KR20100067515A - Imaging lens - Google Patents

Abstract

PURPOSE: An imaging lens is provided to improve an aberration property by forming all surfaces with aspheric surfaces and arranging a fifth lens with an aspheric inflection point. CONSTITUTION: A first lens(10) has positive power. A second lens has positive power. A third lens(30) has positive power. A fourth lens has negative power. A fifth lens(50) has negative power. The first, second, third, fourth, and fifth lenses are successively arranged from an object. An iris diaphragm is arranged on the object side of the first 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 positive power; A third lens having positive power; A fourth lens having a negative power; And a fifth lens having negative power, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in order from the object side.

The imaging lens according to the embodiment is formed of a lens in which the first lens, the second lens, and the third lens have positive power, and the fourth and fifth lenses have negative power. It provides an imaging lens.

In addition, since all surfaces of all the lenses are formed aspherical, and the fifth lens having the aspherical inflection point is disposed, an imaging lens having excellent aberration characteristics can be implemented.

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

1 is a side 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 embodiment is configured to have an aperture 5, a first lens 10, a second lens 20, and a third in order from the object side toward the image surface R13 side. The lens 30 includes a fourth lens 40, a fifth lens 50, a filter 60, and a light receiving element 70.

In order to obtain a subject image, light corresponding to the image information of the subject may include the aperture 5, the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, and the third lens. The light enters the light receiving element 70 through the five lenses 50 and the filter 60.

The first lens 10 has a positive power, and the second lens 20 is formed of a lens having a positive power.

The first lens 10 and the second lens 20 are both formed of a meniscus type lens having a convex surface on the object side.

The aperture 5 may be formed on the same surface as the object side surface of the first lens 10.

The third lens 30 has a positive power, and the fourth lens 40 is formed of a lens having a negative power.

The third lens 30 and the fourth lens 40 are formed of a meniscus type lens having a convex surface on the image side.

The fifth lens 50 has a negative power and is formed to include at least one aspherical inflection point.

The first lens 10 is made of glass, and the second lens 20, the third lens 30, the fourth lens 40, and the fifth lens 50 are all made of plastic. ) May be formed of a material.

In addition, all surfaces of the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, and the fifth lens 50 are formed as aspherical surfaces, and thus spherical aberration (spherical) Aberration, comatic aberration and astigmatism can be corrected.

The filter 60 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.

The light receiving element 70 in which an image is formed may be configured as an image sensor for converting an optical signal corresponding to an object image into an electrical signal, and the image sensor may be 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 * 1.82459 0.418028 1.583 R2 * 2.93809 0.177709 R3 * 1.95528 0.473528 1.62 R4 * 1.89353 0.488422 R5 * -8.01116 0.749728 1.53 R6 * -1.97707 0.521663 R7 * -1.49895 0.4 1.53 R8 * -1.73566 0.488816 R9 * 25.2727 0.504512 1.53 R10 * 2.74625 0.2 R11 ∞ 0.3 1.5 filter R12 ∞ 0.615501 filter R13 ∞ 0 sensor

(* Indicates aspherical surface)

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

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 A ₅ R1 0.25948 1.16 × 10 ^-3 -0.725492 × 10 ^-2 5.16 × 10 ^-3 -0.158598 × 10 ^-2 0 R2 0 -0.515628 × 10 ^-1 -0.870845 × 10 ^-3 9.3 × 10 ^-3 -0.450836 × 10 ^-2 0 R3 0 -0.896247 × 10 ^-1 -0.54687 × 10 ^-2 -0.148585 × 10 ^-1 1.26 × 10 ^-2 -0.268267 × 10 ^-2 R4 0 -0.309272 × 10 ^-1 1.14 × 10 ^-3 -0.950418 × 10 ^-2 7.66 × 10 ^-3 7.39 × 10 ^-3 R5 25.2597 -0.460277 × 10 ^-1 3.26 × 10 ^-3 5.56 × 10 ^-4 1.67 × 10 ^-2 1.6 × 10 ^-3 R6 0 -0.272054 × 10 ^-1 -0.613627 × 10 ^-2 1.5 × 10 ^-2 4.55 × 10 ^-3 -0.586713 × 10 ^-3 R7 -0.09577 4.39 × 10 ^-2 2.13 × 10 ^-2 7.1 × 10 ^-3 -0.222476 × 10 ^-2 0 R8 -2.76398 3.62 × 10 ^-2 -0.731907 × 10 ^-2 4.63 × 10 ^-3 -0.109471 × 10 ^-2 0 R9 -136332 -0.444683 × 10 ^-1 2.98 × 10 ^-3 8.37 × 10 ^-4 3.57 × 10 ^-5 -0.210139 × 10 ^-4 R10 -7.9066 -0.590735 × 10 ^-1 1.19 × 10 ^-2 -0.227 128 × 10 ^-2 2.13 × 10 ^-4 -0.743647 × 10 ^-5

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, spherical aberration by using the first lens 10, the second lens 20, the third lens 30, the fourth lens 40 and the fifth lens 50 having the above aspherical coefficient value. , Coma and astigmatism can be corrected, and distortion can also be corrected well.

The focal length f of the entire optical system of the imaging lens according to the exemplary embodiment described above, the focal length of each lens, and the distance ∑T from the object-side surface R1 to the image surface R13 of the first lens 10 are Table 3 below.

Focal length of optical system (f) 4.5 mm Focal length f1 of the first lens 7.22 mm Focal length f2 of the second lens 50.000002 mm Focal Length (f3) of Third Lens 4.73 mm Focal Length (f4) of Fourth Lens -50.000001 mm Focal length f5 of the fifth lens 4.903 mm Distance (∑T) from the object-side surface R1 to the image surface R13 of the first lens 10 5.34 mm | f2 / f1 | 6.925208033 1 / (1 / f4 + 1 / f5) 5.436060037

In this case, the ratio f1 / f of the focal length f1 of the first lens 10 to the focal length f of the optical system is 1.604444444, and the first lens 10 with respect to the focal length f of the optical system. ) The ratio (∑ T / f) of the distance (∑ T) from the object-side surface R1 to the upper surface R13 is 1.1866666667.

However, the object side of the first lens 10 relative to the focal length f of the optical system and the ratio f1 / f of the focal length f1 of the first lens 10 to the focal length f of the optical system The ratio? T / f of the distance? T from the plane R1 to the upper surface R13 is not limited to the above numerical value, and the following condition can be satisfied.

1 <f1 / f <2 (1)

1 <∑T / f <2 (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 focal length f1 of the first lens 10, the focal length f2 of the second lens 20, the focal length f4 of the fourth lens 40, and the fifth lens 50. The aberration can be corrected by satisfying the following conditional formula for the focal length f5.

| f2 / f1 | <10 (3)

0 <1 / (1 / f4 + 1 / f5) <8 (4)

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 to 3C show 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.

The imaging lens according to the above embodiment is a lens in which the first lens, the second lens, and the third lens have positive power, and the fourth and fifth lenses have negative power. The formed imaging lens is provided.

In addition, since all surfaces of all the lenses are formed aspherical, and the fifth lens having the aspherical inflection point is disposed, an imaging lens having excellent aberration characteristics can be implemented.

Although described above with reference to the embodiment is only an example and is not intended to limit the invention, those of ordinary skill in the art to which the present invention does not exemplify the above within the scope not departing from the essential characteristics of this embodiment 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 and 3A to 3C 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 positive power; A third lens having positive power; A fourth lens having a negative power; And A fifth lens having a negative power, And the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in order from an object side. The method of claim 1, And an aperture diaphragm disposed on an object side surface of the first lens. The method of claim 1, The first lens and the second lens are meniscus-type lenses having a convex surface on the object side. And the third lens and the fourth lens are formed of a meniscus type lens having a convex surface on an image side. The method of claim 1, The fifth lens of claim 5, wherein the aspherical inflection point is formed. The method of claim 1, And all surfaces of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are aspherical surfaces. The method of claim 1, When the total focal length of the imaging lens is f, the focal length of the first lens is f1, and the distance from the incident surface on the object side of the first lens to the image surface is? T, 1 <f1 / f <2 1 <∑T / f <2 An imaging lens that satisfies the conditional expression of. The method of claim 1, When the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the fourth lens is f4, and the focal length of the fifth lens is f5, | f2 / f1 | <10 0 <1 / (1 / f4 + 1 / f5) <8 Imaging lens that satisfies the condition of.

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