KR20120106021A - Lens system and mobile apparatus using the same - Google Patents

Abstract

The present invention provides a diaphragm, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a negative refractive power in an order from the object side to the image side along the optical axis. It provides a compact lens system including a four lens and a portable device using the same.

Description

Miniature lens system and portable device using same {Lens system and mobile apparatus using the same}

The present invention relates to a compact lens system and a portable device using the same.

Due to the development of sensors and the like in small devices such as mobile phones, the demand for high optical performance for the lens system employed in small devices is gradually increasing. Various technologies have been developed to meet the high performance optical requirements, but it is difficult to achieve miniaturization to achieve high performance, and to achieve high performance, it is difficult to satisfy high optical performance and manufacturing cost at the same time. have.

One embodiment of the present invention relates to a high resolution small lens system and a portable device using the same.

According to an aspect of the present invention, in the order from the object side to the image side along the optical axis, the aperture; A first lens having positive refractive power; A second lens having negative refractive power; A third lens having positive refractive power; And a fourth lens having negative refractive power, and provides a compact lens system that satisfies the following equation.

<Expression>

Here, L represents the distance from the aperture to the image plane, and 2Y represents the diagonal length of the effective image plane.

According to one feature of the invention, the compact lens system may satisfy the following equation.

<Expression>

Here, f1 represents a focal length of the first lens, f represents an entire focal length, f3 represents a focal length of the third lens, and f4 represents a focal length of the fourth lens.

According to another feature of the invention, the second lens may satisfy the following equation.

<Expression>

22 <vd2 <25

Here, vd2 represents the Abbe number of the d line of the second lens.

According to another feature of the present invention, the first lens, the third lens and the fourth lens may satisfy the following equation.

<Expression>

Here, nd1 represents a refractive index at the d line of the first lens, nd3 represents a refractive index at the d line of the third lens, and nd4 represents a refractive index at the d line of the fourth lens.

According to another feature of the invention, each of the first lens, the second lens, the third lens, and the fourth lens may include an aspherical surface.

According to another feature of the invention, the first lens may be a biconvex lens.

According to another feature of the present invention, the second lens may be a bilateral lens.

According to another feature of the invention, the third lens may be a meniscus lens with a convex surface facing the image side.

According to another feature of the invention, each of the image-side surface and the object-side surface of the fourth lens has at least one inflection point so that the convex surface near the optical axis based on the inflection point may face the object side.

According to another aspect of the invention, the compact lens system according to any one of claims 1 to 9; And an imaging sensor for converting an image formed by the lens system into an electrical signal.

According to one embodiment of the present invention as described above, high resolution, small size, good telecentricity, and a long rear focal length can be provided, for example, a variety of portable devices requiring high resolution of 3Mega or higher. Can be used.

1 schematically shows a compact lens system according to a first embodiment of the present invention.
FIG. 2 shows an MTF graph showing the resolution of the small lens system of FIG. 1.
3 illustrates aberration diagrams relating to longitudinal spherical aberration, astigmatism, and distortion aberration of the small lens system of FIG.
4 illustrates aberration diagrams regarding coma aberration for each field of the small lens system of FIG. 1.
5 schematically illustrates a compact lens system according to a second embodiment of the present invention.
FIG. 6 shows an MTF graph showing the resolution of the small lens system of FIG. 5.
FIG. 7 illustrates aberration diagrams relating to longitudinal spherical aberration, astigmatism, and distortion aberration of the small lens system of FIG.
FIG. 8 illustrates aberration diagrams regarding coma aberration for each field of the small lens system of FIG. 5.
9 schematically illustrates a compact lens system according to a third embodiment of the present invention.
FIG. 10 illustrates an MTF graph showing the resolution of the compact lens system of FIG. 9.
FIG. 11 illustrates aberration diagrams relating to longitudinal spherical aberration, astigmatism, and distortion aberration of the small lens system of FIG.
FIG. 12 illustrates aberration diagrams regarding coma aberration for each field of the compact lens system of FIG. 9.
13 schematically illustrates a compact lens system according to a fourth embodiment of the present invention.
FIG. 14 shows an MTF graph showing the resolution of the small lens system of FIG.
FIG. 15 illustrates aberration diagrams relating to longitudinal spherical aberration, astigmatism, and distortion aberration of the small lens system of FIG.
FIG. 16 illustrates aberration diagrams regarding coma aberration for each field of the small lens system of FIG. 13.
17 schematically illustrates a portable device having a small lens system according to an embodiment of the present invention.

Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions. The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another.

1, 5, 9, and 13 illustrate a compact lens system according to an embodiment of the present invention.

Referring to the drawings, the compact lens system includes an aperture ST, a first lens 10, a second lens 20, a third lens 30, and a third in order from the object side O to the image side I. Four lenses 40 are included.

The first lens 10 has a positive refractive power. For example, the first lens 10 may be a biconvex lens.

The second lens 20 has negative refractive power. For example, the second lens 20 may be a biconvex lens.

The third lens 30 has a positive refractive power. For example, the third lens 30 may be a meniscus lens having a convex surface facing the image side.

The fourth lens 40 has negative refractive power. The fourth lens 40 is a meniscus lens having the convex surface facing the object side, and the image side surface and the object side surface each have at least one inflection point, and the convex surface is near the optical axis based on the inflection point. It may have a shape facing.

The first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 may include the same material. For example, the first to fourth lenses 10. 2, 30, and 40 may include a resin material such as plastic. By using plastic lenses, lenses of various shapes can be manufactured and manufacturing costs can be minimized.

The first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 may include aspherical surfaces. For example, both the object-side surface and the image-side surface of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 may be aspherical. By using the lenses 10, 20, 30, and 40 having aspherical surfaces, the optical performance of the lens can be compensated, thereby realizing a compact lens system having high optical performance.

The aperture stop ST may be disposed adjacent to the object-side surface of the first lens 10, and reference numeral 50 denotes an optical filter.

The compact lens system according to the exemplary embodiment of the present invention may satisfy the following conditions.

First, the compact lens system of the present invention may satisfy Equation 1 below.

(식 1)

(Equation 1)

Here, L represents the distance from the aperture ST to the image plane, and 2Y represents the diagonal length of the effective image plane.

Equation 1 defines the ratio of the distance from the diaphragm ST to the image plane with respect to the diagonal length of the effective plane, and may implement a compact lens system having a short overall length. On the other hand, the compact lens system according to an embodiment of the present invention can implement a more compact lens system by making the ratio of the distance from the diaphragm ST to the image plane to the diagonal length of the effective image surface to be 0.9 or less.

The compact lens system according to the embodiment of the present invention may satisfy Equations 2 and 3 below.

(식 2)

(Equation 2)

(식 3)

(Equation 3)

Here, f1 represents a focal length of the first lens 10, f represents an entire focal length, f3 represents a focal length of the third lens 30, and f4 represents a focal length of the fourth lens 40.

Equation 2 defines the ratio of the focal length of the first lens 10 to the total focal length of the compact lens system, and Equation 3 is the focal length of the third lens 30 with respect to the focal length of the fourth lens 40. By defining the ratio, if these values exceed the upper and lower limits, coma and astigmatism are difficult to correct and curvature occurs. In addition, it is difficult to maintain balance between aberrations and to stabilize the sensitivity. On the other hand, in order to minimize aberration, it is preferable to keep the ratio of the focal length of the third lens 30 to the focal length of the fourth lens 40 close to about −1.

The second lens 20 according to the embodiment of the present invention may satisfy Equation 4 below.

22 <vd2 <25 (Equation 4)

Here, vd2 represents the Abbe's number on the d line of the second lens 20.

Equation 4 shows the Abbe's number on the d line of the second lens 20. If this value exceeds the upper and lower limit, it is difficult to correct chromatic aberration.

The first lens 10, the third lens 30, and the fourth lens 40 according to the embodiment of the present invention may satisfy Equation 5 below.

(식 5)

(Equation 5)

(식 6)

(Equation 6)

Here, nd1 represents a refractive index at the d line of the first lens 10, nd3 represents a refractive index at the d line of the third lens 30, and nd4 represents a refractive index at the d line of the fourth lens 40.

Equation 5 defines the ratio of the refractive index at the d line of the first lens 10 to the refractive index at the d line of the fourth lens 40, and Equation 6 is the refractive index at the d line of the fourth lens 40 The ratio of the refractive index of the third lens 30 to the d-line with respect to the lens system by defining the ratio of the refractive index of the first lens 10, the third lens 30 and the fourth lens 40 to have a similar value. It can be miniaturized while maintaining performance.

The definition of the aspherical surface in the embodiment of the present invention is as follows.

The aspherical shape of the lens system according to the embodiment of the present invention may be represented by the following equation with the light beam traveling direction being positive when the optical axis direction is the x axis and the direction perpendicular to the optical axis direction is the y axis. . 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, and A, B, C, D, E and F are Aspheric coefficients, R denote curvature radii at the vertices, respectively.

The following shows design data of a compact lens system according to an embodiment of the present invention.

Hereinafter, R denotes a radius of curvature, Dn denotes a lens center thickness or a distance between a lens and a lens, nd denotes a d-line refractive index, and vd denotes an Abbe number of d-lines.

&Lt; Embodiment 1 >

Table 1 shows design data of the compact lens system according to the exemplary embodiment shown in FIG. 1, and Table 2 shows aspherical data. In Table 1, S1 represents the diaphragm ST surface.

Lens surface R Dn nd vd S1 INFINITY 0.050000 S2 1.56549 0.556998 1.53 56.3 S3 -22.64830 0.109750 S4 -14.03000 0.300000 1.641 23.8 S5 3.81875 0.893801 S6 -2.35917 0.872083 1.537 56.3 S7 -0.94848 0.235529 S8 6.06358 0.400000 1.537 56.3 S9 1.06823 0.443262

K A B C D E F S2 -1.404486 0.590090E-0 0.219364E-01 -.644349E-02 -.110456E-01 - - S3 -17.386688 0.576766E-01 -.351627E-01 -.909728E-01 0.547909E-01 - - S4 0.000000 0.112378E + 00 -.117213E + 00 -.734543E-01 0.101098E + 00 - - S5 11.828968 0.870588E-01 -.669453E-01 -.226953E-01 0.574834E-01 - - S6 2.483543 -.347250E-02 -.348238E-01 0.327365E-01 0.000000E + 00 - - S7 -4.098588 -.203635E + 00 0.176246E + 00 -.143151E + 00 0.697990E-01 -.121503E-01 0.000000E + 00 S8 -99.000000 -.102501E + 00 0.415609E-01 -.668889E-02 0.344433E-03 0.224865E-04 -.251146E-05 S9 -6.387218 -.888639E-01 0.350686E-01 -.104163E-01 0.192683E-02 -.191085E-03 0.750624E-05

FIG. 2 is a MTF (Modulation Transfer Fuction) graph showing the resolution of the compact lens system shown in FIG. 1. In FIG. 2, the x-axis represents the relative distance to the center (0) in the image plane, and the y-axis represents the modulation or contrast. 2 shows an MTF graph for a spatial frequency of 140 c / mm.

FIG. 3 shows longitudinal spherical aberration, astigmatism and distortion of the compact lens system shown in FIG. 1. 3B and 3C show astigmatism and distortion aberration for light having a wavelength of 546.0740 nm.

4 illustrates coma aberration for each field of the compact lens system illustrated in FIG. 1.

Second Embodiment

Table 3 shows design data of the compact lens system according to the exemplary embodiment shown in FIG. 5, and Table 4 shows aspherical data. In Table 3, S1 represents the diaphragm ST surface.

Lens surface R Dn nd vd S1 INFINITY 0.050000 S2 1.58437 0.565193 1.537 56.3 S3 -9.58849 0.096437 S4 -10.95336 0.410000 1.641 23.8 S5 3.75810 0.791459 S6 -2.99212 1.010837 1.537 56.3 S7 -1.17373 0.390536 S8 -64.45183 0.400000 1.537 56.3 S9 1.47287 0.443404

K A B C D E F S2 -3.237476 0.200793E + 00 -.325966E-01 0.279125E-01 -.239685E-01 -.241206E-01 0.000000E + 00 S3 30.281955 0.614000E-01 -.895860E-01 0.140613E-01 -.259927E-01 - - S4 0.000000 0.856281E-01 -.914719E-01 -.297619E-01 0.604587E-01 - - S5 6.034796 0.620955E-01 -.330714E-01 -.345769E-02 0.311922E-01 - - S6 6.951737 -.949400E-02 -.316148E-01 0.286761E-01 -.771816E-02 - - S7 -4.491088 -.147726E + 00 0.106639E + 00 -.749171E-01 0.334420E-01 -.572251E-02 -.735914E-04 S8 -99.000000 -.110356E + 00 0.467215E-01 -.734920E-02 0.312901E-03 0.356442E-04 -.336175E-05 S9 -7.487938 -.868896E-01 0.343161E-01 -.101024E-01 0.180111E-02 -.164965E-03 0.578191E-05

FIG. 6 is an MTF graph showing the resolution of the small lens system illustrated in FIG. 5. In FIG. 6, the x-axis represents the relative distance to the center 0 in the image plane, and the y-axis represents the modulation or contrast. 6 shows an MTF graph for a spatial frequency of 140 c / mm.

FIG. 7 shows longitudinal spherical aberration, astigmatism and distortion of the compact lens system shown in FIG. 5. 7B and 7C show astigmatism and distortion aberration for light having a wavelength of 546.0740 nm.

FIG. 8 shows coma aberration for each field of the compact lens system of FIG. 5.

Third Embodiment

Table 5 shows design data of the compact lens system according to the exemplary embodiment shown in FIG. 9, and Table 6 shows aspherical data. In Table 5, S1 represents the diaphragm ST surface.

Lens surface R Dn nd vd S1 INFINITY 0.050000 S2 1.53000 0.496677 1.537 56.3 S3 -19.74503 0.146561 S4 -10.06439 0.485469 1.641 23.8 S5 3.89386 0.836865 S6 -2.40208 0.921386 1.537 56.3 S7 -0.96237 0.305192 S8 84.48956 0.400000 1.537 56.3 S9 1.25445 0.443285

K A B C D E F S2 -1.231466 0.632767E-01 0.181196E-01 0.221645E-01 -.155765E-01 - - S3 99.000000 0.683897E-01 -.440147E-01 0.377869E-01 -.708595E-01 - - S4 0.000000 0.930802E-01 -.112772E + 00 0.478923E-01 -.673263E-01 - - S5 13.757586 0.722680E-01 -.565355E-01 0.468310E-02 -.622427E-03 - - S6 3.478089 -.253341E-02 -.281912E-01 0.354667E-01 -.963388E-03 - - S7 -3.900970 -.190624E + 00 0.166396E + 00 -.137099E + 00 0.676595E-01 -.127357E-01 0.000000E + 00 S8 -99.000000 -.845109E-01 0.378053E-01 -.632488E-02 0.376951E-03 0.139154E-04 -.209299E-05 S9 -7.475003 -.795991E-01 0.329728E-01 -.101942E-01 0.196409E-02 -.194970E-03 0.746580E-05

FIG. 10 is an MTF graph illustrating the resolution of the small lens system illustrated in FIG. 9. In FIG. 10, the x-axis represents the relative distance from the center (0) in the image plane, and the y-axis represents the modulation or contrast. 10 shows an MTF graph for a spatial frequency of 140 c / mm.

FIG. 11 shows longitudinal spherical aberration, astigmatism and distortion of the small lens system shown in FIG. 9. 11B and 11C show astigmatism and distortion aberration for light having a wavelength of 546.0740 nm.

FIG. 12 shows coma aberration for each field of the compact lens system of FIG. 9.

<Fourth Embodiment>

Table 7 shows design data of the compact lens system according to the exemplary embodiment shown in FIG. 13, and Table 8 shows aspherical data. In Table 7, S1 represents the diaphragm ST surface.

Lens surface R Dn nd vd S1 INFINITY 0.050000 S2 1.57965 0.721273 1.537 56.3 S3 -12.50990 0.100000 S4 -8.89768 0.300000 1.641 23.8 S5 4.65167 0.801581 S6 -2.03583 0.959022 1.537 56.3 S7 -0.82028 0.141205 S8 8.54463 0.400000 1.537 56.3 S9 0.92805 0.443134

K A B C D E F S2 1.391835 0.523222E-01 -.901719E-02 0.317632E-01 -.595240E-01 - - S3 52.763827 0.269247E-01 -.103915E + 00 -.130764E + 00 0.106271E + 00 - - S4 81.835092 0.105471E + 00 -.198149E + 00 0.857965E-02 -.329381E-01 0.139475E + 00 0.000000E + 00 S5 0.008540 0.998905E-01 -.514915E-01 -.122210E + 00 0.226802E + 00 -.107976E + 00 0.000000E + 00 S6 3.174860 -.112207E-02 0.764179E-02 -.139063E-01 0.218252E-01 - - S7 -4.048971 -.196075E + 00 0.180068E + 00 -.147459E + 00 0.704499E-01 -.137415E-01 0.000000E + 00 S8 -69.967758 -.817978E-01 0.356167E-01 -.614553E-02 0.417359E-03 0.409147E-05 -.151687E-05 S9 -6.699036 -.811703E-01 0.330685E-01 -.101723E-01 0.196275E-02 -.198642E-03 0.780995E-05

FIG. 14 is an MTF graph illustrating a resolution of the compact lens system illustrated in FIG. 13. In FIG. 14, the x-axis represents the relative distance to the center (0) in the image plane, and the y-axis represents the modulation or contrast. 14 shows an MTF graph for a spatial frequency of 140 c / mm.

FIG. 15 shows longitudinal spherical aberration, astigmatism and distortion of the small lens system shown in FIG. 15B and 15C show astigmatism and distortion aberration for light having a wavelength of 546.0740 nm.

FIG. 16 shows coma aberration for each field of the compact lens system illustrated in FIG. 13.

Table 9 shows that the first to fourth embodiments satisfy Equations 1 to 6, respectively.

Example Equation 1 Equation 2 Equation 3 Equation 4 Equation 5 Equation 6 First Embodiment 0.882 0.652 -0.97 23.8 1.0 1.0 Second Embodiment 0.882 0.595 -1.12 23.8 1.0 1.0 Third Embodiment 0.881 0.622 -1.02 23.8 1.0 1.0 Fourth Embodiment 0.881 0.625 -1.01 23.8 1.0 1.0

The compact lens system according to the embodiment of the present invention can be used in a portable device using a solid-state image sensor such as a CCD or a CMOS. For example, it can be used for a mobile phone, an ultra-small digital still camera, a PDA, and the like.

17 illustrates a mobile phone as a portable device having a small lens system according to an embodiment of the present invention. FIG. 17 includes a compact lens system described above with reference to FIGS. 1 to 16.

Referring to FIG. 17, the portable device 1700 according to the present exemplary embodiment includes a small lens system 100 and an imaging sensor 300 for converting light focused by the small lens system into an electrical image signal.

Information about the image of the subject photoelectrically converted from the imaging sensor 300 may be stored in the recording means 400 accommodated inside the housing 200, and the information about the image may be transmitted to the user through a display unit (not shown). Can be output as an image.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, it is intended that the appended claims cover all such modifications and variations as fall within the true spirit of the invention.

10: first lens 20: second lens
30: third lens 40: fourth lens
ST: Aperture 100: Compact lens system
200: housing 300: imaging sensor
400: recording means 1700: portable device

Claims (10)

In order from object side to image side along the optical axis,
iris;
A first lens having positive refractive power;
A second lens having negative refractive power;
A third lens having positive refractive power; And
And a fourth lens having negative refractive power.
A compact lens system satisfying the following formula.
<Expression>

Here, L represents the distance from the aperture to the image plane, and 2Y represents the diagonal length of the effective image plane. The method of claim 1,
The small lens system is a small lens system satisfying the following equation.
<Expression>

Here, f1 represents a focal length of the first lens, f represents an entire focal length, f3 represents a focal length of the third lens, and f4 represents a focal length of the fourth lens. The method of claim 1,
The second lens is a compact lens system that satisfies the following equation.
<Expression>
22 <v2 <25
Here, v2 represents the Abbe number of the d line of the second lens. The method of claim 1,
The first lens, the third lens and the fourth lens is a compact lens system that satisfies the following equation.
<Expression>

Here, nd1 represents a refractive index at the d line of the first lens, nd3 represents a refractive index at the d line of the third lens, and nd4 represents a refractive index at the d line of the fourth lens. The method of claim 1,
The small lens system of each of the first lens, the second lens, the third lens, and the fourth lens includes an aspherical surface. The method of claim 1,
The first lens is a compact lens system is a biconvex lens. The method of claim 1,
The second lens is a bifocal lens. The method of claim 1,
And said third lens is a meniscus lens having a convex surface facing toward the image side. The method of claim 1,
Each of the image-side surface and the object-side surface of the fourth lens has at least one inflection point such that the convex surface near the optical axis is toward the object side with respect to the inflection point. The compact lens system according to any one of claims 1 to 9; And
And an imaging sensor converting an image formed by the lens system into an electrical signal.

Images