KR101373019B1 - Wide field-of-view zoom lens - Google Patents

Abstract

A wide angle zoom lens is disclosed. The disclosed wide-angle zoom lens includes a first lens group having negative refractive powers sequentially arranged from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power. The following conditional expression is satisfied.

<Conditional expression>

Where φ _w is the total refractive power at the wide end, Φ _t is the total refractive power at the telephoto end, fw is the focal length at the wide end, and wfno is fno at the wide end.

Description

Wide field-of-view zoom lens

FIG. 1 shows the optical arrangement of the wide-angle end, the intermediate end, and the telephoto end of the wide-angle zoom lens according to the first embodiment of the present invention.

2 illustrates aberration diagrams at the wide-angle ends of the wide-angle zoom lens according to the first embodiment of the present invention.

3 illustrates aberration diagrams at the telephoto end of the wide-angle zoom lens according to the first embodiment of the present invention.

4 shows optical arrangement of the wide-angle end, the intermediate end, and the telephoto end of the wide-angle zoom lens according to the second embodiment of the present invention.

5 shows aberration diagrams at the wide-angle ends of the wide-angle zoom lens according to the second embodiment of the present invention.

6 illustrates aberration diagrams at the telephoto end of the wide-angle zoom lens according to the second embodiment of the present invention.

FIG. 7 shows the optical arrangement of the wide-angle end, the middle end, and the telephoto end of the wide-angle zoom lens according to the third embodiment of the present invention.

8 shows aberration diagrams at the wide-angle ends of the wide-angle zoom lens according to the third embodiment of the present invention.

9 illustrates aberration diagrams at a telephoto end of a wide-angle zoom lens according to a third exemplary embodiment of the present invention.

FIG. 10 shows the optical arrangement of the wide-angle end, the middle end, and the telephoto end of the wide-angle zoom lens according to the fourth embodiment of the present invention.

11 illustrates aberration diagrams at the wide-angle ends of the wide-angle zoom lens according to the fourth embodiment of the present invention.

12 illustrates aberration diagrams at the telephoto end of the wide-angle zoom lens according to the fourth embodiment of the present invention.

Description of the Related Art

100-1, 100-2, 100-3, 100-4 ... First lens group

200-1, 200-2, 200-3, 200-4 ... Second lens group

300-1, 300-2, 300-3, 300-4 ... Third lens group

D1, D2, D3 ... variable distance

The present invention relates to a zoom lens suitable for a camera using a solid-state image sensor, and more particularly, to a wide-angle zoom lens having a small compact structure and a wide angle of view and high magnification.

Background Art In recent years, imaging optical devices such as digital cameras or digital camcorders using imaging devices such as CCDs and CMOS are rapidly expanding. Such imaging optical devices are required to have high performance, which is gradually increased in magnification and wide angle of view, and miniaturization is being pushed along with them, and high performance and miniaturization are required in the zoom lens employed therein.

In this regard, Japanese Patent Laid-Open No. 2006-139187 discloses a zoom lens of a three-group zoom method. The disclosed zoom lens realizes a high magnification of about 4 times by configuring the first lens on the object side of the second lens group having high sensitivity as a single lens in order to suppress optical performance variations due to thickness tolerances. However, when a large angle of view is 68 degrees or less and thus close, there is a problem that it is difficult to include on one screen.

On the other hand, the zoom lens disclosed in Japanese Patent Laid-Open No. 2006-184763 has three groups of negative, positive, and positive groups in order from the object side, and each of the first, second, and third groups has at least one aspherical surface. . This zoom lens has an angle of view of more than 70 degrees, but has a disadvantage that the zoom magnification is three times or less.

The zoom lens of the three-group zoom method disclosed in Japanese Laid-Open Patent Publication No. 2003-329512 has a high magnification of 3.4 times or more and a wide angle of view of 77 degrees to 78.5 degrees, but the refractive index of the first group of positive lenses is about 1.8 and wide angle compared to fno. The focal length of the stage is large and the ratio of the distance from the last lens to the solid-state image pickup device is small, which limits the miniaturization of the zoom lens.

The present invention has been made to solve the above-mentioned problems and other problems, and an object thereof is to provide a wide-angle zoom lens having a small size, a large angle of view, and a high aspect ratio.

The present invention provides a lens assembly comprising: a first lens group having negative refractive powers sequentially arranged from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power, and providing a wide-angle zoom lens that satisfies the following conditional expression.

<Conditional expression>

Where φ _w is the total refractive power at the wide end, Φ _t is the total refractive power at the telephoto end, fw is the focal length at the wide end, and wfno is fno at the wide end.

In addition, the present invention is the first lens group having a negative refractive power arranged in sequence from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power, and providing a wide-angle zoom lens that satisfies the following conditional expression.

<Conditional expression>

Here, 1Nd is the refractive index of the positive lens near the image surface in the first lens group, fw is the focal length at the wide-angle end, and fb represents the distance from the last lens at the wide-angle end to the image surface.

In addition, the present invention is the first lens group having a negative refractive power arranged in sequence from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power, and satisfying the following conditional expressions.

<Conditional expression>

75 ° ≤ wfov ≤85 °

Here, 1Nd is the refractive index of the positive lens near the image surface in the first lens group, and wfov represents the angle of view at the wide-angle end, respectively.

The first lens group of the present invention is characterized by consisting of three lenses.

The second lens group is composed of four lenses.

The first lens group is composed of negative, negative, and positive lenses sequentially from the object side.

The second lens group may include at least one positive or negative bonded lens.

The second lens group is characterized in that at least one lens is aspherical.

The first lens group is characterized in that at least one lens is aspherical.

Hereinafter, a wide angle zoom lens according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments exemplified below are not intended to limit the scope of the present invention, but are provided to fully explain the present invention to those skilled in the art. In the following drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of explanation.

1 is a view showing the optical arrangement of the wide-angle end, the intermediate end and the telephoto end of the wide-angle zoom lens according to the first embodiment of the present invention.

Referring to the drawings, the wide-angle zoom lens according to the present invention has a first lens group 100-1 having a negative refractive power, a second lens group 200-1 having a positive refractive power, and a positive refractive power from an object OBJ side. The branch includes the third lens group 300-1. In addition, between the first lens group 100-1 and the second lens group 200-1, an aperture ST which is moved in association with the second lens group 200-1 is further provided. Shifting is performed by moving the first to third lens groups 100-1, 200-1, and 300-1 on the optical axis. The interval between the first lens group 100-1 and the second lens group 200-1 decreases when the shift is performed from the wide angle end to the middle end, and the second lens group 200-1 and the third lens group 300 are reduced. The interval between -1) is increased.

More specifically, the lens configuration of each of the first to third lens groups 100-1, 200-1, and 300-1 is as follows.

The first lens group 100-1 is configured to have negative refractive power as a whole, and the first lens group 100-1 of the first lens 110-1, the second lens 120-1, and the third lens 130-1 from the object side. It consists of hawks. The first lens 110-1 and the second lens 120-1 are composed of negative lenses, and the third lens 130-1 is composed of positive lenses, and the first two negative lenses widen the angle of view. By convergence of the last positive lens, the power of the first lens group for wide angle can be properly adjusted. In addition, preferably, at least one lens of the first lens group 100-1 is used to reduce the burden of distortion as a wide angle and reduce the size of the overall system by using an aspherical surface. Can be.

The second lens group 200-1 is configured to have positive refractive power as a whole, and includes the fourth lens 210-1, the fifth lens 220-1, the sixth lens 230-1, and the seventh lens ( It consists of four sheets of 240-1). In this case, the second lens group 200-1 may include at least one positive and negative bonding lens. For example, in the present exemplary embodiment, since the fifth lens 220-1 and the sixth lens 230-1 are composed of a bonded lens, chromatic aberration correction is easy and productivity is advantageous. Also preferably, at least one lens of the second lens group 200-1 is used to correct spherical aberration by using an aspherical surface.

The third lens group 300-1 is configured to have a positive refractive power as a whole, and includes, for example, a seventh lens 310-1 of one positive lens. The lens surface of the eighth lens 310-1 may be spherical or aspheric.

The wide-angle zoom lens according to the preferred embodiment of the present invention satisfies Equations 1 and 2 below.

In the above equations, φ _w is the total refractive power at the wide end, Φ _t is the total refractive power at the telephoto end, fw is the focal length at the wide end, and wfno represents fno at the wide end.

A wide-angle zoom lens that satisfies the above equation may implement a high magnification of 3 times or more. In addition, by narrowing the focal length at the wide-angle end to a smaller than the fno at the wide-angle end, a wide-angle lens system is implemented rather than a general angle of view, so that many subjects can be contained in the lens system in a narrow space, and the lens system can be miniaturized. Can be implemented.

The wide-angle zoom lens according to the preferred embodiment of the present invention satisfies Equation 4 together with Equation 3 below.

Here, 1Nd is the refractive index of the positive lens near the image surface in the first lens group, fw is the focal length at the wide-angle end, and fb represents the distance from the last lens at the wide-angle end to the image surface.

In the case of the three-group type lens system composed of negative, positive, and positive like the present invention, the first lens group is the key to wide angle, and the refractive power of the first lens group must be large for wide angle. The refractive power of the first lens group may be large when the power of the positive lens closest to the image plane in the first lens group is large. The power can also be controlled as a shape, but in this case, problems may occur in miniaturization and manufacturability. Accordingly, the present invention increases the refractive index of the positive lens closest to the top of the first lens group to 1.9 or more for wide angle, while increasing the power of the positive lens closest to the top of the first lens group while maintaining the existing general shape. You can.

In addition, a lens system using a solid state image pickup device may include an infrared filter (IR filter) or an optical low pass filter (OLPF) between the lens system and the solid state image pickup device and the last lens of the lens system for focus correction occurring in the lens module. The distance between and the solid state imaging device should be increased. Equation 4 increases the distance between the last lens of the lens system and the solid-state image pickup device and the distance between the last lens of the same lens system and the solid-state image pickup device as compared to the same focal length, while reducing the focal length of the wide-angle end. Contribute to anger If it is out of this range, the gap between the last lens and the solid state image pickup device may be narrow, which may cause problems in the design of the focus and the instrument.

The wide-angle zoom lens according to the preferred embodiment of the present invention satisfies Equation 5 together with Equation 3 above.

75 ° ≤ wfov  ≤85 °

Here, wfov represents the angle of view at the wide-angle end, respectively.

The angle of view of the wide-angle end is 75 degrees or more and 85 degrees or less, so that wide angles are possible. If the angle of view of the wide-angle end is more than 85 degrees, distortion is greatly generated and the shape of the subject is changed like a fisheye lens. Therefore, in order to achieve wide angle and maintain the shape of the subject as the real thing, the angle of view of the wide-angle end is less than 85 degrees. It is preferable to construct.

On the other hand, the definition of the aspherical surface (ASP) appearing in the embodiments of the present invention are as follows.

Where x is the distance from the vertex of the lens in the optical axis direction, y is the distance in the direction perpendicular to the optical axis, K is the conic constant, A, B, C, D are aspherical coefficients, c ' Is the inverse of the radius of curvature at the vertex of the lens (1 / R).

Next, specific lens data of various embodiments of the wide-angle zoom lens according to the present invention will be described. Hereinafter, EFL denotes the combined focal length of the entire zoom lens, Fno denotes the number of F, ω denotes the angle of view, R denotes the radius of curvature, and nd denotes the Abbe number of the refractive index. In addition, ST represents a diaphragm, and the variable distance between lenses in each embodiment is represented by D1, D2, and D3. In addition, the embodiment number is displayed in association with the reference number of each component for each embodiment.

&Lt; Embodiment 1 >

1 illustrates a wide-angle zoom lens according to a first embodiment, in which the first lens group 100-1 includes a first lens 110-1, a second lens 120-1, and a third lens 130-. 1) and the second lens group 200-1 includes fourth, fifth, sixth, and seventh lenses 210-1, 220-1, 230-1, and 240-1. The third lens group 300-1 is configured of the eighth lens 310-1. Reference numeral 400-1 denotes an infrared filter and 410-1 denotes an OLPF. The following is the lens data of the first embodiment.

EFL: 4.15mm ~ 12.45mm, Fno: 2.88 ~ 5.14, ω: 32.4 ° ~ 84.8 °

 Cotton (S) The radius of curvature (R) Thickness or distance between lenses Refractive index (nd) Abbe's (v) One 23.240 2.108 1.729 54.7 2 7.364 1.878 3 58.871 1.548 1.854 40.4 4 7.524 1.846 5 8.133 1.814 1.923 20.9 6 14.939 D1 ST infinity 0.200 8 5.381 1.460 1.659 54.5 9 45.266 0.407 10 7.829 1.164 1.741 52.6 11 -36.754 0.466 12 3.960 0.424 1.728 28.3 13 106.453 0.926 1.613 58.6 14 -11.195 D2 15 11.538 1.750 1.497 81.6 16 -83.402 D3 17 (filter) infinity 0.300 1.517 64.2 18 infinity 0.500 19 (filter) infinity 0.500 1.517 64.2 20 infinity 0.175

Table 2 shows the aspherical surface coefficients of the first embodiment.

Cotton (S) K A B C D 3 0 0.00165254 -3.301540E-05 3.270460E-07 0 4 -4.494945E-01 0.001945154 8.144343E-07 -1.780079E-06 3.698558E-08 8 -0.915455 9.468356E-05 2.038663E-06 0  0

Table 3 shows examples of the variable distances D1, D2, and D3 of the wide-angle zoom lens according to the first embodiment at the wide-angle end, the intermediate end, and the telephoto end, respectively.

Wide angle Middle Telephoto D1 13.338 4.737 1.718 D2 4.661 10.719 16.169 D3 2.526 1.910 1.780

Fig. 2 shows longitudinal spherical aberration at the wide-angle end of the wide-angle zoom lens according to the first embodiment for light having wavelengths of 486.1300 (nm), 587.5600 (nm), and 656.2800 (nm), respectively, and astigmatic field. curvature, that is, tangential field curvature (T) and sagittal field curvature (S), and% distortion. 3 illustrates longitudinal spherical aberration, image curvature, and distortion aberration at the telephoto end of the wide-angle zoom lens according to the first embodiment.

&Lt; Embodiment 2 >

4 illustrates a wide-angle zoom lens according to a second embodiment, in which the first lens group 100-2 includes a first lens 110-2, a second lens 120-2, and a third lens 130-. 2), and the second lens group 200-2 includes fourth, fifth, sixth, and seventh lenses 210-2, 220-2, 230-2, and 240-2. The third lens group 300-2 is configured of the eighth lens 31-2. Reference numeral 400-2 denotes an infrared filter and 410-2 denotes an OLPF. The following is lens data of the second embodiment.

EFL: 4.88mm ~ 118.91mm, Fno: 2.8 ~ 6.02, ω: 21.4 ° ~ 75.8 °

 Cotton (S) The radius of curvature (R) Thickness or distance between lenses Refractive index (Nd) Abbe's (v) One 15.594 0.800 1.635 36.2 2 7.787 1.960 3 7.847 1.200 1.818 45.4 4 3.711 2.330 5 8.414 1.860 1.923 20.9 6 14.234 D1 ST infinity 0.300 8 5.411 1.750 1.624 58.0 9 -35.839 0.300 10 8.951 1.350 1.732 54.4 11 -14.606 0.580 1.735 30.9 12 3.732 0.600 13 14.344 1.010 1.612 36.3 14 104.464 D2 15 16.210 1.650 1.523 63.3 16 -66.062 D3 17 (filter) infinity 0.300 1.517 64.2 18 infinity 0.500 19 (filter) infinity 0.500 1.517 64.2 20 infinity 0.690

Table 5 shows the aspherical surface coefficients of the second embodiment.

Cotton (S) K A B C D 3 0 -0.001921 3.866472E-05 -3.956268E-07 0 4 -1.641319 -0.000294 2.108687E-05 8.286039E-07 -1.997044E-08 8 -0.962111 4.366338E-05 -2.649779E-06 0 0

Table 6 shows examples of the variable distances D1, D2, and D3 of the wide-angle zoom lens according to the second embodiment at the wide-angle end, the intermediate end, and the telephoto end, respectively.

Wide angle Middle Telephoto D1 15.713 4.303 1.781 D2 4.906 11.626 20.513 D3 1.830 2.898 1.800

 Fig. 5 shows longitudinal spherical aberration, image curvature, and distortion aberration at the wide-angle end of the wide-angle zoom lens according to the second embodiment, respectively, and Fig. 6 shows the longitudinal direction at the telephoto end of the wide-angle zoom lens according to the second embodiment, respectively. It shows spherical aberration, top curvature, and distortion.

&Lt; Third Embodiment >

FIG. 7 illustrates a wide-angle zoom lens according to a third embodiment, in which the first lens group 100-3 includes the first lens 110-3, the second lens 120-3, and the third lens 130-. 3), and the second lens group 200-3 includes fourth, fifth, sixth, and seventh lenses 210-3, 220-3, 230-3, and 240-3. The third lens group includes the eighth lens 310-3. Reference numeral 400-3 denotes an infrared filter, and 410-3 denotes an OLPF. The following is lens data of the third embodiment.

EFL: 4.15mm ~ 14.32mm, Fno: 2.87 ~ 5.48, ω: 28.3 ° ~ 84.8 °

 Cotton (S) The radius of curvature (R) Thickness or distance between lenses Refractive index (Nd) Abbe's (v) One 16.541 0.800 1.883 40.8 2 7.911 1.960 3 18.251 1.200 1.816 46.6 4 5.746 2.330 5 8.816 1.860 1.923 20.9 6 15.385 D1 ST infinity 0.300 8 5.918 1.624 1.625 56.5 9 -97.707 0.300 10 7.050 1.350 1.741 52.6 11 -81.695 0.580 12 3.785 0.686 1.728 28.3 13 -63.928 1.010 1.613 58.6 14 -12.868 D2 15 18.049 1.650 1.497 81.6 16 -28.486 D3 17 (filter) infinity 0.300 1.517 64.2 18 infinity 0.500 19 (filter) infinity 0.500 1.517 64.2 20 infinity 0.600

Table 8 shows the aspherical surface coefficients of the third embodiment.

Cotton (S) K A B C D 3 0 0.000437 -6.922135E-06 6.689734E-08 0 4 -0.945700 0.000810 -1.060849E-06 -1.563061E-07 2.459893E-09 8 -0.981070 2.372118E-05 8.437109E-07 0 0

Table 9 shows examples of the variable distances D1, D2, and D3 of the wide-angle zoom lens according to the third embodiment at the wide-angle end, the intermediate end, and the telephoto end, respectively.

Wide angle Middle Telephoto D1 15.743 5.059 1.760 D2 4.281 10.850 17.007 D3 2.270 1.830 1.801

8 illustrates longitudinal spherical aberration, image curvature, and distortion aberration at the wide-angle ends of the wide-angle zoom lens according to the third embodiment, respectively, and FIG. 9 is the longitudinal direction at the telephoto end of the wide-angle zoom lens according to the third embodiment, respectively. It shows spherical aberration, top curvature, and distortion.

<Fourth Embodiment>

FIG. 10 illustrates a wide-angle zoom lens according to a fourth embodiment, in which the first lens group 100-4 includes the first lens 110-4, the second lens 120-4, and the third lens 130-. 4), and the second lens group 200-4 includes fourth, fifth and sixth lenses. The seventh lens 210-4, 220-4, 230-4, and 240-4 is formed, and the third lens group 300-4 is composed of the eighth lens 310-4. Reference numeral 400-4 denotes an infrared filter and 410-4 denotes an OLPF. The following is lens data of the fourth embodiment.

EFL: 4.15mm ~ 14.25mm, Fno: 3.10 ~ 6.11, ω: 27.8 ° ~ 84.2 °

 Cotton (S) The radius of curvature (R) Thickness or distance between lenses Refractive index (Nd) Abbe's (v) One 22.385 0.800 1.743 50.7 2 8.414 1.440 3 16.470 0.810 1.738 51.9 4 4.965 2.039 5 8.439 1.666 2.001 25.5 6 14.532 D1 ST infinity 0.000 8 4.727 1.602 1.726 45.2 9 -277.262 0.100 10 9.965 1.165 1.654 54.7 11 -9.678 0.420 1.773 30.2 12 3.730 0.408 13 43.352 0.934 1.497 81.6 14 -8.742 D2 15 30.690 1.416 1.746 49.9 16 -20.725 D3 17 (filter) infinity 0.300 1.517 64.2 18 infinity 0.500 19 (filter) infinity 0.500 1.517 64.2 20 infinity 0.600

Table 11 shows the aspherical surface coefficients of the fourth embodiment.

Cotton (S) K A B C D 4 -2.776746 0.002116 -5.079250E-05 1.200641E-06 -1.384562E-08 8 -0.299184 -0.000519 -7.427100E-06 0 0 15 47.400909 -0.000544 1.008466E-05 -3.905875E-07 -2.990265E-08

Table 12 shows examples of the variable distances D1, D2, and D3 of the wide-angle zoom lens according to the fourth embodiment at the wide-angle end, the intermediate end, and the telephoto end, respectively.

Wide angle Middle Telephoto D1 12.898 3.920 1.053 D2 3.656 10.446 16.064 D3 2.508 1.711 1.658

10 illustrates longitudinal spherical aberration, image curvature, and distortion aberration at the wide-angle ends of the wide-angle zoom lens according to the fourth embodiment, respectively. It shows spherical aberration, top curvature, and distortion.

The following shows that the embodiments satisfy the equations 1 to 5 and the corresponding values are as follows.

Example 1 Example 2 Example 3 Example 4 Equation 1 3.10 3.88 3.45 3.43 Equation 2 1.46 1.69 1.45 1.34 Equation 3 1.923 1.923 1.923 2.001 Equation 4 1.042 1.282 0.996 0.948 Equation 5 84.8 75.8 84.8 84.2

The present invention has excellent optical performance by realizing high magnification and wide angle while miniaturizing through a lens configuration satisfying the above-described equations.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Therefore, the true technical protection scope of the present invention should be defined within the following claims.

The wide-angle zoom lens according to the present invention realizes high magnification by adjusting the ratio of the refractive power at the wide end and the refractive power at the telephoto end. In addition, by adjusting the focal length at the wide-angle end smaller than the fno at the wide-angle end and adjusting the refractive index of the positive lens close to the image surface of the first lens group, the lens system having a wide angle of view can be realized. In addition, by maintaining a distance between the last lens of the lens system and the solid-state image pickup device, the focal length of the wide-angle end can be reduced to realize wide-angle and miniaturization.

Claims (9)

A first lens group having negative refractive powers sequentially arranged from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power. A wide-angle zoom lens that satisfies the following conditional expression. <Conditional expression>

Where φ _w is the total refractive power at the wide end, Φ _t is the total refractive power at the telephoto end, fw is the focal length at the wide end, and wfno is fno at the wide end. A first lens group having negative refractive powers sequentially arranged from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power. A wide-angle zoom lens that satisfies the following conditional expression. <Conditional expression>

Here, 1Nd is the refractive index of the positive lens near the image surface in the first lens group, fw is the focal length at the wide-angle end, and fb represents the distance from the last lens at the wide-angle end to the image surface. A first lens group having negative refractive powers sequentially arranged from the object side; A second lens group having a positive refractive power; And a third lens group having positive refractive power, A wide-angle zoom lens that satisfies the following conditional expression. <Conditional expression>

75 ° ≤ wfov ≤85 ° Here, 1Nd is the refractive index of the positive lens near the image surface in the first lens group, and wfov represents the angle of view at the wide-angle end, respectively. 4. The method according to any one of claims 1 to 3, And the first lens group comprises three lenses. 4. The method according to any one of claims 1 to 3, And the second lens group comprises four lenses. 4. The method according to any one of claims 1 to 3, And the first lens group comprises negative, negative and positive lenses sequentially from the object side. 4. The method according to any one of claims 1 to 3, And the second lens group comprises at least one positive or negative bonded lens. 4. The method according to any one of claims 1 to 3, The second lens group is a wide-angle zoom lens, characterized in that at least one lens is aspherical. 4. The method according to any one of claims 1 to 3, The first lens group is a wide-angle zoom lens, characterized in that at least one lens is aspherical.

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