JP5094225B2 - Zoom lens and imaging apparatus having the same - Google Patents

Description

  The present invention relates to a zoom lens suitable for a video camera, a silver salt photography camera, a broadcast camera, a digital still camera, and the like, and an imaging apparatus having the same.

  In recent years, imaging devices such as a video camera using a solid-state imaging device, a digital still camera, a broadcasting camera, and a still camera using a silver halide film have been improved in function and downsized as a whole.

  Along with this, a photographing optical system used for these is required to be a zoom lens with a short overall lens length and a high zoom ratio.

  As a compact zoom lens with a high zoom ratio, there is known a four-group zoom lens which is composed of lens groups having positive, negative, positive and positive refractive powers in order from the object side to the image side, and performs zooming by moving each lens group. (Patent Documents 1 to 3).

  Among such four-group zoom lenses, there is known a four-group zoom lens in which the second lens group is composed of two lenses, a negative lens and a positive lens (Patent Documents 4 and 5).

  Patent Document 4 discloses a zoom lens including a third lens group including three independent lenses: a positive lens, a positive lens, and a negative lens.

Patent Document 5 discloses a zoom lens including a third lens group including a positive lens and a cemented lens of a positive lens and a negative lens.
JP-A-3-296706 JP 2003-315676 A JP 2004-94233 A Japanese Patent Laid-Open No. 11-271616 JP 2002-107624 A

  In recent years, a retractable zoom lens has been used to achieve both a compact camera and a high zoom ratio of the zoom lens. The retractable zoom lens reduces the projection amount of the lens from the camera body by reducing the distance between the lens groups to a different distance from the photographing state when not in use (when not photographing).

  In general, when the number of lenses in each lens group constituting the zoom lens is large, the length of each lens group on the optical axis increases.

  Further, if the amount of movement of each lens group during zooming and focusing is large, the total lens length becomes long. As a result, the retractable length increases.

  On the other hand, in a zoom lens used in an image pickup apparatus, it is also important that the entire lens system is downsized and has a predetermined zoom ratio and has good optical performance over the entire zoom range. For this purpose, it is necessary to appropriately set the movement condition of each lens group accompanying zooming, the refractive power of each lens group, the lens configuration of each lens group, and the like. For example, regarding the miniaturization of the zoom lens, if the refractive power of each lens group is increased, the amount of movement of each lens group during zooming is reduced, and the total lens length can be shortened. However, if the refracting power of each lens group is simply increased, aberration fluctuations accompanying zooming increase, and it becomes difficult to correct this well.

  That is, the miniaturization of the optical system and the good optical performance are contradictory conditions, and it is an important issue for the zoom lens to achieve both of them.

  It is an object of the present invention to provide a zoom lens that achieves high optical performance over the entire zoom range with a high zoom ratio while having a simple and compact lens configuration.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens having a positive refractive power. The fourth lens group is configured such that the first lens group is located on the object side at the telephoto end compared to the wide-angle end, and the distance between the first lens group and the second lens group is changed, so that the second lens In the zoom lens in which each lens group moves during zooming so that the distance between the third lens group and the third lens group becomes smaller and the distance between the third lens group and the fourth lens group becomes larger, the second lens group is , in order from the object side to the image side, and a negative lens, a positive lens, said third lens group comprises, in order from the object side to the image side, a cemented lens and a positive lens obtained by cementing a positive lens and a negative lens, the second Thickness on the optical axis of the two lens groups and the third lens group Each TD2, TD3, and a focal length of the entire system at the telephoto end and ft,
0.28 <(TD2 + TD3) / ft <0.34
It is characterized by satisfying the following conditions .

  According to the present invention, it is possible to obtain a zoom lens that achieves high optical performance over the entire zoom range with a high zoom ratio while having a simple and compact lens configuration.

  Embodiments of the zoom lens of the present invention and an image pickup apparatus having the same will be described below.

The zoom lens according to the present invention includes, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive lens having a positive refractive power. It is composed of a fourth lens group.

  The distance between the first lens group and the second lens group changes during zooming. The first lens group is located closer to the object side at the telephoto end than at the wide-angle end. This is a zoom lens in which each lens group moves during zooming so that the distance between the second lens group and the third lens group is smaller and the distance between the third lens group and the fourth lens group is larger at the telephoto end than at the wide-angle end. .

FIG. 1 is a lens cross-sectional view of a zoom lens according to Example 1 of the present invention. 2A, 2B, and 2C are aberration diagrams at the wide-angle end (short focal length end), the intermediate zoom position, and the telephoto end (long focal length end), respectively, of the zoom lens according to the first exemplary embodiment. The first embodiment is a zoom lens having a zoom ratio of 4.76 and an F number of 3.24 to 5.88.

FIG. 3 is a lens cross-sectional view of a zoom lens according to Example 2 of the present invention. 4A, 4B, and 4C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the second embodiment. The second embodiment is a zoom lens having a zoom ratio of 4.79 and an F number of 3.30 to 5.69 .

FIG. 5 is a lens cross-sectional view of a zoom lens according to Example 3 of the present invention. FIGS. 6A, 6B, and 6C are aberration diagrams at the wide-angle end, the intermediate zoom position, and the telephoto end, respectively, of the zoom lens according to the third exemplary embodiment. The third exemplary embodiment is a zoom lens having a zoom ratio of 4.79 and F-numbers of 2.93 to 5.35 .

  In the lens cross-sectional view, (A) shows the wide-angle end, (B) shows the intermediate zoom position, and (C) shows the telephoto end.

  FIG. 7 is a schematic diagram of a main part of an imaging apparatus including the zoom lens according to the present invention.

  The zoom lens of each embodiment is a photographing lens system used in an imaging apparatus such as a digital still camera or a silver salt film camera. In the lens cross-sectional view, the left side is the object side (front), and the right side is the image side (rear).

  When the zoom lens of each embodiment is used as a projection lens such as a projector, the left side is the screen and the right side is the projected image.

  In the lens cross-sectional view, L1 is a first lens group having a positive refractive power (optical power = reciprocal of focal length), L2 is a second lens group having a negative refractive power, and L3 is a third lens group having a positive refractive power. , L4 is a fourth lens unit having a positive refractive power. G is an optical block corresponding to an optical filter, a face plate, a quartz low-pass filter, an infrared cut filter, or the like.

  IP is an image plane, and corresponds to an imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor when used as a photographing optical system of a video camera or a digital still camera.

  In the aberration diagrams, Fno is the F number, d and g are the d-line and g-line, respectively, and ΔM and ΔS are the meridional image surface and sagittal image surface of the d-line. Lateral chromatic aberration is represented by the g-line. ω is a half angle of view.

  In each of the following embodiments, the zoom positions at the wide-angle end and the telephoto end are determined when the zoom lens unit is located at both ends of a range in which the zoom lens unit can move on the optical axis on the mechanism (second and third lens units). The zoom position.

  In each embodiment, the lens units L1 to L4 are moved as indicated by arrows during zooming from the wide-angle end to the telephoto end.

  Specifically, it is as follows.

  The first lens unit L1 moves along a locus convex toward the image side. And it moves so that it may be located in the object side in the telephoto end compared with the wide-angle end. The second lens unit L2 moves along a locus convex toward the image side. Then, the zoom lens moves so as to be located closest to the image side at a substantially intermediate zoom position. The third lens unit L3 moves monotonously toward the object side. The fourth lens unit L4 moves so as to draw a convex locus toward the object side.

  The distance between the first lens unit L1 and the second lens unit L2 (the axial distance from the rear end of the first lens unit L1 to the front end of the second lens unit L2) decreases once during zooming from the wide-angle end to the telephoto end. And then increase.

  The focal length of the entire system at the zoom position where the distance between the first lens unit L1 and the second lens unit L2 at this time is the minimum value d1min is hereinafter referred to as fa.

  In addition, each lens group has a telephoto end that is larger than a wide-angle end, and the distance between the first lens group L1 and the second lens group L2 is large, and the distance between the second lens group L2 and the third lens group L3 is small. The lens unit L3 and the fourth lens unit L4 are moved so that the distance between them is increased.

  In each of the embodiments, a substantially retrofocus type refractive power arrangement is adopted as a whole at the wide-angle end. Further, the telephoto end has a substantially telephoto type refractive power arrangement as a whole. As a result, a zoom lens having a high zoom ratio (about 5 zoom ratio) is obtained.

  In addition, efficient distribution of refractive power is facilitated by moving all the lens groups to correct image plane variation accompanying zooming and zooming.

  Furthermore, the optical total length can be shortened at the wide-angle end, and for example, a compact zoom lens is configured with a high zoom ratio optimum for a digital camera.

  In each embodiment, a rear focus type that performs focusing by moving the fourth lens unit L4 on the optical axis is employed.

When focusing from an infinitely distant object to a close object at the telephoto end, the fourth lens group is moved forward as indicated by an arrow 4c. A solid line curve 4a and a solid line curve 4b of the fourth lens unit L4 are for correcting image plane fluctuations when following zooming from the wide-angle end to the telephoto end when focusing on an object at infinity and a short-distance object, respectively. The movement locus | trajectory of the 4th lens group L4 is shown.

  In each embodiment, quick focusing is facilitated by moving the lightweight fourth lens unit L4 for focusing.

  In each embodiment, each lens group has the following lens configuration in order from the object side to the image side. The first lens unit L1 includes a cemented lens in which a negative lens and a positive lens are cemented. At this time, the cemented lens has a meniscus shape having a convex surface on the object side.

  The second lens unit L2 includes a negative lens and a positive lens. At least one surface of the negative lens is aspherical. Specifically, the object side and image side surfaces are composed of a concave (biconcave) negative lens, and the object side surface is a convex meniscus positive lens. At this time, both surfaces of the negative lens are aspherical.

  The third lens unit L3 includes a cemented lens in which a positive lens and a negative lens are cemented, and a biconvex positive lens. At this time, the cemented lens has a meniscus shape having a convex surface on the object side.

  The fourth lens unit L4 includes a single positive meniscus lens having a convex surface on the object side.

  As described above, in each of the embodiments, a high number of lenses as a whole is configured to achieve high optical performance while reducing the size of the entire zoom lens.

In each embodiment, the first lens unit L1 having a positive refractive power is a lens unit having the largest effective diameter. Since the first lens unit L1 has a two-lens configuration, the number of constituent lenses is reduced and a compact optical system is realized.

  Further, the two lenses are used as a cemented lens of a positive lens and a negative lens, so that achromaticity is favorably performed. In particular, the lateral chromatic aberration from the wide-angle end to the telephoto end and the axial chromatic aberration at the telephoto end are corrected well.

  In the four-group zoom lens composed of four lens groups in each embodiment, when the second lens unit L2 has a two-lens configuration, compared to a case where three or more lens configurations are used, the second lens unit L2 has a peripheral portion of the screen by zooming. Correction of field curvature changes becomes difficult.

  According to the present invention, by adopting the aforementioned zoom locus as the zoom locus in zooming of the first and second lens groups, the curvature of field around the screen due to the zooming equivalent to the case where the number of lenses is three or more. Is corrected well.

  The second lens unit L2 having negative refracting power partially shares the variable magnification, and the negative refracting power is strong and the aberration generation inside the second lens unit L2 increases.

  Since the second lens unit L2 has a lens configuration of two lenses in two groups, it is possible to correct aberrations while maintaining a strong negative refractive power. In particular, a zoom lens having a high zoom ratio and high optical performance has been achieved with a simple lens configuration.

  In the four-group zoom lens, if the lens configuration of the third lens unit L3 is a three-lens configuration including a positive lens, a positive lens, and a negative lens and the principal point is disposed on the front side, the second lens unit and the third lens unit at the telephoto end. The distance between the principal points can be reduced, and both a reduction in size and a high zoom ratio can be achieved.

  However, when the configuration of the second lens group is a two-lens configuration, it is difficult to correct aberrations at the periphery of the screen in the wide angle region.

  Therefore, in each embodiment, the third lens unit is constructed from a positive lens and a negative lens in order from the object side to the image side, so that coma flare at the periphery of the screen is corrected well in a wide angle range. is doing.

  Compared with the case where the third lens group is composed of positive, positive, and negative lenses, the total lens length is slightly longer at the time of photographing, but the total lens length at the time of retracting is not changed. In the case of a zoom ratio of about 5 times, the lens configuration can correct various aberrations better.

  The third lens unit L3 having a positive refractive power is configured to correct on-axis aberration generated by the positive lens by the negative lens, and is configured by the three lenses as described above, thereby obtaining good optical performance. .

  The fourth lens unit L4 having positive refractive power efficiently corrects on-axis aberrations and off-axis aberrations that could not be corrected by the third lens unit L3.

  As described above, according to each embodiment, a zoom lens having a high zoom ratio of about 5 times and a bright optical performance is achieved despite the reduction of the number of lenses and the shortening of the total lens length. Is obtained.

  In the zoom lens according to each embodiment, one or more of the following configurations are satisfied in order to obtain good optical performance or to reduce the size of the entire lens system. Thereby, the effect equivalent to each structure is acquired.

  The curvature radii of the object side and image side surfaces of the positive lens closest to the object side in the third lens unit L3 are R5a and R5b, respectively.

  Let the radius of curvature of the image side surface of the negative lens of the third lens unit L3 be R6b.

  The thicknesses on the optical axis of the second lens unit L2 and the third lens unit L3 are TD2 and TD3, respectively. The focal lengths of the entire system at the wide-angle end and the telephoto end are denoted by fw and ft, respectively.

  The distances between the first lens unit L1 and the second lens unit L2 at the wide-angle end and the telephoto end are d1w and d1t, respectively. The interval between the first lens unit L1 and the second lens unit L2 takes a minimum value during zooming, and the minimum value at this time is d1min.

At this time, −0.9 <(R5a−R5b) / (R5a + R5b) <− 0.1 (1)
0.28 <(TD2 + TD3) / ft <0.34 (2)
-1.9 <f2 / fw <-1.3 (3)
0.1 <R6b / ft <0.17 (4)
30 <(d1t−d1min) / (d1w−d1min) <80 (5)
One or more of the following conditional expressions are satisfied.

  Next, the technical meaning of each conditional expression will be described.

  Conditional expression (1) relates to the shape factor (lens shape) of the positive lens in the third lens group L3. When the upper limit value or lower limit value of conditional expression (1) is exceeded, it is difficult to correct coma flare at the periphery of the screen in the wide-angle range.

  Conditional expression (2) is obtained by normalizing the sum of the axial thicknesses of the second lens unit L2 and the third lens unit L3 with the focal length at the telephoto end.

  If the upper limit of conditional expression (2) is exceeded and the axial thickness of the second lens unit L2 or the third lens unit L3 becomes too thick, the entire system becomes large.

  If the axial thickness of the second lens unit L2 or the third lens unit L3 becomes too thin beyond the lower limit value of the conditional expression (2), the air space between the two lenses in the second lens unit L2 becomes too narrow. The arrangement of the two lenses becomes difficult. Further, it is not good because it becomes difficult to correct the peripheral coma aberration in the wide angle region.

  Conditional expression (3) is obtained by normalizing the focal length of the second lens unit L2 with the focal length of the entire system at the wide-angle end.

  If the upper limit of conditional expression (3) is exceeded and the refractive power of the second lens unit L2 becomes too loose, the entire system will become large, which is not good.

  If the lower limit of conditional expression (3) is exceeded and the refractive power of the second lens group becomes too strong, it will be difficult to satisfactorily correct coma flare at the periphery of the screen in the wide-angle region.

  Conditional expression (4) is obtained by normalizing the radius of curvature of the image side surface of the negative lens of the third lens unit L3, that is, the image side surface of the cemented lens, with the focal length at the telephoto end.

  If the radius of curvature of the image side surface of the cemented lens becomes too large beyond the upper limit of conditional expression (4), the coma aberration at the periphery of the screen varies greatly from the intermediate zoom position to the telephoto range. . As a result, it becomes difficult to correct coma in the telephoto range from the intermediate zoom position.

  If the lower limit of conditional expression (4) is exceeded and the radius of curvature of the image side surface of the cemented lens becomes too small, that is, the shape of the concave surface becomes too strong, making it difficult to manufacture a negative lens.

  In each embodiment, the change in the interval between the first lens unit L1 and the second lens unit L2 is reduced by a minute amount at the zoom position (focal length fa) near the wide-angle end, and then increases greatly.

  Specifically, conditional expression (5) is satisfied. As a result, the curvature of field is favorably corrected at the zoom position near the wide-angle end.

  If the change in the interval in the wide-angle region becomes too small beyond the upper limit value of conditional expression (5), it becomes difficult to correct the curvature of field at the zoom position (focal length fa) near the wide-angle end.

  If the change in the interval in the wide-angle region becomes too large beyond the lower limit of conditional expression (5), it is necessary to ensure a sufficiently long interval between the first lens unit L1 and the second lens unit L2 at the wide-angle end, and the entire system is large. It is not good because it will turn into a

  In each embodiment, it is more preferable to set the numerical ranges of conditional expressions (1) to (5) as follows.

−0.8 <(R5a−R5b) / (R5a + R5b) <− 0.2 (1a)
0.30 <(TD2 + TD3) / ft <0.34 (2a)
−1.8 <f2 / fw <−1.4 (3a)
0.11 <R6b / ft <0.15 (4a)
33 <(d1t−d1min) / (d1w−d1min) <70 (5a) In each embodiment, a lens having a small refractive power on the object side of the first lens unit L1 or the image side of the fourth lens unit L4. Groups may be added.

  A teleconverter lens, a wide converter lens, or the like may be disposed on the object side or the image side.

  As described above, according to each embodiment, the lens configuration of each lens group, the moving method of each lens group during zooming, and the like are appropriately set. As a result, a zoom lens suitable for, for example, a digital still camera having a bright and high optical performance while having a zoom ratio of about 5 times while reducing the total length of the lens with a small number of lenses can be obtained. Yes.

  Next, numerical examples of the present invention will be shown. In each numerical example, i indicates the order of the surfaces from the object side, Ri is the radius of curvature of the i-th lens surface (i-th surface), and Di is the distance between the i-th surface and the (i + 1) -th surface. is there. Ni is the refractive index with respect to the d-line, and νi is the Abbe number.

  The two surfaces closest to the image side are surfaces constituting the optical block G.

The aspherical shape is defined as x when the displacement in the optical axis direction at the position of the height h from the optical axis is x with respect to the surface vertex.
X = (h ² / R) / [1+ {1− (1 + k) (h / R) ² } ^1/2 ] +
Ah ² + Bh ⁴ + Ch ⁶ + Dh ⁸ + Eh ¹⁰
It is represented by

  Where k is a conic constant, A, B, C, D, and E are second-order, fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients, and R is a paraxial radius of curvature.

“E-0X” means “× 10 ^−x ”. f represents a focal length, Fno represents an F number, and ω represents a half angle of view.

Table 1 shows the relationship between each conditional expression described above and each numerical example.

Numerical example 1

f = 6.76 to 32.19 Fno = 3.24 to 5.88 2ω = 59.6 to 13.6

R 1 = 36.425 D 1 = 0.90 N 1 = 1.846660 ν 1 = 23.9
R 2 = 20.870 D 2 = 2.60 N 2 = 1.804000 ν 2 = 46.6
R 3 = 423.219 D 3 = variable
* R 4 = -120.928 D 4 = 1.65 N 3 = 1.848620 ν 3 = 40.0
* R 5 = 5.369 D 5 = 1.97
R 6 = 9.531 D 6 = 1.70 N 4 = 1.922860 ν 4 = 18.9
R 7 = 21.305 D 7 = Variable
* R 8 = 5.124 D 8 = 2.30 N 5 = 1.882997 ν 5 = 40.8
R 9 = 16.216 D 9 = 0.70 N 6 = 1.808095 ν 6 = 22.8
R10 = 4.203 D10 = 0.52
R11 = 10.171 D11 = 1.80 N 7 = 1.487490 ν 7 = 70.2
R12 = -14.353 D12 = variable
R13 = 12.341 D13 = 1.80 N 8 = 1.487490 ν 8 = 70.2
R14 = 131.500 D14 = variable
R15 = ∞ D15 = 1.00 N 9 = 1.516 330 ν 9 = 64.1
R16 = ∞


\ Focal length 6.76 14.94 32.19
Variable interval \
D 3 1.20 6.79 16.40
D 7 15.09 4.97 1.17
D12 5.85 11.02 21.19
D14 4.69 6.23 3.85


Aspheric coefficient

4th: k = 0.00000e + 00 A = 0 B = 1.11274e-05
C = 0.00000e + 00 D = 0.00000e + 00 E = 0.00000e + 00

5th: k = -2.79279e + 00 A = 0 B = 1.72320e-03
C = -3.57723e-05 D = 8.38261e-07 E = -9.90647e-09

8th: k = -2.67014e-01 A = 0 B = -9.28612e-05
C = 2.70007e-06 D = -1.61409e-07 E = 0.00000e + 00

Numerical example 2

f = 6.76 to 32.35 Fno = 3.30 to 5.69 2ω = 59.6 to 13.6

R 1 = 33.137 D 1 = 0.90 N 1 = 1.846660 ν 1 = 23.9
R 2 = 19.192 D 2 = 2.80 N 2 = 1.804000 ν 2 = 46.6
R 3 = 242.172 D 3 = variable
* R 4 = -96.261 D 4 = 1.65 N 3 = 1.848620 ν 3 = 40.0
* R 5 = 5.396 D 5 = 1.89
R 6 = 9.316 D 6 = 1.80 N 4 = 1.922860 ν 4 = 18.9
R 7 = 20.239 D 7 = Variable
* R 8 = 5.232 D 8 = 2.10 N 5 = 1.882997 ν 5 = 40.8
R 9 = 8.992 D 9 = 0.90 N 6 = 1.922860 ν 6 = 18.9
R10 = 4.476 D10 = 0.49
R11 = 10.995 D11 = 1.70 N 7 = 1.603112 ν 7 = 60.6
R12 = -17.967 D12 = variable
R13 = 11.887 D13 = 1.80 N 8 = 1.487490 ν 8 = 70.2
R14 = 91.923 D14 = Variable
R15 = ∞ D15 = 1.00 N 9 = 1.516 330 ν 9 = 64.1
R16 = ∞

\ Focal length 6.76 15.26 32.35
Variable interval \
D 3 1.20 7.43 16.37
D 7 16.47 5.78 1.68
D12 7.50 12.19 20.99
D14 3.91 5.67 3.96


Aspheric coefficient

4th: k = 0.00000e + 00 A = 0 B = 1.61717e-05
C = 0.00000e + 00 D = 0.00000e + 00 E = 0.00000e + 00

5th: k = -2.66336e + 00 A = 0 B = 1.62355e-03
C = -3.08981e-05 D = 7.08247e-07 E = -8.07232e-09

8 sides: k = -2.08095e-01 A = 0 B = -1.18950e-04
C = 7.75056e-07 D = -1.84441e-07 E = 0.00000e + 00

Numerical example 3

f = 6.76 to 32.35 Fno = 2.93 to 5.35 2ω = 59.6 to 13.6

R 1 = 37.196 D 1 = 0.90 N 1 = 1.846660 ν 1 = 23.9
R 2 = 21.532 D 2 = 2.70 N 2 = 1.804000 ν 2 = 46.6
R 3 = 440.672 D 3 = variable
* R 4 = -107.214 D 4 = 1.65 N 3 = 1.848620 ν 3 = 40.0
* R 5 = 5.516 D 5 = 1.93
R 6 = 9.693 D 6 = 1.80 N 4 = 1.922860 ν 4 = 18.9
R 7 = 21.867 D 7 = Variable
* R 8 = 5.118 D 8 = 2.30 N 5 = 1.882997 ν 5 = 40.8
R 9 = 16.888 D 9 = 0.70 N 6 = 1.808095 ν 6 = 22.8
R10 = 4.211 D10 = 0.52
R11 = 10.186 D11 = 1.80 N 7 = 1.487490 ν 7 = 70.2
R12 = -14.473 D12 = variable
R13 = 14.277 D13 = 1.80 N 8 = 1.603112 ν 8 = 60.6
R14 = 91.600 D14 = variable
R15 = ∞ D15 = 0.50 N 9 = 1.516330 ν 9 = 64.1
R16 = ∞


\ Focal length 6.76 14.94 32.35
Variable interval \
D 3 1.20 7.61 17.46
D 7 14.85 4.83 1.01
D12 5.25 9.95 20.08
D14 4.84 6.36 3.70


Aspheric coefficient

4th: k = 0.00000e + 00 A = 0 B = 6.10931e-06
C = 0.00000e + 00 D = 0.00000e + 00 E = 0.00000e + 00

5th: k = -2.94241e + 00 A = 0 B = 1.67564e-03
C = -3.45129e-05 D = 7.52887e-07 E = -8.61464e-09

8 sides: k = -2.30344e-01 A = 0 B = -1.37478e-04
C = 2.42068e-06 D = -2.36697e-07 E = 0.00000e + 00

  Next, an embodiment of a digital still camera using the zoom lens as shown in the first to third embodiments as a photographing optical system will be described with reference to FIG.

  In FIG. 7, reference numeral 20 denotes a camera body, and reference numeral 21 denotes a photographing optical system constituted by any of the zoom lenses described in the first to fourth embodiments. Reference numeral 22 denotes a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor that receives a subject image formed by the photographing optical system 21 and is built in the camera body. A memory 23 records information corresponding to a subject image photoelectrically converted by the solid-state imaging device 22. Reference numeral 24 denotes a finder for observing a subject image formed on the solid-state image sensor 22, which includes a liquid crystal display panel or the like.

  In this way, by applying the zoom lens of the present invention to an imaging apparatus such as a digital still camera, a compact imaging apparatus having high optical performance can be realized.

Lens cross-sectional view of the zoom lens of Example 1 Various aberration diagrams at the wide-angle end of the zoom lens of Example 1 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 1 Various aberration diagrams at the telephoto end of the zoom lens of Example 1 Lens sectional view of the zoom lens of Example 2 Various aberration diagrams at the wide-angle end of the zoom lens of Example 2 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 2 Various aberration diagrams at the telephoto end of the zoom lens of Example 2 Lens sectional view of the zoom lens of Example 3 Various aberration diagrams at the wide-angle end of the zoom lens of Example 3 Various aberration diagrams at the intermediate zoom position of the zoom lens of Example 3 Various aberration diagrams at the telephoto end of the zoom lens of Example 3 Schematic diagram of main parts of an imaging apparatus of the present invention

Explanation of symbols

L1 1st lens group L2 2nd lens group L3 3rd lens group L4 4th lens group IP image plane d d line g g line ΔM d line meridional image plane ΔS d line sagittal image plane

Claims (10)

In order from the object side to the image side, the lens unit includes a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, and a fourth lens group having a positive refractive power. The first lens group is located on the object side at the telephoto end compared to the wide-angle end, the distance between the first lens group and the second lens group is changed, and the second lens group and the third lens group In the zoom lens in which each lens group moves during zooming so that the distance between the third lens group and the fourth lens group increases, the second lens group moves from the object side to the image side. order, and a negative lens, a positive lens, said third lens group comprises, in order from the object side to the image side, a cemented lens and a positive lens obtained by cementing a positive lens and a negative lens, the said second lens group 3 The thickness of the lens group on the optical axis is TD2, TD3, When the focal length of the entire system at the far end and ft,
0.28 <(TD2 + TD3) / ft <0.34
A zoom lens characterized by satisfying the following conditions: When the curvature radii of the object side surface and the image side surface of the positive lens closest to the object side in the third lens group are R5a and R5b, respectively.
−0.9 <(R5a−R5b) / (R5a + R5b) <− 0.1
The zoom lens according to claim 1 , wherein the following condition is satisfied. Wherein the first lens group, a zoom lens according to claim 1 or 2, characterized in that made of a cemented lens of a negative lens and a positive lens. The negative lens of the second lens group, at least one surface aspherical, the positive lens in the second lens group, 1 to claim, wherein the surface on the object side is a meniscus having a convex 4. The zoom lens according to any one of items 3 . The fourth lens group, the zoom lens according to any one of claims 1 to 4, characterized in that consists of a single positive lens. When the focal length of the second lens group is f2 and the focal length of the entire system at the wide angle end is fw, -1.9 <f2 / fw <-1.3.
The zoom lens according to any one of claims 1 to 5, characterized by satisfying the following condition. When the radius of curvature of the image side surface of the negative lens of the third lens group is R6b and the focal length of the entire system at the telephoto end is ft ,
0.1 <R6b / ft <0.17
The zoom lens according to any one of claims 1 to 6, characterized by satisfying the following condition. Each the distance between the second lens group and the third lens group at the wide-angle end and the telephoto end d1w, d1t, the interval between the second lens group and the first lens group minimum between the wide-angle end and the telephoto end When the minimum value at this time is d1min ,
30 <(d1t−d1min) / (d1w−d1min) <80
The zoom lens according to any one of claims 1 to 7, characterized by satisfying the following condition. The zoom lens according to any one of claims 1 to 8 and forming an image on a solid-state image sensor. An image pickup apparatus comprising: the zoom lens according to claim 1 ; and a solid-state image pickup device that receives an image formed by the zoom lens.