KR20080024886A - Compact optical system for digital photographing device - Google Patents

Abstract

A compact optical system for a digital photographing device is provided to improve a production yield by lowering the sensitivity while sequentially including a diaphragm, a positive refracting power, a negative refracting power, and the positive refracting power in the optical system. A compact optical system for a digital photographing device comprises a diaphragm(STOP), a first lens(L1), a second lens(L2), and a third lens(L3) from an object side and satisfies a predetermined condition of 0.75< fL1/f <1.15. The fL1 is a paraxial focal length of a first lens. The f is a paraxial focal length of an overall optical system. Both sides of the first lens are aspheric, and the first lens has a positive refracting power. A convex side of the first lens faces the object. Both sides of the second lens are aspheric, and the second lens has a negative refracting power. A convex side of the second lens faces an image side. Both sides of the third lens are aspheric, and the third lens has the positive refracting power. The third lens is made of a plastic.

Description

Compact optical system for digital photographing device

1 is a block diagram of a compact optical system for a digital photographing apparatus according to a first preferred embodiment of the present invention.

FIG. 2 is an aberration diagram of the compact optical system according to Embodiment 1 of FIG. 1.

3 is a block diagram of a compact optical system for a digital photographing apparatus according to a second preferred embodiment of the present invention.

4 is an aberration diagram of the compact optical system according to Embodiment 1 of FIG. 3.

5 is a block diagram of a compact optical system for a digital photographing apparatus according to a third preferred embodiment of the present invention.

FIG. 6 is an aberration diagram of the compact optical system according to the third embodiment of FIG. 5.

7 is a block diagram of a compact optical system for a digital photographing apparatus according to a fourth preferred embodiment of the present invention.

FIG. 8 is an aberration diagram of the compact optical system according to the fourth embodiment of FIG. 7.

9 is a block diagram of a compact optical system for a digital photographing apparatus according to a fifth preferred embodiment of the present invention.

FIG. 10 is an aberration diagram of the compact optical system according to the fifth exemplary embodiment of FIG. 9.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small lens optical system used in a small digital photographing apparatus such as a mobile phone camera or a digital camera, and relates to an imaging optical system for an image sensor, which has good aberration correction and high resolution.

In general, a digital optical system using an image pickup device such as a CCD or a CMOS converts input light into an electrical signal by the image pickup device. Therefore, a bright lens having a large aperture is used as a component photographing lens, and an optical element between the lens and the image pickup device The in filter is inserted.

For this reason, the conventional imaging device imaging optical system requires a long back focal length compared to the effective focal length, and the chief ray of the light beam incident on the surroundings is perpendicular to the imaging device. It should be a telecentric optical system that is incident on the system.

Conventional techniques related to a zoom lens optical system using such an imaging device include the following.

⑴ Korean Patent Publication No. 2006-44514

⑵ Korean Patent Publication No. 2006-44602

⑶ US Patent US6,795,253B2

⑷ US Patent US6,985,307B2

⑸ US Patent No. 6,989,947B2

⑹ US Patent US7,031,079B2

⑺ US Patent US6,980,372B1

In the prior art, the array of refractive power is composed of a first lens of positive refracting power, an aperture, a second lens of positive refractive power, and a third lens of positive refracting power It is. These technologies have good manufacturing productivity due to low manufacturing sensitivity, but the highest performance is degraded due to chromatic aberration, and the electric field of the optical system is longer than or equal to the maximum top height.

In the conventional art, the arrangement of refractive power is composed of a first lens having a positive refractive power, an aperture, a second lens having a negative refractive power, and a third lens, so that the aberration correction is good. There is a disadvantage in that the angle of incidence (Chief Ray Angle) is increased and manufacturing sensitivity is large.

Therefore, the technical problem to be achieved by the present invention is that the optical system has an aperture, positive refractive power, negative refractive power, and positive refractive power in order to have a low sensitivity and high manufacturing yield, and the optical path length is smaller than the height of the top surface. To provide.

A compact optical system for a digital photographing apparatus according to the present invention for solving the above technical problem, the aperture from the object side; A first lens having a positive refractive power of a double-sided aspherical surface having a convex surface facing the object side; A second lens having a negative refractive power of a double-sided aspherical surface of which a convex surface faces an image surface; And a third lens made of a plastic material composed of a double-sided aspherical surface having positive refractive power, characterized by satisfying the following conditions.

f _L1 : paraxial focal length of the L1 lens, f: paraxial focal length of the whole optical system

The compact optical system preferably satisfies the following conditions.

R1 _L1 : radius of curvature R1 of the object-side surface of the first lens L1, R2 _L2 : radius of curvature R2 of the image-side surface of the first lens L1.

d2: distance between the first lens and the second lens, f: paraxial focal length of the entire optical system

d2: distance between the first lens and the second lens, f _L2 : paraxial focal length of the second lens

Nd _L2 : Refractive index of d-line of L2 lens, Vd _L2 : Dispersion coefficient of d-line of L2 lens

Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote components that perform the same function.

1 shows a configuration of a compact optical system according to a first embodiment of the present invention.

Referring to FIG. 1, the zoom lens optical system of the present invention provides positive refractive power of an aperture stop arranged in order from an object O side to an image side I and a double-sided aspherical surface having a convex surface facing the object side. And a third lens L3 made of a plastic material comprising a first lens L1 having an excitation surface, a second lens L2 having a negative refractive power of a double-sided aspherical surface having a convex surface facing the image plane, and a double-sided aspherical surface having a positive refractive power. In addition, an IR cut filter may be provided.

The compact optical system of the present invention is characterized by arranging an aperture STOP closest to the object O in order to reduce an incident angle of chief rays of light according to the image height from the object O side.

The first lens L1 having the positive refractive power of the double-sided aspherical surface with the convex surface facing the object side and easy to correct the meniscus shape aberration, adjusts the angle of incidence according to the image height and has the greatest sensitivity of the whole optical system. do.

The second lens L2 having a double-sided aspherical surface having a convex surface facing the image surface has a negative refractive power in order to shorten the optical field. In order to correct chromatic aberration, the second lens L2 may be formed of a material having a dispersion coefficient Vd _L2 of 20 to 30.

The third lens ㅣ 3 made of a plastic material composed of a double-sided aspherical surface having positive refractive power has a function of finely adjusting the incident angle according to the image height, and serves to correct astigmatism.

The compact optical system of the present invention preferably satisfies the condition of the following Equation 1 in order to improve the optical sensitivity while miniaturizing the optical system.

f _L1 : paraxial focal length of the L1 lens, f: paraxial focal length of the whole optical system

In Equation 1, when the value is biased to the lower limit, the manufacturing sensitivity is improved, but the optical field is increased, and when the value is biased to the upper limit, the optical field is smaller, but the manufacturing sensitivity is decreased, which lowers the manufacturing yield.

In addition, it is preferable that the compact optical system of the present invention satisfies the following Equations 2 to 4 in order to further improve manufacturing sensitivity and miniaturization of the optical system.

R1 _L1 : radius of curvature R1 of the object-side surface of the first lens L1, R2 _L2 : radius of curvature R2 of the image-side surface of the first lens L1.

d2: distance between the first lens and the second lens, f: paraxial focal length of the entire optical system

d2: distance between the first lens and the second lens, f _L2 : paraxial focal length of the second lens

When the value of Equation 2 is biased to the lower limit, the sensitivity of Decenter of the object-side surface R1 of the first lens is increased to decrease the manufacturing yield, and when it is biased to the upper limit, the optical path length is long.

When the value of Equation 3 is biased to the lower limit, the effective image of the second lens is smaller, so that the sensitivity is increased, and when it is biased to the upper limit, the optical field becomes longer.

If the value of Equation 4 is skewed to the lower limit, the optical field increases as the distance between the first lens and the first lens becomes longer, and if it skews to the upper limit, the optical length decreases but the sensitivity increases as the effective diameter of the second lens decreases. Production yield is inferior.

In addition, the compact optical system of the present invention preferably satisfies the following Equations 5 and 6 in order to compensate for the performance degradation caused by the shortening of the optical field.

Nd _L2 : d-line refractive index of L2 lens

Vd _L2 : Dispersion coefficient at line d of L2 lens

The condition of Equations 5 and 6 compensates for the performance degradation caused by the short optical field by correcting chromatic aberration of the optical system.

Table 1 below is an example of data of each lens of the compact optical system of the present invention having the configuration of the embodiment of FIG.

Lens (j) Face number (i) Bending radius (R, mm) Surface spacing (di, mm) Refractive Index (Ndj) Abbe (Vdj) STOP ∞ 0.000 L1 One 1.000 0.563 1.58640 60.89 2 1.786 0.816 L2 3 -1.084 0.400 1.63200 23.41 4 -2.182 0.100 L3 5 1.423 0.840 1.53113 55.73 6 2.128 0.500 L4 7 ∞ 0.300 1.51680 60.89 8 ∞ 0.384 IMAGE ∞ 0.000

The double-sided aspherical lenses of Table 1 satisfy the aspherical equation (7) for the aspherical coefficients of Table 2 below.

Face number One 2 3 4 5 6 R 1.00000E + 00 1.78572E + 00 -1.08363E + 00 -2.18223E + 00 1.42320E + 00 2.12760E + 00 K -2.78241E-01 6.43576E + 00 -1.31847E + 00 2.74060E + 00 -1.22358E + 01 -1.63077E + 01 A 7.43235E-02 1.06326E-01 1.39880E-01 -1.56538E-01 -1.39498E-01 -6.11331E-02 B 9.01370E-02 -1.08927E + 00 -1.56189E + 00 8.67471E-02 5.98485E-02 6.07845E-04 C 1.09976E-01 7.74195E + 00 3.67612E + 00 -2.90762E-02 -5.73237E-03 2.39751E-03 D -4.66207E-02 -2.52845E + 01 -8.79277E + 00 3.37013E-02 -2.23056E-03 -1.19383E-03 E 7.14582E-01 3.70674E + 01 1.29085E + 01 4.53751E-03 6.64914E-04 2.80873E-04 F -5.49214E-01 -1.18994E + 01 -1.00749E + 01 1.60808E-02 -5.54200E-05 -2.41405E-05

Here, x is the distance from the lens vertex to the optical axis direction, y is the distance in the direction perpendicular to the optical axis, c is the reciprocal of the radius of curvature at the vertex of the lens (1 / R), K is the Conic Constant, A, B, C, D, E, and F are aspherical coefficients (Table 2).

In the present invention, the optical system having the configuration shown in Table 1 as the small optical system embodiment of FIG. 1 has a focal length of 3.54 mm, a Fno of 3.00, and an angle of view of 66 degrees. The ratio of ambient light to center is 50%, and has a low sensitivity compared to an optical system having the same structure. FIG. 2 is an aberration diagram of the compact optical system according to Embodiment 1 of FIG. 1.

3 shows a configuration of a compact optical system according to a second embodiment of the present invention, and FIG. 4 is an aberration diagram of the compact optical system according to Embodiment 2 of FIG.

Table 4 below is an example of data of each lens of the compact optical system having the configuration of the embodiment of FIG. 3.

Lens (j) Face number (i) Bending radius (R, mm) Surface spacing (di, mm) Refractive Index (Ndj) Abbe (Vdj) STOP ∞ 0.000 L1 One 0.968 0.551 1.54410 56.09 2 1.631 0.511 L2 3 -58.445 0.390 1.60710 26.63 4 2.965 0.323 L3 5 1.250 0.710 1.54410 56.09 6 2.040 0.500 L4 7 ∞ 0.300 1.51680 64.19 8 ∞ 0.400 IMAGE ∞ -0.020

The double-sided aspherical lenses of Table 3 satisfy the aspherical equation (7) for the aspherical surface coefficient of Table 4 below.

Face number One 2 3 4 5 6 R 9.67989E-01 1.63097E + 00 -5.84450E + 01 2.96502E + 00 1.25002E + 00 2.04011E + 00 K -9.96108E-02 4.76238E + 00 4.59923E + 03 -9.03078E + 01 -6.43057E + 00 -2.40728E + 00 A 4.67243E-02 4.38662E-02 -2.52653E-01 -1.76375E-01 -7.69349E-02 -1.19105E-01 B 1.25908E-01 -6.88474E-02 2.15646E-01 1.26955E-01 1.54196E-02 3.31033E-02 C -2.90246E-01 1.48477E + 00 -8.79369E-01 -1.50195E-02 3.00019E-03 -9.27581E-03 D 1.26728E + 00 -5.95901E + 00 1.64702E + 00 -8.84190E-02 -4.09777E-04 3.03881E-04 E -1.05263E + 00 1.17996E + 01 -2.03283E + 00 5.37632E-02 -2.50056E-04 6.95027E-04 F 0.00000E + 00 0.00000E + 00 -3.25649E-02 -8.33358E-03 3.53400E-05 -1.18731E-04

3, Table 3, and Table 4 have a focal length of 3.24 mm, a Fno of 2.89, and an angle of view of 71 degrees.

FIG. 5 shows a configuration of a compact optical system according to a third embodiment of the present invention, and FIG. 6 is an aberration diagram of the compact optical system according to the third embodiment of FIG.

Table 5 below is an example of data of each lens of the compact optical system having the configuration of the embodiment of FIG. 5.

Lens (j) Face number (i) Bending radius (R, mm) Surface spacing (di, mm) Refractive Index (Ndj) Abbe (Vdj) STOP ∞ 0.000 L1 One 1.030 0.765 1.53113 55.73 2 2.148 0.616 L2 3 -1.125 0.420 1.63200 23.41 4 -2.631 0.141 L3 5 1.420 0.855 1.53113 55.73 6 2.679 0.500 L4 7 ∞ 0.300 1.51680 64.19 8 ∞ 0.397 IMAGE ∞ 0.000

The double-sided aspherical lenses of Table 5 satisfy the aspherical equation (7) for the aspheric coefficients of Table 6 below.

Face number One 2 3 4 5 6 R 1.03004E + 00 2.14847E + 00 -1.12518E + 00 -2.63137E + 00 1.41993E + 00 2.67923E + 00 K 6.10771E-01 3.18164E + 00 -1.01995E + 00 4.67824E + 00 -9.90211E + 00 -2.84729E + 00 A -4.37906E-02 2.31147E-01 7.94920E-02 -2.17725E-01 -1.24977E-01 -1.00045E-01 B -4.66415E-02 -1.67676E + 00 -1.32495E + 00 1.85860E-01 5.42107E-02 1.32791E-02 C -6.43596E-01 9.95372E + 00 3.65011E + 00 2.36754E-02 -4.15430E-03 1.01044E-04 D 2.30677E + 00 -1.90764E + 01 -8.73943E + 00 -6.29772E-02 -2.19080E-03 -1.80638E-03 E -3.85136E + 00 -6.46297E + 00 1.18896E + 01 2.94569E-02 4.84695E-04 8.36444E-04 F 1.49436E + 00 4.78605E + 01 -9.12356E + 00 1.36139E-02 -3.21404E-05 -1.15137E-04

5, Table 5, and Table 6 have a focal length of 3.50 mm, a Fno of 2.89, and an angle of view of 64 degrees.

FIG. 7 shows a configuration of a compact optical system according to a fourth embodiment of the present invention, and FIG. 8 is an aberration diagram of the compact optical system according to Embodiment 4 of FIG.

The following Table 7 is an example of data of each lens of the compact optical system having the configuration of the embodiment of FIG.

Lens (j) Face number (i) Bending radius (R, mm) Surface spacing (di, mm) Refractive Index (Ndj) Abbe (Vdj) STOP ∞ 0.000 L1 One 1.245 0.765 1.58445 59.60 2 2.359 0.662 L2 3 -3.071 0.410 1.63200 23.41 4 -94.950 0.268 L3 5 1.428 0.760 1.53113 55.73 6 2.3278 0.500 L4 7 ∞ 0.300 1.51680 64.19 8 ∞ 0.520 IMAGE ∞ 0.000

The double-sided aspherical lenses of Table 7 satisfy the aspherical equation (7) for the aspheric coefficients of Table 8 below.

Face number One 2 3 4 5 6 R 1.24485E + 00 2.35851E + 00 -3.07115E + 00 -9.49502E + 01 1.42792E + 00 2.32780E + 00 K -1.89028E-01 7.10785E + 00 -8.88217E + 00 1.20000E + 01 -6.51924E + 00 -6.48477E + 00 A 2.39298E-02 1.51157E-02 -6.64442E-02 -1.99195E-01 -1.00219E-01 -7.81533E-02 B 1.66192E-02 -1.40597E-01 -2.36325E-01 1.09051E-01 3.02151E-02 2.11348E-02 C -1.33355E-02 6.13583E-01 2.29957E-02 2.63051E-02 -1.67361E-04 -6.90130E-03 D 2.35338E-01 -1.46741E + 00 7.26825E-01 -4.40945E-02 -8.82680E-04 1.02934E-03 E -3.54706E-01 1.42745E + 00 -1.38342E + 00 -3.37643E-03 -1.05901E-04 9.38403E-05 F 0.00000E + 00 0.00000E + 00 4.82220E-01 9.61011E-03 3.42993E-05 -3.68042E-05

The compact optical system according to FIGS. 7, Table 7, and Table 7 has a focal length of 3.66 mm, a Fno of 3.00, and an angle of view of 62 degrees.

FIG. 9 shows a configuration of a compact optical system according to a fifth embodiment of the present invention, and FIG. 10 is an aberration diagram of the compact optical system according to Embodiment 5 of FIG.

The following Table 9 is an example of data of each lens of the compact optical system having the configuration of the embodiment of FIG.

Lens (j) Face number (i) Bending radius (R, mm) Surface spacing (di, mm) Refractive Index (Ndj) Abbe (Vdj) STOP ∞ 0.000 L1 One 1.142 0.860 1.53113 55.73 2 2.392 0.672 L2 3 -1.529 0.426 1.63200 23.41 4 -17.526 0.118 L3 5 1.111 0.890 1.53113 55.73 6 2.37807 0.500 L4 7 ∞ 0.300 1.51680 64.19 8 ∞ 0.432 IMAGE ∞ 0.000

The double-sided aspherical lenses of Table 9 satisfy the aspherical equation (7) for the aspherical surface coefficient of Table 10 below.

Face number One 2 3 4 5 6 R 1.14181E + 00 2.39234E + 00 -1.52870E + 00 -1.75257E + 01 1.11095E + 00 2.37807E + 00 K -1.60870E-01 5.25237E + 00 -1.57944E + 01 3.83648E + 01 -7.19263E + 00 -6.78283E + 00 A 1.99405E-02 9.59369E-02 -2.75518E-01 -2.59344E-01 -1.01268E-01 -8.21252E-02 B 6.77720E-02 -3.71530E-01 -1.32914E-01 1.13273E-01 3.21297E-02 2.05105E-02 C -1.83001E-01 1.49734E + 00 -2.02894E-01 1.72174E-02 -6.64581E-04 -6.76647E-03 D 5.34427E-02 -6.46682E-01 1.09495E + 00 -3.55514E-02 -8.80115E-04 1.07235E-03 E 1.22750E + 00 -5.88746E + 00 -1.87631E + 00 -6.25830E-03 -8.40152E-05 1.43952E-04 F -1.70656E + 00 9.96191E + 00 3.45073E-01 1.03959E-02 2.85242E-05 -4.74668E-05

9, Table 9 and Table 10 have a focal length of 3.67 mm, a Fno of 2.98, and an angle of view of 63 degrees.

The compact optical system of the present invention having the configuration of the embodiments of FIGS. 1 to 10 satisfies the conditions of Equations 1 to 6 described above, and the values of the equations according to the lens data of each embodiment are shown in Table 11 below. .

Equation 1 Equation 2 Equation 3 Equation 4 Equation 5 Equation 6 Example 1 0.86 0.56 0.23 -0.21 1.632 23.410 Example 2 1.04 0.59 0.16 -0.11 1.607 26.630 Example 3 0.85 0.48 0.18 -0.18 1.632 23.410 Example 4 0.98 0.53 0.18 -0.13 1.632 23.410 Example 5 0.89 0.48 0.18 -0.26 1.632 23.410

The best embodiments have been disclosed in the drawings and specification above. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the present invention, it is possible to provide a compact optical system for a digital photographing apparatus that satisfies performance while lowering manufacturing sensitivity to improve manufacturing yield and miniaturizing a product.

The invention is not limited to the examples described above and represented in the drawings. Those skilled in the art having been taught by the above-described embodiments may make many modifications to the above-described embodiments by substitution, erasure, merging, etc. within the scope and object of the present invention described in the following claims.

Claims (5)

Aperture from the object side; A first lens having a positive refractive power of a double-sided aspherical surface having a convex surface facing the object side; A second lens having a negative refractive power of a double-sided aspherical surface of which a convex surface faces an image surface; And A compact optical system for a digital photographing apparatus, comprising a third lens made of a plastic material composed of a double-sided aspherical surface having positive refractive power, and satisfying the following conditions.

f _L1 : paraxial focal length of the L1 lens, f: paraxial focal length of the whole optical system The compact optical system according to claim 1, wherein the following conditions are satisfied.

R1 _L1 : radius of curvature R1 of the object-side surface of the first lens L1, R2 _L2 : radius of curvature R2 of the image-side surface of the first lens L1. The compact optical system for a digital photographing apparatus according to claim 1, wherein the following conditions are satisfied.

d2: distance between the first lens and the second lens, f: paraxial focal length of the entire optical system The compact optical system according to claim 1, wherein the following conditions are satisfied.

d2: distance between the first lens and the second lens, f _L2 : paraxial focal length of the second lens The compact optical system according to claim 1, wherein the following conditions are satisfied.

Nd _L2 : Refractive index of d-line of L2 lens, Vd _L2 : Dispersion coefficient of d-line of L2 lens

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