JP5252709B2 - Zoom lens - Google Patents

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, a camera module is mounted not only on a digital still camera but also in a small device such as a mobile phone, a portable information terminal, and an internet camera. In these small devices, it is known that since the mounting space of the camera module is limited, not only the performance of the imaging lens is improved but also the demand for miniaturization is very strong. Conventionally, such space constraints have been addressed by installing an unnecessary pan focus type photographing lens such as a focus adjustment mechanism.

  However, recently, even in the above-described small apparatus, mounting of a zoom lens has been studied in the same manner as a digital still camera. The zoom lens is a lens system that can change the photographing magnification by moving a part of lenses or a lens group constituting the lens system along the optical axis. In order to perform zooming and focusing in the zoom lens, it is necessary to move at least two lens groups among the lens groups constituting the zoom lens. For this reason, it is necessary to secure a space for moving these lens groups in the zoom lens, and it has been difficult to realize a small zoom lens having a short overall length.

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

  By the way, in a small device such as the above-described cellular phone, in parallel with the miniaturization of the device itself, an increase in the number of pixels of the image sensor is also achieved. Along with this, zoom lenses are also strongly required to have high performance such as good aberration correction capability and high resolution. Although the zoom lens described in Patent Document 1 corrects aberrations relatively well with a small number of lenses, the overall length of the lens system is relatively long, and there remains a problem from the viewpoint of high performance and miniaturization. Met.

  Such demands for high performance and miniaturization are not limited to small devices such as mobile phones, and even in digital still cameras for general use, image scaling, especially optical transformation with little image degradation. On the other hand, a reduction in thickness for improving portability is also 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, as a zoom lens, in order from the object side, a first lens group including two lenses, a lens having a negative refractive power and a lens having a positive refractive power, and an object The second lens group having a negative refractive power with the concave surface facing the side, the stop, the front group lens having a positive refractive power, and the rear group lens having a negative refractive power are arranged in this order, and positive refraction as a whole The third lens group having power and the fourth lens group having positive or negative refractive power are included.

  In the zoom lens according to the present invention, in zooming from the wide-angle end to the telephoto end, the first lens group and the fourth lens group are fixed, and the second lens group moves to the image plane side. Then, the third lens group is moved to the object side linearly.

  In the above configuration, the first lens group includes two positive and negative lenses. Among these, the positive lens has a function of correcting chromatic aberration and distortion of magnification at the wide angle end. In the present invention, since the two positive and negative lenses constituting the first lens group are fixed at the time of zooming, deterioration of aberrations during zooming is suitably suppressed. On the other hand, there remains a concern that the curvature of the image plane is generated by the positive lens constituting the first lens group. Therefore, in the present invention, the first lens is further arranged by disposing the second lens group having a negative refractive power on the image surface side of the positive lens constituting the first lens group with the concave surface facing the object side. The configuration is such that the curvature of field that occurs in the group, particularly the worsening of curvature of field at the wide-angle end is suppressed. Therefore, by adopting such a configuration as a zoom lens, both high performance and small size can be achieved.

  In the zoom lens having such a configuration, it is desirable that each of the front lens group and the rear lens group of the third lens group is composed of one lens from the viewpoint of reducing the size and weight of the zoom lens.

  Furthermore, if the fourth lens group is composed of a single lens, the zoom lens can be further reduced in size and weight.

In the present invention, when the focal length of the lens having the negative refractive power in the first lens group is f1n and the focal length of the lens having the positive refractive power is f1p, the following conditional expression ( It was configured to satisfy 1).
−1.5 <f1n / f1p <−0.3 (1)

  Here, conditional expression (1) is a condition for satisfactorily correcting chromatic aberration over the entire zooming range and limiting the maximum effective diameter of the lens having negative refractive power in the first lens group. .

  In the conditional expression (1), when the lower limit “−1.5” is not reached, the refractive power of a lens having a positive refractive power in the first lens group becomes strong. Since the short wavelength is in the + direction with respect to the wavelength, it is overcorrected. On the other hand, the axial chromatic aberration is undercorrected because the short wavelength is in the-direction with respect to the reference wavelength. As a result, it becomes difficult to obtain good imaging performance.

  Further, if the upper limit “−0.3” is exceeded, the refractive power of the lens having the positive refractive power in the first lens group becomes weak. Therefore, the off-axis lateral chromatic aberration is shorter than the reference wavelength. Since the wavelength is in the negative direction, the correction is insufficient. On the other hand, the axial chromatic aberration is excessively corrected because the short wavelength is in the positive direction with respect to the reference wavelength. Therefore, also in this case, it is difficult to obtain good imaging performance. In addition, the effective diameter of the lens having negative refractive power in the first lens group is increased, and it is difficult to reduce the size and weight of the zoom lens.

In the present invention, when the focal length of the second lens group is f2, and the focal length of the third lens group is f3, the following conditional expression (2) is satisfied.
−1.675 ≦ f2 / f3 <−1.0 (2)

  Here, the conditional expression (2) is a condition for defining the movement mode of the second lens group. By satisfying the conditional expression (2), the position of the second lens unit on the optical axis at the wide-angle end and the position of the second lens unit on the optical axis at the telephoto end substantially coincide in zooming. become. 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.

  In general, even if a good aberration is obtained when the distance from the zoom lens to the subject (hereinafter referred to as the object distance) is infinite, if the object distance changes, for example, if the object distance changes, the aberration will deteriorate. Become. By satisfying conditional expression (2), the difference between the position on the optical axis of the second lens group when the object distance is infinite and the position on the optical axis of the second lens group when the object distance is close (Feeding amount) is substantially the same value at the wide-angle end and the telephoto end. For this reason, according to the zoom lens of the present invention, it is possible to satisfactorily suppress the deterioration of aberration in the entire zooming range from the close range to infinity (∞).

In the conditional expression (2), if the upper limit “−1.0” is exceeded, the second lens unit largely moves toward the object side at the wide-angle end, so that it is difficult to reduce the size of the zoom lens. On the other hand, when the value is below the lower limit “ −1.675 ”, the second lens unit moves greatly toward the image plane at the telephoto end, which also becomes an obstacle to miniaturization of the zoom lens. Further, in this case, since the refractive power of the third lens group becomes stronger than the refractive power of the second lens group, it is difficult to balance spherical aberration and off-axis coma aberration in the entire zooming range.

In the present invention, when the focal length of the front lens group having the positive refractive power in the third lens group is f3p and the focal length of the rear lens group having the negative refractive power is f3n, the following conditions are satisfied. It comprised so that Formula (3) might be satisfied.
−0.460 ≦ f3p / f3n <0 (3)

  Here, conditional expression (3) is a condition for further reducing the size of the zoom lens and maintaining the balance of each aberration such as spherical aberration and coma aberration stably over the entire zooming range.

In the conditional expression (3), when the upper limit value “0” is exceeded, the refractive power of the rear lens group of the third lens group becomes positive, which makes it difficult to reduce the size of the zoom lens. On the other hand, if the value falls below the lower limit “ −0.460 ”, the refracting power of the rear lens group of the third lens group becomes strong, so that axial chromatic aberration is overcorrected and spherical aberration at the wide-angle end and the telephoto end. It becomes difficult to balance coma. In addition, since the radius of curvature of the lenses constituting the third lens group is a small value, the processability of the lenses is deteriorated and the cost of the zoom lens is increased.

In the present invention, when the focal length of the third lens unit is f3 and the combined focal length of the first to fourth lens units at the wide angle end is fw, the following conditional expression (4) is satisfied. .
1.0 <f3 / fw ≦ 1.492 (4)

  Conditional expression (4) is a condition for defining the size of the entire zoom lens and the refractive power of each lens group.

In the conditional expression (4), if the upper limit “ 1.492 ” is exceeded, the refractive power of the third lens group becomes weak and effective in correcting each aberration, but the zoom lens can be made smaller and lighter. It becomes difficult to plan. On the other hand, when the value is below the lower limit “1.0”, the refractive power of the third lens unit that moves during zooming becomes strong, which is advantageous for downsizing of the zoom lens. It is difficult to keep the balance of curvature of field and curvature of field stable. In addition, since the radius of curvature of the lenses constituting each lens group becomes a small value, the processability of the lenses deteriorates, and the cost of the zoom lens increases.

In the present invention, when the focal length of the first lens unit is f1, and the combined focal length of the first to fourth lens units at the wide angle end is fw, the following conditional expression (5) is satisfied. .
-0.15 <fw / f1 <0.15 (5)

  Here, the conditional expression (5) is a condition for defining the amount of movement of the second lens group in the entire zooming range by keeping the distance between the first lens group and the second lens group almost constant in the entire zooming range. It is.

  In the above conditional expression (5), when the upper limit “0.15” is exceeded, the refractive power of the second lens group becomes strong, so the amount of movement for image point correction of the second lens group decreases, and the wide-angle end. And the deterioration of the aberration at an intermediate position between the telephoto end and the telephoto end increases. Further, at close distances, the image quality of the peripheral portion deteriorates particularly at the wide-angle end side.

  On the other hand, when the value falls below the lower limit “−0.15”, the refractive power of the second lens group becomes weak, so the amount of movement for image point correction of the second lens group becomes large, and the distance between the wide-angle end and the telephoto end increases. The lateral chromatic aberration at the intermediate position will increase.

  If the fourth lens group is a lens group having negative refractive power, the position of the principal point moves to the object side, so that the overall length of the zoom lens can be further shortened.

  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.

  Hereinafter, a zoom lens embodying the present invention will be described in detail with reference to the drawings.

  1, 8, 15, 22, 29, and 36 are sectional views of zoom lenses corresponding to the first to sixth embodiments, respectively. Each drawing 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.

  Each of the zoom lenses according to each embodiment has a four-group configuration, and in order from the object side, a first lens group including two lenses, a first lens having a negative refractive power and a second lens having a positive refractive power. And a second lens group having a negative refractive power with the concave surface facing the object side, a stop, a front group lens having a positive refractive power, and a rear group lens having a negative refractive power, are arranged in this order. The third lens group has a positive refractive power and the fourth lens group has a positive or negative refractive power.

  The zoom lens according to the first and second embodiments is a zoom lens having a four-group configuration of positive / negative / positive / positive, and the zoom lens according to the third embodiment is positive / negative / positive / positive. This is a negative four-group zoom lens. The zoom lenses according to the fourth and fifth embodiments are negative, negative, positive, and positive four-group zoom lenses. The zoom lens according to the sixth embodiment includes negative, negative, This is a positive / positive four-group zoom lens.

  In the zoom lenses according to these embodiments, the first lens group and the fourth lens group are fixed, and the second lens group and the third lens group move along the optical axis during zooming. . Specifically, in zooming from the wide-angle end to the telephoto end, the second lens group moves toward the object side after moving toward the image plane side, and the third lens group moves linearly toward the object side. It has become.

  Hereinafter, the zoom lens according to each embodiment will be described in detail.

(First embodiment)
As shown in FIG. 1, the zoom lens according to the first embodiment includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, The lens unit includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power. A cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor. This cover glass 10 can be omitted (the same applies to the second to sixth embodiments).

  In the zoom lens according to the present embodiment, the first lens group G1 and the fourth lens group G4 are fixed, and the second lens group G2 and the third lens group G3 are configured to be movable along the optical axis. Has been. In such a lens 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. Move to the object side. Specifically, the second lens group G2 moves along the optical axis so that its movement locus is concave on the object side (see FIG. 43), and the third lens group G3 approaches the second lens group G2. And move along the optical axis so that the movement trajectory is 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 throughout the entire area.

  In the zoom lens, the first lens group G1 includes, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface facing the object side, and a second lens L2 that is a biconvex lens. . The second lens group G2 includes a third lens L3 that is a biconcave lens.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens L5 that is a negative meniscus lens having a convex surface facing the object side.

  The fourth lens group G4 includes a sixth lens L6 that is a positive meniscus lens having a concave surface directed toward the object side. In the sixth lens L6, the surface on the image plane side is an aspheric surface in which the vicinity of the optical axis is convex on the image plane side and the peripheral portion is concave on the image plane side, that is, an aspheric surface having an inflection point. It is formed into a shape.

In the present embodiment, the lens surface of each lens is formed as an aspherical 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 perpendicular to the optical axis is H, the conic coefficient is k, and the aspherical coefficients are A ₄ , A ₆ , A ₈ , A _{When 10} , it is represented by the following formula. In the second to sixth embodiments described later, the lens surfaces of the respective lenses are formed as aspherical surfaces as necessary, and the aspherical shape adopted for these lens surfaces is the present embodiment. Like the above, it is expressed by the following equation.

In the zoom lens according to the present embodiment, the focal length of the first lens L1 having negative refractive power in the first lens group G1 is f1n, and the focal length of the second lens L2 having positive refractive power is set. When f1p
−1.5 <f1n / f1p <−0.3 (1)
By satisfying the above, it is possible to reduce the size of the zoom lens while satisfactorily correcting chromatic aberration over the entire zooming range.

In the zoom lens according to the present embodiment, in order to suppress the deterioration of the aberration in the entire zooming range from the close range to infinity (∞) and to balance the spherical aberration and the coma aberration in the entire zooming range, When the focal length of the second lens group G2 is f2, and the focal length of the third lens group G3 is f3,
−1.675 ≦ f2 / f3 <−1.0 (2)
To be satisfied.

In the third lens group G3, when the focal length of the front lens group L4 having positive refractive power is f3p and the focal length of the rear lens group L5 having negative refractive power is f3n,
−0.460 ≦ f3p / f3n <0 (3)
By satisfying the above, it is possible to further reduce the size of the zoom lens and stably maintain the balance of each aberration such as spherical aberration and coma aberration over the entire zooming range.

Further, in order to keep a stable balance of spherical aberration, coma aberration, and field curvature in the entire zooming range, the focal length of the third lens group G3 is f3, and the first lens group G1 to the fourth lens group G4 at the wide angle end. When the combined focal length of fw is fw,
1.0 <f3 / fw ≦ 1.492 (4)
To be satisfied.

Furthermore, in the zoom lens according to the present embodiment, when the focal length of the first lens group G1 is f1, and the combined focal length of the first lens group G1 to the fourth lens group G4 at the wide angle end is fw,
-0.15 <fw / f1 <0.15 (5)
To be satisfied.

  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 Example 1 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 sixth lens L6 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 side surface of the sixth lens L6.

  Further, 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, Nd indicates a refractive index with respect to d-line, and νd Indicates the Abbe number for 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 * 12.569 0.7000 1.52470 56.2
2 * 5.716 1.4000
3 66.174 1.2000 1.58500 29.0
4 * -14.368 variable
5 * -4.570 0.5000 1.52470 56.2
6 45.300 Variable
7 (Aperture) ∞ 0.1040
8 * 2.686 1.6000 1.49700 81.58
9 * -7.728 0.1000
10 5.512 0.5200 1.68893 31.15
11 * 2.923 Variable
12 * -8.979 0.8000 1.52470 56.2
13 * -6.230 0.3200
14 ∞ 0.3000 1.51633 64.12
15 ∞ 3.9401
(Image plane) ∞

Various data Zoom ratio 2.800
Wide-angle end Medium Telephoto end total focal length f 4.119 7.566 11.532
F number 3.006 3.938 5.120
Half angle of view ω (°) 28.65 16.56 11.04
Image height 2.250 2.250 2.250
Total length L 21.78 21.78 21.78
Back focus BF 4.458 4.458 4.458

d4 1.000 2.532 1.000
d6 7.400 3.067 1.240
d11 2.000 4.801 8.159

f1 = 205.377
f2 = −7.884
f3 = 5.725
f1p = 20.291
f1n = -20.708
f3p = 4.226
f3n = −9.839
fw = 4.119

Aspheric data 1st surface k = 6.599463, A ₄ = 3.416438E-04, A ₆ = 2.851814E-05
2nd surface k = 1.055102, A ₄ = -5.756793E-05, A ₆ = 7.948342E-05
4th surface k = 7.735239, A ₄ = 1.279692E-05, A ₆ = 4.370683E-06
5th surface k = -1.319628, A ₄ = -3.729453E-04, A ₆ = -7.198537E-05
8th surface k = -6.824011E-01, A ₄ = 8.718491E-04, A ₆ = 3.637688E-04
9th surface k = -6.878265, A ₄ = 1.370503E-03, A ₆ = 4.535967E-04
11th surface k = 3.775105E-01, A ₄ = 3.649554E-03, A ₆ = 1.077501E-03
12th surface k = 4.190434, A ₄ = 4.187359E-03, A ₆ = 9.409032E-04
13th surface k = -1.268690E + 01, A ₄ = -2.811247E-03, A ₆ = 1.320957E-03

The value of each conditional expression is shown below.
f1n / f1p = −1.021
f2 / f3 = −1.377
f3p / f3n = −0.430
f3 / fw = 1.390
fw / f1 = 0.020
Thus, the zoom lens according to Numerical Example 1 satisfies the conditional expressions (1), (2), (3), and (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). 13, 16, 18, 20, 23, 25, 27, 30, 32, 34, 34, 37, 39, and 41). 2 shows lateral aberrations at the wide-angle end (W) (the same applies to FIGS. 9, 16, 23, 30, and 37), and FIG. 4 shows lateral aberrations at the intermediate position (N) (FIGS. 11 and 11). 18, FIG. 25, FIG. 32, and FIG. 39) and FIG. 6 show lateral aberrations at the telephoto end (T) (the same applies to FIGS. 13, 20, 27, 34, and 41). .

  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. . FIG. 3 shows aberrations at the wide-angle end (W), FIG. 5 shows aberrations at the intermediate position (N), and FIG. 7 shows aberrations at the telephoto end (T). 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. The aberration diagrams show the aberration amount on the sagittal image surface S and the aberration amount on the tangential image surface T, respectively (FIGS. 10, 12, 14, 17, 19, 19, 21, 24, 26, 28, 31, 33, 35, 38, 40, and 42). Thus, according to the zoom lens according to Numerical Example 1, various aberrations are favorably corrected. 2 to 7, 9 to 14, 16 to 21, 23 to 28, 30 to 35, and 37 to 42, the object distance is infinity (∞). ) Shows the aberrations in FIG.

(Second Embodiment)
As shown in FIG. 8, the zoom lens according to the second embodiment, in the same manner as the zoom lens according to the first embodiment, includes a first lens group G1 having positive refractive power in order from the object side. The second lens group G2 having negative refractive power, the third lens group G3 having positive refractive power, and the fourth lens group G4 having positive refractive power. A cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor.

  Similarly to the zoom lens according to the first embodiment, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and the third lens. The group G3 is configured to move along the optical axis, and 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.

  In the zoom lens, the first lens group G1 is, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface facing the object side, and a plano-convex lens having a convex surface facing the image surface side. It consists of a lens L2. The second lens group G2 includes a third lens L3 that is a biconcave lens.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens L5 that is a negative meniscus lens having a convex surface facing the object side.

  The fourth lens group G4 includes a sixth lens L6 that is a positive meniscus lens having a concave surface directed toward the object side. The sixth lens L6 is also formed in an aspheric shape having an inflection point, like the sixth lens L6 of the zoom lens according to the first embodiment.

  In the zoom lens according to the present embodiment, the thickness of the second lens L2 in the optical axis direction is formed thicker than the thickness of the second lens L2 of the zoom lens according to the first embodiment. For this reason, a bent type (L type) zoom lens can be configured by forming the second lens L2 as a prism that reflects incident light and bends the optical path at a right angle, for example, a right angle prism. In particular, in a small portable device such as a cellular phone, there is usually no room in the thickness direction of the device. Therefore, if the zoom lens according to the present embodiment is embodied as a bent zoom lens, the thickness of the device can be significantly reduced, and the portable device can be suitably reduced in size and thickness. It becomes possible.

Hereinafter, Numerical Example 2 of the zoom lens according to the present embodiment will be described.

Numerical example 2

Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 13.000 0.7200 1.52470 56.2
2 * 6.300 2.5000
3 ∞ 5.6500 1.61420 26.0
4 * -11.817 Variable
5 * -4.598 0.5000 1.52470 56.2
6 20.819 Variable
7 (Aperture) ∞ 0.1040
8 * 2.690 1.6000 1.49700 81.58
9 * -6.768 0.1000
10 5.760 0.5200 1.68893 31.15
11 * 2.864 Variable
12 * -9.120 0.8000 1.52470 56.2
13 * -8.600 0.3200
14 ∞ 0.3000 1.51633 64.12
15 ∞ 4.4262
(Image plane) ∞

Various data Zoom ratio 2.800
Wide angle end Intermediate Telephoto end focal length f 4.098 7.682 11.474
F number 3.091 4.107 5.333
Half angle of view ω (°) 28.77 16.32 11.09
Image height 2.250 2.250 2.250
Total lens length L 27.84 27.84 27.84
Back focus BF 4.944 4.944 4.944

d4 1.000 2.532 1.000
d6 7.400 3.067 1.240
d11 2.000 4.801 8.159

f1 = 44.365
f2 = −7.130
f3 = 5.730
f1p = 19.240
f1n = −24.192
f3p = 4.104
f3n = −8.992
fw = 4.098

Aspherical data first surface k = 4.766502, A ₄ = 1.219633E-04, A ₆ = 1.785927E-05
Second surface k = 1.024709, A ₄ = -2.513164E-04, A ₆ = 3.610654E-05
4th surface k = 4.244278E-01, A ₄ = 1.057420E-04, A ₆ = -2.144668E-05
5th surface k = -1.777443, A ₄ = -5.466467E-04, A ₆ = -1.054255E-05
8th surface k = -7.162179E-01, A ₄ = 6.055964E-04, A ₆ = 3.158362E-04
9th surface k = -6.116667, A ₄ = 9.530777E-04, A ₆ = 3.603312E-04
11th surface k = 3.545927E-01, A ₄ = 3.276385E-03, A ₆ = 1.144716E-03
12th surface k = 1.087563E + 01, A ₄ = -8.905962E-04, A ₆ = 1.736165E-03
13th surface k = -1.624268E + 01, A ₄ = -6.281024E-03, A ₆ = 1.476907E-03

The value of each conditional expression is shown below.
f1n / f1p = −1.257
f2 / f3 = -1.244
f3p / f3n = −0.460
f3 / fw = 1.398
fw / f1 = 0.092
As described above, the zoom lens according to Numerical Example 2 satisfies the conditional expressions (1), (2), (3), and (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 described above, also with the zoom lens according to the present embodiment, the image plane is corrected satisfactorily and various aberrations are preferably corrected as in the first embodiment.

(Third embodiment)
As shown in FIG. 15, the zoom lens according to the third embodiment has the same basic configuration as the zoom lens according to the second embodiment. However, unlike the zoom lens according to the second embodiment, the refractive power of the fourth lens group G3 is negative. That is, in the zoom lens according to the present embodiment, in order from the object side, the first lens group G1 having a positive refractive power, the second lens group G2 having a negative refractive power, and the first lens group having a positive refractive power. The third lens group G3 includes a fourth lens group G4 having negative refractive power, and a cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor.

  Similarly to the zoom lens according to the second embodiment, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and the third lens. The group G3 is configured to move along the optical axis, and 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.

  In the zoom lens, the first lens group G1 is, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface facing the object side, and a plano-convex lens having a convex surface facing the image surface side. It consists of a lens L2. The second lens group G2 includes a third lens L3 that is a biconcave lens.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens L5 that is a negative meniscus lens having a convex surface facing the object side.

  The fourth lens group G4 includes a sixth lens L6 that is a negative meniscus lens having a concave surface directed toward the object side. Similarly to the sixth lens L6 of the zoom lens according to the second embodiment, the sixth lens L6 is also formed in an aspheric shape having an inflection point.

  The zoom lens according to the present embodiment is also formed so that the thickness of the second lens L2 in the optical axis direction is thicker than the thickness of the second lens L2 of the zoom lens according to the first embodiment. If the zoom lens according to the present embodiment is embodied as a bent zoom lens, the thickness of a mobile device such as a mobile phone can be significantly reduced as in the second embodiment, and the mobile device Can be suitably reduced in size and thickness.

Hereinafter, Numerical Example 3 of the zoom lens according to the present embodiment will be described.

Numerical Example 3

Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 13.000 0.7200 1.52470 56.2
2 * 6.300 2.3000
3 ∞ 5.6500 1.61420 26.0
4 * -15.000 variable
5 * -4.486 0.5000 1.52470 56.2
6 40.554 Variable
7 (Aperture) ∞ 0.1040
8 * 2.732 1.6000 1.49700 81.58
9 * -7.532 0.1000
10 5.478 0.5200 1.68893 31.15
11 * 2.956 variable
12 * -8.900 0.8000 1.52470 56.2
13 * -9.200 0.3200
14 ∞ 0.3000 1.51633 64.12
15 ∞ 4.5660
(Image plane) ∞

Various data Zoom ratio 2.807
Wide-angle end Medium Telephoto end focal length f 4.122 7.614 11.571
F number 3.135 4.174 5.428
Half angle of view ω (°) 28.61 16.45 10.99
Image height 2.248 2.248 2.247
Total lens length L 27.78 27.78 27.78
Back focus BF 5.084 5.084 5.084

d4 1.000 2.532 1.000
d6 7.400 3.067 1.240
d11 2.000 4.801 8.159

f1 = 115.649
f2 = −7.669
f3 = 5.712
f1p = 24.422
f1n = −24.192
f3p = 4.254
f3n = -10.176
fw = 4.122

Aspherical data 1st surface k = 4.419659, A ₄ = 2.430352E-04, A ₆ = 9.527961E-06
2nd surface k = 7.645790E-01, A ₄ = 1.491287E-05, A ₆ = 2.268837E-05
4th surface k = 7.507986, A ₄ = 1.573236E-04, A ₆ = 2.367703E-06
5th surface k = -1.269399, A ₄ = -3.890321E-04, A ₆ = -7.917652E-05
8th surface k = -6.651494E-01, A ₄ = 1.005119E-03, A ₆ = 3.752474E-04
9th surface k = -6.943619, A ₄ = 1.352969E-03, A ₆ = 4.383178E-04
11th surface k = 3.806014E-01, A ₄ = 3.697106E-03, A ₆ = 1.198858E-03
12th surface k = 6.926998, A ₄ = 2.440399E-03, A ₆ = 1.021846E-03
13th surface k = -1.698821E + 01, A ₄ = -2.382719E-03, A ₆ = 1.012267E-03

The value of each conditional expression is shown below.
f1n / f1p = −0.991
f2 / f3 = −1.343
f3p / f3n = −0.418
f3 / fw = 1.386
fw / f1 = 0.036
Thus, the zoom lens according to Numerical Example 3 satisfies the conditional expressions (1), (2), (3), and (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, also with the zoom lens according to the present embodiment, the image plane is corrected satisfactorily and various aberrations are preferably corrected as in the first embodiment.

(Fourth embodiment)
Unlike the zoom lenses according to the first to third embodiments, the zoom lens according to the fourth embodiment has a configuration in which the first lens group G1 has a negative refractive power. That is, in the zoom lens according to the present embodiment, as shown in FIG. 22, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a negative refractive power, The lens unit includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power. A cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor.

  Similarly to the zoom lenses according to the first to third embodiments, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and The third lens group G3 moves along the optical axis, and 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. Done.

  In the zoom lens, the first lens group G1 includes, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface directed toward the object side, and a second lens L2 that is biconvex. . The second lens group G2 includes a third lens L3 that is a biconcave lens.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens L5 that is a negative meniscus lens having a convex surface facing the object side.

  The fourth lens group G4 includes a sixth lens L6 that is a positive meniscus lens having a concave surface directed toward the object side. The sixth lens L6 is also formed in an aspheric shape having an inflection point, like the sixth lens L6 of the zoom lens according to the first to third embodiments.

Hereinafter, Numerical Example 4 of the zoom lens according to the present embodiment will be described.

Numerical Example 4

Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 12.408 0.7000 1.52470 56.2
2 * 5.776 1.4000
3 188.097 1.2000 1.62090 24.0
4 * -15.495 variable
5 * -4.609 0.5000 1.52470 56.2
6 67.301 Variable
7 (Aperture) ∞ 0.1040
8 * 2.663 1.6000 1.49700 81.58
9 * -7.210 0.1000
10 5.716 0.5200 1.68893 31.15
11 * 2.886 Variable
12 * -8.746 0.8000 1.52470 56.2
13 * -6.172 0.3200
14 ∞ 0.3000 1.51633 64.12
15 ∞ 3.9423
(Image plane) ∞

Various data Zoom ratio 2.800
Wide-angle end Medium Telephoto end focal length f 4.120 7.514 11.534
F number 3.006 3.938 5.120
Half angle of view ω (°) 28.50 16.57 11.00
Image height 2.237 2.236 2.243
Total length L 21.78 21.78 21.78
Back focus BF 4.460 4.460 4.460

d4 1.000 2.532 1.000
d6 7.400 3.067 1.240
d11 2.000 4.801 8.159

f1 = −7471.09
f2 = −8.201
f3 = 5.724
f1p = 23.109
f1n = -21.372
f3p = 4.135
f3n = -9.147
fw = 4.120

Aspheric data 1st surface k = 6.880566, A ₄ = 2.885364E-04, A ₆ = 2.894835E-05
2nd surface k = 1.118198, A ₄ = -2.698204E-05, A ₆ = 8.170796E-05
4th surface k = 7.462498, A ₄ = -4.918836E-05, A ₆ = 1.587022E-06
5th surface k = -1.442643, A ₄ = -3.900528E-04, A ₆ = -9.808240E-05
8th surface k = -6.902892E-01, A ₄ = 8.137100E-04, A ₆ = 3.451952E-04
9th surface k = -7.286052, A ₄ = 1.388372E-03, A ₆ = 4.359649E-04
11th surface k = 3.618683E-01, A ₄ = 3.589999E-03, A ₆ = 9.580870E-04
12th surface k = 2.621573, A ₄ = 4.189142E-03, A ₆ = 9.812322E-04
13th surface k = -1.223659E + 01, A ₄ = -2.763689E-03, A ₆ = 1.376604E-03

The value of each conditional expression is shown below.
f1n / f1p = −0.925
f2 / f3 = −1.433
f3p / f3n = −0.452
f3 / fw = 1.389
fw / f1 = −0.000551
Thus, the zoom lens according to Numerical Example 4 satisfies the conditional expressions (1), (2), (3), and (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, also with the zoom lens according to the present embodiment, the image plane is corrected satisfactorily and various aberrations are preferably corrected, as in the first to third embodiments.

(Numerical example 5)
As shown in FIG. 29, the zoom lens according to the fifth embodiment has a first lens group G1 having negative refractive power in order from the object side, as in the zoom lens according to the fourth embodiment. The second lens group G2 having negative refractive power, the third lens group G3 having positive refractive power, and the fourth lens group G4 having positive refractive power. A cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor.

  Similarly to the zoom lens according to the fourth embodiment, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and the third lens. The group G3 is configured to move along the optical axis, and 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.

  However, unlike the zoom lens according to the fourth embodiment, the zoom lens according to the present embodiment is a third lens in which the second lens group G2 is a negative meniscus lens having a concave surface facing the object side. L3.

  Specifically, the first lens group G1 includes, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface facing the object side, and a second lens L2 that is a biconvex lens. The second lens group G2 includes a third lens L3 that is a negative meniscus lens having a concave surface directed toward the object side.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens L5 that is a negative meniscus lens having a convex surface facing the object side. The fourth lens group G4 includes a sixth lens L6 that is a positive meniscus lens having a concave surface directed toward the object side. The sixth lens L6 is also formed in an aspheric shape having an inflection point, like the sixth lens L6 of the zoom lens according to the first embodiment.

Hereinafter, Numerical Example 5 of the zoom lens according to the present embodiment will be described.

Numerical Example 5

Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 22.000 0.7000 1.52470 56.2
2 * 5.870 1.4000
3 172.300 1.2000 1.62090 24.0
4 * -15.700 variable
5 * -4.836 0.5000 1.52470 56.2
6 -808.645 Variable
7 (Aperture) ∞ 0.1040
8 * 2.630 1.6000 1.49700 81.58
9 * -7.357 0.1000
10 5.763 0.5200 1.68893 31.15
11 * 2.873 variable
12 * -9.589 0.8000 1.52470 56.2
13 * -6.331 0.3200
14 ∞ 0.3000 1.51633 64.12
15 ∞ 3.8575
(Image plane) ∞

Various data Zoom ratio 2.799
Wide-angle end Medium Telephoto end focal length f 3.838 7.151 10.743
F number 3.006 4.010 5.086
Half angle of view ω (°) 30.38 17.47 11.83
Image height 2.250 2.250 2.250
Total lens length L 21.80 21.80 21.80
Back focus BF 4.375 4.375 4.375

d4 1.100 2.594 1.105
d6 7.400 2.844 1.240
d11 2.000 5.062 8.155

f1 = −61.718
f2 = −9.274
f3 = 5.727
f1p = 23.231
f1n = -15.490
f3p = 4.117
f3n = −8.975
fw = 3.838

Aspherical data first surface k = 2.044348E + 01, A ₄ = 8.592904E-04, A ₆ = 2.279711E-05
2nd surface k = 1.484784, A ₄ = 3.999859E-04, A ₆ = 5.488247E-05
4th surface k = 1.585229E + 01, A ₄ = 8.238320E-05, A ₆ = 6.769823E-06
5th surface k = -1.347238, A ₄ = -2.554949E-04, A ₆ = -1.574010E-04
8th surface k = -6.772508E-01, A ₄ = 9.075904E-04, A ₆ = 3.986278E-04
9th surface k = -7.433216, A ₄ = 1.653771E-03, A ₆ = 4.823817E-04
11th surface k = 3.758604E-01, A ₄ = 3.796517E-03, A ₆ = 9.951504E-04
12th surface k = 5.598553, A ₄ = 4.985902E-03, A ₆ = 1.220063E-03
13th surface k = -1.525732E + 01, A ₄ = -3.035012E-03, A ₆ = 1.767618E-03

The value of each conditional expression is shown below.
f1n / f1p = −0.667
f2 / f3 = −1.619
f3p / f3n = −0.459
f3 / fw = 1.492
fw / f1 = −0.0622
Thus, the zoom lens according to Numerical Example 5 satisfies the conditional expressions (1), (2), (3), and (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, also with the zoom lens according to the present embodiment, the image plane is corrected satisfactorily and various aberrations are preferably corrected, as in the fourth embodiment.

(Numerical example 6)
As shown in FIG. 36, the zoom lens according to the sixth embodiment is a first lens having negative refractive power in order from the object side, like the zoom lenses according to the fourth and fifth embodiments. The lens unit includes a group G1, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power. A cover glass 10 is disposed between the fourth lens group G4 and the image plane of the image sensor.

  Similarly to the zoom lens according to the first embodiment, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and the third lens. The group G3 is configured to move along the optical axis, and 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.

  However, the zoom lens according to the present embodiment differs from the zoom lenses according to the fourth and fifth embodiments in that the thickness of the second lens L2 in the optical axis direction is the same as in the fourth and fifth embodiments. The second lens L2 of the zoom lens according to the first embodiment is formed thicker than the second lens L2. Therefore, if the zoom lens according to the present embodiment is embodied as a bent zoom lens, the thickness of the device can be greatly reduced, and the portable device can be suitably reduced in size and thickness. Can do.

  In the zoom lens according to the present embodiment, the rear lens group of the third lens group G3 is constituted by a cemented lens composed of two positive and negative lenses. By configuring the rear lens group of the third lens group in this manner, chromatic aberration can be corrected more favorably. The rear group lens may be a combination of a lens having a positive refractive power and a lens having a negative refractive power. For example, a cemented lens composed of a biconvex lens and a biconcave lens, or two separated positive and negative lenses. You may comprise from the lens of.

  Specifically, in the zoom lens, the first lens group G1 includes, in order from the object side, a first lens L1 that is a negative meniscus lens having a convex surface facing the object side, and a flat surface having the convex surface facing the image surface side. The second lens L2 is a convex lens, and the second lens group G2 is a third lens L3 that is a biconcave lens.

  The third lens group G3 includes, in order from the object side, a stop ST, a front group lens L4 that is a biconvex lens, and a rear group lens formed by joining two positive and negative lenses. In this embodiment, the rear lens group includes an object-side fifth lens L51 that is a positive meniscus lens having a convex surface facing the object side, and an image-surface-side fifth lens that is a negative meniscus lens having a convex surface facing the object side. It is configured by bonding with the lens L52.

  The fourth lens group G4 includes a sixth lens L6 that is a positive meniscus lens having a concave surface directed toward the object side. The sixth lens L6 is also formed in an aspheric shape having an inflection point, like the sixth lens L6 of the zoom lens according to the first embodiment.

Hereinafter, Numerical Example 6 of the zoom lens according to the present embodiment will be described.

Numerical Example 6

Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 13.000 0.7500 1.52470 56.2
2 * 5.900 1.8500
3 ∞ 6.0000 1.55850 29.0
4 * -20.000 variable
5 -5.980 0.5000 1.49700 81.58
6 24.933 Variable
7 (Aperture) ∞ 0.1000
8 * 3.914 1.1000 1.52470 56.2
9 * -17.730 0.2000
10 4.478 1.2000 1.72000 50.3
11 45.163 0.5500 1.80486 24.7
12 * 3.563 variable
13 * -8.115 0.9000 1.58500 29.0
14 * -6.726 0.3200
15 ∞ 0.6400 1.51633 64.12
16 ∞ 3.905
(Image plane) ∞

Various data Zoom ratio 2.799
Wide-angle end Medium Telephoto end focal length f 3.997 7.385 11.186
F number 3.166 4.329 5.561
Half angle of view ω (°) 29.38 16.94 11.37
Image height 2.250 2.250 2.250
Total lens length L 27.90 27.90 27.90
Back focus BF 4.647 4.647 4.647

d4 1.100 2.604 1.118
d6 7.500 2.992 1.293
d12 1.500 4.503 7.690

f1 = −83.441
f2 = −9.653
f3 = 5.763
f1p = 35.810
f1n = -21.365
f3p = 6.219
f3n = −37.152
fw = 3.997

Aspheric data 1st surface k = 2.064060, A ₄ = 1.035352E-05, A ₆ = 1.095930E-05
2nd surface k = 5.348029E-01, A ₄ = -3.053542E-04, A ₆ = 2.791519E-05
4th surface k = 1.767077E + 01, A ₄ = -3.367300E-04, A ₆ = 3.931349E-06
8th surface k = -4.834554E-01, A ₄ = 2.847822E-04, A ₆ = 1.070941E-04, A ₈ = -1.466055E-06, A ₁₀ = -9.283126E-07
9th surface k = 1.936009, A ₄ = -2.275825E-05, A ₆ = -2.413247E-05, A ₈ = 1.005583E-05, A ₁₀ = 1.239154E-05
12th surface k = 9.535272E-01, A ₄ = 3.102478E-03, A ₆ = 1.033215E-03, A ₈ = 1.591105E-04, A ₁₀ = -2.843224E-04
13th surface k = -1.101930E + 01, A ₄ = 2.412330E-03, A ₆ = -1.115892E-04
14th surface k = -7.841902, A ₄ = 2.631136E-03, A ₆ = -1.016464E-04

The value of each conditional expression is shown below.
f1n / f1p = −0.597
f2 / f3 = −1.675
f3p / f3n = −0.167
f3 / fw = 1.442
fw / f1 = −0.0479
Thus, the zoom lens according to Numerical Example 6 satisfies the conditional expressions (1), (2), (3), and (4).

  37, 39, and 41 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 6, and FIGS. 38, 40, and 42 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, also with the zoom lens according to the present embodiment, the image plane is corrected satisfactorily and various aberrations are preferably corrected as in the first embodiment.

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

  By the way, the zoom lens according to these embodiments satisfies the above conditional expression (2), so that in zooming, the position on the optical axis of the second lens group G2 at the wide angle end and the second lens at the telephoto end. The position on the optical axis of the group G2 is substantially matched. This point will be described below.

  As described above, the zoom lenses according to the first to sixth embodiments are configured such that the focus and the back focus are adjusted by the movement of the second lens group G2. For this reason, as shown in FIG. 43, when the object distance is infinite (∞), the second lens group G2 moves along a trajectory as indicated by a solid line, whereas the object distance is close. For example, when the object distance is 20 cm, the object moves by following a locus shifted toward the object side by the feed amount Δz, that is, a locus as indicated by a broken line in the drawing.

  Table 1 shows, for each of Numerical Examples 1 to 6, the position on the optical axis of the second lens group G2 when the object distance is infinite, and the optical axis of the second lens group G2 when the object distance is 20 cm. The difference from the upper position (feed amount Δz) is shown.

  As shown in Table 1, in the zoom lenses according to Numerical Examples 1 to 6, the feeding amount Δz is substantially the same at the wide-angle end and the telephoto end. 44 to 49 are aberration diagrams at the wide-angle end, the intermediate position, and the telephoto end when the object distance is 20 cm in the zoom lens having the configuration of the numerical example 1, and FIGS. FIG. 56 to FIG. 61 are graphs showing aberrations when the object distance is 20 cm in the zoom lens having the configuration of Example 2, and FIGS. 56 to 61 are graphs showing cases when the object distance is 20 cm in the zoom lens having the configuration of Numerical Example 3. It is an aberration diagram. FIGS. 62 to 67 are aberration diagrams at the wide-angle end, the intermediate position, and the telephoto end when the object distance is 20 cm in the zoom lens having the configuration of the numerical value example 4. FIGS. FIG. 74 to FIG. 79 are graphs showing aberrations when the object distance is 20 cm in the zoom lens having the structure according to Numerical Example 5. FIGS. 74 to 79 are diagrams when the object distance is 20 cm in the zoom lens having the structure according to Numerical Example 6. FIG.

  As shown in these aberration diagrams, in the zoom lenses according to the first to sixth embodiments, there is almost no deterioration in aberration between the close distance and the object distance is infinite, and the zoom lens changes from the close distance to infinity. Aberrations are corrected satisfactorily over the entire magnification range.

FIG. 2 is a cross-sectional view of each lens at the wide-angle end, an intermediate position, and a telephoto end of the zoom lens according to the first embodiment. 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. 5 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 a second embodiment. 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. 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 a third embodiment. 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; It is each lens sectional drawing in the wide angle end of a zoom lens concerning a 4th embodiment, an intermediate position, and a telephoto end. 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. 10 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 a fifth embodiment. FIG. 10 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; It is each lens sectional drawing in the wide-angle end, intermediate position, and telephoto end of the zoom lens which concerns on 6th Embodiment. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 6; 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 6; FIG. 10 is an aberration diagram showing lateral aberration at the intermediate position of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 6; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 6; In the zoom lenses according to the first to sixth embodiments, lens cross-sectional views illustrating the movement locus of the second lens group when the object distance is infinite and when the object distance is close. FIG. 6 is an aberration diagram illustrating lateral aberration at the wide-angle end when the object distance is 20 cm in 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 when the object distance is 20 cm in the zoom lens according to Numerical Example 1 of the same numerical value. FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position when the object distance is 20 cm in the zoom lens according to Numerical Example 1 of the same numerical value. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position in the zoom lens according to Numerical Example 1 when the object distance is 20 cm. FIG. 6 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 1 of the same numerical value. FIG. 9 is an aberration diagram showing lateral aberration at the wide-angle end when the object distance is 20 cm in 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 when the object distance is 20 cm in the zoom lens according to Numerical Example 2 of the same numerical value. FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position when the object distance is 20 cm 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 when the object distance is 20 cm in the zoom lens according to Numerical Example 2; FIG. 11 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end when the object distance is 20 cm in the zoom lens according to Numerical Example 3. FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide angle end when the object distance is 20 cm in the zoom lens according to Numerical Example 3; FIG. 11 is an aberration diagram showing lateral aberration at an intermediate position when the object distance is 20 cm in the zoom lens according to Numerical Example 3; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position in the zoom lens according to Numerical Example 3 when the object distance is 20 cm. FIG. 11 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 3; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 3; In the zoom lens according to Numerical Example 4, it is an aberration diagram showing lateral aberration at the wide angle end when the object distance is 20 cm. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide angle end when the object distance is 20 cm in the zoom lens according to Numerical Example 4; FIG. 11 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 4 when the object distance is 20 cm. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position in the zoom lens according to Numerical Example 4 when the object distance is 20 cm. FIG. 12 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 4; In the zoom lens according to Numerical Example 5, it is an aberration diagram showing lateral aberration at the wide angle end when the object distance is 20 cm. FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide angle end when the object distance is 20 cm in the zoom lens according to Numerical Example 5; FIG. 12 is an aberration diagram showing lateral aberration at an intermediate position when the object distance is 20 cm 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 when the object distance is 20 cm in the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 5; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 5; In the zoom lens according to Numerical Example 6, it is an aberration diagram showing lateral aberration at the wide angle end when the object distance is 20 cm. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide angle end when the object distance is 20 cm in the zoom lens according to Numerical Example 6; FIG. 12 is an aberration diagram showing lateral aberration at an intermediate position when the object distance is 20 cm in the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position when the object distance is 20 cm in the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end when the object distance is 20 cm in the zoom lens according to Numerical Example 6;

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1 1st lens L2 2nd lens L3 3rd lens ST Aperture L4 4th lens L5 5th lens L51 Object side 5th lens L52 Image Surface side fifth lens L6 Sixth lens 10 Cover glass

Claims (5)

From the object side,
A first lens group comprising two lenses, a lens having a negative refractive power and a lens having a positive refractive power;
A second lens group having negative refractive power with the concave surface facing the object side;
A third lens group having a positive refractive power as a whole, which is arranged in the order of a stop, a front group lens having a positive refractive power, and a rear group lens having a negative refractive power;
A fourth lens group having a positive or negative refractive power,
In zooming from the wide-angle end to the telephoto end, the first lens group and the fourth lens group are fixed,
The second lens group is moved to the object side after moving to the image plane side,
The third lens group is linearly moved toward the object side,
The focal length of the second lens group is f2, the focal length of the third lens group is f3, and the focal length of the front lens group having the positive refractive power among the third lens groups is f3p, and the negative refraction. When the focal length of the rear group lens having power is f3n and the combined focal length of the first to fourth lens groups at the wide angle end is fw,
−1.675 ≦ f2 / f3 <−1.0
−0.460 ≦ f3p / f3n <0
1.0 <f3 / fw ≦ 1.492
A zoom lens characterized by satisfying The front lens group and the rear lens group of the third lens group are each composed of one lens.
The zoom lens according to claim 1. The fourth lens group is composed of one lens.
The zoom lens according to claim 1, wherein: When the focal length of the lens having the negative refractive power in the first lens group is f1n and the focal length of the lens having the positive refractive power is f1p, the following conditional expression is satisfied: The zoom lens according to claim 1.
−1.5 <f1n / f1p <−0.3 The following conditional expression is satisfied, where f1 is a focal length of the first lens group, and fw is a combined focal length of the first to fourth lens groups at the wide-angle end. The zoom lens according to any one of the above.
-0.15 <fw / f1 <0.15