JP5518530B2 - Telephoto zoom lens - Google Patents

Description

  The present invention relates to a telephoto zoom lens suitable for a still camera, a video camera, and the like, and more particularly to a reduction in the overall length of an optical system and a reduction in diameter of a telephoto lens having a narrow angle of view and a long focal length.

  In recent years, interchangeable-lens digital cameras equipped with a single-lens reflex system or an electronic viewfinder have become widespread. These cameras are suitable for use with interchangeable lenses having various angles of view because there is no parallax between the viewfinder image and the captured image.

  In particular, the telephoto lens is greatly affected by parallax, and thus becomes a problem when used for a camera having a large parallax between the viewfinder and the photographing lens. For this reason, the telephoto lens is suitable for use as an interchangeable lens of a single-lens reflex system or an interchangeable lens digital camera equipped with an electronic viewfinder, and an interchangeable lens system equipped with a single-lens reflex system or electronic viewfinder. With the spread of digital cameras, demand is expanding.

  In general, in a telephoto zoom lens, if the angle of view is narrowed, the focal length becomes longer.Therefore, the entire lens system is enlarged, the amount of movement of each lens unit accompanying zooming, the weight of the focus lens unit and the amount of movement are increased, and Many problems occur, such as a decrease in autofocus driving speed.

  Many technologies related to downsizing of a telephoto zoom lens and high speed of focus drive have been proposed.

  As a small telephoto zoom lens, a configuration including a positive first lens group, a negative second lens group, a positive third lens group, and a negative fourth lens group in order from the object side is well known. It is described in Patent Document 1, Patent Document 2, and the like.

  In the telephoto zoom lens of the type described in Patent Document 1 and Patent Document 2, the first lens group and the second lens group approach each other at the wide-angle end, and the refraction of the combined system of the first lens group and the second lens group. The power is weak positive or weak negative refractive power. Further, when the third lens group and the fourth lens group are separated from each other, a telephoto power arrangement is formed between the third lens group and the fourth lens group.

  On the other hand, when the distance between the first lens group and the second lens group is widened at the telephoto end, the lens groups from the second lens group to the fourth lens group approach each other, and the second lens group to the fourth lens group The composite system has negative refractive power, and a telephoto type refractive power arrangement is formed between the first lens group and the second lens group to the fourth lens group. With such a configuration, the zoom ratio is ensured while suppressing the overall length of the optical system.

  An example of a zoom lens that achieves better aberration correction by increasing the number of lens groups that move during zooming is described in Patent Document 3, for example.

  Conventionally, in general, focusing to a short distance is often performed by moving the first lens group as in the lens described in Patent Document 3. However, since the first lens group is the heaviest in the zoom lens system, performing the focusing operation using the first lens group reduces the focus drive speed or increases the size of the actuator, resulting in a larger lens barrel. Cause problems.

  In addition, zoom lenses that focus on a short distance with a small lens group inside the zoom lens have been proposed, and are described in, for example, Patent Document 4 and Patent Document 5.

JP-A-01-197713

JP 08-86961 A

JP-A-11-258504

Japanese Patent No. 4364359

JP 2009-265652 A

  When trying to achieve further miniaturization and maintenance of zoom magnification compared to conventional telephoto zoom lenses, in addition to shortening the overall length of the zoom lens optical system, the movement amount of each lens group and the movement amount of the focus lens group And weight reduction is required.

  In a telephoto zoom lens, the amount of movement of the first lens unit and the lens unit having a negative refractive power behind the lens system tends to be large. The tilt of the zoom cam is increased, and the amount of movement of the lens unit relative to the unit rotation angle is increased. Need to increase. However, if the tilt of the zoom cam is increased, the torque becomes heavier, causing a problem in the operation feeling of the zoom operation.

In order to alleviate the tilt of the zoom cam, it is effective to increase the diameter of the cam barrel. However, if the diameter of the cam barrel is increased, the entire lens barrel inevitably increases, which is not desirable.

In addition, since the telephoto lens has a long focal length and a large movement of the image plane with a change in the photographing distance, the movement amount of the focus lens group tends to increase.
If the amount of movement of the focus lens is large, focusing will take time unless the focus lens group is moved quickly. Therefore, it is necessary to use an actuator with power that can move the focus lens group quickly. However, since the actuator with power is large and heavy, if this is installed, the zoom lens optical system will be reduced in size and weight. In order to reduce the size of the actuator that drives the focus lens group, it is desirable to suppress the movement amount of the focus lens group and further reduce its weight.

  Furthermore, in recent years, it has been required to cope with shooting of moving images, and it has been required to drive the autofocus more silently, and the weight reduction of the focus lens group is strongly demanded.

  It is necessary to satisfactorily correct axial chromatic aberration and spherical aberration, which are problems in telephoto lenses, after satisfying the above requirements.

  The telephoto zoom lens described in Patent Document 1 is very compact with a telephoto ratio at the telephoto end of approximately 0.66, but the zoom ratio is slightly low at approximately 3 times. Further, there are problems such as insufficient correction of chromatic aberration and spherical aberration and large fluctuation of spherical aberration due to zooming, and the performance is insufficient.

  Further, the amount of movement of the first lens group accompanying zooming is larger than the focal length and zoom ratio, and the amount of movement of the fourth lens group is also almost as large as that of the first lens group. In order to ensure the small diameter of the lens barrel and light and smooth zoom operability, it is necessary to reduce the amount of movement of at least one of the first lens group and the fourth lens group.

  The telephoto zoom lens described in Patent Document 2 has a telephoto ratio of less than 0.65 at the telephoto end and is extremely miniaturized, and a zoom ratio of about 4 times is ensured. However, correction of spherical aberration is insufficient, fluctuation due to zooming is large, and performance is insufficient.

  Further, since the first lens unit and the fourth lens unit have the same amount of movement due to zooming, at least one of them can be reduced by reducing the lens barrel diameter and light and smooth zoom operation. Is necessary to ensure.

  The telephoto zoom lens described in Patent Document 3 includes six lens groups that move by zooming, suppresses variations in spherical aberration while maintaining a zoom ratio of about five times, and the amount of movement of the first lens group is also the focal length. Compared with the zoom ratio, the amount of movement of the rear lens unit is also suppressed. However, the telephoto ratio at the telephoto end is 0.74, and it is desirable to achieve a telephoto ratio of about 0.65 at the telephoto end in order to improve portability.

  The telephoto zoom lens described in Patent Document 4 is provided with seven lens groups that move by zooming, and while maintaining a zoom ratio of about 10 times, it corrects spherical aberration and chromatic aberration well and obtains high imaging performance. The movement amount of the first lens group and the rear lens group is also suppressed. However, the telephoto ratio at the telephoto end is about 0.71, and the overall length of the optical system is not sufficiently shortened. Although the seventh lens group is used as the focus lens group to reduce the size of the focus lens group, the number of the seventh lens group is as many as four, and the weight reduction is insufficient to support high-speed autofocus. It is.

  The telephoto zoom lens described in Patent Document 5 is provided with five or six lens groups that move by zooming, suppresses aberration fluctuations associated with zooming, and uses one or two focus lens groups behind the lens group. It is configured to reduce weight. However, the telephoto ratio at the telephoto end is about 0.8, and the miniaturization is insufficient. Further, the amount of movement of the first lens unit, the fifth lens unit, and the sixth lens unit accompanying zooming is larger than the focal length, which is preferable in order to ensure a small diameter of the lens barrel and a light and smooth zoom operability. Absent.

The present invention reduces the overall length and moves each lens group while maintaining high imaging performance especially in a zoom lens having a diagonal angle of view of 5 degrees or less at the telephoto end and a zoom ratio of 3.75 times or more. The purpose is to achieve further reduction in size of the entire lens barrel by reducing the amount and reducing the weight and moving amount of the focus lens group.

The telephoto zoom lens of the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive refractive power. a fourth lens group having a, and a fifth lens group having negative refractive power, upon zooming from the wide-angle end to the telephoto end, the interval between the first lens group and the second lens group increases, the third lens The distance between the second lens group and the fourth lens group is decreased, the distance between the fourth lens group and the fifth lens group is decreased, and the distance between the second lens group and the third lens group is minimized at the wide angle end. The lens group is composed of a 5a lens group having a negative refractive power and a 5b lens group having a negative refractive power, and the 5a lens group emits light from the object side to the image side during focusing from an infinite focus state to a short distance. It moves along the axis and satisfies the following conditions.
(1) 0.025 <| (f4 · f5) / (fW · fT) | <0.050
(2) 0.020 <| (f [1-2] T · f [3-5] T) / fT ² | <0.050
(3) 4.0 <| (f2 / f3) | <11.0
However,
f2: Composite focal length of the second lens group f3: Synthetic focal length of the third lens group f4: Synthetic focal length of the fourth lens group f5: Synthetic focal length f [1- 2] T: Composite focal length at the telephoto end from the first lens group to the second lens group f [3-5] T: Composite at the telephoto end from the third lens group to the fifth lens group and focusing at infinity Focal length fW: Total focal length of the entire lens system at the wide-angle end fT: Total focal length of the entire lens system at the telephoto end

  The 5a lens group is composed of only a cemented lens made up of two lenses.

Further, the composite magnification of the third lens group to the fifth lens group satisfies the following condition.
(4) 1.05 <(β [3-5] W / β [3-5] T) · (fT / fW) <1.30
However,
β [3-5] W: Composite magnification from the third lens group to the fifth lens group at the wide-angle end β [3-5] T: Composite magnification from the third lens group to the fifth lens group at the telephoto end

The imaging magnification of the fifth lens group satisfies the following conditions.
(5) 2.85 <| β5T | <3.5
However,
β5T: imaging magnification at the telephoto end of the fifth lens unit

According to the present invention, in a telephoto zoom lens having a diagonal angle of view of about 5 degrees or less at the telephoto end and a zoom ratio of 3.75 times or more, while maintaining high imaging performance, it is further compact than conventional ones. It is possible to provide a telephoto zoom lens that can achieve this.

FIG. 6 is a lens cross-sectional view of the zoom lens according to Embodiment 1 in an infinitely focused state at the wide-angle end. Longitudinal aberration diagram in the infinite focus state at the wide-angle end of the zoom lens of Example 1 Longitudinal aberration diagram of the zoom lens of Example 1 in an infinitely focused state at an intermediate focal length Longitudinal aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 1 Lateral aberration diagram of the zoom lens of Example 1 in the infinitely focused state at the wide angle end Lateral aberration diagram of the zoom lens of Example 1 in the infinite focus state at the intermediate focal length Lateral aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 1 Sectional view of the zoom lens of Example 2 in the infinitely focused state at the wide-angle end Longitudinal aberration diagram in the infinite focus state at the wide-angle end of the zoom lens of Example 2 Longitudinal aberration diagram of the zoom lens of Example 2 in an infinitely focused state at an intermediate focal length Longitudinal aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 2 Lateral aberration diagram in the infinite focus state at the wide-angle end of the zoom lens of Example 2 Lateral aberration diagram of the zoom lens of Example 2 in the infinitely focused state at the intermediate focal length Lateral aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 2 FIG. 6 is a lens cross-sectional view of the zoom lens according to the third embodiment in the infinitely focused state at the wide angle end. Longitudinal aberration diagram in the infinite focus state at the wide angle end of the zoom lens of Example 3 Longitudinal aberration diagram of the zoom lens of Example 3 in the infinite focus state at the intermediate focal length Longitudinal aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 3 Lateral aberration diagram of the zoom lens of Example 3 in the infinitely focused state at the wide-angle end Lateral aberration diagram of the zoom lens of Example 3 in the infinitely focused state at the intermediate focal length Lateral aberration diagram of the zoom lens of Example 3 in the infinitely focused state at the telephoto end Sectional view of the zoom lens of Embodiment 4 in the infinitely focused state at the wide-angle end Longitudinal aberration diagram in the infinite focus state at the wide angle end of the zoom lens of Example 4 Longitudinal aberration diagram of the zoom lens of Example 4 in the infinitely focused state at the intermediate focal length Longitudinal aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 4 Lateral aberration diagram in the infinite focus state at the wide-angle end of the zoom lens of Example 4 Lateral aberration diagram of the zoom lens of Example 4 in the infinitely focused state at the intermediate focal length Lateral aberration diagram in the infinite focus state at the telephoto end of the zoom lens of Example 4

  The telephoto zoom lens of the present invention has a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive refractive power. A fourth lens group and a fifth lens group having negative refractive power;

  In the wide-angle end state, the first lens group to the third lens group approach each other, and the refractive power of the combined system becomes negative. The fourth lens group and the fifth lens group are separated from each other, and the refractive power of the combined system is reduced. Become positive.

  Further, a telephoto type refractive power arrangement is formed by the fourth lens group and the fifth lens group, which contributes to shortening the total length of the optical system at the wide angle end.

  In the telephoto end state, the first lens group and the second lens group are separated from each other, and the refractive power of the combined system becomes positive. The third lens group is separated from the second lens group and approaches the fourth lens group. The fifth lens group also approaches the fourth lens group, the refractive power of the composite system from the third lens group to the fifth lens group becomes negative, the composite system of the first lens group and the second lens group, and the third lens group A telephoto type refractive power arrangement is formed between the combining system from the first lens unit to the fifth lens unit.

  In order to suppress the movement amount of the first lens unit having a positive refractive power during zooming from the wide-angle end to the telephoto end, the third lens unit has a strong negative refractive power so that the telephoto side is telephoto. It is effective to set the ratio small to suppress the total length of the optical system on the telephoto side.

  However, when the negative refractive power of the third lens group becomes strong, the negative refractive power of the composite system from the first lens group to the third lens group becomes strong at the wide angle end, and from the first lens group to the third lens group. A strong retrofocus type refracting power arrangement is formed between this combination system and the combination system of the fourth lens group and the fifth lens group, making it difficult to shorten the total length of the optical system at the wide angle end.

Therefore, if the refractive power of the third lens group is made strongly negative and the refractive power of the composite system from the first lens group to the third lens group at the wide angle end is weakened, zooming from the wide angle end to the telephoto end is prevented. In this case, it is possible to prevent the entire length of the optical system from being increased while suppressing the movement amount of the first lens group.

In order to weaken the refractive power of the composite system from the first lens group to the third lens group at the wide angle end, the refractive power of the second lens group is made positive, and at the wide angle end, the second lens group and the third lens group. It is effective to reduce the influence of the strong negative refractive power of the third lens unit by bringing the third lens group close to each other.

  In focusing in the short distance direction, in order to reduce the weight of the lens, it is preferable to use a part of the lens group closer to the image side as much as possible in the entire optical system.

  Furthermore, when the refractive power of the composite system before the focus lens group is positive, using a lens group having a negative refractive power as the focus lens group makes it easy to reduce the amount of movement of the focus lens group, and it is behind the focus lens group. Further, if there is a lens group having a negative refractive power, the amount of movement of the focus lens group can be further reduced.

For this reason, in the telephoto zoom lens according to the present invention, the fifth lens group is composed of a 5a lens group having a negative refractive power and a 5b lens group having a negative refractive power, and focusing is performed by the 5a lens group. It was decided.

  Conditional expression (1) is an expression relating to the focal lengths of the fourth lens group and the fifth lens group, and shows preferable conditions for achieving miniaturization at the wide-angle end of the entire zoom lens system. To reduce the size at the wide-angle end, the positive refracting power of the fourth lens group and the negative refracting power of the fifth lens group are strengthened, thereby providing a strong telephoto type between the fourth lens group and the fifth lens group. It is effective to form a refractive power arrangement.

  If the upper limit of conditional expression (1) is exceeded, the respective refractive powers of the fourth lens group and the fifth lens group are too weak, and the total length of the optical system is not sufficiently shortened.

  If the lower limit of conditional expression (1) is not reached, the positive refractive power of the fourth lens group and the negative refractive power of the fifth lens group become too strong, making it difficult to correct spherical aberration, coma aberration, astigmatism, etc. As a result, the performance deteriorates.

  Conditional expression (2) is an expression relating to the combined focal length of the first lens group and the second lens group at the telephoto end and the combined focal length from the third lens group to the fifth lens group. A preferable condition for reducing the amount of movement of the first lens unit due to shortening and zooming is shown.

  In order to reduce the total length of the optical system at the telephoto end and suppress the movement amount of the first lens unit due to zooming, the positive refractive power of the combined system of the first lens unit and the second lens unit at the telephoto end, It is effective to strongly set the negative refractive power of the composite system from the third lens group to the fifth lens group to form a strong telephoto refractive power arrangement.

  If the combined focal length of the first lens unit and the second lens unit at the telephoto end or the combined focal length from the third lens unit to the fifth lens unit becomes longer than the upper limit of the conditional expression (2), the optical system at the telephoto end It becomes difficult to shorten the overall length.

  If the combined focal length of the first lens unit and the second lens unit at the telephoto end or the combined focal length from the third lens unit to the fifth lens unit becomes shorter than the lower limit of the conditional expression (2), the spherical aberration is corrected particularly. In addition to increasing the spherical aberration variation due to zooming, the coma aberration and astigmatism variation due to the decentering of each lens group and lens element increases, leading to performance degradation.

  Conditional expression (3) defines the relationship between the focal lengths of the second lens group and the third lens group, and suppresses the movement amount of the first lens group due to the shortening of the overall length of the optical system at the wide-angle end and zooming. Preferred conditions for are shown.

When the upper limit of conditional expression (3) is exceeded and the focal length of the third lens group becomes shorter than the focal length of the second lens group, the synthesis system from the first lens group to the third lens group at the wide-angle end is negative. Since the refractive power becomes strong, it becomes difficult to suppress the entire length of the optical system at the wide angle end.

If the lower limit of conditional expression (3) is not reached and the focal length of the third lens group becomes longer than the focal length of the second lens group, the negative value of the composite system from the third lens group to the fifth lens group at the telephoto end is reduced. Since it is difficult to increase the refractive power, it is difficult to suppress the telephoto ratio at the telephoto end, the amount of movement of the first lens group cannot be suppressed, and it is difficult to reduce the diameter of the lens barrel. Or, the operability during zooming is hindered.

  Further, the focus lens group can be reduced in weight by configuring the 5a lens group only with a bonded lens composed of two lenses.

  In order to further reduce the weight of the focus lens group, it may be possible to use a single lens, but it is impossible to achromatic the focus lens group alone, and it is difficult to suppress fluctuations in chromatic aberration due to focusing. Therefore, it is not particularly suitable for a telephoto lens having a long focal length.

  Conditional expression (4) is an expression relating to the ratio of the change in the combined magnification after the third lens group and the zoom ratio at the wide-angle end and the telephoto end, and shows preferable conditions for reducing the movement amount of the lens group after the third lens group. Is.

  If the lower limit of conditional expression (4) is not reached, it is necessary to increase the change in magnification after the third lens group, so the amount of movement of the lens group after the third lens group becomes large, and the diameter of the lens barrel decreases. It becomes difficult, or the operability during zooming is hindered.

  If the upper limit of conditional expression (4) is exceeded, the change in magnification after the third lens group becomes small, and the change in magnification between the first lens group and the second lens group becomes large in order to obtain the necessary zoom effect. Must. At this time, in order to suppress the movement amount of the first lens group, it is necessary to increase the refractive power of the first lens group and the second lens group, so that it is difficult to correct spherical aberration and coma aberration.

  Conditional expression (5) defines the imaging magnification at the telephoto end of the fifth lens group, and indicates a desirable range related to the amount of movement of the image plane with respect to the movement of the 5a lens group accompanying focusing on the telephoto end side.

  When the absolute value of the magnification of the fifth lens unit increases beyond the upper limit of conditional expression (5), the amount of movement of the image plane increases with respect to the amount of movement of the 5a lens unit, and the fifth lens unit stops at the stop position of the 5a lens unit. Since high accuracy is required, it becomes difficult to control focusing.

  If the absolute value of the magnification of the fifth lens unit becomes smaller than the lower limit of conditional expression (5), the amount of movement of the 5a lens unit required for focusing to a predetermined shooting distance increases, and the focusing speed decreases. Or, it becomes difficult to shorten the total length of the optical system.

  Numerical Examples 1 to 4 according to the telephoto zoom lens of the present invention are shown below.

In each numerical example, f in [Overall specifications] indicates a focal length, Fno indicates an F number, and 2ω indicates a diagonal angle of view. The number in the first column in [Lens Specifications] indicates the lens surface number from the object side, R in the second column indicates the radius of curvature of the lens surface, D in the third column indicates the lens surface interval, The column nd represents the refractive index of the d-line (wavelength 587.56 nm), and the fifth column νd represents the Abbe number based on the d-line. Bf represents back focus.
The d-line, g-line, and C-line in the figure indicate aberrations at the respective wavelengths. ΔS represents a sagittal image plane of d line, and ΔM represents a meridional image plane of d line.

  The variable magnification optical system of each numerical example satisfies all the above conditions.

  In each embodiment, the second lens group does not move during zooming. A mechanism such as a cam required for moving the second lens group is not necessary, which is advantageous in reducing the size of the lens barrel. Since the number of lens groups that move during zooming is four, the mechanism is avoided from becoming complicated compared to a conventional zoom lens having a four-group configuration, while increasing the number of lens groups.

In each embodiment, the plane parallel plate disposed between the fourth lens group and the image plane is a low-pass filter.

  In each embodiment, the back focus indicates the distance between the image-side surface of the low-pass filter and the imaging surface.

Next, [lens specifications], [overall specifications], [variable intervals], and [conditional expression corresponding values] of Numerical Example 1 according to the present invention will be shown.

[Lens specifications]
R D nd νd
[1] 112.9610 1.5000 1.80610 40.73
[2] 58.0481 6.1492 1.49700 81.61
[3] -669.5860 0.1500
[4] 56.4392 5.3036 1.45860 90.19
[5] 551.3780 D5
[6] -741.6060 1.2000 1.77250 49.62
[7] 33.5614 1.1294
[8] 25.7417 4.1983 1.51680 64.20
[9] -93.6540 D9
[10] -51.1065 0.8500 1.77250 49.62
[11] 21.3631 5.3306
[12] 33.0061 2.2788 1.84666 23.78
[13] 377.5260 D13
[14] Aperture stop 13.6796
[15] 465.8500 2.1485 1.51742 52.15
[16] -65.4992 0.6985
[17] -220.1610 2.9307 1.51680 64.20
[18] -25.5107 1.0687
[19] -27.5867 0.8500 1.91082 35.25
[20] 31.9369 4.4621 1.51680 64.20
[21] -28.2108 0.1500
[22] 33.5282 3.1842 1.71300 53.94
[23] -106.3470 D23
[24] 394.0260 2.7328 1.80610 33.27
[25] -20.4786 0.8500 1.77250 49.62
[26] 28.3209 11.5161
[27] -94.6533 2.8584 1.56732 42.84
[28] -17.7153 0.8500 1.77250 49.62
[29] -132.0870 D29
[30] Infinite 4.1400 1.51680 64.20
[31] Infinite Bf

[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 71.11 140.00 291.00
Fno 5.42 5.99 6.81
2ω 17.75 8.97 4.32

[Variable interval]
Wide angle end Medium telephoto Telephoto end
D5 3.1579 31.4767 51.1279
D9 3.8278 8.3244 9.5219
D13 12.1681 7.2097 2.9733
D23 21.7767 14.6780 2.0000
D29 18.8700 26.4305 42.1475
Bf 1.0000 1.0000 1.0000

[Conditional expression values]
Conditional expression (1) 0.0426
Conditional expression (2) 0.0428
Conditional expression (3) 9.4417
Conditional expression (4) 1.1036
Conditional expression (5) 3.1103

Next, [lens specifications], [overall specifications], [variable intervals], and [conditional expression corresponding values] of Numerical Example 2 according to the present invention will be shown.

[Lens specifications]
R D nd νd
[1] 152.4860 1.5000 1.80610 40.73
[2] 66.4823 5.7835 1.49700 81.61
[3] -297.8430 0.1500
[4] 53.3189 5.0467 1.45860 90.19
[5] 277.0330 D5
[6] -158.7360 1.0000 1.91082 35.25
[7] 105.5080 0.6988
[8] 49.2056 3.3506 1.54814 45.82
[9] -78.7386 D9
[10] -40.1003 0.8500 1.80420 46.50
[11] 40.1003 0.9754
[12] -1000.0000 0.8500 1.80420 46.50
[13] 45.5732 1.1290
[14] 39.0525 2.6308 1.84666 23.78
[15] -104.8610 D15
[16] Aperture stop 7.3500
[17] 523.9300 2.1707 1.59282 68.62
[18] -71.5233 0.2964
[19] 252.3970 3.8373 1.48749 70.44
[20] -26.7758 0.8500 1.91082 35.25
[21] -105.7420 1.8962
[22] -300.9120 0.8500 1.91082 35.25
[23] 38.0866 4.5773 1.51680 64.20
[24] -38.0866 0.1500
[25] 46.4444 3.6951 1.72916 54.67
[26] -65.3298 D26
[27] 85.6222 1.8824 1.80518 25.46
[28] -65.8633 0.8500 1.77250 49.62
[29] 24.7345 12.1262
[30] -55.0189 2.5659 1.54072 47.20
[31] -17.4397 0.8500 1.72916 54.67
[32] -219.8900 D32
[33] infinity 4.1400 1.51680 64.20
[34] Infinite Bf

[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 76.91 140.00 290.98
Fno 4.95 5.57 6.92
2ω 16.41 8.97 4.33

[Variable interval]
Wide angle end Medium telephoto Telephoto end
D5 3.4219 26.4265 51.3869
D9 3.8900 11.9871 11.7576
D15 13.7317 6.9798 2.6491
D26 21.3940 14.8854 2.0000
D32 18.8700 24.0335 41.4790
Bf 1.0000 1.0000 1.0000

[Conditional expression values]
Conditional expression (1) 0.0339
Conditional expression (2) 0.0328
Conditional expression (3) 6.4662
Conditional expression (4) 1.1630
Conditional expression (5) 3.2458

Next, [lens specifications], [overall specifications], [variable intervals], and [conditional expression corresponding values] of Numerical Example 3 according to the present invention will be shown.

[Lens specifications]
R D nd νd
[1] 145.9100 1.5000 1.80610 40.73
[2] 65.2268 6.0730 1.49700 81.61
[3] -245.7110 0.1500
[4] 55.4613 4.6583 1.45860 90.19
[5] 211.0760 D5
[6] -229.3970 1.0000 1.91082 35.25
[7] 92.7746 1.0683
[8] 40.2097 3.7498 1.53172 48.84
[9] -78.9198 D9
[10] -40.6810 0.8500 1.80420 46.50
[11] 31.3677 1.0945
[12] 1000.0000 0.8500 1.80420 46.50
[13] 39.3831 1.0891
[14] 33.5275 2.7210 1.84666 23.78
[15] -117.5960 D15
[16] Aperture stop 5.9703
[17] 1000.0000 2.2517 1.59282 68.62
[18] -59.1636 0.3076
[19] 1000.0000 3.9569 1.48749 70.44
[20] -23.3027 0.8500 1.91082 35.25
[21] -81.0283 3.4838
[22] -275.2190 0.8500 1.90366 31.31
[23] 43.7933 4.6187 1.51823 58.96
[24] -34.8633 0.1500
[25] 50.3151 3.6277 1.72916 54.67
[26] -66.8332 D26
[27] 90.7110 1.8557 1.84666 23.78
[28] -69.7777 0.8500 1.77250 49.62
[29] 24.1555 12.2682
[30] -38.6393 2.3797 1.51742 52.15
[31] -17.4355 0.8500 1.72916 54.67
[32] -107.7130 D32
[33] infinity 4.1400 1.51680 64.20
[34] Infinite Bf

[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 76.93 140.00 290.99
Fno 4.95 5.58 6.90
2ω 16.39 8.97 4.32

[Variable interval]
Wide angle end Medium telephoto Telephoto end
D5 3.4136 29.1818 51.3786
D9 3.8704 9.8989 12.3890
D15 13.1637 8.3406 2.6801
D26 20.7800 14.5169 2.0000
D32 18.8700 23.9278 39.6150
Bf 1.0000 1.0000 1.0000

[Conditional expression values]
Conditional expression (1) 0.0316
Conditional expression (2) 0.0263
Conditional expression (3) 4.4699
Conditional expression (4) 1.2363
Conditional expression (5) 3.2653

Next, [lens specifications], [overall specifications], [variable intervals], and [[conditional expression corresponding values] of Numerical Example 4 according to the present invention will be described.

[Lens specifications]
R D nd νd
[1] 107.1810 1.5000 1.80610 40.73
[2] 55.2504 5.9501 1.49700 81.61
[3] -5777.6100 0.1500
[4] 58.0589 5.1662 1.45860 90.19
[5] 719.8770 D5
[6] 923.9600 1.0000 1.91082 35.25
[7] 34.9414 1.0526
[8] 30.5921 3.8336 1.62004 36.30
[9] -102.0180 D9
[10] -38.7592 0.8500 1.80420 46.50
[11] 32.2854 3.1403
[12] 38.3271 2.0532 1.84666 23.78
[13] 929.9990 D13
[14] Aperture stop 7.3500
[15] -313.3670 4.5389 1.69680 55.46
[16] -53.8662 0.1500
[17] 99.8609 3.1139 1.51680 64.20
[18] -41.3013 0.8500 1.91082 35.25
[19] 34.3844 4.5151 1.48749 70.44
[20] -46.3375 0.1500
[21] 37.3050 3.2505 1.71300 53.94
[22] -115.9860 D22
[23] 122.6960 1.7964 1.80518 25.46
[24] -56.4885 0.8500 1.77250 49.62
[25] 24.0346 12.0681
[26] -35.5392 2.0856 1.60342 38.01
[27] -18.5229 0.8500 1.77250 49.62
[28] -52.4356 D28
[29] Infinite 4.1400 1.51680 64.20
[30] Infinite Bf

[Overall specifications]
Wide angle end Medium telephoto Telephoto end
f 76.90 140.00 291.00
Fno 4.97 5.77 6.90
2ω 16.42 8.97 4.33

[Variable interval]
Wide angle end Medium telephoto Telephoto end
D5 3.1456 29.0325 51.1106
D9 4.0094 11.2507 14.1631
D13 18.1300 11.8252 6.4832
D22 22.4506 15.8785 2.0000
D28 18.8700 24.5055 40.8137
Bf 1.0000 1.0000 1.0000

[Conditional expression values]
Conditional expression (1) 0.0390
Conditional expression (2) 0.0453
Conditional expression (3) 10.6303
Conditional expression (4) 1.0912
Conditional expression (5) 3.0951

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group L5 5th lens group L5a 5a lens group L5b 5b lens group SP Aperture stop IP Image plane LPF Low pass filter dd line g g line C C line ΔS Sagittal image plane ΔM Meridional image plane

Claims (4)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, a fourth lens group having a positive refractive power, and a negative and a fifth lens group having a refractive power,
Upon zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group increases, the distance between the third lens group and the fourth lens group decreases, and the fourth lens group and the fifth lens group decrease. The distance from the lens group decreases,
The distance between the second lens group and the third lens group is minimum at the wide-angle end,
The fifth lens group includes a negative power 5a lens group and a negative power 5b lens group.
During focusing from an infinitely focused state to a short distance, the 5a lens group moves along the optical axis from the object side to the image side,
A zoom lens satisfying the following conditions:
(1) 0.025 <| (f4 · f5) / (fW · fT) | <0.050
(2) 0.020 <| (f [1-2] T · f [3-5] T) / fT ² | <0.050
(3) 4.0 <| (f2 / f3) | <11.0
However,
f2: Composite focal length of the second lens group f3: Synthetic focal length of the third lens group f4: Synthetic focal length of the fourth lens group f5: Synthetic focal length f [1- 2] T: Composite focal length at the telephoto end from the first lens group to the second lens group f [3-5] T: Composite at the telephoto end from the third lens group to the fifth lens group and focusing at infinity Focal length fW: Total focal length of the entire lens system at the wide-angle end fT: Total focal length of the entire lens system at the telephoto end The zoom lens according to claim 1, wherein the 5a lens group includes only a cemented lens including two lenses.
3. The zoom lens according to claim 1, wherein the combined magnification of the third lens group to the fifth lens group satisfies the following condition.
(4) 1.05 <(β [3-5] W / β [3-5] T) · (fT / fW) <1.30
However,
β [3-5] W: Composite magnification from the third lens group to the fifth lens group at the wide-angle end β [3-5] T: Composite magnification from the third lens group to the fifth lens group at the telephoto end
The zoom lens according to any one of claims 1 to 3, wherein the imaging magnification of the fifth lens group satisfies the following condition.
(5) 2.85 <| β5T | <3.5
However,
β5T: imaging magnification at the telephoto end of the fifth lens unit

Images