JP2015034892A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which has a zoom ratio of about two times and a super wide angle of view with a half angle of view of 55 degrees or more at the wide angle end, achieves excellent optical performance over the entire zoom range, is compact, has a small number of lenses and a small total length, and is excellent in portability.SOLUTION: The zoom lens includes four groups with, in order from the object side, negative, positive, negative and positive refractive power, respectively. The power is changed by changing the air intervals between the groups. During zooming from the wide angle end to the telephoto end, the interval between the first group L1 and the second group L2 is decreased, and the interval between the third group L3 and the fourth group L4 is changed. The first group L1 includes four lenses including three negative lenses. The zoom lens satisfies the following conditional expressions: (1) -1.1<f1/f2<-0.7, and (2) 2.5<f4/(fw×tanωW)<3.5, where fw is the focal distance of the system at the wide angle end, ft is the focal distance of the system at the telephoto end, f1 is the focal distance of the first group, f2 is the focal distance of the second group, f4 is the focal distance of the fourth group, and ωW is the half angle of view (degrees) at the wide angle end.

Description

The present invention relates to a compact and ultra-wide angle zoom lens suitable for an interchangeable-lens digital still camera and the like, and in particular, a zoom with excellent portability while ensuring a predetermined zoom ratio and shortening the total lens length. It relates to lenses.

  In recent years, in an imaging apparatus such as a digital still camera using a solid-state imaging element, the size of the entire apparatus has been reduced along with enhancement of functionality. In recent years, in the interchangeable lens type digital camera, with the abolition of the optical viewfinder, a digital camera genre that does not have a quick return mirror with a short flange back of the interchangeable lens has appeared. Along with this, as a wide-angle photographic optical system used for these, a zoom lens having a short lens total length and a compact and high performance is required.

  As a zoom lens having an ultra-wide angle of view at the wide-angle end, it consists of lens groups having negative, positive, positive, negative, and positive refractive power in order from the object side to the image side, and zooming is performed by moving each lens group. There is known a zoom lens in which the first group is composed of five lenses in the group zoom lens and has a super wide angle with a half angle of view of 55 degrees or more and a zoom ratio of about 2 (Patent Document 1). .

  A 4-group zoom that is compact and has a wide angle of view with a comparatively half angle of view of about 50 degrees, and is composed of lens groups with negative, positive, negative, and positive refractive power from the object side, and performs zooming by moving each lens group. There is known a zoom lens having a zoom ratio of about 2 in which the first group is composed of four lenses (Patent Document 2).

JP 2010-176096 A Japanese Patent Laid-Open No. 2002-244044

  In recent years, with the interchangeable lens digital camera, with the abolition of the optical viewfinder, a digital camera genre that does not have a quick return mirror with a short flange back of the interchangeable lens has appeared. Wide-angle lenses of these genres are expected to be ultra-wide-angle zoom lenses that have a wider angle of view than conventional ultra-wide-angle zooms, have a lens overall length and a front lens diameter that is smaller, and a zoom ratio of about 2 times. .

  Patent Document 1 discloses a zoom lens having a super wide angle with a half angle of view of 55 degrees or more and a zoom ratio of about 2 times. However, since it has five groups of negative, positive, positive, negative, and positive, the mechanical mechanism for making each lens group move as desired is complicated, and one group is composed of five lenses. Since the front lens diameter is large and the total lens length is long, it was not satisfactory in terms of portability.

  In Patent Document 2, the wide angle of view has a wide angle of view of about 50 degrees, and the total length of the four lenses in the group consisting of four groups of negative, positive, negative, and positive from the object side, and a wide angle for reducing the front lens diameter. A zoom lens is disclosed. However, there is a problem that the entire lens system becomes large when trying to cope with the desired super wide angle of 55 degrees or more in the same refractive power arrangement.

  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.

  In the interchangeable zoom lens used in the imaging apparatus described above, it is important that the entire lens system is downsized and has a predetermined angle of view and zoom ratio, and has good optical performance over the entire zoom range. It is.

  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 refractive power of each lens group is simply increased, aberration fluctuations accompanying zooming increase, and it becomes difficult to correct this well.

  The present invention has a simple and compact lens configuration, has a zoom ratio of about 2 times, has a super-wide angle of 55 ° or more at the wide angle end, and has achieved high optical performance over the entire zoom range. Nevertheless, the objective is to provide a zoom lens having excellent portability by reducing the front lens diameter, reducing the number of lenses and reducing the total length.

The configuration for achieving the above object is as follows:
A. In a zoom lens system comprising four groups of negative, positive, negative, and positive from the object side, and performing zooming by changing the air interval of each group,
B, During zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the third group and the fourth group changes.

    C, the first group is composed of four lenses including three negative lenses and satisfies the following conditional expression.

−1.1 <f1 / f2 <−0.7 (1)
2.5 <f4 / (fw × tan ωW) <3.5 (2)
fw: focal length of front system at wide angle end
ft: Focal length of the front system at the telephoto end
f1: Focal length of the first group
f2: Focal length of the second group
f4: Focal length of the fourth group
ωW: Half angle of view (degree)
Furthermore, a desirable configuration for approaching the best mode is to satisfy the following conditions.

    A, The following conditional expression must be satisfied in the lens system.

−1.8 <f1 / (fw × tan ωW) <− 1.2 (3)
−1.3 <d1W / f1 <−0.9 (4)
A. In the lens system, the first group is composed of four negative, negative, negative, and positive elements from the object side,
B, Satisfy the following conditional expression.

1.8 <R32 / fW <2.5 (5)
R32: Image-side radius of curvature of the third negative lens in the first lens group
A. In the lens system, the third group is composed of a single negative lens, and focusing is performed by retracting the third group to the image side.
B, Satisfy the following conditional expression.

0.15 <f1 / f3 <0.35 (6)
f3: Focal length of the third group
In the lens system, during the zooming from the wide-angle end to the telephoto end, the distance between the second group and the third group changes minutely, and the distance between the third group and the fourth group increases.

  According to the present invention, the above-described configuration further improves the conventional negative, positive, negative, and positive four groups, the lens, the refractive power arrangement of each group, the lens configuration of each group, the position of the aspheric surface, the moving method, Despite optimal arrangement of glass material usage, reduction in the number of lenses, and reduction in total lens length, the lens configuration is simple and has a zoom ratio of about 2 times, and a half angle of view at the wide-angle end. In spite of having an ultra wide angle of 55 ° or more and achieving high optical performance over the entire zoom range, it is possible to provide a zoom lens excellent in portability with a small front lens diameter.

Example 1 Lens cross section Example 2 Lens Cross Section Example 3 Lens Cross Section Example 4 Lens Cross Section Example 5 Lens Cross Section Example 1 Longitudinal aberration diagram Example 2 Longitudinal aberration diagram Example 3 Longitudinal aberration diagram Example 4 Longitudinal aberration diagram Example 5 Longitudinal aberration diagram

  In the present invention, the negative first group L1, the positive second group L2, the negative third group L3, and the positive fourth group L4 are sequentially arranged from the object side, and the magnification is changed by changing the air interval of each group. In the zoom lens, at least the first to third lens units move during zooming from the wide-angle end to the telephoto end. The air gap between the first and second groups decreases, the air gap between the second and third groups changes, and the air gap between the third and fourth groups increases.

  In the embodiment of the present invention, the configuration of each lens unit is set to the minimum number of lenses within a range in which excellent aberration correction can be performed while having a desired specification of an ultra-wide angle while having a zoom ratio of about 2 times.

  The first lens group includes 11 negative lenses on the object-side convex meniscus from the object side, 12 negative lenses on the object-side convex meniscus, 13 negative lenses with a strong concave surface on the image side, and a convex surface with a strong curvature on the object side. It consists of a total of four lenses, 14 positive lenses.

  The eleventh lens or the twelve lens has an aspherical surface and corrects distortion aberration in a wide angle region. The second group includes a positive 21 lens having a convex surface whose curvature on the object side is stronger than that on the object side, and a cemented lens in which a negative 22 lens having a strong concave surface on the image side and a positive 23 lens are cemented. The entire second group is composed of 3 to 4 lenses, and the stop SP is arranged in the second group or on the object side of the second group, and moves together with the second group during zooming.

  The third group is composed of a negative single lens having a concave surface on the image side, thereby reducing the weight of the focus group and enabling high-speed focus driving. The fourth group includes three lenses including two positive lenses and one negative lens, and includes one aspherical surface.

  In the present invention, a multi-group zoom type having a super wide field angle of ω55 ° or more and preceded by a negative group for avoiding an increase in the front lens diameter is adopted. Four groups of negative, positive, negative, and positive are used to secure the desired zoom ratio with a simple configuration. However, the speed of focus drive during still images is increased, and moving images are used. Considering the wobbling of the time, the third group, which is the focus group, is made lighter and is composed of a single lens, and since the power of the third group is set loosely, the zooming effect cannot be expected in the fourth group. .

Therefore, in the configuration of the present invention, the second group is responsible for main scaling, and the first to third groups as a whole have a positive power. In order to make the second group the main zooming ratio, it is necessary to leave a certain distance between the first group and the second group at the wide-angle end in order to ensure the desired zooming ratio. For this purpose, it is necessary to reduce the number of lenses in the first group and to appropriately set the refractive power of the first group with respect to the second group.

That is, the focal lengths of the first group and the second group are −1.1 <f1 / f2 <−0.7 (1)
f1: Focal length of the first group
f2: It may be set so as to satisfy the focal length of the second group.

  Further, as described above, in order to reduce the front lens diameter, it is desired to reduce the number of lenses in the first group to the limit. However, the power of the first group is maintained strong enough to satisfy the expression (1). In order to satisfactorily correct the desired off-axis aberration in the super-wide-angle region, at least four lenses are required, so a four-lens configuration including three negative lenses is adopted.

  In the present invention, the first to third groups as a whole have a group configuration having a positive power. Therefore, in order to shorten the overall lens length, it is necessary to appropriately set the focal length of the fourth group as follows. is there.

2.5 <f4 / (fw × tan ωW) <3.5 (2)
fw: focal length of front system at wide angle end
f4: focal length of the fourth lens unit ωW: half angle of view (degrees) at wide angle end
By making the power of the fourth group moderately strong, it is possible to shorten the total lens length while maintaining a desired focal length as the entire system.

  As described above, the expression (1), the expression (2), and the lens configuration of the first group make it possible to provide a compact lens system including a super wide angle and a desired zoom ratio.

  The object of the present invention can be achieved by the above two formulas, but more preferably, the power and angle of view constituting the first group and the air spacing between the first and second groups at the wide angle end are appropriately set as follows: It is desirable to set to.

−1.8 <f1 / (fw × tan ωW) <− 1.2 (3)
−1.3 <d1W / f1 <−0.9 (4)
d1w: Air spacing between the first group and the second group at the wide-angle end As described above, in the present invention, the second group is set as the main zooming ratio. The air separation of the second group needs to be increased to some extent. For this reason, the first group power is set to be strong enough to satisfy the expression (3) and the expression (4) is satisfied in order to reduce the front lens diameter. It is desirable to set the air interval.

  Thus, a desirable lens system of the present invention can be obtained. However, in order to further reduce the front lens diameter, it is desirable to appropriately set the lens configuration of the first group. That is, the front lens diameter is kept small by reducing the height of the off-axis light beam passing through the first group by making the principal point position of the first group fly to the object side.

  In other words, the first group is composed of four negative, negative, negative, and positive elements from the object side, and the image side surface of the negative lens is a strong concave surface. In particular, the shape of the third concave lens on the image side is preferably set so as to satisfy the following conditional expression.

1.8 <R32 / fW <2.5 (5)
R32: Image-side radius of curvature of the third negative lens in the first lens group
Thus, a desirable lens system according to the present invention can be obtained. However, in order to further increase the focus speed, the third group is composed of a single negative lens for weight reduction. It is preferable that focusing be performed by moving the lens toward the image side.

If the third lens unit is a single lens, it is necessary to set the power of the third lens unit relatively loosely and appropriately in order to correct the variation in curvature of field due to the focus, and the first lens unit is the focal point of the third lens unit. The distance ratio is
0.15 <f1 / f3 <0.35 (6)
f3: Focal length of the third group
It is better to satisfy

  In this way, the third lens group is relatively loose and the combined power of the first lens group to the third lens group is positive, and the zooming effect of the fourth lens group cannot be expected. Therefore, in order to suppress aberration fluctuation during zooming of the previous system, During zooming from the wide-angle end to the telephoto end, the distance between the second group and the third group changes minutely, the distance between the third group and the fourth group increases, and the movement of the fourth group is a minute amount. Or fixed.

  Next, the meaning of each conditional expression will be described. The expression (1) relates to the ratio of the focal lengths of the first group and the second group. If the focal length of the first group becomes too short beyond the upper limit of the expression (1), the frame at the periphery of the screen in the wide-angle range will be described. It becomes difficult to correct flare.

  If the focal length of the first group becomes too long beyond the lower limit of the expression (1), the height of the off-axis light beam passing through the first group in the wide angle region becomes high, and the front lens diameter increases.

  The expression (2) is obtained by normalizing the focal length of the fourth group by the product of the total system focal length at the wide angle end and the tan of the angle of view at the wide angle end, and exceeds the upper limit of the expression (2). If the focal length of the lens becomes too long, the total lens length increases, which is not good. If the focal length of the fourth group becomes too short beyond the lower limit of the expression (2), it is not good because it becomes difficult to correct distortion aberration in the telephoto range.

  Equation (3) is obtained by normalizing the focal length of the first group by the product of the focal length of the entire system and the tan of the angle of view at the wide angle end. The focal length of the first group exceeds the upper limit of equation (3). If it becomes too short, it becomes difficult to correct the frame flare around the screen in the wide-angle range.

  Formula (4) is obtained by standardizing the air gap between the first group and the second group at the wide-angle end by the focal length of the first group, and exceeds the upper limit value of the formula (4) and the air of the first group and the second group. If the interval is too small, it is necessary to increase the power of each group in order to obtain a desired zoom ratio, and it becomes difficult to correct off-axis coma flare in the wide angle region and spherical aberration in the telephoto region. If the air gap between the first group and the second group becomes too large beyond the lower limit of the expression (4), the height of the off-axis light beam passing through the first group becomes high, and the front lens diameter increases.

  Expression (5) is obtained by normalizing the image-side curvature radius on the image side of the third negative lens in the first group by the focal length of the entire system at the wide-angle end, and exceeds the upper limit of expression (5). If the image side radius of curvature on the image side of the middle third negative lens becomes too large, the principal point position of the first group becomes the image side from the desired value and the front lens diameter increases, which is not good. If the image side curvature radius on the image side of the third negative lens in the first group becomes too small beyond the lower limit of the expression (5), off-axis coma flare in the wide angle region increases and aberration correction becomes difficult. So not good.

  Expression (6) relates to the ratio of the focal lengths of the first group and the third group. If the focal length of the third group becomes too short beyond the upper limit of the expression (6), the chromatic aberration during focusing in the entire zoom range will be described. This is not good because the fluctuation will increase and the optical performance in the immediate vicinity will deteriorate. When the focal length of the third lens unit becomes too long beyond the lower limit of equation (6), the amount of movement at the time of focusing increases, and if a desired close distance is ensured, an air gap from the fourth lens unit in the infinite state must be kept. This is not good because the entire lens system becomes larger.

In order to bring the object of the present invention closer to the best, it is better to satisfy the following conditions.
−1.0 <f1 / f2 <−0.8 (1) ′
2.8 <f4 / (fw × tan ωW) <3.4 (2) ′


−1.6 <f1 / (fw × tan ωW) <− 1.2 (3) ′
−1.2 <d1W / f1 <−1.0 (4) ′


1.9 <R32 / fW <2.2 (5) ′
0.16 <f1 / f3 <0.30 (6) ′

[Numerical example 1]
Unit mm

Surface data surface number rd nd vd
1 52.236 2.27 1.80 400 46.6
2 22.643 5.08
3 * 39.699 2.14 1.76802 49.2
4 * 11.651 8.96
5 565.221 1.32 1.49700 81.5
6 20.184 0.33
7 20.337 5.80 1.80610 33.3
8 156.960 (variable)
9 * 19.789 2.50 1.85135 40.1
10 161.265 2.38
11 (Aperture) ∞ 2.51
12 -1322.224 0.88 1.80610 33.3
13 9.075 2.95 1.59282 68.6
14 -45.568 1.50
15 -9.097 1.00 1.74400 44.8
16 -10.342 0.20
17 145.222 3.00 1.48749 70.2
18 -16.432 (variable)
19 41.382 1.01 1.60311 60.6
20 21.057 (variable)
21 41.899 3.50 1.69680 55.5
22 88.238 1.47
23 -207.607 1.20 1.80518 25.4
24 82.361 5.50 1.55332 71.7
25 * -25.235 (variable)
Image plane ∞

Aspheric data 3rd surface
K = 1.73749e + 000 A 4 = -2.00471e-006 A 6 = -2.73232e-008 A 8 = 4.05418e-011 A10 = -2.83725e-014

4th page
K = -5.54985e-001 A 4 = -2.77946e-005 A 6 = 5.27189e-008 A 8 = -1.01452e-009 A10 = 2.86908e-012 A12 = -4.11559e-015

9th page
K = -3.04293e + 000 A 4 = 3.50635e-005

25th page
K = -8.55389e + 000 A 4 = -6.88696e-006 A 6 = -1.29326e-007 A 8 = 2.99310e-009 A10 = -1.82976e-011 A12 = 3.80322e-014

Various data Zoom ratio 1.90
Wide angle Medium telephoto focal length 9.22 14.67 17.50
F number 3.45 4.02 4.63
Angle of view 55.92 42.90 37.92
Image height 13.63 13.63 13.63
Total lens length 94.76 85.16 91.16
BF 13.06 15.35 13.60

d 8 21.40 4.12 2.43
d18 0.72 3.87 2.81
d20 4.08 6.32 16.82
d25 13.06 15.35 13.60

Zoom lens group data group Start surface Focal length
1 1 -19.96
2 9 22.57
3 19 -72.44
4 21 43.42


[Numerical Example 2]

Unit mm

Surface data surface number rd nd vd
1 34.999 2.10 1.77250 49.6
2 22.427 7.27
3 * 48.838 1.80 1.85400 40.4
4 * 10.945 8.97
5 -299.505 1.20 1.49700 81.5
6 18.827 0.33
7 19.250 6.00 1.80610 33.3
8 391.349 (variable)
9 * 14.902 2.50 1.85135 40.1
10 58.539 2.38
11 (Aperture) ∞ 2.51
12 -171.910 0.80 1.80610 33.3
13 8.065 3.00 1.59282 68.6
14 -80.205 0.20
15 63.619 1.50 1.48749 70.2
16 -21.679 (variable)
17 84.987 1.01 1.60311 60.6
18 35.313 (variable)
19 -742.321 3.00 1.48749 70.2
20 -70.847 0.30
21 -99.264 1.20 1.80518 25.4
22 1657.363 4.00 1.55332 71.7
23 * -21.133 (variable)
Image plane ∞

Aspheric data 3rd surface
K = 3.22156e + 000 A 4 = -1.15092e-005 A 6 = 2.28900e-009

4th page
K = -5.31573e-001 A 4 = -3.62301e-005 A 6 = -4.22166e-008 A 8 = -6.52894e-010 A10 = 1.67100e-012 A12 = -4.10228e-015

9th page
K = -2.96389e-001 A 4 = -1.18437e-005

23rd page
K = -5.28699e-001 A 4 = 4.41358e-005 A 6 = -2.20924e-007 A 8 = 1.76980e-009 A10 = -3.59267e-012 A12 = -9.21025e-015

Various data Zoom ratio 1.90
Wide angle Medium telephoto focal length 9.22 13.78 17.50
F number 3.41 4.03 4.63
Angle of view 55.92 44.68 37.91
Image height 13.63 13.63 13.63
Total lens length 89.75 83.68 86.02
BF 14.29 15.85 16.07

d 8 19.98 6.84 2.12
d16 0.73 3.17 4.00
d18 4.68 7.75 13.76
d23 14.29 15.85 16.07

Zoom lens group data group Start surface Focal length
1 1 -19.03
2 9 21.93
3 17 -100.94
4 19 41.13


[Numerical Example 3]


Unit mm

Surface data surface number rd nd vd
1 37.271 2.10 1.77250 49.6
2 21.903 6.80
3 * 44.028 1.80 1.80610 40.7
4 * 10.574 8.93
5 -142.155 1.20 1.49700 81.5
6 19.083 0.33
7 19.620 6.00 1.80610 33.3
8 253.506 (variable)
9 * 14.543 2.50 1.85 135 40.1
10 65.640 2.38
11 (Aperture) ∞ 2.51
12 -260.717 0.80 1.80610 33.3
13 7.765 3.00 1.59282 68.6
14 -196.362 0.20
15 50.064 1.50 1.48749 70.2
16 -18.968 (variable)
17 78.617 1.01 1.60311 60.6
18 33.578 (variable)
19 -69.130 1.20 1.80518 25.4
20 -265.624 4.00 1.55332 71.7
21 * -19.443 0.30
22 -57.133 2.30 1.69680 55.5
23 -45.231 (variable)
Image plane ∞

Aspheric data 3rd surface
K = 2.35102e + 000 A 4 = -1.58566e-005 A 6 = 3.29848e-009

4th page
K = -5.56155e-001 A 4 = -4.81002e-005 A 6 = -5.03501e-008 A 8 = -8.23037e-010 A10 = 1.77719e-012 A12 = -5.03583e-015

9th page
K = -1.36588e + 000 A 4 = 2.72102e-005

21st page
K = -9.29437e-001 A 4 = 4.24397e-005 A 6 = -9.47681e-008 A 8 = 2.00252e-009 A10 = -1.58386e-011 A12 = 4.79917e-014

Various data Zoom ratio 1.93
Wide angle Medium Telephoto focal length 9.05 13.80 17.50
F number 3.31 3.97 4.63
Angle of view 56.41 44.64 37.92
Image height 13.63 13.63 13.63
Total lens length 87.28 81.88 85.17
BF 13.60 14.72 13.98

d 8 18.62 6.31 2.70
d16 0.63 4.15 4.02
d18 5.58 7.83 15.61
d23 13.60 14.72 13.98

Zoom lens group data group Start surface Focal length
1 1 -17.01
2 9 20.45
3 17 -98.01
4 19 45.57


[Numeric Example 4]

Unit mm

Surface data surface number rd nd vd
1 * 36.138 2.10 1.77250 49.6
2 * 16.216 6.42
3 44.824 1.80 1.83481 42.7
4 14.107 8.77
5 -145.804 1.20 1.49700 81.5
6 18.004 0.33
7 18.089 6.00 1.80610 33.3
8 110.432 (variable)
9 * 16.505 2.50 1.85135 40.1
10 112.363 2.38
11 (Aperture) ∞ 2.51
12 710.621 0.80 1.80610 33.3
13 7.939 3.00 1.59282 68.6
14 -256.107 0.20
15 39.095 1.50 1.48749 70.2
16 -21.225 (variable)
17 -208.408 1.01 1.60311 60.6
18 35.031 (variable)
19 321.728 2.30 1.69680 55.5
20 -74.152 0.30
21 -107.035 1.20 1.80518 25.4
22 536.307 4.00 1.55332 71.7
23 * -21.743 (variable)
Image plane ∞

Aspheric data 1st surface
K = -1.55315e-001 A 4 = -4.45719e-007 A 6 = 2.36421e-009

Second side
K = -4.85781e-001 A 4 = -8.57586e-006 A 6 = -1.63780e-008 A 8 = 1.02830e-011 A10 = -2.31214e-013 A12 = 3.58450e-017

9th page
K = -6.38403e-001 A 4 = -2.35589e-006

23rd page
K = -1.92669e + 000 A 4 = 2.50414e-005 A 6 = -4.54234e-007 A 8 = 5.48879e-009 A10 = -3.02194e-011 A12 = 6.33221e-014

Various data Zoom ratio 1.90
Wide angle Medium telephoto focal length 9.22 14.46 17.50
F number 3.45 4.07 4.63
Angle of view 55.92 43.31 37.92
Image height 13.63 13.63 13.63
Total lens length 89.91 83.13 88.10
BF 14.39 17.97 17.89

d 8 19.15 4.75 2.10
d16 0.80 3.77 4.71
d18 7.24 8.32 15.07
d23 14.39 17.97 17.89


[Numerical example 5]


Unit mm

Surface data surface number rd nd vd
1 38.127 2.10 1.77250 49.6
2 22.633 6.85
3 * 42.938 1.80 1.80610 40.7
4 * 10.737 8.92
5 645.666 1.20 1.49700 81.5
6 19.581 0.33
7 19.669 6.00 1.80610 33.3
8 338.400 (variable)
9 (Aperture) ∞ 1.00
10 * 14.399 2.50 1.85 135 40.1
11 75.359 2.50
12 75.790 0.80 1.80610 33.3
13 7.149 3.00 1.59282 68.6
14 60.806 0.20
15 260.990 1.50 1.48749 70.2
16 -17.123 (variable)
17 48.334 1.01 1.60311 60.6
18 23.645 (variable)
19 -153.617 2.30 1.69680 55.5
20 -66.497 0.30
21 -100.917 1.20 1.80518 25.4
22 93.931 4.00 1.55332 71.7
23 * -19.752 (variable)
Image plane ∞

Aspheric data 3rd surface
K = 1.46085e + 000 A 4 = -1.97045e-005 A 6 = 1.89775e-008

4th page
K = -5.51089e-001 A 4 = -4.02384e-005 A 6 = -1.05185e-007 A 8 = -2.91571e-010 A10 = 1.44932e-012 A12 = -4.04448e-015

10th page
K = -1.29404e + 000 A 4 = 2.63753e-005

23rd page
K = -3.42770e + 000 A 4 = 6.66588e-006 A 6 = -1.95765e-007 A 8 = 3.59816e-009 A10 = -1.85487e-011 A12 = 2.78836e-014

Various data Zoom ratio 1.90

Focal length 9.22 13.18 17.50
F number 3.63 4.14 4.63
Angle of view 55.92 45.97 37.92
Image height 13.63 13.63 13.63
Total lens length 92.01 84.54 82.03
BF 13.47 14.54 16.19

d 8 23.76 10.45 2.10
d16 0.71 1.20 2.65
d18 6.56 10.84 13.59
d23 13.47 14.54 16.19

Zoom lens group data group Start surface Focal length
1 1 -21.38
2 9 20.94
3 17 -77.95
4 19 42.00


Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view of Example 1 according to the embodiment of the present invention.

[Example 1]
The configuration of the first embodiment of the present invention will be described below with reference to FIG. A) B) C) respectively show the wide-angle end, the middle, and the telephoto end. At the three zoom positions, the first and second groups decrease, the second and third group intervals increase from the wide-angle end to the middle, and decrease from the middle to the telephoto end. The air interval at the telephoto end at the second and third group intervals is larger than at the wide angle end. The distance between groups 3 and 4 increases.

[Examples 2 to 5]
Hereinafter, sectional views of Examples 2 to 5 are shown in FIGS. In the third embodiment, the basic interval change is the same as in the first embodiment. In Examples 2, 4, and 5, the distance between the second and third lens groups increases from the wide-angle end to the middle, and further increases slightly from the middle to the telephoto end. In the second to fifth embodiments, the third and fourth group intervals increase as in the first embodiment.

  In Examples 1 to 5, the first group reciprocates along the convex locus toward the image side. The second group and the third group move to the object side. The fourth group moves toward the minute object side. The fourth group moves a minute amount in Examples 1 to 5, but may be fixed during zooming. Further, focusing is performed by moving the third lens group toward the image side.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact and ultra-wide angle zoom lens suitable for an interchangeable lens digital still camera and the like, and in particular, a zoom lens excellent in portability that ensures a predetermined zoom ratio and shortens the overall length of the lens. It is about.

In aberration diagrams, d is d-line, g is g-line, ΔM is meridional image plane, IP is image plane

Claims (5)

A, consisting of four groups, negative, positive, negative, positive from the object side, in a zoom lens system that performs zooming by changing the air spacing of each group,
B, During zooming from the wide-angle end to the telephoto end, the distance between the first group and the second group decreases, and the distance between the third group and the fourth group changes.
C. The zoom lens according to claim 1, wherein the first lens group includes four lenses including three negative lenses and satisfies the following conditional expression.
−1.1 <f1 / f2 <−0.7 (1)
2.5 <f4 / (fw × tan ωW) <3.5 (2)
fw: focal length of front system at wide angle end
ft: Focal length of the front system at the telephoto end
f1: Focal length of the first group
f2: Focal length of the second group
f4: Focal length of the fourth group
ωW: Half angle of view (degree) A. The zoom lens according to item 1, which satisfies the following conditional expression in the lens system:
−1.8 <f1 / (fw × tan ωW) <− 1.2 (3)
−1.3 <d1W / f1 <−0.9 (4)
d1w: Air spacing between the first group and the second group at the wide-angle end A. In the lens system, the first group is composed of four negative, negative, negative, and positive elements from the object side,
3. The zoom lens according to claim 1, wherein the zoom lens satisfies the following conditional expression.
1.8 <R32 / fW <2.5 (5)
R32: Image-side radius of curvature of the third negative lens in the first lens group A. In the lens system, the third group is composed of a single negative lens, and focusing is performed by retracting the third group to the image side.
The zoom lens according to any one of claims 1 to 3, wherein B satisfies the following conditional expression.
0.15 <f1 / f3 <0.35 (6)
f3: Focal length of the third group In the lens system, during zooming from the wide-angle end to the telephoto end, the distance between the second group and the third group changes minutely, and the distance between the third group and the fourth group increases. The zoom lens according to any one of claims 1 to 4.