JP2011232410A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized zoom lens with high performance and high image quality.SOLUTION: A zoom lens comprises a first lens group G1 being negative, a second lens group G2 being negative, and a third lens group G3 being positive. The first lens group G1 comprises a first lens L1 being negative and a prism P, the second lens group G2 comprises a second lens L2 being positive and a third lens L3 being negative, and the third lens group G3 comprises a diaphragm ST, a fourth lens L4 being positive, and a fifth lens L5 being negative. In variable power from wide-angle end to telephoto end in this structure, the first lens group G1 is fixed, the second lens group G2 is moved to an image side and then moved to an object side, and the third lens group G3 is moved linearly to the object side.

Description

  The present invention relates to a zoom lens that forms a subject image on an image sensor such as a CCD sensor or a CMOS sensor.

  In recent years, not only digital still cameras but also small devices such as mobile phones, personal digital assistants, internet cameras, etc., mounting of zoom lenses has begun to be considered as a new added value, and actually mounted devices have also appeared. I'm starting. The zoom lens is an optical system in which a part of lenses and a lens group constituting the lens system move along the optical axis, and can continuously change the photographing magnification. By mounting the zoom lens, the user can enlarge or reduce the subject image to an arbitrary size at the time of shooting.

  When it is assumed that the zoom lens is mounted on a small device, it is desirable that the total length of the zoom lens is as short as possible. However, in a zoom lens, at the time of zooming and focusing, it is necessary to move at least two lens groups among the lens groups constituting the zoom lens, so that a space for moving these lens groups is provided in the zoom lens. Must be secured. This is an obstacle to downsizing the zoom lens.

On the other hand, the number of pixels of an image sensor that captures an object image as an electrical signal is increasing year by year, and zoom lenses are also required to have high performance such as good aberration correction capability and high resolution. In Patent Document 1, a first lens group composed of one lens having negative refractive power, a second lens group composed of two positive and negative lenses and having negative refractive power as a whole, and positive lenses are disclosed. There is described a zoom lens composed of a third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power. This zoom lens can be reduced in size relatively well while keeping the combined focal length at the wide-angle end of the first lens group and the second lens group within a certain range while having a high variable magnification of about 3 times. It is illustrated.
JP 2001-343588 A

  However, although the zoom lens described in Patent Document 1 corrects aberrations relatively well with a small number of lenses, it does not sufficiently satisfy the demands for high performance and miniaturization.

  Note that such demands for high performance and miniaturization are not limited to small devices such as mobile phones. In devices such as digital still cameras, image scaling, in particular optical scaling with little image degradation, is desired. On the other hand, a reduction in thickness for improving portability is also strongly desired.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a high-performance and compact zoom lens that satisfies high image quality.

  In order to solve the above problems, in the present invention, in order from the object side to the image plane side, a first lens group having a negative refractive power, a second lens group having a negative refractive power, and a positive refractive power. In the zoom lens configured by arranging the third lens group having the first lens group, the first lens group includes a lens having a negative refractive power in which the radius of curvature of the surface on the image plane side is positive, and the progress of incident light. An optical path changing member that changes the direction, and the second lens group includes a lens having a positive refractive power with a positive radius of curvature of the object side surface and a negative radius of curvature of the object side surface. The third lens group is composed of a lens having a positive refractive power and a lens having a negative refractive power with a radius of curvature of the object side surface being positive.

  In the zoom lens according to the present invention, in zooming from the wide-angle end to the telephoto end, the first lens group is fixed, and the second lens group is moved to the object side after moving to the image plane side, The third lens group is configured to move linearly toward the object side.

  According to the above configuration, the lens groups that are moved during zooming and focusing are only two lens groups, the second lens group and the third lens group. Of these, the second lens group is composed of two positive and negative lenses. For this reason, the lateral chromatic aberration and distortion generated in the first lens group are corrected well by the two positive and negative lenses in the second lens group. In addition, in zooming from the wide-angle end to the telephoto end, the second lens group temporarily moves to the image plane side and then moves to the object side. Therefore, the movement locus becomes concave on the object side. According to the zoom lens of the present invention, the space to be secured for moving the lens group can be minimized as compared with the zoom lens of the type in which the second lens group moves linearly or parabolically. It becomes possible. Therefore, by adopting such a configuration as a zoom lens, both high performance and small size can be achieved.

  In the zoom lens having the above configuration, a prism that reflects incident light and bends the optical path can be applied as the optical path changing member. By applying the prism, a bent (L type) zoom lens can be configured. In particular, a small portable device such as a mobile phone has a very limited space in which a zoom lens can be mounted. According to the present invention, the thickness of a device on which a zoom lens is mounted can be greatly reduced.

In the zoom lens having the above configuration, when the combined focal length at the wide angle end of the first lens group, the second lens group, and the third lens group is fw, and the focal length of the first lens group is f1, the following conditional expression It is desirable to satisfy (1).
−0.3 <fw / f1 <−0.05 (1)

  Conditional expression (1) is a condition for suppressing on-axis chromatic aberration and off-axis lateral chromatic aberration within a favorable range while shortening the length of the zoom lens in the optical axis direction. If the upper limit value “−0.05” is exceeded, the refractive power of the first lens group becomes relatively weak, so that the refractive power of the second lens group needs to be relatively strong. In this case, although axial chromatic aberration and off-axis lateral chromatic aberration can be suppressed within a favorable range, the diameter of the lens constituting the first lens group becomes large, and it becomes difficult to reduce the size of the zoom lens. . On the other hand, if the value falls below the lower limit “−0.3”, the refractive power of the first lens group becomes relatively strong, which is advantageous for downsizing of the zoom lens, but on-axis chromatic aberration and off-axis magnification. It becomes difficult to suppress chromatic aberration within a favorable range.

In the zoom lens configured as described above, it is desirable that the following conditional expression (2) is satisfied, where f1 is the focal length of the first lens group and f3 is the focal length of the third lens group.
−0.5 <f3 / f1 <−0.1 (2)

  Conditional expression (2) is a condition for prescribing the movement mode of the second lens group and maintaining off-axis imaging performance at a constant level in the entire zooming range. By satisfying the conditional expression (2), the position on the optical axis of the second lens group at the wide-angle end and the position on the optical axis of the second lens group at the telephoto end substantially coincide in zooming. That is, by satisfying this conditional expression (2), the distance between the first lens group and the second lens group becomes a substantially constant value at the wide-angle end and the telephoto end, and the zoom lens can be reduced in size.

  Here, if the upper limit “−0.1” in conditional expression (2) is exceeded, the refractive power of the first lens group becomes relatively weak, the diameter of the lens constituting the first lens group becomes large, and Since the second lens group moves greatly toward the image plane at the telephoto end, it is difficult to reduce the size of the zoom lens. On the other hand, when the value falls below the lower limit “−0.5”, the refractive power of the first lens group becomes relatively strong, so that the second lens group moves greatly toward the object side at the telephoto end, and the It becomes difficult to suppress chromatic aberration, off-axis lateral chromatic aberration, and off-axis coma aberration within a favorable range. Also in this case, it is difficult to reduce the size of the zoom lens.

In the zoom lens configured as described above, it is desirable that the following conditional expression (3) is satisfied, where f2 is the focal length of the second lens group and f3 is the focal length of the third lens group.
−0.6 <f3 / f2 <−0.3 (3)

  Conditional expression (3) is a condition for suppressing various aberrations within a favorable range over the entire zooming range. When the value exceeds the upper limit “−0.3”, the refractive power of the second lens group becomes relatively weak, which is effective in suppressing chromatic aberration within a favorable range. Since it moves greatly to the image plane side, it is difficult to reduce the size of the zoom lens. In addition, it is difficult to correct off-axis coma and maintain the flatness of the image surface. On the other hand, when the value is below the lower limit “−0.6”, the refractive power of the second lens group becomes relatively strong, which is advantageous for downsizing the zoom lens, but the axial chromatic aberration is within a favorable range. If it is attempted to suppress, the off-axis lateral chromatic aberration will be overcorrected, making it difficult to suppress both in a balanced manner. Further, inward coma due to off-axis light increases on the wide-angle end side, and outward coma aberration increases on the telephoto end side, making it difficult to obtain good imaging performance over the entire zooming range.

Further, in the zoom lens having the above-described configuration, the Abbe number of the lens having positive refractive power in the second lens group is νd2p, the Abbe number of the lens having negative refractive power in the second lens group is νd2n, and the third lens group. When the Abbe number of a lens having positive refractive power at νd3p and the Abbe number of a lens having negative refractive power in the third lens group are νd3n, it is desirable to satisfy the following conditional expression (4).
0.5 <| νd2p−νd2n | / | νd3p−νd3n | <0.8 (4)

  Conditional expression (4) is a condition for suppressing the axial chromatic aberration and the off-axis lateral chromatic aberration within a favorable range in a well-balanced manner over the entire zooming range. When the value exceeds the upper limit “0.8”, the imaging position for each wavelength is greatly different, particularly on the telephoto end side, and the short wavelength is in the plus direction (image plane side) with respect to the reference wavelength. As a result, the axial chromatic aberration is overcorrected, and it is difficult to obtain good imaging performance over the entire zooming range. On the other hand, when the value is below the lower limit “0.5”, the short wavelength is in the minus direction (object side) with respect to the reference wavelength, and both on-axis chromatic aberration and off-axis lateral chromatic aberration are undercorrected. Also in this case, it is difficult to obtain good imaging performance over the entire zooming range.

  According to the zoom lens of the present invention, it is possible to provide a high-performance and compact zoom lens that satisfies high image quality.

1 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 1 according to an embodiment that embodies the present invention. FIG. 6 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1 of the same numerical value. FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position of the zoom lens according to Numerical Example 1; FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Example 1 of the same numerical value. FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 2. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 2; FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 2; FIG. 4 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 3. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 3; FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 4. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 4; FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 5. FIG. 12 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 5; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 5; FIG. 12 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 5;

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  1, 8, 15, 22, and 29 are sectional views of zoom lenses corresponding to Numerical Examples 1 to 5 of the present embodiment. Each drawing also shows a lens cross-sectional view at the wide-angle end, a lens cross-sectional view at an intermediate position between the wide-angle end and the telephoto end, and a lens cross-sectional view at the telephoto end. Since any of the numerical examples has the same basic lens configuration, the lens configuration of the present embodiment will be described with reference to the lens cross-sectional view of Numerical Example 1.

  The zoom lens according to the present embodiment has a three-group configuration. As shown in FIG. 1, in order from the object side, a first lens group G1 having a negative refractive power and a second lens group having a negative refractive power. G2 and a third lens group G3 having a positive refractive power. A filter 10 is disposed between the third lens group G3 and the image plane IM of the image sensor. This filter 10 can be omitted.

  In the zoom lens according to the present embodiment, the first lens group G1 is fixed, and the second lens group G2 and the third lens group G3 are configured to be movable along the optical axis X. In this configuration, when zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the object side after moving to the image plane side, and the third lens group G3 moves along the optical axis X. Will move to the side. That is, the second lens group G2 moves along the optical axis X so that its movement locus is concave toward the object side, and the third lens group G3 has its movement locus in a direction approaching the second lens group G2. It moves along the optical axis X so as to be linear.

  Thus, in the zoom lens according to the present embodiment, zooming is performed by the movement of the third lens group G3, and focusing and back focus are adjusted by the movement of the second lens group G2. The image point is kept constant over the entire area.

  In the zoom lens configured as described above, the first lens group G1 includes, in order from the object side, a first lens L1 having negative refractive power and a prism P (optical path changing member) that reflects incident light and bends the optical path at a right angle. Composed. Of these, the first lens L1 has a shape in which both the radius of curvature of the object-side surface and the radius of curvature of the image-side surface are positive, that is, a shape that becomes a meniscus lens with a convex surface facing the object side in the vicinity of the optical axis X. Formed.

  In the present embodiment, the prism P is applied as the optical path changing member. By adopting the prism P as the optical path changing member in this way, it becomes possible to configure a bent (L type) zoom lens. In particular, in a small portable device such as a mobile phone, a space in which a zoom lens can be mounted is very limited, and there is often no design margin in the thickness direction of the device. If the present invention is embodied as a bent zoom lens, the thickness of the device can be greatly reduced, which contributes to the reduction in size and thickness of the portable device.

  The optical path changing member is not limited to the prism P of the present embodiment. For example, a flat mirror may be disposed behind the first lens L1, and the optical path may be bent at a right angle by reflecting incident light from the first lens L1 by this mirror (optical path changing member). Further, when it is relatively easy to secure a space for mounting the zoom lens, a lens may be applied as the optical path changing member. By applying a lens as the optical path changing member, various aberrations can be corrected more satisfactorily. In short, as the optical path changing member, various members can be applied as long as they are optical members having a negative refractive power combined with the first lens L1 constituting the first lens group G1, and any one of a prism, a mirror, and a lens is applicable. Alternatively, or a combination thereof can be applied as appropriate. For convenience, in each of the lens cross-sectional views of FIGS. 1, 8, 15, 22, and 29, the prism P is represented as a plane parallel plate equivalent to its optical path length.

  The second lens group G2 includes, in order from the object side, a second lens L2 having a positive refractive power and a third lens L3 having a negative refractive power. The second lens L2 is formed into a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are positive, that is, a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X. Is done. The shape of the second lens L2 is not limited to a shape that becomes a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X, and may be a shape in which the radius of curvature of the object side surface is positive. That's fine. In Numerical Examples 2 to 5, the shape of the second lens L2 is such that the curvature radius of the object side surface is positive and the curvature radius of the image side surface is negative, that is, both in the vicinity of the optical axis X. It is an example of the shape used as a convex lens.

  The third lens L3 is formed in a shape in which the radius of curvature of the object side surface is negative and the radius of curvature of the image side surface is positive, that is, a shape that becomes a biconcave lens in the vicinity of the optical axis X. Note that the shape of the third lens L3 is not limited to a shape that becomes a biconcave lens in the vicinity of the optical axis X, and may be any shape as long as the radius of curvature of the object side surface is negative. The shape of the third lens L3 is a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are negative, that is, a meniscus lens having a concave surface facing the object side in the vicinity of the optical axis X. Shapes can also be applied.

  As described above, in the present embodiment, the second lens group G2 has a configuration in which the second lens L2 having a positive refractive power and the third lens L3 having a negative refractive power are sequentially arranged from the object side. did. The configuration of the second lens group G2 may be any configuration in which the combined refractive power of the second lens and the third lens is negative, and the second lens having negative refractive power and the third lens having positive refractive power. A configuration may be employed in which the lens is disposed in order from the object side.

  The third lens group G3 includes, in order from the object side, a stop ST, a fourth lens L4 having a positive refractive power, and a fifth lens L5 having a negative refractive power. Among these, the 4th lens L4 is formed in the shape used as the biconvex lens in the vicinity of the optical axis X. FIG. The fifth lens L5 is formed in a shape that becomes a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X.

In the present embodiment, the lens surface of each lens is formed as an aspheric surface as necessary. The aspherical shape adopted for these lens surfaces is that the axis in the optical axis direction is Z, the height in the direction orthogonal to the optical axis X is H, the conic coefficient is k, the aspheric coefficient is A ₄ , A ₆ , A ₈ When A ₁₀ , A ₁₂ , A ₁₄ , and A ₁₆ are used, they are expressed by the following formula.

In the zoom lens according to the present embodiment, the focal length of the first lens group G1 is f1, the focal length of the second lens group G2 is f2, the focal length of the third lens group G3 is f3, and the first lens group G1. The combined focal length at the wide angle end of the third lens group G3 is fw, the Abbe number of the second lens L2 is νd2p, the Abbe number of the third lens L3 is νd2n, the Abbe number of the fourth lens L4 is νd3p, and the fifth lens L5 When the Abbe number of νd3n is satisfied, the following conditional expressions (1) to (4) are satisfied.
−0.3 <fw / f1 <−0.05 (1)
−0.5 <f3 / f1 <−0.1 (2)
−0.6 <f3 / f2 <−0.3 (3)
0.5 <| νd2p−νd2n | / | νd3p−νd3n | <0.8 (4)

  In addition, it is not necessary to satisfy all of the conditional expressions (1) to (4), and by obtaining each of the conditional expressions (1) to (4) independently, an effect corresponding to each conditional expression is obtained. Therefore, it is possible to construct a small zoom lens with high image quality and high performance as compared with a conventional zoom lens.

  Next, numerical examples of the zoom lens according to the present embodiment will be described. In each numerical example, the back focus BF indicates the distance from the image plane side surface of the fifth lens L5 to the paraxial image plane in terms of the air-converted length, and the total lens length L is the length of the first lens L1. The value of the back focus BF is added to the distance from the object side surface to the image surface side surface of the fifth lens L5.

  In addition, i indicates a surface number counted from the object side, R indicates a radius of curvature, d indicates a distance (surface interval) between lens surfaces along the optical axis X, Nd indicates a refractive index with respect to the d line, νd indicates the Abbe number with respect to the d line. An aspheric surface is indicated by adding a symbol of * (asterisk) after the surface number i.

Numerical example 1
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 22.894 0.9000 1.52470 56.2
2 * 9.756 5.0000
3 0.000 11.0000 1.71300 53.9
4 0.000 Variable
5 * 11.390 1.2600 1.61420 26.0 (= νd2p)
6 * 150.296 0.5850
7 -7.726 0.6120 1.61800 63.4 (= νd2n)
8 16.195 Variable
9 (Aperture) ∞ 0.1400
10 * 3.534 2.2100 1.49700 81.6 (= νd3p)
11 * -13.825 0.0700
12 * 7.890 0.7200 1.61420 26.0 (= νd3n)
13 * 3.867 Variable
14 ∞ 0.3000 1.51633 64.1
15 ∞ 6.5844
(Image plane IM) ∞

Various data Zoom ratio 3.877
Wide-angle end Medium Telephoto end focal length f 4.326 8.521 16.770
F number 2.605 3.627 5.433
Half angle of view ω (°) 31.97 17.58 9.15
Image height 2.700 2.700 2.700
Full length L 47.099 47.099 47.099
Back focus BF 9.702 14.247 21.668

d4 1.000 5.143 1.000
d8 13.900 5.212 1.934
d13 2.920 7.465 14.886

f1 = −33.183
f2 = −16.650
f3 = 8.184
fw = 4.326
| Νd2p−νd2n | = 37.4
| Νd3p−νd3n | = 55.6

Aspherical data first surface k = -3.232422E-01, A ₄ = 2.378219E-04, A ₆ = -9.479640E-07, A ₈ = 1.503126E-08
A ₁₀ = -1.653783E-10
2nd surface k = -5.487345E-02, A ₄ = 5.057938E-05, A ₆ = 1.609065E-06, A ₈ = -1.757842E-08
A ₁₀ = -1.203175E-10, A ₁₂ = -2.064675E-12, A ₁₄ = -1.617405E-14
5th surface k = -1.850000, A ₄ = -1.260197E-03, A ₆ = -5.691917E-05, A ₈ = -4.679930E-06
A ₁₀ = 1.610750E-07, A ₁₂ = 2.284490E-08, A ₁₄ = -2.748551E-10
6th surface k = 5.000000E-01, A ₄ = -1.864404E-03, A ₆ = -1.171388E-04, A ₈ = 9.509283E-07
A ₁₀ = 4.363748E-07
10th surface k = -7.513911E-01, A ₄ = 1.037444E-03, A ₆ = -1.231682E-05
11th surface k = -2.611095E-01, A ₄ = 0.000000, A ₆ = -4.218384E-06, A ₈ = -6.239724E-07
A ₁₀ = -4.182303E-08
12th surface k = -1.400000, A ₄ = 5.532891E-05, A ₆ = -1.923531E-05, A ₈ = -4.376703E-06,
A ₁₀ = -1.011446E-06
13th surface k = 9.478743E-01, A ₄ = 1.695413E-03, A ₆ = 2.328653E-04, A ₈ = -9.189209E-06,
A ₁₀ = -2.252695E-06, A ₁₂ = -5.441142E-08, A ₁₄ = -2.072506E-08, A ₁₆ = 4.988290E-09

The value of each conditional expression is shown below.
fw / f1 = −0.130
f3 / f1 = −0.247
f3 / f2 = −0.492
| Νd2p−νd2n | / | νd3p−νd3n | = 0.673
Thus, the zoom lens according to Numerical Example 1 satisfies the conditional expressions (1) to (4).

  2, 4, and 6 show the lateral aberration corresponding to the half angle of view ω in the tangential direction and the sagittal direction for the zoom lens of Numerical Example 1 (FIGS. 9, 11, and 11). (Same in FIGS. 13, 16, 18, 20, 23, 25, 27, 30, 32, and 34). 2 shows lateral aberration at the wide-angle end (W) (the same applies to FIGS. 9, 16, 23, and 30), and FIG. 4 shows lateral aberration at the intermediate position (N) (FIGS. 11, 18, and FIG. 25 and FIG. 32 are the same), and FIG. 6 shows the lateral aberration at the telephoto end (T) (the same applies to FIGS. 13, 20, 27, and 34).

  3, 5, and 7 show the spherical aberration SA (mm), astigmatism AS (mm), and distortion aberration DIST (%), respectively, for the zoom lens of Numerical Example 1. FIG. (Same in FIG. 10, FIG. 12, FIG. 14, FIG. 17, FIG. 19, FIG. 21, FIG. 24, FIG. 26, FIG. 28, FIG. 31, FIG. 33, FIG. 35). 3 shows aberrations at the wide-angle end (W) (the same applies to FIGS. 10, 17, 24, and 31), and FIG. 5 shows aberrations at the intermediate position (N) (FIGS. 12, 19, and FIG. FIG. 7 shows aberrations at the telephoto end (T) (the same applies to FIGS. 14, 21, 28, and 35). In these aberration diagrams, the spherical aberration diagram shows the amount of aberration for each wavelength of 587.56 nm, 435.84 nm, 656.27 nm, 486.13 nm, and 546.07 nm as well as the sine condition violation amount OSC. In the aberration diagram, an aberration amount on the sagittal image surface S and an aberration amount on the tangential image surface T are shown. Thus, according to the zoom lens according to Numerical Example 1, various aberrations are favorably corrected. The aberration diagrams in FIGS. 2 to 7, 9 to 14, 16 to 21, 23 to 28, and 30 to 35 show aberrations at object distance = infinity (∞), respectively. It is a thing.

Numerical example 2
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 20.000 0.9000 1.52470 56.2
2 * 8.754 4.7000
3 0.000 10.0000 1.71300 53.9
4 0.000 Variable
5 * 13.994 1.4000 1.61420 26.0 (= νd2p)
6 * -622.451 0.6500
7 -8.440 0.6800 1.61800 63.4 (= νd2n)
8 18.662 Variable
9 (Aperture) ∞ 0.1400
10 * 3.550 2.2100 1.49700 81.6 (= νd3p)
11 * -14.011 0.0700
12 * 8.061 0.7200 1.61420 26.0 (= νd3n)
13 * 3.908 Variable
14 ∞ 0.3000 1.51633 64.1
15 ∞ 6.3772
(Image plane IM) ∞

Various data Zoom ratio 3.809
Wide angle end Intermediate Telephoto end focal length f 4.132 8.060 15.738
F number 2.600 3.598 5.241
Half angle of view ω (°) 31.88 17.69 9.27
Image height 2.570 2.570 2.570
Total lens length L 46.965 46.965 46.965
Back focus BF 9.495 13.815 20.799

d4 1.000 6.459 3.080
d8 15.000 5.220 1.616
d13 2.920 7.240 14.224

f1 = −30.511
f2 = -18.289
f3 = 8.277
fw = 4.132
| Νd2p−νd2n | = 37.4
| Νd3p−νd3n | = 55.6

Aspherical data first surface k = -3.232422E-01, A ₄ = 1.784839E-04, A ₆ = -7.354696E-07, A ₈ = 6.917614E-09
A ₁₀ = 2.027098E-11
2nd surface k = -5.487345E-02, A ₄ = 2.127292E-05, A ₆ = -3.388475E-07
5th surface k = -2.000000, A ₄ = -8.338734E-04, A ₆ = -3.578158E-05, A ₈ = -1.962185E-06
A ₁₀ = 7.575606E-08, A ₁₂ = 7.502725E-09, A ₁₄ = -7.374939E-11
6th surface k = 5.000000E-01, A ₄ = -1.252272E-03, A ₆ = -6.520776E-05, A ₈ = 6.636696E-07
A ₁₀ = 1.893346E-07
10th surface k = -7.513911E-01, A ₄ = 1.003321E-03, A ₆ = -9.013698E-06
11th surface k = -2.246486E-01, A ₄ = 0.000000, A ₆ = -1.765226E-06, A ₈ = -2.116077E-07
A ₁₀ = 2.622456E-08
12th surface k = -1.500000, A ₄ = 6.418626E-05, A ₆ = 1.302554E-06, A ₈ = -1.543861E-06,
A ₁₀ = -6.061007E-07
13th surface k = 9.478743E-01, A ₄ = 1.695413E-03, A ₆ = 2.344735E-04, A ₈ = -6.029137E-06,
A ₁₀ = -5.833969E-07, A ₁₂ = 3.493718E-07, A ₁₄ = 2.904576E-08, A ₁₆ = -2.175734E-09

The value of each conditional expression is shown below.
fw / f1 = −0.135
f3 / f1 = −0.271
f3 / f2 = −0.453
| Νd2p−νd2n | / | νd3p−νd3n | = 0.673
Thus, the zoom lens according to Numerical Example 2 satisfies the conditional expressions (1) to (4).

  9, 11, and 13 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 2, and FIGS. 10, 12, and 14 show the spherical aberration SA (mm ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As can be seen from these figures, the zoom lens according to Numerical Example 2 also corrects the image plane well and corrects various aberrations well.

Numerical Example 3
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 18.252 0.8000 1.52470 56.2
2 * 8.793 5.1300
3 0.000 10.1000 1.71300 53.9
4 0.000 Variable
5 * 15.773 1.5000 1.58500 29.0 (= νd2p)
6 * -143.706 0.7000
7 -9.022 0.7000 1.61800 63.4 (= νd2n)
8 21.266 Variable
9 (Aperture) ∞ 0.1500
10 * 3.837 2.4000 1.49700 81.6 (= νd3p)
11 * -14.744 0.0700
12 * 8.788 0.7000 1.58500 29.0 (= νd3n)
13 * 4.171 Variable
14 ∞ 0.3000 1.51633 64.1
15 ∞ 6.9336
(Image plane IM) ∞

Various data Zoom ratio 3.895
Wide-angle end Medium Telephoto end focal length f 4.485 11.110 17.467
F number 2.605 4.034 5.241
Half angle of view ω (°) 31.98 14.15 9.11
Image height 2.800 2.800 2.800
Total length L 49.881 49.881 49.881
Back focus BF 10.331 17.308 22.878

d4 1.000 6.595 3.170
d8 16.300 3.727 1.583
d13 3.200 10.177 15.747

f1 = −33.306
f2 = −19.760
f3 = 8.964
fw = 4.485
| Νd2p−νd2n | = 34.4
| Νd3p−νd3n | = 52.6

Aspherical data first surface k = -3.232422E-01, A ₄ = 1.579793E-04, A ₆ = -3.113780E-07, A ₈ = 3.276658E-09
A ₁₀ = 3.595640E-11
2nd surface k = -5.487345E-02, A ₄ = 1.561082E-05, A ₆ = 3.196792E-07
5th surface k = -2.000000, A ₄ = -6.620709E-04, A ₆ = -2.401432E-05, A ₈ = -1.126251E-06
A ₁₀ = 3.272483E-08, A ₁₂ = 2.891937E-09, A ₁₄ = -1.845412E-11
6th surface k = 5.000000E-01, A ₄ = -9.941032E-04, A ₆ = -4.425167E-05, A ₈ = 3.365067E-07
A ₁₀ = 8.685140E-08
10th surface k = -7.513911E-01, A ₄ = 8.051168E-04, A ₆ = -5.649812E-06
11th surface k = -1.729905E-01, A ₄ = 0.000000, A ₆ = 2.246011E-07, A ₈ = 6.870985E-08
A ₁₀ = 2.600986E-08
12th surface k = -1.886715, A ₄ = 5.796865E-05, A ₆ = -3.768984E-07, A ₈ = -1.083125E-06,
A ₁₀ = -2.964459E-07
13th surface k = 9.478743E-01, A ₄ = 1.309170E-03, A ₆ = 1.530600E-04, A ₈ = -3.046220E-06,
A ₁₀ = -2.988755E-07, A ₁₂ = 1.046141E-07, A ₁₄ = -1.838972E-09, A ₁₆ = -3.830619E-09

The value of each conditional expression is shown below.
fw / f1 = −0.135
f3 / f1 = −0.269
f3 / f2 = −0.454
| Νd2p−νd2n | / | νd3p−νd3n | = 0.654
Thus, the zoom lens according to Numerical Example 3 also satisfies the conditional expressions (1) to (4).

  FIGS. 16, 18, and 20 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 3, and FIGS. 17, 19, and 21 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 3 also corrects the image plane well and corrects various aberrations.

Numerical Example 4
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 19.223 0.9800 1.52470 56.2
2 * 9.012 5.1230
3 0.000 10.9000 1.71300 53.9
4 0.000 Variable
5 * 15.210 1.5300 1.58500 29.0 (= νd2p)
6 * -216.823 0.7100
7 -8.983 0.7400 1.61800 63.4 (= νd2n)
8 21.487 Variable
9 (Aperture) ∞ 0.1530
10 * 3.879 2.4100 1.49700 81.6 (= νd3p)
11 * -15.129 0.0760
12 * 8.860 0.7800 1.58500 29.0 (= νd3n)
13 * 4.187 Variable
14 ∞ 0.3000 1.51633 64.1
15 ∞ 6.9853
(Image plane IM) ∞

Various data Zoom ratio 3.901
Wide-angle end Medium Telephoto end focal length f 4.509 11.173 17.589
F number 2.605 4.096 5.304
Half angle of view ω (°) 29.68 12.95 8.31
Image height 2.570 2.570 2.570
Total lens length L 51.215 51.215 51.215
Back focus BF 10.363 17.424 23.063

d4 1.090 6.564 3.073
d8 16.360 3.825 1.676
d13 3.180 10.241 15.880

f1 = −33.439
f2 = −19.866
f3 = 9.031
fw = 4.509
| Νd2p−νd2n | = 34.4
| Νd3p−νd3n | = 52.6

Aspherical data first surface k = -3.232422E-01, A ₄ = 1.559157E-04, A ₆ = -3.937052E-07, A ₈ = 2.991504E-09
A ₁₀ = 2.618615E-11
2nd side k = -5.487345E-02, A ₄ = 2.111460E-05, A ₆ = 4.231874E-08
5th surface k = -2.000000, A ₄ = -6.464539E-04, A ₆ = -2.429161E-05, A ₈ = -1.119076E-06
A ₁₀ = 3.356262E-08, A ₁₂ = 2.912184E-09, A ₁₄ = -1.968106E-11
6th surface k = 5.000000E-01, A ₄ = -1.009507E-03, A ₆ = -4.372005E-05, A ₈ = 3.420970E-07
A ₁₀ = 8.661957E-08
10th surface k = -7.513911E-01, A ₄ = 7.642670E-04, A ₆ = -5.600395E-06
11th surface k = -3.722910E-01, A ₄ = 0.000000, A ₆ = -6.909496E-07, A ₈ = 2.798667E-08
A ₁₀ = 3.631056E-08
12th surface k = -1.886715, A ₄ = 3.002887E-05, A ₆ = 1.909695E-06, A ₈ = -8.241926E-07,
A ₁₀ = -2.931363E-07
13th surface k = 9.478743E-01, A ₄ = 1.309170E-03, A ₆ = 1.454141E-04, A ₈ = -4.628919E-06,
A ₁₀ = -4.527095E-07, A ₁₂ = 1.017764E-07, A ₁₄ = 1.243878E-09, A ₁₆ = -2.797638E-09

The value of each conditional expression is shown below.
fw / f1 = −0.135
f3 / f1 = −0.270
f3 / f2 = −0.455
| Νd2p−νd2n | / | νd3p−νd3n | = 0.654
Thus, the zoom lens of Numerical Example 4 also satisfies the conditional expressions (1) to (4).

  23, 25, and 27 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 4, and FIGS. 24, 26, and 28 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 4 also corrects the image plane well and appropriately corrects various aberrations.

Numerical Example 5
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 19.519 0.9000 1.52470 56.2
2 * 9.086 5.0000
3 0.000 11.0000 1.71300 53.9
4 0.000 Variable
5 * 14.595 1.4000 1.61420 26.0 (= νd2p)
6 * -221.684 0.6500
7 -8.490 0.6800 1.61800 63.4 (= νd2n)
8 18.422 Variable
9 (Aperture) ∞ 0.1400
10 * 3.614 2.2100 1.49700 81.6 (= νd3p)
11 * -14.898 0.0700
12 * 8.288 0.7200 1.61420 26.0 (= νd3n)
13 * 3.960 Variable
14 ∞ 0.3000 1.51633 64.1
15 ∞ 7.1708
(Image plane IM) ∞

Various data Zoom ratio 3.926
Wide-angle end Middle Telephoto end focal length f 4.610 7.266 18.101
F number 2.717 3.396 5.788
Half angle of view ω (°) 31.27 21.07 8.79
Image height 2.800 2.800 2.800
Total lens length L 51.215 51.215 51.215
Back focus BF 10.363 17.424 23.063

d4 1.000 5.226 0.997
d8 14.500 7.318 1.777
d13 2.920 5.876 15.646

f1 = −33.389
f2 = -18.202
f3 = 8.630
fw = 4.610
| Νd2p−νd2n | = 37.4
| Νd3p−νd3n | = 55.6

Aspherical data first surface k = -3.232422E-01, A ₄ = 2.461558E-04, A ₆ = -7.424809E-07, A ₈ = 1.668413E-08
A ₁₀ = -1.243675E-10
2nd surface k = -5.487345E-02, A ₄ = 8.144623E-05, A ₆ = 1.871189E-06, A ₈ = -1.178571E-08
A ₁₀ = -1.799687E-11, A ₁₂ = -2.409216E-12, A ₁₄ = 2.097088E-15
5th surface k = -2.000000, A ₄ = -9.365247E-04, A ₆ = -4.235107E-05, A ₈ = -2.385914E-06
A ₁₀ = 5.927485E-08, A ₁₂ = 7.223636E-09, A ₁₄ = -5.353479E-11
6th surface k = 5.000000E-01, A ₄ = -1.361759E-03, A ₆ = -7.293523E-05, A ₈ = 3.336044E-07
A ₁₀ = 1.657809E-07
10th surface k = -7.513911E-01, A ₄ = 1.000158E-03, A ₆ = -8.289912E-06
11th surface k = 7.798179E-01, A ₄ = 0.000000, A ₆ = -1.600505E-06, A ₈ = -1.305265E-07
A ₁₀ = 4.887785E-08
12th surface k = -1.500000, A ₄ = 1.072264E-04, A ₆ = 4.757766E-06, A ₈ = -1.264428E-06,
A ₁₀ = -6.033042E-07
13th surface k = 9.478743E-01, A ₄ = 1.695413E-03, A ₆ = 2.156536E-04, A ₈ = -8.104906E-06,
A ₁₀ = -9.909974E-07, A ₁₂ = 2.607879E-07, A ₁₄ = 1.583277E-08, A ₁₆ = -2.014458E-09

The value of each conditional expression is shown below.
fw / f1 = −0.138
f3 / f1 = −0.258
f3 / f2 = −0.474
| Νd2p−νd2n | / | νd3p−νd3n | = 0.673
Thus, the zoom lens of Numerical Example 5 also satisfies the conditional expressions (1) to (4).

  30, FIG. 32 and FIG. 34 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 5, and FIGS. 31, 33 and 35 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 5 also corrects the image plane well and appropriately corrects various aberrations.

  Therefore, when the zoom lens according to the present embodiment is applied to an imaging optical system such as a mobile phone, a digital still camera, a portable information terminal, a security camera, etc., both high performance and downsizing of the camera are to be achieved. Can do.

  The present invention can be applied to a zoom lens mounted on a device that is required to have a small aberration and good aberration correction capability, such as a mobile phone or a digital still camera.

G1 1st lens group G2 2nd lens group G3 3rd lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens P Prism ST Aperture 10 Filter

Claims (6)

A first lens group having a negative refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power are arranged in order from the object side to the image plane side. A zoom lens comprising:
The first lens group is composed of a lens having a negative refractive power in which the radius of curvature of the surface on the image plane side is positive, and an optical path changing member that changes the traveling direction of incident light,
The second lens group includes a lens having a positive refractive power that makes the radius of curvature of the object side surface positive, and a lens having a negative refractive power that makes the radius of curvature of the object side surface negative. And
The third lens group includes a lens having a positive refractive power and a lens having a negative refractive power in which the radius of curvature of the object side surface is positive.
In zooming from the wide-angle end to the telephoto end, the first lens group is fixed, the second lens group is moved to the object side and then moved to the object side, and the third lens group is linearly moved to the object side. Moved to the side,
A zoom lens characterized by that. The optical path changing member is a prism that reflects incident light and bends the optical path.
The zoom lens according to claim 1. When the combined focal length at the wide angle end of the first lens group, the second lens group, and the third lens group is fw, and the focal length of the first lens group is f1, the following conditional expression is satisfied: The zoom lens according to claim 1 or 2.
−0.3 <fw / f1 <−0.05 4. The following conditional expression is satisfied, where f1 is a focal length of the first lens group and f3 is a focal length of the third lens group. 5. Zoom lens.
−0.5 <f3 / f1 <−0.1 5. The following conditional expression is satisfied, where f <b> 2 is a focal length of the second lens group and f <b> 3 is a focal length of the third lens group. Zoom lens.
−0.6 <f3 / f2 <−0.3 The Abbe number of a lens having positive refractive power in the second lens group is νd2p, the Abbe number of a lens having negative refractive power in the second lens group is νd2n, and has positive refractive power in the third lens group. The following conditional expression is satisfied, where the Abbe number of the lens is νd3p, and the Abbe number of the lens having negative refractive power in the third lens group is νd3n. The zoom lens according to item.
0.5 <| νd2p−νd2n | / | νd3p−νd3n | <0.8

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