KR20100040357A - Imaging lens - Google Patents

Abstract

PURPOSE: An imaging lens is provided to improve aberration property by using a sixth lens having more than one point of inflection of aspherical curved plane. CONSTITUTION: A pick-up lens a first lens(10), a second lens(20), a third lens(30), a fourth lens(40), a fifth lens(50), and a sixth lens(60). The first lens has a positive power. A second lens has a negative power. The third lens has a positive power. The fourth lens has a positive power. The fifth lens has a negative power. The sixth lens has a negative power. An iris(35) is interposed between the third lens and the fourth lens.

Description

Imaging Lens

Embodiments relate to an imaging lens used in a camera module using a high resolution image sensor.

Recently, a camera module for a communication terminal, a digital still camera (DSC, digital still camera), a camcorder, and a PC camera (image pickup device included with a personal computer) have been studied in relation to an image pickup system. The most important component for the camera module associated with such an image pickup system to obtain an image is an imaging lens that forms an image.

The embodiment provides an imaging lens that is excellent in optical aberration characteristics.

The imaging lens according to the embodiment includes a first lens having positive power; A second lens having negative power; A third lens having positive power; A fourth lens having positive power; A fifth lens having a negative power; And a sixth lens having negative power, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are disposed in order from the object side.

In the imaging lens according to the embodiment, the first lens, the third lens, and the fourth lens have positive power, and the second lens, the fifth lens, and the sixth lens have negative power. And an aperture lens disposed between the third lens and the fourth lens.

In addition, all surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are aspherical, and the imaging lens is implemented by using a sixth lens having at least one aspherical inflection point. It is possible to implement an imaging lens having excellent aberration characteristics.

Hereinafter, an imaging lens according to an exemplary embodiment will be described in detail with reference to the accompanying drawings.

1 is a side cross-sectional view schematically showing an internal structure of an imaging lens according to an embodiment.

As shown in FIG. 1, the imaging lens according to the exemplary embodiment may include the first lens 10, the second lens 20, the third lens 30, and the aperture in order from the object side toward the image surface R16 side. 35, the fourth lens 40, the fifth lens 50, the sixth lens 60, the filter 70, and the light receiving element 80.

The light corresponding to the image information of the subject to obtain a subject image is the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50 The light passing through the sixth lens 60 and the filter 70 is incident on the light receiving device 80.

The first lens 10 has a positive power, has a convex surface on the object side, and the second lens 20 is formed of a lens having a negative power.

In addition, the third lens 30 and the fourth lens 40 have positive power, and an aperture 35 is disposed between the third lens 30 and the fourth lens 40.

The stop 35 performs a function of selectively converging the light incident from the incident light to adjust a focus length.

The fifth lens 50 may be formed of a meniscus type lens having negative power and having a concave surface on the object side.

The sixth lens 60 has negative power and is formed to include at least one aspherical inflection point.

In this case, one or a plurality of aspherical inflection points may be formed on the object side surface R12 and the image side surface R13 of the sixth lens 60.

The object-side surface R12 and the image-side surface R13 of the sixth lens 60 are bent toward the image toward the periphery from the center, and bent toward the object side toward the outermost region from the periphery to form an aspherical inflection point. .

The aspherical inflection point formed on the sixth lens 60 may adjust the maximum exit angle of chief rays of light incident on the light receiving element 80.

When the light receiving element 80 of the upper surface R16 is a Charge Coupled Device (CCD) or a Complementary Metal Oxide Semiconductor (CMOS) sensor, there is an angle at which light amount is secured at each pixel. The periphery of the screen darkens.

Therefore, in the present embodiment, aspherical inflection points are formed on the object side surface R12 and the image side surface R13 of the sixth lens 60 to adjust the maximum exit angle of the chief ray, thereby preventing the periphery of the screen from darkening. can do.

The first lens 10 is made of glass, and the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, and the sixth lens All 60 may be formed of a plastic material.

In addition, all surfaces of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, and the sixth lens 60 are aspherical. Can be formed.

All surfaces of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, and the sixth lens 60 are aspherical. In addition, aspherical inflection points are formed on the object side surface R12 and the image side surface R13 of the sixth lens 60 to correct spherical aberration, comatic aberration, and astigmatism. have.

The filter 70 may be an IR cut filter.

The infrared cut filter serves to block radiant heat emitted from external light from being transmitted to the light receiving device 400.

That is, the infrared cut filter has a structure that transmits visible light and reflects infrared light so as to flow out.

In addition, the light receiving element 80 having an image may be configured as an image sensor for converting an optical signal corresponding to a subject image into an electrical signal, and the image sensor may be configured as a CCD or a CMOS sensor.

The imaging lens according to the embodiment has the optical characteristics as shown in Table 1 below.

Lens surface Bending Radius (mm) Thickness (mm) Refractive index (N) Remarks R1 * 2.53 0.83 1.58 glass R2 * 87.56 0.2 R3 * -28.72 0.43 1.61 plastic R4 * 5.19 0.2 R5 * 12.54 0.43 1.53 plastic R6 * -35.2 0.2 R7 ∞ 0.2 iris R8 * 7.18 0.46 1.53 plastic R9 * -3.89 0.72 R10 * -1.01 0.5 1.61 plastic R11 * -1.27 0.2 R12 * 3.21 0.43 1.53 plastic R13 * 1.64 0.25 R14 ∞ 0.3 1.52 filter R15 ∞ 0.73 filter R16 ∞ 0 sensor

(* Indicates aspherical surface)

The thickness shown in Table 1 represents the distance from each lens surface to the next lens surface.

The Abbe's number V of the second lens 20, the third lens 30, and the fourth lens 40 according to the embodiment may satisfy the following conditions.

20 <V2 <30 [second lens]

50 <V3 <60 [Third Lens]

50 <V4 <60 [4th lens]

The chromatic aberration can be satisfactorily corrected by satisfying the above conditional expression relating to the Abbe's number (V).

Table 2 below is aspherical coefficient values for the aspherical lens of the embodiment.

Lens surface K A ₁ A ₂ A ₃ A ₄ R1 0 -0.170770 × 10 ^-2 0.532367 × 10 ^-2 -0.162382 × 10 ^-1 0.215139 × 10 ^-1 R2 0 0.125653 × 10 ^-1 -0.161798 × 10 ^-2 0.177699 × 10 ^-1 -0.210512 × 10 ^-1 R3 -1633.563875 -0.141596 × 10 ^-1 0.223480 × 10 ^-1 -0.109349 × 10 ^-1 -0.183460 × 10 ^-1 R4 -17.673899 0.135415 × 10 ^-2 0.508368 × 10 ^-2 -0.189173 × 10 ^-1 -0.270758 × 10 ^-1 R5 152.194321 0.560688 × 10 ^-3 -0.292138 × 10 ^-1 -0.539585 × 10 ^-1 -0.146307 × 10 ^-1 R6 1779.381109 -0.193974 × 10 ^-1 -0.419479 × 10 ^-1 -0.203299 × 10 ^-1 -0.343162 × 10 ^-1 R8 91.768593 -0.114000 -0.742252 × 10 ^-1 -0.202829 -0.400345 × 10 ^-1 R9 15.610423 -0.309774 × 10 ^-1 -0.214085 × 10 ^-1 -0.589200 × 10 ^-1 0.133618 × 10 ^-1 R10 -0.021182 0.180223 0.107395 × 10 ^-1 0.204318 × 10 ^-1 0.564446 × 10 ^-1 R11 -0.455606 0.842674 × 10 ^-1 -0.379476 × 10 ^-1 0.396371 × 10 ^-1 -0.117242 × 10 ^-1 R12 -26.859248 -0.133892 -0.198606 × 10 ^-1 -0.326429 × 10 ^-2 0.114178 × 10 ^-1 R13 -6.361442 -0.102361 0.950258 × 10 ^-2 -0.332042 × 10 ^-2 -0.209939 × 10 ^-3

The aspherical coefficient values of Table 2 for the aspherical lens of the embodiment can be obtained from Equation 1 below.

Z: Distance from the vertex of the lens to the optical axis direction

C: basic curvature of the lens

Y: distance in the direction perpendicular to the optical axis

K: Conic constant

A ₁ , A ₂ , A ₃ , A ₄ , A ₅ : Aspheric constant

That is, the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, the fifth lens 50, and the sixth lens 60 having the aspherical coefficient values. By using (), spherical aberration, coma, and astigmatism can be corrected, and distortion can also be corrected well.

The focal length of each lens of the imaging lens according to the exemplary embodiment described above is shown in Table 3 below.

Focal length f1 of the first lens 4.463634 mm Focal length f2 of the second lens -7.120773 mm Focal Length (f3) of Third Lens 17.499062 mm Focal Length (f4) of Fourth Lens 4.836387 mm Focal length f5 of the fifth lens -30.304228 mm Focal length f6 of the sixth lens -6.988166 mm

In this case, an image plane from the first lens object side surface R1 to the focal length f of the optical system and the ratio f1 / f of the focal length f1 of the first lens to the focal length f of the optical system The ratio d / f of the distance d to R16 may satisfy the following conditional expression.

0.5 <f1 / f <1.5 (1)

0.5 <d / f <1.5 (2)

The conditional expressions (1) and (2) above are conditions for miniaturizing the imaging lens and maintaining spherical aberration in a good state.

At this time, if the imaging lens is designed with a value smaller than the conditions of the conditional expressions (1) and (2), the imaging lens can be miniaturized, but the aberration correction becomes difficult, and the image pickup is made larger than the condition of the conditional expressions (1) and (2). If the lens is designed, aberration correction becomes easy, but it becomes difficult to miniaturize the imaging lens.

The ratio f2 / f1 of the focal length f2 of the second lens to the focal length f1 of the first lens of the optical system may satisfy the following condition.

1 <| f2 / f1 | <5 (3)

At this time, by satisfying Conditional Expression (3), the imaging lens according to the embodiment can reduce the lens system while correcting the magnification and the axial chromatic aberration.

2, 3A and 3B are graphs showing aberration characteristics of the imaging lens according to the embodiment.

FIG. 2 is a graph illustrating longitudinal spherical aberration, astigmatic field curves, and distortion.

3A and 3B illustrate graphs of measuring coma aberrations.

As shown in Figs. 2 to 3, since the values of the images appear adjacent to the axis in almost all fields, it can be seen that the imaging lens according to the embodiment has excellent aberration characteristics.

In this case, the spherical aberration represents the spherical aberration according to each wavelength, the astigmatism represents the aberration characteristics of the tangential plane and the sagittal plane according to the height of the upper surface, the distortion aberration is the height of the upper surface Shows the degree of distortion.

In addition, the coma aberration showed the aberration characteristics of tangential and sagittal according to each wavelength according to the field height of the upper surface.

In the imaging lens according to the above embodiment, the first lens, the third lens, and the fourth lens have positive power, and the second lens, the fifth lens, and the sixth lens have negative power. And an imaging lens having an aperture disposed between the third lens and the fourth lens.

In addition, all surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are aspherical, and the imaging lens is implemented by using a sixth lens having at least one aspherical inflection point. It is possible to implement an imaging lens having excellent aberration characteristics.

Although the above description has been made based on the embodiments, these are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains may not have been exemplified above without departing from the essential characteristics of the present embodiments. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a side sectional view schematically showing an internal structure of an imaging lens according to an embodiment.

2, 3A and 3B are graphs showing aberration characteristics of the imaging lens according to the embodiment.

Claims (7)

A first lens having positive power; A second lens having negative power; A third lens having positive power; A fourth lens having positive power; A fifth lens having a negative power; And A sixth lens having negative power, And the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are arranged in order from an object side. The method of claim 1, And an aperture disposed between the third lens and the fourth lens. The method of claim 1, And an inflection point is formed on the object-side surface and the image-side surface of the sixth lens. The method of claim 1, And all surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are aspherical surfaces. The method of claim 1, The first lens is a glass lens, And the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are plastic lenses. The method of claim 1, When the focal length of the first lens of the imaging lens is f1 and the focal length of the second lens is f2, 1 <| f2 / f1 | <5 An imaging lens that satisfies the conditional expression of. The method of claim 1, When f is the total focal length of the imaging lens, f1 is the focal length of the first lens, and d is the distance from the incident surface on the object side of the first lens to the image surface, 0.5 <f1 / f <1.5 0.5 <d / f <1.5 An imaging lens that satisfies the conditional expression of.

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