JP2018189865A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which offers compactness suitable for digital cameras with large image sensors, and comprises constituting lens groups and high-refractive-index, low-dispersion glass materials appropriately disposed therein.SOLUTION: A zoom lens comprises, in order from the object side, a negative first lens group, positive second lens group, and negative third lens group, and is configured to change air gap distance between the lens groups for zooming, where the first lens group and the second lens group move to reduce the distance therebetween when zooming from the wide-angle end to the telephoto end. The second lens group has four lenses consisting of a positive 21 lens, positive 22 lens, negative 23 lens, and positive 24 lens in order from the object side. The zoom lens satisfies the following conditional expressions: -1.22<(R232+R241)/(R232-R241)<-0.15 ...(expression 1), n2p>-0.0073×ν2p+2.11 ...(expression 2), 1.5<n2p<1.85 ...(expression 3), 65<ν2 P<97 ...(expression 4), where R232 represents R on an image side surface of the 23 lens, R241 represents R on an object side surface of the 24 lens, n2p represents a refractive index of the 24 lens, and ν2p represents an Abbe number of the 24 lens.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compact zoom lens having a high magnification suitable for a digital still camera or the like, and more particularly, to a zoom lens excellent in portability in which a predetermined zoom ratio is ensured and the total length of the lens is shortened in a stored state. .

  In recent years, in imaging devices such as digital still cameras and video cameras using electronic image sensors, the wide field angle and high zoom ratio as well as the shallow depth of field have been utilized as a method for expressing drawings. There is a need for a so-called blur expression that makes a subject stand out from the background.

  Conventionally, an electronic image sensor has been required to have telecentricity for an optical system in order to cope with shading and the like. Therefore, the optical system used in a compact digital camera, in particular, where a reduction in the size of the camera is required, reduces the sensor size to about 1 / 2.3-type to 1 / 1.7-type, thereby reducing the telecentricity of the optical system. The camera has been downsized. Since the imaging optical system used at this time is a lens having a short actual focal length, the captured image is an image having a deep depth of field.

  If you try to increase the sensor size while maintaining the telecentricity of the optical system, it is inevitable that the imaging optical system will be enlarged. It was common to use equipment.

  In a compact digital still camera using an electronic image sensor, it is common to calculate the contrast of a subject from a sensor output and perform a focusing operation. At this time, since it is necessary to finely drive the focus lens in order to search for the peak position of the contrast, the focus group is required to be reduced in size and weight for quick focusing operation.

  As an optical system corresponding to a large image sensor while maintaining the miniaturization of the optical system, a zoom lens composed of three lens groups of negative, positive, and negative refractive power in order from the object side is known. (Patent Documents 1 and 2). In this negative group preceding type three-group zoom lens, the second lens group and the third lens group are arranged in a strong telephoto type, thereby shortening the back focus and reducing the overall length of the optical system. Yes.

  In recent years, in an imaging apparatus using an electronic imaging device, a technique for correcting distortion aberration of an optical system by digital processing is known. Also. In a large electronic image pickup device, a technique for expanding the allowable range of the light incident angle on the sensor by optimizing the on-chip microlens arrangement is known.

  On the other hand, in recent years, an optical glass having a high hardness and a Young's modulus that cannot be realized by a general optical glass and having a high refractive index and low dispersion has been known (Patent Document 3). This optical glass realizes a high refractive index and low dispersion optical glass by using a containerless solidification method and appropriately setting a composition containing aluminum oxide (alumina (Al 2 O 3)) as a main component.

JP 05-093866 A JP 2006-119193 A WO2010-071143

  In each example of Patent Document 1, a zoom lens having a zoom ratio of about 3 to about 3 times a half field angle is disclosed. The zoom lens disclosed in Patent Document 1 is an optical system used in a silver salt film camera, and optically corrects distortion to about ± 5% from the wide-angle end to the telephoto end. Regarding the correction of the distortion, the negative distortion generated in the first lens group is canceled by the positive distortion generated in the third lens group.

  Here, in each embodiment, the first lens unit has a strong refractive power in order to reduce the front lens diameter, and it is difficult to correct curvature of field particularly at the wide angle end. In addition, in order to correct distortion, it is difficult to correct aberrations in the entire zoom range because the third lens group must also be arranged with a strong refractive power.

  In the negative / positive / negative three-group zoom embodiment of Patent Document 2, a zoom lens having a zoom ratio of about 30 ° to about 2 × is disclosed. The zoom lens disclosed in Patent Document 2 is an ultra-compact optical system corresponding to a small sensor, and the optical system is miniaturized by extremely reducing the back focus at the wide-angle end. Here, when the small third lens group in the lens group is the focus group, it is difficult to ensure the amount of movement of the focus group at the wide angle end because the back focus is too short. In addition, since the third lens group is disposed in the vicinity of the image plane at the wide-angle end, the diameter of the final ball is increased when it is proportional to the large sensor size.

  The negative, positive, and negative types as in Patent Documents 1 and 2 tend to increase the power of the second group, making it difficult to brighten Fno, and the brightness at the wide-angle end is about F2.8.

  In addition, recent optimization of on-chip microlens has expanded the allowable range of the incident angle of light on the sensor. Therefore, a sensor in which the lens on the image plane side has a negative lens as disclosed in a reference document. Even with an optical system with a large incident angle, shading can be suppressed to some extent.

  In these optical systems, a negative lens is arranged on the front side and the rear side of the lens by arranging a plurality of positive lenses in the vicinity of a diaphragm or a light beam restricting member for determining an Fno light beam. A good aberration correction is performed.

  In these optical systems, the axial chromatic aberration and the peripheral color flare are corrected by using a low-dispersion optical material for the positive lens disposed in the vicinity of the stop or the light beam limiting member. When bright Fno specifications are secured for the optical system, the diameter of the positive lens is required to some extent, so it is necessary to increase the center thickness of the lens to secure the edge. there were.

  In general, optical glass has a graph (hereinafter referred to as “nd-νd diagram”) in which the Abbe number is a large value in the left direction on the horizontal axis so that the refractive index is a large value on the vertical axis. When mapped, it is known to distribute along some straight lines. In general, when the refractive index of the optical glass increases, the Abbe number decreases and the dispersion increases.

  On the other hand, Patent Document 3 discloses an optical glass in which the relationship between the refractive index and the Abbe number exists in a region different from the normal optical glass in the above-mentioned nd-νd diagram by a manufacturing method using a containerless solidification method. . These are known as optical glasses having a high Abbe number and a low dispersion while having a high refractive index as compared with general optical glasses. Use of the optical glass having such properties for the imaging optical system is advantageous for aberration correction and miniaturization of the entire optical system. In order to achieve high optical performance and miniaturization, it is important to appropriately set the glass material, the refractive power of each lens, the lens configuration, and the like as described above.

  The object of the present invention is to appropriately set the configuration and refractive power arrangement of each lens group while realizing the downsizing and large aperture of the optical system corresponding to the large sensor by the negative, positive and negative three-group configuration. Another object of the present invention is to provide a zoom lens suitable for an electronic imaging device in which a glass material having a high refractive index and low dispersion is appropriately arranged.

To achieve the above object, a zoom lens according to the present invention provides:
In a zoom lens comprising a negative first lens group, a positive second lens group, and a negative third lens group from the object side and performing zooming by changing the air interval of each group, the zooming from the wide-angle end to the telephoto end At the time of magnification, the first lens group and the second lens group move so that the group interval is narrowed, and the second lens group includes 21 positive lenses, 22 positive lenses, 23 negative lenses, and positive lenses from the object side. It has 4 lenses of 24 lenses.

-1.22 <(R232 + R241) / (R232-R241) <-0.15 (1)
n2p> −0.0073 × ν2p + 2.11 (2)
1.5 <n2p <1.85 (3)
65 <ν2P <97 (4)
R232; 23 lens image side R
R241; Object side R of 24 lenses
n2p: Refractive index of the 24th lens ν2p: Abbe number of the 24th lens Furthermore, in order to approach the best mode, it is desirable to satisfy the following conditions.

  The following conditional expression is satisfied in the lens system.

0.9 <f24 / f21 <1.6 (5)
-1.9 <f24 / f23 <-0.8 (6)
f21: focal length of the twenty-first lens f23: focal length of the twenty-third lens f24: focal length of the twenty-fourth lens The following conditional expression is satisfied in the lens system.

−0.35 <f2 / f3 <−0.25 (7)
0.37 <f1 / f3 <0.48 (8)
f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group The following conditional expression is satisfied in the lens system.

1.1 <f2 / fw <1.28 (9)
1.2 <f24 / f2 <3.5 (10)
fw: focal length of the entire system at the wide-angle end In the lens system, the second group includes a positive lens having a tight object measurement curvature, a cemented lens in which a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side are cemented, The lens surface is composed of four positive lenses having a convex surface.

  In the lens system, the second group includes a positive lens with a tight object measurement curvature, a cemented lens in which a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, a positive meniscus lens having a concave surface on the object side, and a slow power It was composed of 5 positive lenses.

  According to the present invention, it is possible to provide a zoom lens that can accommodate a large image sensor and has a zoom ratio of about 3 times and can be retracted thinly with the above-described configuration.

Lens sectional view of Example 1 Lens sectional view of Example 2 Lens sectional view of Example 3 Lens sectional view of Example 4 Longitudinal aberration diagram of Example 1 (wide-angle end) Longitudinal aberration diagram of Example 1 (middle) Longitudinal aberration diagram of Example 1 (telephoto end) Longitudinal aberration diagram of Example 2 (wide-angle end) Longitudinal aberration diagram of Example 2 (middle) Longitudinal aberration diagram of Example 2 (telephoto end) Longitudinal aberration diagram of Example 3 (wide-angle end) Longitudinal aberration diagram of Example 3 (middle) Longitudinal aberration diagram of Example 3 (telephoto end) Longitudinal aberration diagram of Example 3 (wide-angle end) Longitudinal aberration diagram of Example 3 (middle) Longitudinal aberration diagram of Example 3 (telephoto end)

  In the present invention, the first lens group is composed of a negative first group, a positive second group, and a negative third group from the object side. Here, by adopting a negative-group-first type zoom lens, it is possible to reduce the size of the wide-angle optical system and to make the second lens group and the third lens group have a positive and negative telephoto type arrangement. As a result, the overall length can be reduced while supporting a large sensor.

  Further, a rear focus method is employed in which the third lens unit is moved to the image side when focusing from an object at infinity to a finite distance object. According to this, a quick focusing operation is realized by using the third lens group having a small outer diameter and a light weight as the focus group.

  In addition, each lens group of the third group is configured by one positive lens and one negative lens. With this configuration, monochromatic aberration and chromatic aberration are corrected in each group, and good optical performance is maintained over the entire zoom range.

  In the present invention, the negative, positive, and negative lenses can be viewed as positive and negative telephoto type configurations as a whole when the first and second lens groups are regarded as one lens group in each zoom state. .

  In the telephoto type, the total lens length can be shortened with respect to the actual focal length of the lens, so that the total length at the time of shooting can be shortened and the configuration can be made compact despite the large sensor.

  On the other hand, the power of each lens group, particularly the second lens group responsible for main image formation, tends to increase, and the number of lenses tends to increase in order to correct spherical aberration and longitudinal chromatic aberration.

In the present invention, n2p> −0.0073 × ν2p + 2.11 (2)
1.5 <n2p <1.85 (3)
65 <ν2P <97 (4)
By using a material having a high refractive index in spite of low dispersion in a region satisfying the above formula, axial chromatic aberration can be corrected well with a small number of lenses.

  The glass characteristics satisfying the above (2) to (4) can be produced by a production method using the aforementioned containerless solidification method.

  An air lens between the negative lens in the second group and its image-side positive lens in order to satisfactorily correct spherical aberration that occurs when the second group is configured with a small number of lenses and the Fno on the telephoto side is made brighter. Is configured to satisfy the following conditional expression.

-1.22 <(R232 + R241) / (R232-R241) <-0.15 (1)
The second group includes a positive 21 lens, a positive 22 lens, a negative 23 lens, and a positive 24 lens from the object side, and the positive 22 lens and the negative 23 lens are cemented. The negative 23 lens has a strong concave surface on the image side, and the object side surface of the 24th lens is a weak concave surface or a weak convex surface, thereby correcting spherical aberration on the telephoto side, and correcting axial chromatic aberration using the 24 lens as the above-mentioned material. ing.

  In particular, the image side surface of the negative 23 lens is a relatively strong surface for correcting spherical aberration on the image surface side. However, in the case of a lens having a small Fno, the diameter of the lens becomes large. Due to the tendency, the range shown in (1) is set.

The object side of the 24 lens should have a concave surface facing the object side in order to correct higher-order spherical aberration.
In order to avoid interference with the 23 lens, the range is set to the range of the expression (1).

  The 21 and 22 lenses are composed of lenses with small dispersion for correcting axial chromatic aberration, and the 23 lenses are composed of lenses with large dispersion.

On the other hand, in order to correct spherical aberration, the twenty-first lens is composed of a lens having a relatively high refractive index.
In addition, since the cemented lenses constituting the 22nd and 23rd lenses are desired to have appropriate power in order to improve the accuracy of the cementation, materials that can balance the chromatic aberration while maintaining the appropriate power are selected.

Equation (1) relates to a positive air lens between the cemented lens and the positive lens, but the air lens acts as a concave lens with a convex shape because the relationship between the front and rear refractive indexes is opposite to that of glass. . The desirable shape of the air lens represented by the expression (1) is a biconvex or meniscus convex lens shape in which the curvature on the object side is tight and the curvature on the image side is gentle.

  In order to maintain the above-described spherical aberration correction, chromatic aberration correction, and bonding accuracy in a well-balanced manner, the focal length ratio between the 21 lens and the 23 lens and the 24 lens is set as follows.

0.9 <f24 / f21 <1.6 (5)
-1.9 <f24 / f23 <-0.8 (6)
f21: Focal length of the 21st lens f23: Focal length of the 23rd lens f24: Focal length of the 24th lens In order to reduce the size of the entire lens system, it is desirable to shorten the focal lengths of the first and second groups. On the other hand, in order to perform a desired aberration correction, it is easier to correct the aberration by increasing the focal length.

  In the third group that performs focusing, it is desired to shorten the focal length in order to reduce the amount of focus movement. However, it is easier to correct the aberration variation of the focus by increasing the focal length.

  Therefore, f2 / f3 and f1 / f3 are set as follows to balance aberration correction and miniaturization.

−0.35 <f2 / f3 <−0.25 (7)
0.37 <f1 / f3 <0.48 (8)
f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group As described above, the axial chromatic aberration is satisfactorily corrected over the entire area within an appropriate second group focal length. As a condition, the focal length of 24 lenses with high refractive index and low dispersion is set as in the following conditional expression.

1.1 <f2 / fw <1.28 (9)
1.2 <f24 / f2 <3.5 (10)
fw: focal length of the entire system at the wide angle end Next, the meaning of each conditional expression will be described.

  Equation (1) relates to the shape factor of the air lens between the negative 23 lens and the positive 24 lens constituting the second group, and is a condition for satisfactorily correcting the spherical aberration in the telephoto range. This is not good because the spherical aberration in the telephoto range where the curvature of the second lens negative 23 lens image side becomes too loose beyond the upper limit of the expression (1) becomes insufficiently corrected. The spherical aberration in the telephoto range where the curvature on the second lens negative 23 lens image side is too tight beyond the lower limit of the expression (1) is overcorrected, which is not good.

  Expression (2) is an expression representing the relationship between the refractive index of the positive lens of the 24th lens constituting the second group and the Abbe number. If the lower limit of Expression (2) is exceeded, it is difficult to correct axial chromatic aberration. In other words, a solution that can be corrected is not good because the lens thickness increases and the entire lens system becomes larger.

  Equation (3) relates to the refractive index of the positive lens of the 24th lens constituting the second group. If the refractive index becomes too high exceeding the upper limit value of Equation (3), the material will fall within the desired Abbe number range. Manufacturing becomes difficult. If the refractive index is too low beyond the lower limit of the expression (3), the center thickness of the third lens becomes thick and the entire lens system becomes large, which is not good.

  The expression (4) relates to the positive lens Abbe number of the 24th lens constituting the second group. If the Abbe number becomes too large beyond the upper limit value of the expression (4), it is difficult to manufacture a material within a desired refractive index range. It becomes. If the Abbe number becomes too small beyond the lower limit of the equation (4), it will be difficult to satisfactorily correct the longitudinal chromatic aberration.

  Equation (5) is obtained by normalizing the focal length of the 24th lens constituting the second group by the focal length of the 21st lens, and the focal length of the 24th lens becomes longer than the upper limit of equation (5). If it is too large, it will be difficult to correct axial chromatic aberration in the telephoto range. If the lower limit of equation (5) is exceeded and the focal length of the 21st lens becomes too long, it will be difficult to correct spherical aberration and coma in the telephoto range.

  Formula (6) is obtained by normalizing the focal length of the 24th lens constituting the second group by the focal length of the 23rd lens, and the focal length of the 24th lens is short beyond the upper limit of Formula (6). If it becomes too large, the axial chromatic aberration will be overcorrected in the telephoto range, but good correction becomes difficult. If the lower limit of the expression (6) is exceeded and the focal length of the 23rd lens becomes too long, it is difficult to correct axial chromatic aberration in the telephoto range.

  Expression (7) is obtained by normalizing the focal length of the second group by the focal length of the third group at the wide-angle end. If the upper limit of Expression (7) is exceeded and the focal length of the second group becomes too short, zooming is performed. This is not good because it becomes difficult to correct the spherical aberration variation in the entire area. If the lower limit of the expression (7) is exceeded and the focal length of the second lens unit becomes too long, the zoom stroke of the second lens unit increases and the entire lens system becomes large, which is not good.

  Expression (8) is obtained by standardizing the focal length of the first group with the focal length of the third group. If the focal length of the first group becomes too long beyond the upper limit of expression (8), the lens at the wide-angle end It is not good because the total length increases and the front lens diameter increases. If the focal length of the first lens group becomes too short beyond the lower limit of the equation (8), it will be difficult to correct coma flare at the periphery of the screen in the wide angle region.

  Expression (9) is obtained by normalizing the focal length of the second group by the focal length of the entire system at the wide angle end. If the upper limit of Expression (9) is exceeded and the focal length of the second group becomes too short, the entire zoom range is obtained. This is not good because it becomes difficult to correct the spherical aberration fluctuation in the lens. If the focal length of the second group becomes too long beyond the lower limit of the expression (9), the zoom stroke of the second group increases and the entire lens system becomes large, which is not good.

  Expression (10) is obtained by normalizing the focal length of the 24th lens constituting the second group by the focal length of the second lens group, and the focal length of the 24th lens is longer than the upper limit of Expression (10). If it becomes too much, it will be difficult to correct longitudinal chromatic aberration in the telephoto range. If the focal length of the twenty-fourth lens becomes too short beyond the lower limit of equation (10), it will be difficult to correct spherical aberration and coma in the telephoto range.

  In order to bring the object of the present invention closer to the best, it is better to satisfy the following conditions.

−1.20 <(R232 + R241) / (R232−R241) <− 0.23
... (1d)
n2p> −0.0073 × ν2p + 2.13 (2d)
1.5 <n2p <1.7 (3d)
68 <ν2P <96 (4d)
1.05 <f24 / f21 <1.5 (5d)
-1.85 <f24 / f23 <-0.9 (6d)
−0.33 <f2 / f3 <−0.26 (7d)
0.37 <f1 / f3 <0.46 (8d)
1.12 <f2 / fw <1.26 (9d)
1.5 <f24 / f2 <3.2 (10d)
Next, numerical data of each example is shown. In the numerical data of each example, r is a radius of curvature, d is a surface interval on the optical axis, nd and νd are a refractive index and an Abbe number with respect to the d-line of the optical material.

The aspherical shape is such that X is the amount of variation from the surface vertex in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, r is the paraxial radius of curvature, K is the conic constant, and A _2. , A ₄ , A ₆ ,... Are represented by the following equations when each order has an aspherical shape.

“E ± YY” in each coefficient means “× 10 ^{± YY} ”.

  Table 1 shows the values of the conditional expressions in each example.

[Numerical Example 1]
Unit mm

Surface data surface number rd nd vd
1 * 157.989 0.60 1.85135 40.1
2 * 14.762 2.25
3 -54.268 0.60 1.91082 35.3
4 45.217 1.24
5 20.657 1.61 1.95906 17.5
6 60.762 (variable)
7 * 12.140 2.42 1.76802 49.2
8 * 77.254 0.20
9 7.787 2.31 1.49700 81.5
10 15.316 0.50 1.92286 18.9
11 7.945 1.37
12 * 105.823 2.57 1.63000 70.0
13 * -15.663 0.0
14 ∞ 0.50
15 (Aperture) ∞ (Variable)
16 -28.501 2.03 1.90366 31.3
17 -10.274 0.99
18 * -7.121 0.50 1.85 135 40.1
19 -23.324 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -7.12328e-006

Second side
K = 0.00000e + 000 A 4 = 3.91568e-005 A 6 = 4.76250e-007 A 8 = -3.60782e-009 A10 = 6.51379e-011

7th page
K = 0.00000e + 000 A 4 = 1.78812e-005

8th page
K = 0.00000e + 000 A 4 = 1.33775e-004 A 6 = 1.84996e-007 A 8 = -4.64126e-009

12th page
K = 0.00000e + 000 A 4 = -1.12046e-004 A 6 = 1.74165e-006

Side 13
K = 0.00000e + 000 A 4 = -5.14976e-006 A 6 = 6.75853e-006 A 8 = -1.14362e-007

18th page
K = -7.94861e-001 A 4 = -1.43097e-004 A 6 = 2.17992e-006 A 8 = -8.81870e-008

Various data Zoom ratio 2.85
Wide angle Medium telephoto focal length 10.57 20.35 30.14
F number 2.26 4.72 5.15
Angle of view 37.6 22.5 15.1
Image height 6.56 8.00 8.00
Total lens length 46.44 43.19 46.77
BF 8.65 16.39 23.87

d 6 14.75 4.16 0.40
d15 3.36 2.95 2.81
d19 8.65 16.39 23.87

Zoom lens group data group Start surface Focal length
1 1 -17.91
2 7 13.04
4 16 -47.12

[Numerical Example 2]
Unit mm

Surface data surface number rd nd vd
1 * 157.989 0.60 1.85135 40.1
2 * 13.015 2.62
3 -43.555 0.60 1.91082 35.3
4 56.867 0.64
5 21.046 1.85 1.92286 18.9
6 124.595 (variable)
7 * 14.077 2.37 1.76802 49.2
8 * 473.178 0.20
9 8.592 2.22 1.49700 81.5
10 23.143 0.50 1.92286 18.9
11 10.753 1.92
12 -18.818 1.25 1.52000 85.0
13 * -10.165 0.10
14 * -121.000 1.55 1.52000 85.0
15 * -32.960 0.50
16 ∞ 0.50
17 (Aperture) ∞ (Variable)
18 -30.419 1.97 1.90366 31.3
19 -11.122 1.00
20 * -7.438 0.50 1.85 135 40.1
21 -24.535 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -3.35655e-005

Second side
K = 0.00000e + 000 A 4 = 6.08574e-006 A 6 = 4.26098e-007 A 8 = -9.93791e-009 A10 = 9.13598e-011

7th page
K = 0.00000e + 000 A 4 = 1.92863e-005

8th page
K = 0.00000e + 000 A 4 = 1.13490e-004 A 6 = -7.55275e-008 A 8 = 3.54902e-010

Side 13
K = 0.00000e + 000 A 4 = 9.11210e-004 A 6 = -1.76118e-005 A 8 = 1.60347e-007

14th page
K = 0.00000e + 000 A 4 = 5.80725e-004 A 6 = 1.52505e-005

15th page
K = 3.53916e + 001 A 4 = -5.29695e-006 A 6 = 4.11622e-005

20th page
K = -8.56306e-001 A 4 = -1.26324e-004 A 6 = 2.00122e-006 A 8 = -3.73132e-008

Various data Zoom ratio 2.85
Wide angle Medium Telephoto focal length 10.57 20.29 30.14
F number 2.06 4.64 5.13
Angle of view 37.6 22.5 15.1
Image height 6.56 8.00 8.00
Total lens length 46.74 43.80 47.44
BF 8.12 15.39 22.51

d 6 14.44 4.14 0.44
d17 3.31 3.39 3.62
d21 8.12 15.39 22.51

Zoom lens group data group Start surface Focal length
1 1 -17.28
2 7 13.17
4 18 -42.86

[Numerical Example 3]
Unit mm

Surface data surface number rd nd vd
1 * -107.791 0.80 1.85135 40.1
2 * 10.519 1.97
3 12.149 1.55 2.00272 19.3
4 19.344 (variable)
5 * 7.146 1.64 1.58313 59.5
6 * 60.700 0.20
7 6.818 1.42 1.69680 55.5
8 11.757 0.40 2.00069 25.5
9 5.523 1.17
10 -85.801 1.40 1.55332 95.0
11 * -9.689 0.50
12 (Aperture) ∞ (Variable)
13 -25.641 1.37 2.00330 28.3
14 -10.903 0.63
15 * -7.730 0.30 1.81000 41.0
16 -31.634 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = 3.26701e-005 A 6 = -2.61929e-007

Second side
K = 0.00000e + 000 A 4 = 4.30774e-005 A 6 = 6.10792e-007 A 8 = -1.33657e-008

5th page
K = 0.00000e + 000 A 4 = 2.07236e-005 A 6 = 6.06267e-006

6th page
K = -5.53569e + 002 A 4 = 7.58041e-004 A 6 = -7.72041e-007

11th page
K = -8.64792e + 000 A 4 = -1.15427e-003 A 6 = 3.12838e-005

15th page
K = -6.76287e-001 A 4 = -8.34918e-005 A 6 = 3.67065e-006 A 8 = -1.61635e-007

Various data Zoom ratio 2.85
Wide angle Medium Telephoto focal length 10.56 20.45 30.14
F number 3.29 4.85 6.39
Angle of view 38.0 22.0 15.0
Image height 6.72 8.00 8.00
Total lens length 40.94 36.58 39.40
BF 9.08 15.58 22.29

d 4 15.15 4.30 0.63
d12 3.36 3.35 3.12
d16 9.08 15.58 22.29

Zoom lens group data group Start surface Focal length
1 1 -19.01
2 5 11.88
4 13 -43.56

[Numerical Example 4]
Unit mm

Surface data surface number rd nd vd
1 * 157.989 0.60 1.85135 40.1
2 * 14.087 2.35
3 -47.172 0.60 1.91082 35.3
4 51.706 1.14
5 21.169 1.63 1.95906 17.5
6 67.781 (variable)
7 * 13.080 2.55 1.76802 49.2
8 * 109.149 0.20
9 7.733 2.31 1.49700 81.5
10 12.590 0.50 1.95906 17.5
11 7.811 1.69
12 * 105.823 2.76 1.55000 95.0
13 * -13.146 0.0
14 ∞ 0.50
15 (Aperture) ∞ (Variable)
16 -36.080 1.98 1.90366 31.3
17 -10.770 0.93
18 * -7.398 0.50 1.85 135 40.1
19 -29.831 (variable)
Image plane ∞

Aspheric data 1st surface
K = 0.00000e + 000 A 4 = -1.67283e-005

Second side
K = 0.00000e + 000 A 4 = 2.80368e-005 A 6 = 4.37905e-007 A 8 = -6.00575e-009 A10 = 8.14197e-011

7th page
K = 0.00000e + 000 A 4 = 1.88679e-005

8th page
K = 0.00000e + 000 A 4 = 1.30578e-004 A 6 = 6.38060e-009 A 8 = -7.00276e-010

12th page
K = 0.00000e + 000 A 4 = -2.00804e-004 A 6 = -3.98345e-006

Side 13
K = 0.00000e + 000 A 4 = -6.39019e-005 A 6 = 3.88669e-008 A 8 = -2.52221e-008

18th page
K = -8.45406e-001 A 4 = -1.20828e-004 A 6 = 1.11666e-006 A 8 = -4.54060e-008

Various data Zoom ratio 2.85
Wide angle Medium Telephoto focal length 10.57 20.34 30.14
F number 2.06 4.80 5.28
Angle of view 37.6 22.5 15.1
Image height 6.56 8.00 8.00
Total lens length 46.43 43.90 47.87
BF 8.73 16.70 24.38

d 6 14.12 4.02 0.41
d15 3.33 2.94 2.84
d19 8.73 16.70 24.38

Zoom lens group data group Start surface Focal length
1 1 -17.20
2 7 13.12
4 16 -44.54

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1, 2, 3, and 4 are lens cross-sectional views of Example 1, 2, 3, and 4, respectively. FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7C, and FIGS. 8A to 8C are longitudinal aberration diagrams at the wide-angle end, the middle, and the telephoto end, respectively, for Examples 1 to 4. In the aberration diagrams, d is d-line, g is g-line, and ΔM is a meridional image plane.

  Hereinafter, the configuration of the first embodiment of the present invention will be described with reference to FIG. In the numerical value example 1, it consists of three groups of negative, positive, and negative, the first and second groups decrease, and the second and third group intervals change.

  The first group is a reciprocating movement that once moves to the image side and then moves to the object side. Both the second group and the third group move to the object side during zooming, and the change in the interval between the second group and the third group is smaller than the change in the interval between the first group and the second group.

  The first group consists of a negative lens, a negative lens, and a positive lens. The first and second negative lenses have a strong concave surface facing the image side, and the third positive lens has a convex surface facing the object side. It consists of a meniscus lens. The first negative lens is a double-sided aspheric lens that corrects distortion and coma around the wide-angle end.

  The second group is composed of a positive lens having a strong curvature on the object side, a lens composed of a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, and a positive lens having a strong curvature on the image side. Is done. The positive lens closest to the object side and the positive lens closest to the image side in the second group are composed of double-sided aspheric lenses. The second group has an anti-vibration mechanism that corrects camera shake by shifting the lens group in the direction perpendicular to the optical axis.

  The third group is composed of a positive meniscus lens having a convex surface on the image side and a negative meniscus lens having a convex surface on the image side. The third group has an aspheric surface on the object side of the second negative lens.

  A diaphragm is arranged in the vicinity of the second group and moves together with the second group during zooming.

  In Numerical Example 2, the movement of each group is the same as in Numerical Example 1. In Numerical Example 2, the second group is a positive lens having a strong curvature on the object side, a lens in which a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, and a meniscus shape having a concave surface facing the object side. And a meniscus positive lens with a concave surface facing the object side.

  In the numerical value example 1, Fno at the wide angle end is F2.28. However, in the numerical value example 2, the configuration in which the second group is composed of five elements is further brightened to F2.06 at the wide angle end.

  In Numerical Example 3, the first negative lens has two negative lenses and a positive lens. The first negative lens has a strong concave surface toward the image side, and the second positive lens has a convex surface toward the object side. It consists of a meniscus lens. The first negative lens is a double-sided aspheric lens that corrects distortion and coma around the wide-angle end.

  The second group is composed of a positive lens having a strong curvature on the object side, a lens composed of a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, and a positive lens having a strong curvature on the image side. Is done. The most object-side positive lens in the second group is composed of a double-sided aspheric lens. The second group has an anti-vibration mechanism that corrects camera shake by shifting the lens group in the direction perpendicular to the optical axis.

  The third group is composed of a positive meniscus lens having a convex surface on the image side and a negative meniscus lens having a convex surface on the image side.

  In Numerical Example 4, the movement trajectory and lens configuration of each lens are the same as those in Numerical Example 1. By using a higher refractive index material than that of Example 1 for the 24th lens and optimizing the lens shape. The wide-angle end is brightened to F2.06.

  In the first to fourth embodiments, focusing is performed by moving the third group, so that focusing is possible in the entire zoom range while the first group is fixed during focusing.

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

  For the 24th positive lens in the second lens group of Examples 1 to 4 of the present invention, a material having a low dispersion and a high refractive index satisfying the conditional expressions (2) to (4) is used.

  This material uses a material having a higher refractive index than a low-dispersion glass material made by a conventional method of melting and solidifying a material in a crucible.

  These materials are materials that can be produced by a manufacturing method in which a material is floated and solidified by a method such as jetting gas.

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

  The present invention relates to an imaging apparatus equipped with a small and wide-angle lens suitable for a digital still camera, an action cam, and the like, and relates to a lens having a wide angle of view and excellent portability.

d d line, g g line, ΔM meridional image plane

Claims (8)

In a zoom lens comprising a negative first lens group, a positive second lens group, and a negative third lens group from the object side and performing zooming by changing the air interval of each group, the zooming from the wide-angle end to the telephoto end At the time of magnification, the first lens group and the second lens group move so that the group interval is narrowed, and the second lens group includes 21 positive lenses, 22 positive lenses, 23 negative lenses, and positive lenses from the object side. A zoom lens having four lenses of 24 lenses and satisfying the following conditional expression.
-1.22 <(R232 + R241) / (R232-R241) <-0.15 (1)
n2p> −0.0073 × ν2p + 2.11 (2)
1.5 <n2p <1.85 (3)
65 <ν2P <97 (4)
R232; 23 lens image side R
R241; Object side R of 24 lenses
n2p: Refractive index of the 24th lens ν2p: Abbe number of the 24th lens The zoom lens according to claim 1, wherein the following conditional expression is satisfied in the lens system.
0.9 <f24 / f21 <1.6 (5)
-1.9 <f24 / f23 <-0.8 (6)
f21: focal length of the 21st lens f23: focal length of the 23rd lens f24: focal length of the 24th lens The zoom lens according to claim 1, wherein the following conditional expression is satisfied in the lens system.
−0.35 <f2 / f3 <−0.25 (7)
0.37 <f1 / f3 <0.48 (8)
f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group The zoom lens according to any one of claims 1 to 3, wherein the following conditional expression is satisfied in the lens system.
1.1 <f2 / fw <1.28 (9)
1.2 <f24 / f2 <3.5 (10)
fw: focal length of the entire system at the wide angle end   In the lens system, the second lens group is a positive lens having a tight object measurement curvature, a cemented lens in which a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, and a positive lens having convex surfaces on both lens surfaces. The zoom lens according to any one of claims 1 to 4, wherein the zoom lens is configured by a lens.   In the lens system, the second group includes a positive lens with a tight object measurement curvature, a cemented lens in which a positive meniscus lens having a convex surface on the object side and a negative meniscus lens having a convex surface on the object side, a positive meniscus lens having a concave surface on the object side, and a slow power The zoom lens according to claim 1, wherein the zoom lens includes five positive lenses.   In the lens system, the first group is composed of three lenses, a negative lens, a negative lens, and a positive lens. The first and second negative lenses are lenses having a strong concave surface facing the image side, and the third lens. The positive lens comprises a meniscus lens having a convex surface facing the object side, and the third group is composed of two lenses, a positive meniscus lens having a convex surface on the image side and a negative meniscus lens having a convex surface on the image side. The zoom lens according to any one of claims 1 to 6, wherein the focusing operation is performed by moving the third lens group toward the image side.   An imaging device equipped with the zoom lens according to any one of claims 1 to 7.