KR20160000759A - Slim telephoto lens system - Google Patents

Abstract

A telephoto lens system disposed in order from an object side to an image surface, comprises: a first lens having a positive refractive power; an optical path switching member having a reflective surface which bends an optical path; a focusing lens group which moves along an optical axis, performing focusing in accordance with a position of an object wherein the focusing lens group has a general positive refractive power, and provided with at least one or more lenses.

Description

[0001] Slim telephoto lens system [0002]

The present disclosure relates to a compact telephoto lens system.

2. Description of the Related Art In recent years, digital cameras and video cameras having solid-state image pickup devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor) have become widespread.

2. Description of the Related Art [0002] An imaging device using a solid-state imaging device is suitable for miniaturization, and has recently been applied to a small information terminal including a cellular phone. In addition, as the consumer's expertise in cameras continues to increase, miniaturization and optical performance suitable for applications such as wide angle, high magnification or telephoto performance are realized, and designs for aberration correction are sought Is further demanded.

The present disclosure seeks to provide a compact telephoto lens system.

The telephoto lens system according to one type is arranged in order from the object side to the image side, comprising: a first lens having positive refractive power; An optical path changing member having a reflecting surface for bending the optical path; And a group of focusing lenses moving along the optical axis and performing focusing according to the position of the object, the focusing lens group having at least one lens having a positive refractive power as a whole.

And a second lens having a negative refractive power may be disposed between the optical path member and the focusing lens group.

The second lens may be a convex meniscus lens on the object side.

Only the first lens may be disposed on the object side of the optical path changing member.

The telephoto lens system may satisfy the following conditions.

1.5? N1? 1.7

Here, n1 is the refractive index of the first lens.

The first lens may be an aspherical lens having at least one aspheric surface.

The telephoto lens system may satisfy the following conditions.

0.5? L1 / f? 2.0

Here, L1 is the distance from the reflection surface to the image plane of the optical path changing member, and f is the focal length of the telephoto lens system.

The telephoto lens system may satisfy the following conditions.

1.5? N3? 1.7

Here, n3 is the refractive index of the first lens on the object side of the focusing lens group.

The first lens on the object side of the focusing lens group has positive refractive power and may include at least one aspherical surface.

The focusing lens group may include a cemented lens having a positive refractive power lens and a negative refractive power lens joined together.

The focusing lens group may include a third lens of positive refractive power, a fourth lens of positive refractive power, and a fifth lens of negative refractive power, which are arranged in order from the object side.

The telephoto lens system may satisfy the following conditions.

1.5? N3? 1.7

Here, n3 is the refractive index of the first lens on the object side of the focusing lens group.

The fourth lens and the fifth lens may be joined to each other to form a cemented lens.

The telephoto lens system may satisfy the following conditions.

5 ° ≤2ω≤40 °

Where 2? Is the angle of view of the telephoto lens system.

The telephoto lens system described above is small and slim, and realizes an angle of view smaller than 20 degrees.

The above-described telephoto lens system has an optical path switching member that folds the optical path, thereby reducing the overall size and minimizing the number of object side lenses on the reflection surface, contributing to the thinning of the apparatus employing the telephoto lens system .

1 is a view showing the optical arrangement of the telephoto lens system according to the first embodiment of the present invention in infinity and macro positions.
2 is an aberration diagram showing longitudinal spherical aberration, astigmatism, and distortion of the telephoto lens system according to the first embodiment of the present invention.
3 is a view showing the optical arrangement of the telephoto lens system according to the second embodiment of the present invention in infinity and macro positions.
4 is an aberration diagram showing longitudinal spherical aberration, astigmatism, and distortion of the telephoto lens system according to the second embodiment of the present invention.
5 is a view showing the optical arrangement of the telephoto lens system according to the third embodiment of the present invention in infinity and macro positions.
6 is an aberration diagram showing longitudinal spherical aberration, astigmatism, and distortion of the telephoto lens system according to the third embodiment of the present invention.

Hereinafter, a telephoto lens system 100, 200, 300 according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1, 3 and 5 show optical arrangements of the telephoto lens systems 100, 200, and 300 according to the first through third embodiments of the present invention, respectively.

The positions indicated by infinity and macro respectively represent the case where the position of the object OBJ is infinite from the first lens surface of the telephoto lens system 100, 200, 300 and about 1 m.

The telephoto lens systems 100, 200 and 300 are arranged in order from the object OBJ side to the image plane IMG side and include a first lens 110 having a positive refractive power and a reflecting surface 4 for bending the optical path. The switching member 120 includes a focusing lens group 150 that moves along an optical axis and performs focusing according to an object position.

A second lens 130 having a negative refractive power may be disposed between the optical path changing member 120 and the focusing lens group 150. [

The first lens 110 is formed of a lens having a positive refractive power to reduce the total length of the telephoto optical system and miniaturize the optical path changing member 120 while realizing a narrow angle of view, for example, an angle of view of less than 20 degrees .

The first lens 110 satisfies the following conditions.

1.5? N? 1? 1.7 (1)

Here, n1 is the d-line refractive index of the first lens.

The above-mentioned refractive index range is a range easily realized as a plastic material. When a lens is made of a plastic material, it is lighter and more economical than a glass material.

The first lens 110 may be an aspherical lens having at least one aspheric surface.

The light path switching member 120 is for bending the optical path, for example, as shown, and serves to fold the optical axis by about 90 degrees. Although the prism is shown as the optical path changing member 120, this is merely an example, and in addition to this, various optical members such as a mirror having a reflecting surface for bending the optical path can be used.

The light path switching member 120 is typically used to reduce the size of a telephoto lens system that has a longer total length than a wide-angle lens system. When the telephoto lens system is employed in an electronic apparatus, since only some lenses disposed on the object side of the optical path changing member 120 among the lenses constituting the telephoto lens system are arranged in the thickness direction, PC, and the like.

In this embodiment, only one lens, that is, only the first lens 110, is disposed on the object side of the optical path changing member 120. Such a structure enables a design that minimizes the amount of protrusion of the lens protruding to the outside of the product when it is applied to a thin type product such as a cellular phone or a tablet PC.

The telephoto lens system can satisfy the following conditions.

0.5? L1 / f? 2.0 (2)

Here, L1 is the distance from the reflecting surface 4 to the image plane IMG of the optical path changing member 120, and f is the focal length of the telephoto lens system.

The above conditions are proposed for realizing a compact telephoto optical system.

When the upper limit of the above condition is exceeded, the focal length of the telephoto lens system is reduced, so that the telephoto optical system is not implemented well or the optical system length is increased. In the case of deviating from the lower limit of the above condition, a small optical system configuration is possible, but the aberration of the entire optical system increases, and it becomes difficult to secure the optical performance.

The condition (2) may be modified and applied to the following range.

0.6? L1 / f? 1.9 (2 ')

The second lens 130 may have a convex meniscus shape toward the object side. The second lens 130 has a negative refractive power to advantageously compensate for peripheral side aberration and astigmatism generated in the telephoto optical system.

The focusing lens group 150 includes a plurality of lenses and is configured to have a positive refractive power as a whole. The focusing lens group 150 moves along the optical axis and performs top-surface movement and focus position correction according to the change in object distance. When the position of the object OBJ changes from a long distance to a short distance, the focusing lens group 150 moves from the image surface IMG side to the object OBJ side and performs a focusing operation. In addition, in the focusing operation, the positions of the first lens 110 and the second lens 130 are fixed, that is, the optical length of the optical system is not changed at the time of focusing.

The n3 representing the d-line refractive index of the first lens on the object side of the focusing lens group 150 may satisfy the following condition.

1.5? N3? 1.7 (3)

As in the condition (1), the above condition is easily implemented with a plastic material. By adopting a plastic material, weight reduction and cost reduction can be achieved.

The focusing lens group 150 may include a cemented lens in which a lens having a positive refractive power and a lens having a negative refractive power are bonded so as to be advantageous for chromatic aberration correction.

Specifically, the focusing lens group 150 may include a third lens 151, a fourth lens 153, and a fifth lens 155, which are arranged in order from the object side.

The third lens 151 may have a positive refractive power and may be configured to satisfy the condition (3). Also, at least one surface of the third lens 151 may be an aspherical surface aspherical surface. When the third lens 151 is an aspherical surface positive lens, it is advantageous to correct spherical aberration of the entire optical system. The third lens 151 may be a biconvex lens.

The fourth lens 153 may be a lens having a positive refractive power and a convex shape on the object OBJ side. The fourth lens 153 may be a biconvex lens or a meniscus lens convex on the object side.

The fifth lens 155 may have a negative refractive power and may have a concave shape on the upper surface IMG side. The fifth lens 155 may be a double concave lens or a meniscus lens concave on the upper surface side.

The fourth lens 153 and the fifth lens 155 may be joined to each other to form a cemented lens.

A diaphragm ST may be disposed between the second lens 130 and the focusing lens group 150 and an infrared blocking filter 160 may be disposed between the focusing lens group 150 and the upper surface IMG. The infrared cutoff filter 160 may be omitted or an infrared shielding coating may be formed on the object side surface of the first lens 110. [

An imaging device (not shown) such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor) is placed on the upper surface IMG.

The angle of view 2? Of the telephoto lens system can satisfy the following condition.

5??? 2? 40 (4)

Or preferably, the following conditions can be satisfied.

5 ≤ 2 ≤

Hereinafter, specific lens data according to various embodiments of the present invention will be described. In the lens data, ST denotes an iris, and an asterisk (*) after a surface number indicates that the surface is aspherical. F is the total focal length, Fno is the F number, and 2ω is the angle of view. The variable distances according to the movement of the focusing lens group 150 are denoted by D1 and D2. The unit of focal length, distance, radius of curvature, thickness or interval is mm, and unit of angle of view is degrees (°).

The definition of aspheric surface is as follows.

Where K is the conic constant, A, B, C, and DF are the aspheric coefficients, c is the aspherical coefficient, and Z is the distance from the vertex of the lens to the optical axis direction, Y is the distance in the direction perpendicular to the optical axis, (1 / R) of the radius of curvature at the apex of the lens.

≪ Embodiment 1 >

The lens data of the first embodiment is as follows.

Surface number Curvature Radius Thickness or spacing Refractive index Abbe number

1 *: 9.15402 1.731886 1.531200 56.5000

ASP:

K: 1.000000

A: -0.121326E-03 B: -0.197700E-04 C: 0.150628E-05 D: 0.432350E-07

2 *: -100.79914 0.301864

ASP:

K: -21.769111

A: 0.352147E-04 B: 0.232127E-04 C: 0.190427E-05 D: 0.580525E-07

3: INFINITY 3.700000 1.834810 42.7100

4: INFINITY 3.700000 1.834810 42.7100

5: INFINITY 0.100000

6: 32.68617 0.653522 1.840679 22.5032

7: 8.20130 1.342159

ST: INFINITY D1

9 *: 5.53465 1.573619 1.531200 56.5000

ASP:

K: -0.955809

A: 0.387093E-03 B: 0.146119E-05 C: 0.100563E-05 D: -0.518760E-07

10 *: -25.33863 0.511364

ASP:

K: 0.000000

A: 0.459281E-03 B: 0.000000E + 00 C: 0.000000E + 00 D: 0.000000E + 00

11: 42.97558 1.015018 1.817099 23.0845

12: -43.34401 0.400000 1.673765 57.0802

13: 4.93207 D2

14: INFINITY 0.300000 1.516798 64.1983

15: INFINITY 0.384212

IMG: INFINITY

The following shows the infinity position and the variable distance from the macro position.

Infinity Macro D1 1.652 0.8222 D2 9.6186 10.4483

FIG. 2 is a graph showing the relationship between the longitudinal spherical aberration, the astigmatic field curves, and the distortion of the object position infinity of the telephoto lens system 100 according to the first embodiment of the present invention. . The longitudinal spherical aberration is shown for light with wavelengths of 656.28 (nm), 587.56 (nm), and 486.13 (nm), respectively, and astigmatism and distortion for light with wavelength 587.56 (nm). Also, in the astigmatism graph, the curvature in the sagittal field curvature and the tangential field curvature is represented by S, T.

≪ Embodiment 2 >

The lens data of the second embodiment is as follows.

Surface number Curvature Radius Thickness or spacing Refractive index Abbe number

1 *: 9.19228 1.741467 1.531200 56.5000

ASP:

K: 0.000000

A: 0.114694E-03 B: 0.196626E-04 C: -0.149002E-05 D: 0.427613E-07

2 *: -68.84134 0.221856

ASP:

K: -50.000000

A: -. 0276497E-04 B: 0.230272E-04 C: 0.189912E-05 D: 0.577104E-07

3: INFINITY 3.700000 1.846663 23.7848

4: INFINITY 3.700000 1.846663 23.7848

5: INFINITY 0.100000

6: 32.08965 0.648100 1.803500 29.6519

7: 7.97445 1.350301

ST: INFINITY D1

9 *: 5.74084 1.406592 1.531200 56.5000

ASP:

K: -0.835857

A: 0.488765E-03 B: 0.172225E-05 C: 0.492525E-06 D: 0.136820E-07

10 *: 79.93754 0.100000

ASP:

K: 0.000000

A: 0.410665E-03 B: 0.000000E + 00 C: 0.000000E + 00 D: 0.000000E + 00

11: 12.03923 1.218970 1.912364 23.8479

12: 36.34766 0.532164 1.780783 33.3796

13: 4.77462 D2

14: INFINITY 0.300000 1.516798 64.1983

15: INFINITY 0.370478

IMG: INFINITY

The following shows the infinity position and the variable distance from the macro position.

Infinity Macro D1 1.9353 1.0318 D2 9.6453 10.5488

FIG. 4 is a graph showing the relationship between the longitudinal spherical aberration, astigmatism field curves, and distortion for the object position infinity of the telephoto lens system 200 according to the second embodiment of the present invention. .

≪ Third Embodiment >

The lens data of the third embodiment is as follows.

Surface number Curvature Radius Thickness or spacing Refractive index Abbe number

1 *: 9.20130 1.737057 1.528904 74.2700

ASP:

K: 0.000000

A: 0.112752E-03 B: 0.196837E-04 C: -0.148810E-05 D: 0.426039E-07

2 *: -71.57346 0.225073

ASP:

K: -50.000000

A: -0.252724E-04 B: 0.230600E-04 C: 0.189508E-05 D: 0.573333E-07

3: INFINITY 3.699867 1.819186 27.6837

4: INFINITY 3.699867 1.819186 27.6837

5: INFINITY 0.100000

6: 31.53523 0.635780 1.789949 46.0065

7: 7.88945 1.366440

ST: INFINITY D1

9: 5.73662 1.436267 1.538766 72.4133

ASP:

K: -0.853868

A: 0.476007E-03 B: 0.236832E-05 C: 0.607978E-06D: -0.293300E-07

10 *: 155.29411 0.100000

ASP:

K: 0.000000

A: 0.416771E-03 B: 0.000000E + 00 C: 0.000000E + 00 D: 0.000000E + 00

11: 13.77507 1.207646 1.922860 20.8804

12: 77.20153 0.547795 1.776302 30.6856

13: 4.85268 D2

14: INFINITY 0.300000 1.516798 64.1983

15: INFINITY 0.388880

IMG: INFINITY

The following shows the infinity position and the variable distance from the macro position.

Infinity Macro D1 1.8687 0.9664 D2 9.6756 10.5778

FIG. 6 is a graph showing the relationship between the longitudinal spherical aberration, the astigmatism field curves, and the distortion of the object position infinity of the telephoto lens system 300 according to the third embodiment of the present invention. .

The following table shows the focal length, F-number, and angle of view of the telephoto lens system.

First Embodiment Second Embodiment Third Embodiment f 26.0 25.93 26.0 Fno 3.45 3.40 3.40 2ω 12.88 12.92 12.88

The following table shows the values associated with the above conditions (1), (2) and (3) of the telephoto lens system according to the embodiments, and shows that the above conditions are satisfied.

First Embodiment Second Embodiment Third Embodiment (1) n1 1.5312 1.5312 1.5289 (2) L1 / f 0.818 0.822 0.821 (3) n3 1.5312 1.5312 1.5387

The embodiments described above provide a telephoto lens system that realizes excellent optical performance in a miniaturized and slimmed structure.

The telephoto lens system according to the embodiments can be applied to various kinds of image pickup devices together with an image pickup device for converting an optical image formed through such an image pickup lens system into an electric signal. In addition, such an imaging apparatus can be employed in various electronic apparatuses including mobile phones, tablet PCs, and the like.

The telephoto lens system according to the present invention has been described with reference to the embodiments shown in the drawings to facilitate understanding of the present invention. However, it should be understood that various modifications and equivalent embodiments can be made by those skilled in the art without departing from the scope of the present invention. I will understand that. Accordingly, the true scope of the present invention should be determined by the appended claims.

100, 200, 300 ... Telephoto lens system
110 ... first lens 120 ... light path switching member
130 ... second lens 150 ... focusing lens group
151 ... third lens 153 ... fourth lens
155 ... fifth lens

Claims (16)

In order from the object side to the image side,
A first lens having a positive refractive power;
An optical path changing member having a reflecting surface for bending the optical path;
And a focusing lens group that moves along an optical axis and performs focusing according to an object position, the focusing lens group having at least one lens having a positive refractive power as a whole. The method according to claim 1,
And a second lens having a negative refractive power is disposed between the optical path member and the focusing lens group. 3. The method of claim 2,
And the second lens is a convex meniscus lens toward the object side. The method according to claim 1,
And the first lens is disposed on the object side of the light path changing member. The method according to claim 1,
A telephoto lens system satisfying the following conditions:
1.5? N1? 1.7
Here, n1 is the refractive index of the first lens. The method according to claim 1,
Wherein the first lens is an aspherical lens having at least one aspheric surface. The method according to claim 1,
A telephoto lens system satisfying the following conditions:
0.5? L1 / f? 2.0
Here, L1 is the distance from the reflection surface to the image plane of the optical path changing member, and f is the focal length of the telephoto lens system. The method according to claim 1,
A telephoto lens system satisfying the following conditions:
1.5? N3? 1.7
Here, n3 is the refractive index of the first lens on the object side of the focusing lens group. The method according to claim 1,
Wherein the first lens on the object side of the focusing lens group has a positive refractive power and at least one surface is an aspherical surface. The method according to claim 1,
Wherein the focusing lens group includes a cemented lens having a positive refractive power lens and a negative refractive power lens joined together. The method according to claim 1,
Wherein the focusing lens group includes a third lens of positive refractive power, a fourth lens of positive refractive power, and a fifth lens of negative refractive power, which are arranged in order from the object side. 12. The method of claim 11,
1.5? N3? 1.7
Here, n3 is the refractive index of the first lens on the object side of the focusing lens group. 12. The method of claim 11,
And the fourth lens and the fifth lens are joined to each other to form a cemented lens. 14. The method according to any one of claims 1 to 13,
A telephoto lens system satisfying the following conditions:
5 ° ≤2ω≤40 °
Where 2? Is the angle of view of the telephoto lens system. A telescopic lens system according to any one of claims 1 to 13;
And an image pickup element for converting the optical image formed by the telephoto lens system into an electric signal. An electronic device comprising the imaging device of claim 15.

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