KR101771968B1 - Wide small optical system - Google Patents

Abstract

The present invention relates to a small wide-angle optical system, comprising a first lens group, a second lens group, and a third lens group, which are placed in the order from a top side down. The first lens group comprises: a first lens (L1) having a negative refractive power; and a second lens (L2) having a positive refractive power, to have a positive refractive power overall. The second lens group comprises: a third lens (L3) having a negative refractive power; a fourth lens (L4) having a positive refractive power; and a fifth lens (L5) having a negative refractive power, to have a positive refractive power overall. The third lens group comprises a sixth lens (L6) having a positive refractive power, to satisfy all of the following formulas: 1.5 < A/AOI < 3.0, 0.2 < f/1 < 0.6, 0.8 < TTL/2Y < 1.8 (A: half angle of view in a full field of an image sensor, AOI: CRA in a full field, 1: total focal distance of the first lens group, f: total focal distance of the entire optical system, TTL: distance from a first surface of the first lens to the image sensor, 2Y: diagonal size of the image sensor). According to the present invention, the present invention is able to minimize a full length of the optical system, to secure a wide angle of view, to make it easier to compose or design an instrument, and to have a high resolution power.

Description

Wide small optical system &lt; RTI ID = 0.0 &gt;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-angle small optical system, and more particularly, to a wide-angle small optical system mounted on a smart device or the like.

In recent years, the demand for camera modules has been rapidly increasing due to the application of camera functions to basic specifications for portable electronic devices, home appliances, and automobiles, and the technical requirements for camera modules have also been diversified.

The technical requirements for the camera module can be classified into resolution, size, and angle of view. In the past, the demand for high resolution and miniaturization has been a major factor. Recently, however, there has been a growing demand for a wider viewing angle.

In recent years, as the use of smart phones equipped with a camera module as a basic specification has become common, photographing using a smart phone is becoming common, and in particular, users are increasingly taking a picture with a wide background using a self- As a result, the need for a wide viewing angle as well as high resolution performance is emphasized.

However, since aberration correction becomes more difficult as the angle of view of an optical system increases, it is difficult to realize a resolution high enough to be applied to a high-resolution image sensor, and it is also difficult to downsize an optical system, so it is very difficult to design an optical system satisfying all technical requirements .

In particular, in the case of a high-resolution optical system mounted on a smart device, there is a demand for miniaturization. However, in order to realize a high resolution performance corresponding to a high-resolution image sensor, at least three or more lenses must be used in the optical system, and recently, a large number of six-lens lenses are used. In addition, a wide angle lens having an angle of view of 85 degrees or more has poor optical performance and is difficult to apply to a high-resolution image sensor.

Therefore, in order to miniaturize the optical system, it is necessary to develop an optimal optical system capable of realizing a high resolution and a wide angle of view while minimizing the electric field.

Korean Patent Publication No. 10-2017-0058601 (published on May 27, 2019)

An object of the present invention is to provide an optical system having a bright and high resolving power that can be applied to a high pixel while ensuring a wide angle of view and minimizing the optical field.

According to one aspect of the present invention, there is provided a zoom lens comprising a first lens group, a second lens group, and a third lens group arranged in order from an object side to an image side, A second lens group having positive refracting power and a second lens group having positive refracting power, and having a positive refracting power as a whole, wherein the second lens group includes a third lens having a negative refracting power, And a fifth lens L5 having a negative refracting power and having a positive refracting power as a whole and the third lens group L6 having a positive refracting power, the fourth lens L4 having a positive refracting power and the fifth lens L5 having a negative refracting power, (A: Half angle of field in full field of image sensor, AOI: Full field of CRA (AOI)), and the following conditional expression: 1.5 <A / AOI <3.0, 0.2 <f / , F1: total focal length of the first lens group, f: total focal length of the entire optical system, TTL: from the first surface of the first lens to the image sensor Distance, 2Y: provides a compact wide angle optical system that satisfies all of the diagonal dimension) of the image sensor.

In the wide-angle compact optical system according to one aspect of the present invention, all of the four lens surfaces of the first lens L1 and the second lens L2 may be aspherical.

Further, in the wide-angle small optical system according to one aspect of the present invention, the fourth lens L4 of the second lens group satisfies the following conditional expression: 0.3 <ET4 / CT4 <0.6 (ET4: Thickness (edge thickness), and CT4: center thickness of the fourth lens).

Further, in the wide-angle small optical system according to one aspect of the present invention, the second lens group is configured such that, in order to correct chromatic aberration, 20 <| V4 - V3 | <40 (V3: dispersion value of the third lens, The dispersion value of the lens).

Further, in the wide-angle small optical system according to one aspect of the present invention, the third lens group satisfies the following conditional expression: 0 <f /? 3 <0.7 (? 3: total focal length of the third lens group, f: ). &Lt; / RTI &gt;

Another aspect of the present invention is a zoom lens comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in order on the object side in an upward direction, Wherein the second lens has a negative refractive power and the third lens has a concave meniscus lens having an upward refracting power and the fourth lens has a positive refracting power, A / A0I <3.0, 0.2 <f /? 1 <0.6, 0.8 or more, and the sixth lens has an aspherical surface having at least one inflexion point, <TTL / 2Y <1.8 where A: Half angle of field in the full field of the image sensor, AOI: CRA of full field, PHI 1: Total focal length of the first lens group, f: Total focal length of the entire optical system, TTL: Distance from the first side of the lens to the image sensor, 2Y: diagonal size of the image sensor) Both offer a compact wide-angle optical system that satisfies.

According to the present invention, it is possible to secure a wide angle of view while minimizing the total length of the optical system, and there is an advantage that the mechanism configuration and design can be made easier. In particular, it is possible to secure a short overall length of 5.2 mm or less and a wide angle of view of 110 degrees or more, thereby realizing a compact wide-angle small optical system as compared with the prior art. It is also possible to realize a wide-angle small optical system having a wide angle of view and high resolution performance.

1A is a configuration diagram of an optical system according to a first embodiment of the present invention
FIG. 1B is a graph showing the aberration degree of the optical system according to the first embodiment of the present invention
1C is a perspective view of a distortion grid of an optical system according to a first embodiment of the present invention.
2A is a configuration diagram of an optical system according to a second embodiment of the present invention
FIG. 2B is a graph showing the aberration degree of the optical system according to the second embodiment of the present invention
FIG. 2C is a perspective view of the distortion grid of the optical system according to the second embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in Figs. 1A and 2A, the lens optical system according to the embodiment of the present invention is arranged from the object side in the order of the first lens group, the second lens group, and the third lens group, Or more. The diaphragm is preferably disposed between the first lens group and the second lens group.

Specifically, the first lens group includes a first lens L1 having a negative refracting power and a second lens L1 having a positive refracting power, and has a positive refracting power as a whole.

It is preferable that the first lens L1 and the second lens L2 are arranged in order from the object side and that both surfaces of the first lens L1 and both surfaces of the second lens L2 are aspherical surfaces.

On the other hand, if the first lens group has a strong positive refractive power, it is possible to construct a wide-angle system. If the opposite refractive power is distributed to the first lens L1 and the second lens L2 and both surfaces of the first lens L1 and the second lens L2 are made aspheric surfaces, The structure and the design of the mechanism are made easier, and a high resolution performance can be realized.

The second lens group includes a third lens L3 having a negative refracting power, a fourth lens L4 having a positive refracting power, and a fifth lens L5 having a negative refracting power, .

The third lens L3, the fourth lens L4, and the fifth lens L5 are arranged in order from the object side. Here, it is preferable that the third lens L3 is a meniscus lens concave upward, the fourth lens L4 is a double-convex lens, and the fifth lens L5 is a meniscus lens convex upward.

It is preferable that the third lens group includes a sixth lens L6 having a positive refractive power and the lens surface of the sixth lens L6 includes an aspherical surface having at least one inflection point.

It is preferable that all lenses constituting the first to third lens groups use a plastic lens in view of ease of processing and degree of freedom of shape, but the present invention is not limited thereto.

Meanwhile, in order to realize a wide angle and a high resolution, the optical system according to an embodiment of the present invention is preferably designed to satisfy the following conditional expressions 1 and 2.

<Conditional Expression 1>

1.5 < A / AOI < 3.0

(A: Half angle of field in image sensor, AOI: Chief Ray Angle (CRA) in Full Field)

The conditional expression (1) relates to the half angle of view of the image sensor and the incident angle (CRA) of the principal ray incident on the image sensor. When the upper limit is exceeded, optical performance such as high resolution is hardly obtained. It is difficult to do.

<Conditional expression 2>

0.2 <f /? 1 <0.6

(? 1: total focal length of the first lens unit, f: total focal length of the entire optical system)

When the upper limit is surpassed, it is difficult to secure the optical system configuration and the focal length. If the lower limit is smaller than the lower limit, it is difficult to appropriately allocate the refractive power.

In order to achieve miniaturization and high resolution, the second lens unit of the optical system according to an embodiment of the present invention is preferably designed to satisfy the following conditional expression 3 and conditional expression 4.

<Conditional expression 3>

0.3 < ET4 / CT4 < 0.6

(ET4: lens thickness (edge thickness) at the back side effective diameter of the fourth lens, CT4: center thickness of the fourth lens)

If the upper limit is exceeded, it is difficult to secure the incident angle (CRA) of the principal ray incident on the image plane, thereby making it difficult to downsize the optical system. If the value is smaller than the lower limit, It is difficult to produce a lens because of poor injection property.

<Conditional expression 4>

20 <| V4 - V3 | <40

(V3: dispersion value of the third lens, V4: dispersion value of the fourth lens)

The above conditional expression (4) relates to chromatic aberration correction. If the chromatic aberration is out of the above range, it becomes difficult to correct the chromatic aberration, and it becomes difficult to realize a resolution performance enough to be used for a high pixel.

In order to improve the performance, the third lens unit of the optical system according to the embodiment of the present invention is preferably designed to satisfy the following conditional expression (5).

<Conditional expression 5>

0 < f /? 3 < 0.7

(? 3: total focal length of the third lens group, f: total focal length of the entire optical system)

When the upper limit is exceeded, the refractive power of the third lens group is excessively large, so that the distortion aberration and chromatic aberration become large. If the lower limit is smaller than the lower limit, it is difficult to distribute the refractive power, There is a difficult problem.

It is preferable that the optical system according to the embodiment of the present invention is designed to satisfy the following conditional expression (6).

<Conditional Expression 6>

0.8 < TTL / 2Y < 1.8

(TTL: distance from the first surface of the first lens to the image sensor, 2Y: diagonal size of the image sensor)

If the upper limit is larger than the upper limit, it is difficult to realize a wide angle of 110 degrees or more. Also, since the total length is too long, it is difficult to form a small optical system. there is a problem.

On the other hand, Table 1 below shows calculation values for the performance value and the conditional expression for the configuration of the lens described above and the design specifications of the two embodiments satisfying the conditional expressions 1 to 6.

[Table 1]

The data of each embodiment provided for calculating the values of Table 1 are as follows, and the lens configurations of the wide angle small optical system according to the first and second embodiments are as shown in FIGS. 1A and 2A, respectively.

&Lt; Embodiment 1 >

&Lt; Embodiment 2 >

In the data of the first and second embodiments, Y Radius is the radius of curvature of the lens, Thickness is the thickness and air gap of the lens, Nd is the refractive index at the d-line (587.56 nm) of the lens material, vd is the Abbe number to be.

The aspherical surface coefficients shown in the data of the first and second embodiments are coefficients applied to the following relational expression concerning the aspherical shape.

Here, Z is the distance from the apex of the lens to the optical axis direction, h is the distance in the direction perpendicular to the optical axis, C is the reciprocal of the radius of curvature at the apex of the lens, K is the Conic constant, A8, A10, A12, A14, A16 and A18 are aspheric coefficients, respectively.

Figs. 1B and 1C show aberration and distortion grids of the wide-angle small optical system according to the first embodiment, Figs. 2B and 2C show aberration and distortion grids of the wide-angle small optical system according to the second embodiment, It can be confirmed that spherical aberration, astigmatism, distortion aberration, and the like are good in each embodiment.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It is to be understood that the invention is not limited thereto.

L1: first lens L2: second lens
L3: Third lens L4: Fourth lens
L5: fifth lens L6: sixth lens
LF: Filter STOP: Aperture

Claims (6)

A first lens group, a second lens group, and a third lens group arranged in order from the object side to the image side,
The first lens group includes a first lens L1 having a negative refractive power and a second lens L2 having a positive refractive power and having a positive refractive power as a whole,
The second lens group includes a third lens L3 having a negative refracting power, a fourth lens L4 having a positive refracting power, and a fifth lens L5 having a negative refracting power, have,
The third lens group includes a sixth lens (L6) having a positive refractive power,
The optical system satisfies all of the following conditional expressions.
1.5 < A / AOI < 3.0
0.2 <f /? 1 <0.6
0.8 < TTL / 2Y < 1.8
(A: half-angle of view in full field of image sensor, AOI: CRA of full field, 陸 1: total focal length of first lens group, f: total focal length of entire optical system, TTL: , 2Y: diagonal size of the image sensor) The method according to claim 1,
Wherein the four lens surfaces of the first lens (L1) and the second lens (L2) are all aspherical surfaces. 3. The method according to claim 1 or 2,
And the fourth lens (L4) of the second lens group satisfies the following conditional expression:
0.3 < ET4 / CT4 < 0.6
(ET4: lens thickness (edge thickness) at the back side effective diameter of the fourth lens, CT4: center thickness of the fourth lens) 3. The method according to claim 1 or 2,
Wherein the second lens group satisfies the following conditional expression for chromatic aberration correction:
20 <| V4 - V3 | <40
(V3: dispersion value of the third lens, V4: dispersion value of the fourth lens) 3. The method according to claim 1 or 2,
And the third lens group satisfies the following conditional expression
0 < f /? 3 < 0.7
(? 3: total focal length of the third lens group, f: total focal length of the entire optical system) A first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in order from the object side to the image side,
Wherein the first lens and the second lens have opposite refractive powers,
The third lens is an upwardly concave meniscus lens having a negative refracting power,
The fourth lens is a double-sided convex lens having a positive refractive power,
The fifth lens is an upwardly convex meniscus lens having a negative refracting power,
The sixth lens includes an aspherical surface having at least one inflection point,
The optical system satisfies all of the following conditional expressions.
1.5 < A / AOI < 3.0
0.2 <f /? 1 <0.6
0.8 < TTL / 2Y < 1.8
(A: half-angle of view in full field of image sensor, AOI: CRA of full field, 陸 1: total focal length of first lens group, f: total focal length of entire optical system, TTL: , 2Y: diagonal size of the image sensor)

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