773 9.29262 13.95456 15.04328 [Conditional expression corresponding value] Conditional expression (1) f3 / (-fE)=1.33 Conditional expression (2) f1 / (-fE)=1.63 Conditional expression (3) f2 / fE=0.46 Conditional expression (4) f1 / (-f2)=3.54 Conditional expression (5) f1 / f3=1.22 Conditional expression (6) f1 / f4=1.89 Conditional expression (7) (-fF1) / fF2=1.31 Condition (8) νdP = 27.35 Conditional expression (9) ndP+(0.01425×νdP)=2.0536 Conditional expression (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=33.76° Conditional expression (12) 2ωt=12.27° Conditional expression (13) BFw / fw=0.46

[0164] Figures 12(A), 12(B), and 12(C) show the aberration diagrams of the variable magnification optical system according to the sixth embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From each aberration diagram, it can be seen that the variable magnification optical system according to the sixth embodiment has good aberration correction and excellent imaging performance.

[0165] (Seventh Example) The seventh embodiment will be explained using Figures 13-14 and Table 7. Figure 13 is a diagram showing the movement of the lenses when the variable magnification optical system according to the seventh embodiment changes from the wide-angle end state to the telephoto end state. The variable magnification optical system ZL(7) according to the seventh embodiment consists of a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, a fourth lens group G4 having negative refractive power, a fifth lens group G5 having positive refractive power, and a sixth lens group G6 having negative refractive power, arranged in order from the object side. When magnification changes from the wide-angle end state to the telephoto end state, the second lens group G2, the third lens group G3, the fourth lens group G4, and the fifth lens group G5 move separately in the direction indicated by the arrows in Figure 13, and the spacing between adjacent lens groups changes. During magnification, the first lens group G1 and the sixth lens group G6 are fixed relative to the image plane I. The lens group consisting of the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 corresponds to the subsequent lens group GR.

[0166] The first lens group G1 consists of a cemented lens formed by a negative meniscus lens L11 with its convex surface facing the object and a biconvex positive lens L12, arranged in order from the object side, and a positive meniscus lens L13 with its convex surface facing the object.

[0167] The second lens group G2 consists of a negative meniscus lens L21 with its convex surface facing the object, a biconcave negative lens L22, a positive meniscus lens L23 with its convex surface facing the object, and a negative meniscus lens L24 with its concave surface facing the object, arranged in order from the object side.

[0168] The third lens group G3 consists of, arranged in order from the object side, a positive meniscus lens L31 with its convex surface facing the object, a positive meniscus lens L32 with its convex surface facing the object, a biconvex positive lens L33, a cemented lens formed by a biconcave negative lens L34 and a positive meniscus lens L35 with its convex surface facing the object, a negative meniscus lens L36 with its convex surface facing the object, a cemented lens formed by a biconvex positive lens L37 and a negative meniscus lens L38 with its concave surface facing the object, and a positive meniscus lens L39 with its convex surface facing the object. An aperture diaphragm S is positioned between the positive lens L33 and the negative lens L34 in the third lens group G3, and moves together with the third lens group G3 during magnification. The lens surface of the positive lens L37 facing the object is aspherical.

[0169] The fourth lens group G4 consists of a positive meniscus lens L41 with its concave surface facing the object, and a negative lens L42 with a biconcave shape, arranged in order from the object side.

[0170] The fifth lens group G5 consists of a biconvex positive lens L51.

[0171] The sixth lens group G6 consists of a negative meniscus lens L61 with its concave surface facing the object. The negative meniscus lens L61 has an aspherical lens surface facing the object. The image plane I is positioned on the image side of the sixth lens group G6. In other words, the sixth lens group G6 is the final lens group.

[0172] In this embodiment, focusing is achieved from a distant object to a nearby object (from an infinity-far object to a finite-distance object) by moving the fourth lens group G4 toward the image plane I and the fifth lens group G5 toward the object. That is, the fourth lens group G4 corresponds to the first focusing lens group, and the fifth lens group G5 corresponds to the second focusing lens group.

[0173] Table 7 below lists the specifications of the variable magnification optical system according to the seventh embodiment.

[0174] (Table 7) [Overall Specifications] Multiplication ratio 2.74 θgFP = 0.6319 WMT FNO 2.91966 2.90716 2.86166 2ω 34.08866 17.93464 12.307 Y 21.70 21.70 21.70 TL 208.41341 208.41341 208.41341 BF 31.14475 31.14475 31.14475 [Lens Specifications] Face number RD nd νd θgF 1 135.3501 2.8 1.911144 31.13 2 88.2984 9.7 1.49782 82.57 3 -2014.0365 0.1 4 87.0008 7.7 1.433848 95.23 5 1270.4367 D5 (Variable) 6 96.7322 1.9 1.580538 67.89 7 32.0715 9.4 8 -149.5985 1.6 1.49782 82.57 9 84.947 0.8 10 47.7033 4.1051 1.663819 27.35 0.6319 11 132.9068 4.917 12 -59.1191 1.9 1.49782 82.57 13 -410.9838 D13 (Variable) 14 75.2493 4.0117 1.919756 30.42 15 406.1688 3 16 110.8456 3 1.643929 59.34 17 221.1361 0.1 18 55.6433 5 1.510139 69.79 19 -452.609 4.5 20 ∞ 3.5 (Aperture S) 21 -128.1374 1.8 1.924139 29.82 22 38.7647 4.2 1.513006 67.44 23 324.5195 4.1 24 111.4412 1.7 1.77151 22.51 25 58.0313 1.7 26* 61.5731 8.5 1.593493 67 27 -26.7185 1.7 1.627041 46.96 28 -76.4024 1.3 29 47.8194 2.5 1.772125 44.63 30 60.849 D30 (Variable) 31 -289.2655 2.2 1.945944 17.98 32 -56.7163 0.8 33 -62.5979 1.25 1.631431 31.71 34 46.593 D34 (Variable) 35 84.1615 4.75 1.764819 48.75 36 -185.6155 D36 (Variable) 37* -52.3045 1.9 1.49782 82.57 38 -319.0332 BF [Aspherical data] Page 26 κ=0.00,A4=-1.61284E-06,A6=4.35900E-10 A8=-1.44229E-12,A10=4.99341E-15,A12=-5.72670E-18 Page 37 κ=0.00,A4=7.70231E-07,A6=2.20982E-09 A8=-9.92801E-12,A10=2.79429E-14,A12=-2.96640E-17 [Lens group data] Group starting plane focal length G1 1 145.20607 G2 6 -47.94048 G3 14 59.76284 G4 31 -100.34191 G5 35 76.29409 G6 37 -125.96848 [Can change the interval データ] WMTWMT Infinite distance Infinite distance Infinite distance Near distance Near distance f 71.47903 135 196.00001 ― ― ― β ― ― ― -0.07596 -0.13523 -0.18897 D5 1.6 36.65047 53.37203 1.6 36.65047 53.37203 D13 50.34136 17.30611 1.5894 50.34136 17.30611 1.5894 D30 4.89104 5.69832 3.75297 5.82603 9.72514 12.39738 D34 30.18447 22.82939 30.17853 25.97701 9.1382 2.51645 D36 14.96274 19.49533 13.08668 18.23522 29.1597 32.10436 [Conditional expression value] Condition (1) f3 / (-fE)=0.47 Condition (2) f1 / (-fE)=1.15 Condition (3) f2 / fE = 0.38 Condition (4) f1 / (-f2)=3.03 Condition (5) f1 / f3 = 2.43 Condition (6) f1 / f4 = -1.45 Condition (7) (-fF1) / fF2=1.32 Conditional expression (8) νdP=27.35 Conditional expression (9) ndP + (0.01425 × νdP) = 2.0536 Condition (10) θgFP+(0.00316×νdP)=0.7183 Conditional expression (11) 2ωw=34.09° Conditional expression (12) 2ωt=12.31° Conditional expression (13) BFw / fw=0.44

[0175] Figures 14(A), 14(B), and 14(C) show the aberration diagrams of the variable magnification optical system according to the seventh embodiment at the wide-angle end, intermediate focal length, and telephoto end, respectively. From each aberration diagram, it can be seen that the variable magnification optical system according to the seventh embodiment has good aberration correction and excellent imaging performance.

[0176] According to each embodiment, a variable magnification optical system can be realized in which various aberrations such as spherical aberration are well corrected.

[0177] Herein, the above embodiments are merely examples of the present invention, and the present invention is not limited to these.

[0178] The following elements can be appropriately incorporated as long as they do not impair the optical performance of the variable magnification optical system according to this embodiment.

[0179] Numerical examples of variable magnification optical systems have been shown with configurations of 6, 7, 8, 9, and 10 groups, but this application is not limited to these, and variable magnification optical systems with other group configurations (e.g., 5 groups, 11 groups, etc.) can also be constructed. Specifically, a configuration in which a lens or lens group is added to the object side or the image plane side of the variable magnification optical system is also acceptable. A lens group refers to a portion having at least one lens, separated by an air gap that changes during magnification.

[0180] The lens surface may be formed as a spherical, flat, or aspherical surface. A spherical or flat lens surface is preferable because it facilitates lens processing and assembly adjustment, preventing degradation of optical performance due to processing and assembly errors. It is also preferable because it minimizes degradation of image rendering performance even if the image plane is misaligned.

[0181] If the lens surface is aspherical, it can be an aspherical surface created by grinding, a glass molded aspherical surface formed from glass using a mold, or a composite aspherical surface formed by creating an aspherical shape from resin on the surface of glass. Furthermore, the lens surface may also be a diffractive surface, and the lens may be a refractive index distributed lens (GRIN lens) or a plastic lens.

[0182] Each lens surface may be coated with an anti-reflective coating that has high transmittance over a wide wavelength range to reduce flare and ghosting and achieve high contrast optical performance. This reduces flare and ghosting and achieves high contrast optical performance. [Explanation of Symbols]

[0183] G1 First lens group G2 Second lens group G3 3rd lens group GR successor lens group I Image plane S Aperture diaphragm

Claims

[Claim 1] It consists of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a subsequent lens group, arranged in order from the object side. During magnification, the spacing between adjacent lens groups changes, and the first lens group is fixed with respect to the image plane. When changing magnification from the wide-angle end to the telephoto end, the third lens group moves, The aforementioned successor lens group consists of a fourth lens group having positive refractive power, a fifth lens group having negative refractive power, a sixth lens group having positive refractive power, and a final lens group. When focusing occurs, the fifth lens group and the sixth lens group move, A variable magnification optical system that satisfies the following conditions. 0.30<f3 / (-fE)<3.50 2.90<f1 / (-f2)<5.00 However, f3: focal length of the third lens group fE: Focal length of the final lens group f1: Focal length of the first lens group f2: Focal length of the second lens group

Images