KR20050015712A - Lens system being used in portable mobile terminal - Google Patents

Abstract

PURPOSE: A lens system used in handheld terminal is provided to correct distortion of optics and miniaturize a size of lens system by installing an aperture stop between predetermined lens groups. CONSTITUTION: A first lens group(100) is formed with a first lens(110) having a positive refractive index and a second lens(120) having a negative refractive index. An aperture stop(200) is used for preventing unnecessary incident light. A second lens group(300) is formed with a third lens(310) having the positive refractive index and a fourth lens(320) having the negative refractive index. An IR filter(400) is used for filtering IR wavelengths to protect an image plane. The aperture stop is installed between the first lens group and the second lens group.

Description

Lens system being used in portable mobile terminal

The present invention relates to a lens system mounted on a portable terminal. More specifically, by configuring an aperture stop between a predetermined lens group, the distortion correction and the size of the optical system to which the lens system is applied can be miniaturized and compacted. To provide a lens system.

In addition, another object of the present invention is to integrally coat a predetermined lens group by coating an IR filter, thereby protecting the image plane by filtering infrared wavelengths for lens systems that cannot use the IR filter. It is to provide a lens system having a simpler structure.

Recently, the trend of distributing portable terminal products in which cameras are integrated in portable terminals such as mobile phones and PDAs to consumers has become a mainstream, and such cameras attach a lens to an image pickup device such as ccd or cmos to target a subject. And to capture the captured subject data through a predetermined recording medium.

In addition, in the case of a general digital still camera, which is an imaging device that takes a still image formed by a photographing lens and captures an image electrically by an imaging device (hereinafter, a CCD) other than a CCD, it records a liquid crystal monitor. Because it can be used as a finder and as a monitor for playback of captured images, it has the advantages of immediateness and convenience compared to silver salt cameras. Also had.

In the case of a lens system mounted on a portable terminal or a digital camera as described above and used to photograph a subject, the following conditions must be satisfied.

In other words, in order to have mega pixel camera performance, the pixel size of the image pickup device has many sizes less than 4um, so the lens design itself should be designed to have sufficient resolution, and the design should be made larger than the actual sensor size in consideration of the assembly tolerance. do.

In addition, in addition to the above-described conditions of resolution, TV distortion should have a performance of 1% or less. The lower the resolution, the more the distortion is corrected, so the TV distortion is preferably 1% or less.

In addition, since the ambient light amount of the portable terminal is due to the angle of light incident on the sensor and the ambient light ratio of the lens system itself, the amount of ambient light of the camera is improved when the sensor is designed at an angle that allows the incident.

If the angle is designed to be smaller than the desired angle, resolution, distortion, and the length of the optical system are deteriorated, causing problems in combination with the sensor.

In addition, in the case of a lens system mounted on a portable terminal or a digital camera as described above and used for imaging a subject, the shape or form of the subject is deformed by the influence of incident light having different kinds of wavelengths input at the time of imaging the subject. There are various kinds of aberrations such as spherical aberration, astigmatism, and distortion aberration, which should be configured to suppress the occurrence of such aberrations.

Here, spherical aberration (axial aberration) is a chromatic aberration that does not completely reproduce the image of the subject on the basis of the wavelength of light when making the image of the subject in a lens or a spherical mirror, etc., a wide range of aberration except for such aberration It is called spherical aberration of meaning, and the aberration that occurs because the shop made from the beam of light from one point on the optical axis depends on which part of the lens the beam has passed through I say.

Distortion aberration is a phenomenon in which a straight portion of a subject is bent to form an image, and the subject is bent inward like a failure or outward as a barrel. The magnification of each subject increases in proportion to distance, but the overall image is proportionally This happens because it cannot change.

In addition, astigmatism is one of spherical aberrations of a broad meaning, and refers to a phenomenon in which an image of a material point distant from a main axis becomes blurry in a ring shape or a radial shape without becoming a perfect point.

Conventionally, as an example of a lens system designed to have the conditions as described above, the aperture stop is disposed closest to the object side in Korean Patent Application No. 2002-0005279, and then the first lens group and the second lens in turn from the object side. A first lens group having a positive refractive power from the object side and a second lens having a negative refractive power configured by being bonded or separated from the first lens in order from the object side. Wherein the second lens group is composed of only a third lens that is a positive lens having at least one refractive surface aspherical, and the third lens group is a fourth lens that is a negative lens having at least one refractive surface aspherical The contents of the related art related to the photographing lens composed only of the bay are disclosed.

That is, the basic features of the Korean Patent Application No. 2002-0005279 include a first lens group having a large positive power, a second lens group having a positive power subsequent thereto, and a third lens group having a small negative power. Lost, plus, plus, minus the so-called telephoto power arrangement. In addition, the main color correction is performed by the first lens group having a large power to correct chromatic aberration. Therefore, the first lens group mainly corrects spherical aberration, coma aberration, and chromatic aberration, and the second and third lens groups correct distortion aberration, which is mainly axial aberration, and maintain good telecentricity. Has the function of.

However, as described above, in the related art, since a predetermined number of lenses, that is, four lenses, must be used, there is a problem that the volume of the optical system is not only large but also a cost and time are required due to a complicated assembly process.

In addition, since the aperture diaphragm is disposed adjacent to the object side, there is a limit in shortening the length of the optical system to which the lens system is applied. There was a problem that can not produce a mobile terminal.

In order to solve the problems described above, an object of the present invention is to configure an aperture diaphragm between predetermined lens groups so that the distortion correction of the optical system to which the lens system is applied and the size of the lens system can be made smaller and more compact. To provide a lens system.

In addition, the present invention is formed by coating an IR filter on a predetermined lens group integrally, thereby protecting the image plane by filtering the infrared wavelength incident to the optical system even for a lens system that cannot use the IR filter, In addition, to provide a lens system having a simpler structure.

According to an aspect of the present invention, there is provided a lens system of a portable terminal including: a first lens group including a first lens having positive refractive power and a second lens having negative refractive power in order from an object side; An aperture stop disposed at a predetermined interval apart from the first lens group and preventing unnecessary incident light incident on the optical system; Two lens groups disposed spaced apart from the aperture stop by a predetermined distance, the second lens group including a third lens having positive refractive power of both aspherical surfaces and a fourth lens having negative refractive power of both surfaces aspherical; And an IR filter disposed to be spaced apart from the second lens group by a predetermined interval, and filtering an infrared wavelength incident to the optical system to protect an image plane. The first lens group and the second lens. Said aperture stop is provided between groups.

In addition, the lens system of the portable terminal according to the present invention, the first lens group consisting of a first lens having a positive refractive power and a second lens having a negative refractive power in order from the object side; An IR filter coated on one side of the second lens of the first lens group and integrally formed to filter an infrared wavelength incident to an optical system to protect an image plane; An aperture stop disposed at a predetermined interval apart from the first lens group and preventing unnecessary incident light incident on the optical system; And a second lens group which is disposed spaced apart from the aperture stop by a predetermined interval, and comprises a third lens having a positive refractive power of both aspherical surfaces and a fourth lens having a negative refractive power of both surfaces of the aspherical surface, wherein the first lens group and the The said aperture stop is provided between 2nd lens group. It is characterized by the above-mentioned.

Hereinafter, a configuration and an operation process of a lens system of a portable terminal according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing the configuration of a lens system according to an embodiment of the present invention, Figure 3 is a view showing the configuration of a lens system according to another embodiment of the present invention, Figure 4 is a view of the present invention FIG. 5 is a diagram illustrating spherical aberration generated in the lens system according to the present invention. FIG. 5 is a diagram illustrating astigmatism occurring in the lens system according to the present invention. FIG. 5 is a diagram illustrating distortion of aberration generated in the lens system according to the present invention. Figure is shown.

First, the configuration of the lens system according to the first embodiment of the present invention will be described in detail with reference to FIG. 2.

In the lens system of the portable terminal according to the first embodiment of the present invention, as shown in FIG. 2, the lens group of the first lens group 100 having the positive refractive power, the aperture diaphragm 200, and the positive refractive power are sequentially provided from the object side. It is arrange | positioned by the 2nd lens group 300 and IR filter 400 which have, and based on this, the power arrangement of an optical system is comprised so that it may have positive and positive optical power arrangement.

In addition, the present invention is configured to position the aperture stop 200 between the first lens group 100 and the second lens group 300, thereby miniaturizing the distortion correction of the optical system to which the lens system is applied and the size of the lens system And compact.

Hereinafter, the parameters of the components of the lens system according to the first embodiment of the present invention arranged as described above with reference to Table 1 will be described in detail.

Here, Table 1 shows the first lens group 100, the aperture stop 200, the second lens group 300, the IR filter 400 and the image surface 500 constituting the lens system according to the first embodiment of the present invention. The following table lists the radius of curvature, thickness / distance, and index of refraction for.

As shown in Table 1, the lens system according to the present invention has a focal length of 4.2, an F _no of 2.8 and a field angle of 62 ^o over the whole optical system.

Here, the first lens group 100 of the lens system is composed of a first lens 110 having a positive refractive power and a second lens 120 having a negative five refractive power, the first lens 110 and the first lens The second lens 120 is configured to have the same radius of curvature in order to facilitate manufacturing, wherein the first lens 110 is a glass lens made of glass, and the second lens 120 is a plastic lens made of plastic. to be.

In addition, as shown in Table 1, the first lens 110 has a first lens surface 111 having a radius of curvature of 3.40931 (mm), a thickness of 1.200000 (mm), and a refractive power of 1.71 (n). And a second lens surface 112 having a radius of curvature of -3.40931 (mm), a thickness of 0.446293 (mm), and a refractive power of 1.84 (n).

In addition, as shown in Table 1, the second lens 120 is a planar shape having a bone radius radius of ∞ and is composed of a third lens surface 121 having a thickness of 0.100000.

The first lens group 100 serves to set the power arrangement of the optical system to which the lens system is applied.

That is, the first lens group 100 is designed to satisfy the following conditional expression (1), thereby satisfying the power arrangement of the optical system to which the lens system of the present invention is applied to obtain good aberration characteristics.

1.0 <f1 / f <2.0 ........................... (1)

Here, f1 is a focal length of the first lens group 100, and f is a focal length of the entire optical system.

At this time, when the first lens group 100 does not satisfy the conditional expression (1) and exceeds the upper limit, the power of the second lens group 300 which will not be satisfied based on the power arrangement of the optical system will be described later. The arrangement is changed so that good aberration characteristics cannot be obtained.

In addition, the first lens group 100 is designed to satisfy the following condition equation (2), thereby reducing the shape of the lens for preventing the occurrence of spherical and distortion aberration generated in the optical system to which the lens system of the present invention is applied. Regulate.

0.3 <r1 / f <1.0 ............ (2)

Here, r1 is the radius of curvature of the first lens surface of the first lens 110, f is the focal length of the entire optical system.

At this time, when the range is set in excess of the upper limit and the lower limit of the conditional expression (2), the characteristics of the spherical aberration and the distortion aberration of the optical system deteriorate, and based on this, the spherical aberration and distortion in the second lens group 300 to be described later It will not be possible to carry out correction for the aberration.

The aperture stop 200 is for removing unnecessary incident light incident on the optical system. As shown in Table 1, the aperture stop 200 has a planar shape with a radius of curvature ∞ and a thickness of 0.800000 (mm).

In addition, the aperture stop 200 is configured to be disposed between the first lens group 100 and the second lens 300 to be described later, and based on this, the unnecessary incident light in the optical system to which the lens system of the present invention is applied. Not only does it effectively compensate for distortions that occur, it also serves to downsize the outer diameter of the optical system.

The second lens group 300 of the lens system includes a third lens 310 having both surfaces having positive refractive power and an aspherical surface, and a fourth lens 320 having both surfaces having negative five refractive power aspherical. The lens 310 and the fourth lens 320 are plastic lenses made of plastic.

The third lens 310 has a fourth lens surface 311 having a radius of curvature of −1.37869 (mm), a thickness of 0.800000 (mm), and a refractive power of 1.52 (n), as shown in Table 1. And a fifth lens surface 312 having a curvature radius of -0.79047 (mm), a thickness of 0.089259 (mm), and a refractive power of 1.52 (n).

In addition, as shown in Table 1, the fourth lens 320 has a curvature radius of 9.98252 (mm), a thickness of 0.800000, a refractive power of 1.52 (n), and a sixth lens surface 321 and a curvature. The seventh lens surface 322 has a radius of 1.18678 (mm), a thickness of 0944678 (mm), and a refractive power of 1.52 (n).

In addition, aspherical surface coefficients for the fourth lens surface 311 and the fifth lens surface 312 for the third lens 310 having both surfaces forming the second lens group 300 are aspherical equations as follows. Can be calculated by

That is, each aspherical surface can be obtained based on the aspherical equation as follows assuming that the Z axis extends along the optical axis and the Y axis extends in a direction perpendicular to the optical axis.

Here, the shape of the aspherical surface with respect to the fourth lens surface 311 and the fifth lens surface 312 constituting the third lens 310, as shown in Table 2, the radius of curvature of each aspherical lens surface The CURV value, which is the reciprocal value, and the aspherical surface constant values A to J for each aspherical lens surface, and the Y value indicating the height of the lens are determined.

In addition, aspherical surface coefficients for the sixth lens surface 321 and the seventh lens surface 322 for the fourth lens 320 having both surfaces forming the second lens group 300 are aspherical surfaces as described above. It can be calculated by the equation.

In addition, the shape of the aspherical surface with respect to the sixth lens surface 321 and the seventh lens surface 322 constituting the fourth lens 320, as shown in Table 3, the radius of curvature of each aspherical lens surface It is determined based on the CURV value, which is an inverse value for, the aspherical surface constant values A to J for each aspherical lens surface, and the Y value indicating the height of the lens.

Here, the second lens group 300 has a positive refractive power composed of the third lens 310 and the fourth lens 320, both sides of the aspherical surface, and serves to distribute the power of the optical system.

That is, the second lens group 300 is designed to satisfy the following conditional expression (3), thereby allocating power of the optical system to which the lens system of the present invention is applied to correct for axon and coma aberration. .

2.0 <f2 / f <5.0 ............... (3)

Here, f2 represents a focal length of the second lens group, and f represents a focal length of the entire optical system.

Here, when the first lens group 100 of the optical system has excessive power, aberration characteristics such as axial aberration and coma aberration tend to be poor.

As described above, in order to prevent deterioration of aberration characteristics of the optical system due to excessive power of the first lens group 100, the second lens group 300 is configured to satisfy the conditional expression (3). An aberration correction such as axial aberration and coma aberration generated in the optical system is performed by allocating excessively set power to the lens group 100.

Here, the coma aberration does not form a clear image when the subject or the light source is not on the main axis and the light enters the lens at an angle, even if the lens corrects the spherical aberration. A comet-shaped image with a tail appears, which is caused by the fact that the light rays from one point outside the optical axis of the optical system do not collect at one point.

In addition, the second lens group 300 is designed to satisfy the following conditional expression (4), so that the spherical aberration generated in the optical system to which the lens system of the present invention is applied and a good light incident angle on the image plane can be obtained. Define the shape.

0.2 <r4 / f <1.0 ............ (4)

Here, r4 is the radius of curvature of the fourth lens surface 311 of the third lens 310, f is the focal length of the entire optical system.

At this time, when the range is set in excess of the upper limit and the lower limit of the conditional expression (4), the characteristics of the spherical aberration of the optical system and the incident angle of light on the upper surface become poor.

In addition, the second lens group 300 is designed to satisfy the following condition equation (5), thereby defining the shape of the lens to prevent the occurrence of distortion and spherical aberration generated in the optical system to which the lens system of the present invention is applied. .

1.0 <r6 / f <3.0 ............ (5)

Here, r6 is the radius of curvature of the sixth lens surface 321 of the fourth lens 320, f is the focal length of the entire optical system.

At this time, when the range is set in excess of the upper limit of the conditional expression (5), the shape of the sixth lens surface 321 becomes difficult, so that aberration characteristics in other lens groups cannot be corrected.

In addition, when the range is set beyond the lower limit of the conditional expression (5), the characteristics of the distortion aberration and the spherical aberration of the optical system are deteriorated, so that manual correction in other lens groups cannot be performed.

In addition, the lens system of the present invention is designed so as to satisfy the conditional expression (6), thereby defining the length of the lens system that can shorten the length of the optical system and mount it on a predetermined terminal device, for example, a terminal device such as a mobile phone or a PDA. Doing.

1.0 <oal / f <2.0 ......................... (6)

Here, oal is a distance from the first lens surface 111 to the image surface 500 of the first lens group 100, f is the focal length of the optical system.

At this time, when the range is set beyond the upper limit of the conditional expression (6), the length of the optical system to which the lens system is applied is too long to be mounted on a terminal device such as a mobile phone or a PDA.

In addition, when the range is set in excess of the lower limit of the conditional expression (6), the length of the optical system to which the lens system is applied has the advantage of shortening, but the shape of the lens is a shape that can not actually be produced.

In addition, the lens system of the present invention is designed to satisfy the following conditional expression (7), thereby defining the outer diameter of the lens system applied to the optical system.

0.8 <h7 / h1 <1.5 .............. (7)

Here, h1 represents the size of the first lens surface 111 of the first lens group 100, and h7 represents the size of the seventh lens surface 322 of the second lens group 300.

The IR filter 400 serves to protect the upper surface 500 sensitive to infrared wavelengths by filtering the red wavelength input through the optical system to which the lens system of the present invention is applied. As shown in Table 1, the radius of curvature is Planar shape of ∞, first filter surface 401 having a thickness of 0.550000 (mm), refractive power of 1.51 (n), planar shape of curvature radius of ∞, 0.251789 (mm) of thickness, and refractive power of 1.51 The second filter face 402 is formed.

The image plane 500 serves to form an image of an object input through the optical system. As shown in Table 1, the image plane 500 has a planar shape having a curvature radius of ∞ and a thickness of 0.245218 (mm). .

Here, the image plane deteriorates when it is exposed to a predetermined wavelength, particularly an infrared wavelength, and the IR filter 400 as described above to prevent deterioration of the image plane due to the infrared wavelength. ) To filter the infrared wavelengths.

Hereinafter, a configuration of a lens system of a portable terminal according to a second embodiment of the present invention will be described in detail with reference to FIG. 3.

As shown in FIG. 3, the lens system of the portable terminal according to the second exemplary embodiment of the present invention includes a first lens group 100, an IF filter 400, and an aperture stop having positive refractive power in order from an object side. 200) and a second lens group 300 having positive refractive power, and based on this, the power arrangement of the optical system is configured to have a positive and positive optical power arrangement.

Here, the curvature radius, thickness / of the first lens group 100, the IR filter 400, the aperture stop 200 and the second lens group 300 constituting the lens system according to the second embodiment of the present invention The parameters for the distance and the refractive index are the same as shown in Table 1, and thus detailed description thereof will be omitted.

Further, since the respective effects on the conditional expressions (1) to (7) according to the second embodiment of the present invention described below are also the same as those of the first embodiment described above, the detailed description of the effect on the respective conditional expressions is described in the above-mentioned. It may be replaced based on the content described in Example 1.

As described in the first embodiment of the present invention, the first lens group 100 includes a first lens 110 having a positive refractive power and a second lens 120 having a negative five refractive power.

Here, the first lens surface 111 and the second lens surface 112 of the first lens 110 is made of a glass lens made of glass and made of the same radius of curvature in order to facilitate manufacturing.

In addition, the second lens 120 is a plastic lens having a third lens surface 121 having a planar shape having a radius of curvature ∞. The IR filter 400, which will be described later, includes the third lens 120 and the third lens. The lens surface 121 is coated to be integrally formed.

In addition, the first lens group 100, as described in the first embodiment of the present invention, is designed to satisfy the following conditional expression (1) to satisfy the power arrangement of the optical system to which the lens system is applied, good aberration To get the characteristics.

1.0 <f1 / f <2.0 ........................... (1)

Here, f1 is a focal length of the first lens group, and f is a focal length of the entire optical system.

In addition, the first lens group 100 is designed to satisfy the following conditional expression (2), thereby defining the shape of the lens to prevent the generation of spherical and distortion aberration generated in the optical system to which the lens system of the present invention is applied. do.

0.3 <r1 / f <1.0 .............. (2)

Here, r1 is the radius of curvature of the first lens surface of the first lens, f is the focal length of the entire optical system.

The IR filter 400 is integrally formed by coating the third lens surface 121 of the second lens 120 of the first lens group 100, and filters the infrared wavelengths incident on the optical system. Protect the Image Plane 500.

As described above, the IR filter 400 is coated on the first lens group 100 and integrated to filter the infrared wavelength incident to the optical system even on the lens system in which the IR filter 400 cannot be used. In addition to protecting the image plane 500, a simpler structure lens system is provided.

In this case, the IR filter 400 is designed to satisfy the following conditional expression (8) with respect to the side surface for integrally forming by coating the third lens surface 121 of the second lens 120.

30 <│r3 / f │ <1000 ........................ (8)

Here, r3 is the radius of curvature of the third lens surface of the second lens, f is the focal length of the whole optical system.

The aperture stop 200 is for removing unnecessary incident light incident on the optical system. As shown in Table 1 of the first embodiment of the present invention, the aperture diaphragm 200 has a planar shape having a radius of curvature of ∞ and a thickness of 0.800000 (mm).

In addition, the aperture stop 200 is configured to be disposed between the first lens group 100 and the second lens 300 to be described later, and based on this, the unnecessary incident light in the optical system to which the lens system of the present invention is applied. Not only does it effectively compensate for distortions that occur, it also serves to downsize the outer diameter of the optical system.

The second lens group 300 includes a third lens 310 having both surfaces having positive refractive power and an aspherical surface, and a fourth lens 320 having both surfaces having a negative five refractive power aspheric, and the third lens 310 And the fourth lens 320 is a plastic lens made of plastic.

Here, the second lens group 300 has a positive refractive power composed of the third lens 310 and the fourth lens 320, both sides of the aspherical surface, and serves to distribute the power of the optical system.

That is, the second lens group 300 is designed to satisfy the following conditional expression (3) as described in the first embodiment of the present invention, thereby allocating power of the optical system to which the lens system of the present invention is applied. To correct for aberration and coma aberration.

2.0 <f2 / f <5.0 ............... (3)

Here, f2 represents a focal length of the second lens group 300, and f represents a focal length of the entire optical system.

In addition, as described in the first embodiment of the present invention, the second lens group 300 is designed to satisfy the following conditional expression (4), so that spherical aberration and image surface generated in the optical system to which the lens system of the present invention is applied. It defines the shape of the lens to obtain a good light incident angle at.

0.2 <r4 / f <1.0 ............ (4)

Here, r4 is a radius of curvature of the fourth lens surface 311 of the third lens 310 constituting the second lens group 300, and f represents a focal length of the entire optical system.

Further, as described in the first embodiment of the present invention, the second lens group 300 is designed to satisfy the following conditional expression (5), thereby causing distortion and spherical aberration generated in an optical system to which the lens system of the present invention is applied. To define the shape of the lens to prevent the occurrence of aberration.

1.0 <r6 / f <3.0 ............ (5)

Here, r6 is a radius of curvature of the sixth lens surface 321 of the fourth lens 320 constituting the second lens group 300, and f represents a focal length of the entire optical system.

Further, the lens system according to the second embodiment of the present invention is designed to satisfy the following conditional expression (6) as described in the first embodiment of the present invention to shorten the length of the optical system to provide a predetermined terminal device, for example. For example, the length of a lens system that can be attached to a terminal device such as a mobile phone or a PDA is prescribed.

1.0 <oal / f <2.0 ......................... (6)

Here, oal is a distance from the first lens surface 111 to the image surface 500 of the first lens group 100, f is the focal length of the optical system.

In addition, the lens system of the present invention, as described in the first embodiment of the present invention, defines the outer diameter of the lens system to be applied to the optical system by designing to satisfy the following conditional expression (7).

0.8 <h7 / h1 <1.5 .............. (7)

Here, h1 is the size of the first lens surface 111 of the first lens 110, h7 is the size of the seventh lens surface 322 of the fourth lens (320).

As described above, according to the lens system used in the portable terminal according to the present invention, by configuring the aperture stop between the predetermined lens group, the distortion correction of the optical system to which the lens system is applied and the size of the lens system can be miniaturized and Provides effects that can be compacted.

In addition, the present invention is integrally formed by coating an IR filter on a predetermined lens group, thereby protecting the image plane by filtering the infrared wavelength incident to the optical system even for a lens system that cannot use the IR filter. It provides the effect of implementing a lens system having a simpler structure.

Herein, while the present invention has been described with reference to the preferred embodiments, those skilled in the art will variously modify the present invention without departing from the spirit and scope of the invention as set forth in the claims below. And can be changed.

1 is a block diagram showing a conventional lens system.

2 is a block diagram showing a lens system used in the portable terminal according to the first embodiment of the present invention.

3 is a block diagram illustrating a lens system used in a portable terminal according to a second embodiment of the present invention.

4 is a diagram illustrating spherical aberration occurring in the lens system used in the portable terminal according to the present invention.

5 is a diagram illustrating astigmatism occurring in the lens system used in the portable terminal according to the present invention.

6 is a diagram illustrating distortion aberration occurring in the lens system used in the portable terminal according to the present invention.

Explanation of symbols on the main parts of the drawings

100: first lens group

110: first lens

111: first lens surface

112: second lens surface

120: second lens

121: third lens surface

200: aperture stop (STO)

300: second lens group

310: third lens

311: fourth aspherical lens surface

312: fifth aspherical lens surface

320: fourth lens

321: 6th aspherical lens surface

322: seventh aspherical lens surface

400: IR filter

401: first filter surface

402: second filter surface

500: Image Plane

Claims (11)

A first lens group including a first lens having positive refractive power and a second lens having negative refractive power in order from the object side; An aperture stop disposed at a predetermined interval apart from the first lens group and preventing unnecessary incident light incident on the optical system; Two lens groups disposed spaced apart from the aperture stop by a predetermined distance, the second lens group including a third lens having positive refractive power of both aspherical surfaces and a fourth lens having negative refractive power of both surfaces aspherical; And It is arranged to be spaced apart from the second lens group by a predetermined interval, and composed of an infrared filter (IR Filter) to protect the image plane by filtering the infrared wavelength incident to the optical system, The aperture diaphragm is provided between the first lens group and the second lens group. A first lens group including a first lens having positive refractive power and a second lens having negative refractive power in order from the object side; An infrared filter coated on one side of the second lens of the first lens group and integrally formed to protect an image plane by filtering an infrared wavelength incident to an optical system; An aperture stop disposed at a predetermined interval apart from the first lens group and preventing unnecessary incident light incident on the optical system; And A second lens group disposed spaced apart from the aperture stop by a predetermined interval, the second lens group including a third lens having positive refractive power of both aspherical surfaces and a fourth lens having negative refractive power of both surfaces aspheric, And the aperture stop is provided between the first lens group and the second lens group. The method according to claim 1 or 2, The first lens includes a first lens surface and a second lens surface having the same radius of curvature, and the second lens comprises a third lens surface bonded to the second lens surface. Lens system. The method according to claim 1 or 2, Wherein the first lens is a glass lens and the second lens is a plastic lens. The method according to claim 1 or 2, And the third lens includes a fourth lens surface and a fifth lens surface that are aspherical, and the fourth lens includes a sixth lens surface and a seventh lens surface that are aspherical surfaces. The method of claim 2, And the third lens and the fourth lens are plastic lenses. The method of claim 1 or 2, wherein the first lens group, In terms of power for obtaining good aberration characteristics of the optical system, the following conditional expression (1) is satisfied, and for the aspect defining the lens shape for preventing the generation of spherical aberration and distortion aberration generated in the optical system, Is designed to satisfy 1.0 <f1 / f <2.0 ........................... (1) 0.3 <r1 / f <1.0 ............ (2) Here, f1 is the focal length of the first lens group, f is the focal length of the whole optical system, r1 is the radius of curvature of the first lens surface, the lens system of the portable terminal. The method of claim 1 or 2, wherein the second lens group, In terms of power distribution for aberration correction of the optical system, the following conditional expression (3) is satisfied.In terms of defining the shape of the lens with respect to spherical aberration and incident angle characteristics in the image plane, the following conditional equation (4) is satisfied. With respect to the side defining the shape of the lens for correction of distortion and spherical aberration generated in the optical system, it is designed to satisfy the following conditional expression (5), 2.0 <f2 / f <5.0 ......... (3) 0.2 <│r4 / f │ <1.0 ........................ (4) 1.0 <│r6 / f │ <3.0 ........................... (5) Here, f2 is the focal length of the first lens group, f is the focal length of the whole optical system, r4 is the radius of curvature with respect to the fourth lens surface, r6 is the radius of curvature with respect to the sixth lens surface. A lens system of a portable terminal, characterized in that. The method according to claim 1 or 2, With respect to the side of the length of the optical system is designed to satisfy the following conditional formula (6), 1.0 <oal / f <2.0 ......................... (6) Here, oal is the distance from the first lens surface of the first lens to the sensor surface, f is the lens system of the portable terminal, characterized in that the focal length of the optical system. The method of claim 2, With respect to the aspect of the outer diameter of the optical system is designed to satisfy the following condition equation (7), 0.8 <h7 / h1 <1.5 .............. (7) Here, h1 is the size of the first lens surface of the first lens, h7 is the size of the seventh lens surface of the fourth lens, the lens system of the portable terminal. The method of claim 2, It is designed to satisfy the following conditional expression (8) with respect to the side surface for integrally forming the infrared filter by coating the second lens of the first lens group, 30 <│r3 / f │ <1000 ........................ (8) Here, r3 is the radius of curvature of the third lens surface of the second lens, f is the lens system of the portable terminal, characterized in that the focal length of the whole optical system.