KR100716793B1 - Lens unit for camera - Google Patents

Abstract

The present invention provides an imaging lens unit that can reduce the production cost of a product by minimizing the performance degradation due to manufacturing error, while minimizing the overall length and reducing the effective diameter of the third lens. Its purpose is to.

를 만족하도록 구성된다. To this end, the imaging lens unit according to the present invention comprises: a first lens disposed on the subject side, having a positive refractive power, and having a convex surface formed on the subject side and a concave surface formed on the image side; An aperture stop disposed to be spaced apart from the first lens by a predetermined interval and preventing unnecessary incident light incident on the optical system; A second lens disposed to be spaced apart from the aperture by a predetermined distance, having a positive refractive power, and having a concave surface formed on the subject side and a convex surface formed on the image side; A third lens disposed to be spaced apart from the second lens by a predetermined distance, and having a negative refractive power, and having a convex surface formed on the subject side and a concave surface formed on the image side; And an infrared cut-off filter disposed to be spaced apart from the third lens by a predetermined interval, and filtering infrared wavelengths incident on the optical system, wherein an uppermost ray of the light beam traveling at an image height of 3.0 mm is recessed in the third lens. When the height passing through the surface is called H (S42) and the focal length is called EFL,

It is configured to satisfy.

Refractive power, aspherical, glass, lens, slim

Description

Imaging lens unit {LENS UNIT FOR CAMERA}

1 is a block diagram showing an imaging lens unit according to the present invention.

FIG. 2 is a configuration diagram for describing specific parameters in the imaging lens unit shown in FIG. 1. FIG.

3 is a graph showing spherical aberration, astigmatism and distortion for the imaging lens unit according to the embodiment of the present invention.

4 is a graph showing coma aberration for the imaging lens unit according to the embodiment of the present invention;

<Description of the symbols for the main parts of the drawings>

10: First lens S11: Subject side surface of the first lens

S12: Image side of the first lens

20: aperture

30: second lens S31: subject side surface of second lens

S32: Image side of the second lens

40: Third lens S41: Subject side surface of the third lens

S42: image side of the second lens

50: infrared cut filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging lens unit, and more particularly, to an imaging lens unit used in a mobile terminal such as a cellular phone.

Nowadays, mobile terminals such as mobile phones and PDAs are being used for multi-convergence with music, movies, TV, and games as well as simple telephone functions with the development of the technology. One of the things leading the development of such multi-convergence. As a camera module (CAMERA MODULE) is the most representative. The camera module is being changed from the existing 300,000 pixels (VGA level) to the high pixel center of 7 million pixels and is being changed to implement various additional functions such as auto focusing (AF) and optical zoom (OPTICAL ZOOM).

In general, the camera module (CCM: COMPACT CAMERA MOUDULE) is compact and is applied to various IT devices such as a camera phone, a PDA, a smartphone, and a portable mobile communication device such as a toy camera (TOY CAMERA). Increasingly, devices equipped with small camera modules are gradually being released to meet various consumer tastes. Such a camera module is manufactured by using an image sensor such as a CCD or a CMOS as a main component, and collects an image of an object through the image sensor and stores it as data in a memory in the device, and the stored data is stored in an LCD or The image is displayed on a display medium such as a PC monitor.

On the other hand, in the lens unit used in such a camera module, Japanese Patent Laid-Open No. 2001-183578 describes an imaging lens composed of one plastic group according to a CIF class image size and a plastic group 2 according to a VGA class image size. An imaging lens composed of two pieces is disclosed.

However, the lens configuration disclosed in Japanese Patent Laid-Open No. 2001-183578 alone does not solve the problems of optical system design constraints such as the incidence angle limitation on the imaging surface of an image sensor of SXGA class or higher.

Therefore, as a lens unit proposed to solve this problem, it is possible to consider a lens combination in which the first lens has positive (positive) refractive power and the second and third lenses have negative (negative) refractive power.

However, in such a lens unit, the effect of improving the image quality of the image by preventing the occurrence of magnification chromatic aberration can be expected, but the effective diameter of the third lens for minimizing the amount of light loss is inevitably increased. There is a limit to be mounted in a mobile terminal aiming for the same miniaturization, and there is a problem that the mass productivity is lowered as the performance degradation due to manufacturing error increases.

On the other hand, conventionally, spherical glass lenses or aspherical plastic lenses were mainly used as the first lenses.

It is possible to use a high refractive index material when using spherical glass lenses, but the lens surface is spherical, so there is a limit to improving all aberrations including spherical aberration, and aspherical surfaces when using aspherical plastic lenses. By controlling the light beam more effectively, it is advantageous to improve aberration, but due to the limitation of plastic lens material, it is difficult to expect sufficient aberration correction because low refractive index material is used.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the overall length and to reduce the effective diameter of the third lens to make the imaging lens unit slim, and to minimize the performance degradation due to manufacturing errors. It is to provide an imaging lens unit that can reduce the production cost of the product.

를 만족하는 것을 특징으로 한다. The imaging lens unit according to the present invention for achieving the above object comprises: a first lens disposed on the subject side, having a positive refractive power, and having a convex surface formed on the subject side and a concave surface formed on the image side; An aperture stop disposed to be spaced apart from the first lens by a predetermined interval and preventing unnecessary incident light incident on the optical system; A second lens disposed to be spaced apart from the aperture by a predetermined distance, having a positive refractive power, and having a concave surface formed on the subject side and a convex surface formed on the image side; A third lens disposed to be spaced apart from the second lens by a predetermined distance, and having a negative refractive power, and having a convex surface formed on the subject side and a concave surface formed on the image side; And an infrared cut-off filter disposed to be spaced apart from the third lens by a predetermined interval, and filtering infrared wavelengths incident on the optical system, wherein an uppermost ray of the light beam traveling at an image height of 3.0 mm is recessed in the third lens. When the height passing through the surface is called H (S42) and the focal length is called EFL,

Characterized by satisfying.

를 만족하도록 배열되는 것을 특징으로 한다. In addition, when the imaging lens unit is a focal length is EFL, and the distance from the center of the convex surface of the first lens to the image surface is TTL as a value in air from which the infrared cut filter is removed,

Characterized in that arranged to satisfy.

The first lens may be a glass lens having at least one surface aspherical, and the second lens and the third lens may be plastic or glass lenses. As such, when the glass lens is used as the first lens, a high refractive index material is used to reduce aberration by reducing the angle of light incident on the curved surface. Particularly, by using an aspherical glass lens, the incident angle and refractive angle on the curved surface are reduced. By being able to finely control the, there is an effect that can minimize the occurrence of aberration.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when a detailed description of a related well-known configuration or function is apparent to those skilled in the art, or it is determined that the subject matter of the present invention may be obscured, the detailed description thereof will be omitted.

1 and 2 show schematic views of an imaging lens unit according to the present invention.

As shown in FIG. 1, the imaging lens unit according to the present invention includes a first lens 10, an aperture stop 20, and a second lens 30 from a subject (object) side to an image surface (image sensor surface). The third lens 40 and the infrared cut filter 50 are sequentially arranged.

The first lens 10 is disposed on the subject side, has positive (positive) refractive power, and has a convex surface S11 formed on the subject side and a concave surface S12 formed on the image side. Here, the first lens 10 is preferably at least one surface aspherical (aspherical) glass lens. Using a glass lens reduces aberration by reducing the angle of light incident on the curved surface by using a high refractive index material. In particular, by using an aspherical glass lens, the angle of incidence and refractive angle on the curved surface can be finely controlled. By doing so, it is possible to minimize the occurrence of aberration.

That is, in general, since most lenses are spherical, the focus is different according to the light input position, which causes spherical aberration. In addition, when the beam is incident on the axis, comet tail coma aberration occurs. In addition, when focusing on a point object, a phenomenon that sometimes occurs, the so-called astigmatism occurs in which an ellipse up and down before and after the focus becomes an ellipse from side to side. This aberration is fatal in wide-angle lenses with large viewing angles. Aspheric lenses have been used to solve this problem. Conventionally, a large number of lenses were used in combination to reduce aberration of the lens, but the use of aspherical lenses reduces the number of lenses forming the lens system, making it possible to miniaturize and lighten the weight, and reduce the reflection of light on the glass surface. The light transmittance is greatly improved, and a lot of ghost images can be suppressed.

On the other hand, glass lenses are generally manufactured by a grinding or polishing method and a re-heat pressing method, and most spherical glass lenses are manufactured by grinding and polishing a glass material to form an optical surface. It is difficult to mass-produce a glass lens having an aspherical optical surface with the same precision by the above grinding or polishing method. Therefore, the aspherical glass lens according to the present invention is manufactured by the method of pressing the mold by the lith press, and the press is made of a glass material (preliminarily divided into a predetermined size) of the glass material produced by cooling the molten glass once. As a method of manufacturing a glass lens by transferring the shape of a mold to a glass material by heating and pressing, a curved surface can be formed only by a press molding process, so that the process is simplified. In addition, when the mold for the aspherical shape is completed, the aspherical glass lens can be mass-produced with the same precision using the same.

Looking at the method for manufacturing the first lens 10 according to the present invention by using the Richt press process, first, a predetermined necessary material is added to the molten glass and stirred, and the infrared ray blocking material is dissolved. The glass is cooled to form a glass material, and then the glass material is heated, and then the glass material is positioned between upper and lower molds having an aspherical shape, and the mold and glass material are accommodated for the purpose of preventing oxidation of the mold. Replace the inside of the molding chamber with an inert gas such as nitrogen gas, heat the mold and the glass material using an infrared lamp (or a high frequency heating device, etc.), and finally, the mold and the glass material reach a predetermined temperature. The lower and lower molds are used to press the glass material, and finally, the cooled glass lens is pulled out.

The aperture stop 20 is disposed to be spaced apart from the first lens 10 in the image plane direction by a predetermined interval, and serves to prevent unnecessary incident light incident on the optical system.

The second lens 30 is disposed to be spaced apart from the opening aperture 2 in the image plane direction by a predetermined interval, and has a positive (positive) refractive power similarly to the first lens 10, and is formed on the object side (S31). ) And the convex surface S32 formed on the image side. The second lens 30 may be made of plastic or glass material.

The third lens 40 is disposed spaced apart from the second lens 30 in the image plane direction by a predetermined interval, has a negative (negative) refractive power, and has a convex surface S41 formed on the object side and a concave surface formed on the image side ( S42) is provided. In addition, like the second lens 30, the third lens 40 may be formed of a plastic or glass material.

Here, the third lens 40 is a lens for determining the effective diameter determined on the image plane. In the prior art, since the second and third lenses 30 and 40 both have negative refractive power, in order to minimize light loss The outer diameter of the third lens 40 had to be increased. In contrast, in the present invention, the second and third lenses 30 and 40 have positive and negative refractive power, respectively, and at an image height 3.0 mm point (“A”) as shown in FIG. 2. When the highest ray α of the propagating beam passes through the concave surface S42 of the third lens 40 is H (S42), and the focal length is 'EFL', the condition of Equation 1 below Must be satisfied.

When the ratio of 0.5 or more of H (S42) and the focal length EFL in the above Formula 1, the ordinary ray (上光線; α) passing through the concave surface (S42) of the third lens 40, the the higher the position of the The outer diameter of the third lens 40 is increased, which causes a problem that the size of the lens unit is increased.

Finally, the infrared cut filter 50 is disposed spaced apart from the third lens 40 in the image plane direction by a predetermined interval, and serves to filter the infrared wavelength incident to the optical system.

On the other hand, in order to further reduce the size of the lens assembly, the imaging lens unit including the first to third lenses, the focal length is called 'EFL', the value in the air from which the infrared cut filter is removed When the distance from the center of the convex surface S11 of the single lens 10 to the image plane is 'TTL', it is preferable to satisfy the following expression (2).

Example

Tables 1 to 3 below show lens data corresponding to specific examples according to the present invention as described above.

First, Table 1 below shows design values of the lens unit in this embodiment.

Table 2 below shows specific design values for the lenses constituting the lens unit. Here, R is the radius of curvature, t is the distance from the subject side to the adjacent optical surface toward the image plane side, n is the refractive index, and v means the Abbe number, respectively.

On the other hand, 'TTL [the distance from the center of the convex surface S11 of the first lens 10 to the image plane]' and the concave surface S42 of the third lens 4 in the air from which the filter of Table 2 is removed. BFL, the distance from the center to the image plane, is 6.14 mm and 1.717 mm, respectively.

In addition, the height [H (S42)] of the uppermost ray α of the light beam propagating toward “A” at an image height of 3.0 mm passes through the concave surface S42 of the third lens 40 is 2.44. Mm.

Therefore, since the focal length 'EFL' is 5.0 mm, the ratio of H (S42) and EFL according to the present embodiment satisfies the condition of Equation 1 described above corresponding to "0.488", and TTL according to the present embodiment. The ratio of and EFL corresponds to "1.227", which satisfies the condition of Equation 2 described above.

In Table 3, k is an eccentricity in the aspherical formula as described in Equation 3 below, and A to E mean aspherical coefficients of 4th, 6th, 8th, 10th, and 12th order. Z (r) represents the horizontal distance from the apex of the aspherical surface to the height r, and c represents the curvature (1 / R).

The results of spherical aberration, astigmatism, and distortion aberration for each wavelength are shown in FIG. 3 for the performance evaluation of the lens units having the same design values shown in Tables 1 to 3, and the results for the coma aberration for each wavelength are shown in FIG. 4. Is shown. As can be seen from the graph results shown in FIG. 3 and FIG. 4, it can be seen that it has good characteristics for various aberrations.

The above description is merely illustrative of the present invention, and those skilled in the art to which the present invention pertains may various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed herein are not intended to limit the present invention but to describe the present invention, and the spirit and scope of the present invention are not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all the technologies within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to the imaging lens unit of the present invention, the first to third lenses are combined so as to have positive (positive), positive (positive), and negative (negative) refractive power, respectively, and to a height of 3.0 mm. By adjusting the ratio between the height of the light beam passing through the third lens concave and the focal length, the overall length is reduced and the effective diameter of the third lens is reduced, thereby making it possible to slim the imaging lens unit. In addition, the effect of reducing the production cost of the product is created by minimizing the performance degradation due to manufacturing error.

In addition, according to the imaging lens unit of the present invention, by using the aspherical glass lens as the first lens it is possible to finely control the angle of incidence and the angle of refraction on the curved surface, thereby creating an effect that can minimize the occurrence of aberration do.

Claims (3)

A first lens disposed on the subject side and having positive refractive power and having a convex surface formed on the subject side and a concave surface formed on the image side; An aperture stop disposed to be spaced apart from the first lens by a predetermined interval and preventing unnecessary incident light incident on the optical system; A second lens disposed to be spaced apart from the aperture by a predetermined distance, having a positive refractive power, and having a concave surface formed on the subject side and a convex surface formed on the image side; A third lens disposed to be spaced apart from the second lens by a predetermined distance, and having a negative refractive power, and having a convex surface formed on the subject side and a concave surface formed on the image side; And An infrared cut filter disposed at a predetermined interval from the third lens and filtering infrared wavelengths incident on the optical system; When the height at which the uppermost ray of the light beam traveling at an image height of 3.0 mm passes through the concave surface of the third lens is H (S42), and the focal length is EFL,

An imaging lens unit that satisfies. The method of claim 1, When the imaging lens unit is a focal length is EFL and the distance from the center of the convex surface of the first lens to the image surface is TTL as a value in air from which the infrared cut filter is removed,

The imaging lens unit, characterized in that arranged to satisfy. The method according to claim 1 or 2, And the first lens is a glass lens having at least one surface aspherical, and the second lens and the third lens are plastic or glass lenses.

Images