KR20100001525A - Imaging lens - Google Patents

Abstract

PURPOSE: A camera lens having optically aberration characteristic is provided to conveniently design a lens module by arranging an aperture on an object side nearer than a first lens. CONSTITUTION: A first lens(10) has a positive pole(+). A second lens(20) has a negative pole(-). A third lens(30) has the positive pole. A fourth lens(40) has the positive pole. A fifth lens(50) has negative pole and at least one more inflection point. An aperture(5) is located on in the object side nearer than the first lends. The aperture, first lens, second lens, third lens, fourth lens and fifth lens are arranged from the object side. A filter(60) blocks the infrared ray.

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 negative power and including at least one inflection point; And an aperture located closer to the object side than the first lens, wherein the aperture, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged 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 and the fifth lens have a negative power. It provides an imaging lens.

In addition, the fifth lens has a stronger power than the first lens, the second lens, the third lens, and the fourth lens, and implements an imaging lens by using a fifth lens having at least one aspherical inflection point. An imaging lens having excellent characteristics can be implemented.

In addition, by using the first lens, an aspherical glass lens, stable performance can be realized, and the aperture can be disposed closer to the object side than the first lens to reduce the length of the overall length and facilitate the design of the lens module.

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 exemplary embodiment may be provided with an aperture 5, a first lens 10, a second lens 20, and a third lens in order from the object side toward the image surface R14 side. 30, the fourth lens 40, the fifth lens 50, the filter 60, and the 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 negative power.

The third lens 30 has a positive power, and the fourth lens 40 has a positive power.

The fifth lens 50 has a 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 image side surface R11 of the fifth lens 50.

The aspherical inflection point formed on the fifth lens 50 may adjust the maximum exit angle of chief rays of light incident on the light receiving element 70.

When the light receiving element 70, which is the upper surface R14, 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, by forming an aspherical inflection point on the image side surface R11 of the fifth lens 50 to adjust the maximum exit angle of the chief ray, it is possible to prevent the peripheral portion of the screen from darkening.

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 may be formed as an aspherical surface.

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 aspherical, and the fifth lens ( An aspherical inflection point is formed on the upper surface R11 of 50) to correct spherical aberration, comatic aberration, and astigmatism.

The fifth lens 50 has a higher refractive power and a stronger power than the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40.

The diaphragm 5 performs a function of adjusting the focus length by selectively converging the incident light located on the object side rather than the first lens 10.

In this case, since the diaphragm 5 is located on the object side of the first lens 10 rather than between the lenses, the length of the full length can be reduced, and the lens module can be designed more freely.

That is, the length of the overall length can be reduced according to the position of the diaphragm 5, so that the imaging lens can be miniaturized.

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) Abbe number (V) Remarks R1 ∞ 0.8 iris R2 * 2.87 0.8 1.6 61.243 R3 * -4.06164 0.1 R4 * 9.05484 0.5 1.61 25.592 R5 * 2.27414 0.567524 R6 * -2.94814 0.611177 1.53 56.241 R7 * -1.96872 0.163934 R8 * -1.96872 0.163934 1.53 56.241 R9 * -23.98030 0.685700 R10 * -2.00090 0.621662 1.53 56.241 R11 * 4.61446 0.5 R12 ∞ 0.3 filter R13 ∞ 0.5 filter R14 ∞ 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 number V of each lens according to the embodiment is not limited to the values posted in the above table, and the following conditions can be satisfied.

58 <V1 <68 [First Lens]

20 <V2 <30 [second lens]

50 <V3 <65 [Third Lens]

50 <V4 <65 [fourth lens]

50 <V5 <65 [5th lens]

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 R2 -2.621142 -0.142672 × 10 ^-1 -0.168907 × 10 ^-1 -0.190243 × 10 ^-1 0.795767 × 10 ^-2 R3 0 -0.461715 × 10 ^-1 -0.261269 × 10 ^-1 0.986206 × 10 ^-2 -0.450373 × 10 ^-2 R4 0 -0.490588 × 10 ^-1 -0.143914 × 10 ^-2 0.299457 × 10 ^-2 0.127156 × 10 ^-1 R5 -2.485651 0.144293 × 10 ^-2 0.167570 × 10 ^-2 0.164 128 × 10 ^-2 0.115357 × 10 ^-3 R6 0 0.539139 × 10 ^-2 0.297358 × 10 ^-1 0.128181 × 10 ^-1 -0.376092 × 10 ^-2 R7 0 0.953534 × 10 ^-2 0.148576 × 10 ^-1 0.162940 × 10 ^-1 -0.943834 × 10 ^-4 R8 -5 -0.438803 × 10 ^-1 0.145746 × 10 ^-1 -0.126228 × 10 ^-2 0 R9 0 0.462520 × 10 ^-1 -0.689064 × 10 ^-2 0.665956 × 10 ^-2 -0.341696 × 10 ^-3 R10 0 0.320718 × 10 ^-1 0.303792 × 10 ^-2 0.368728 × 10 ^-3 0.115256 × 10 ^-3 R11 -55 -0.891506 × 10 ^-2 -0.621764 × 10 ^-2 0.156730 × 10 ^-2 -0.231125 × 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, 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 embodiment described above, the focal length of each lens, the distance TTL from the first lens object side surface to the image surface, the F-number and the conditional expression of the embodiment Is shown in Table 3 below.

Focal length of optical system (f) 4.50 mm Focal length f1 of the first lens 2.982146 mm Focal length f2 of the second lens -5.087171 mm Focal Length (f3) of Third Lens 9.297 600 mm Focal Length (f4) of Fourth Lens 4.082889 mm Focal length f5 of the fifth lens -2.576693 mm Distance TTL from the first lens object side R1 to the image R14 5.6 mm Distance BFL from the image side surface R11 to the image surface R14 of the fifth lens 1.3 mm F-number 2.5 f1 / TTL 0.532526 f2 / TTL -0.908423 f3 / TTL 1.660285 f4 / TTL 0.729087 f5 / TTL -0.460123 n1 / TTL 0.283773 n2 / TTL 0.288250 n3 / TTL 0.273428 n4 / TTL 0.273428 n5 / TTL 0.273428

In this case, the ratio TTL / f of the distance TTL from the first lens object side surface R1 to the image surface R14 to the focal length f of the optical system is 1.24, and the focal length of the first lens is The ratio TTL / f of the distance TTL from the first lens object side surface R1 to the image surface R14 to f1) is 1.878.

However, the ratio TTL / f of the distance TTL from the first lens object side surface R1 to the image surface R14 to the focal length f of the optical system and the focal length f1 of the first lens The ratio TTL / f of the distance TTL from the first lens object side surface R1 to the image surface R14 is not limited to the above numerical value, and may satisfy the following condition.

1.2 <TTL / f <2.2 (1)

1.5 <TTL / f1 <3.3 (2)

Further, the ratio of the focal length f1 of the first lens to the focal length f of the optical system is 0.663, but is not limited thereto and may satisfy the following conditional expression.

0.6 <f1 / f <1.5 (3)

At this time, if the imaging lens is designed with a value smaller than the condition of Condition (3), the imaging lens can be miniaturized, but aberration correction becomes difficult, and if the imaging lens is designed with a value larger than the condition of Condition (3), aberration correction is easy. However, it becomes difficult to miniaturize the imaging lens.

Further, when the distance from the image side surface to the image surface of the fifth lens is BFL, The conditional expression can be satisfied.

0.2 <BFL / TTL <0.4 (4)

The conditional expressions (1) to (4) above are conditions for miniaturizing the imaging lens and maintaining the spherical aberration in a good state, and by satisfying the conditional expressions (1) to (4) above, aberration correction is easy and miniaturization is achieved. The captured imaging lens can be formed.

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.

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

In addition, the fifth lens has a stronger power than the first lens, the second lens, the third lens, and the fourth lens, and implements an imaging lens by using a fifth lens having at least one aspherical inflection point. An imaging lens having excellent characteristics can be implemented.

In addition, by using the first lens, an aspherical glass lens, stable performance can be realized, and the aperture can be disposed closer to the object side than the first lens to reduce the length of the overall length and facilitate the design of the lens module.

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 (13)

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 negative power and including at least one inflection point; And It includes an aperture located closer to the object than the first lens, And the aperture, 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 the first lens is formed of aspherical glass. The method of claim 1, The fifth lens has an aspherical inflection point formed on at least one surface. The method of claim 1, And an inflection point is formed on an image side surface of the fifth lens. 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, And the fifth lens has greater power than the first lens, the second lens, the third lens, and the fourth lens. The method of claim 1, An imaging lens comprising a filter that can block infrared rays from incident light. The method of claim 1, And the second lens, the third lens, the fourth lens, and the fifth lens are plastic lenses. The method of claim 1, When the total focal length of the imaging lens is f and the focal length of the first lens is f1, 0.6 <f1 / f <1.5 An imaging lens that satisfies the conditional expression of. The method of claim 1, The Abbe's number V of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is 58 <V1 <68 [First Lens] 20 <V2 <30 [second lens] 50 <V3 <65 [Third Lens] 50 <V4 <65 [fourth lens] 50 <V5 <65 [5th lens] Imaging lens comprising the range of. The method of claim 1, When the distance from the incident surface on the object side of the first lens to the image surface is TTL and the distance from the image side surface to the image surface of the fifth lens is BFL, 0.2 <BFL / TTL <0.4 An imaging lens that satisfies the conditional expression of. The method of claim 1, When the total focal length of the imaging lens is f and the distance from the incident surface on the object side of the first lens to the image surface is TTL, 1.2 <TTL / f <2.2 An imaging lens that satisfies the conditional expression of. The method of claim 1, When the focal length of the first lens is f1 and the distance from the incident surface on the object side of the first lens to the image surface is TTL, 1.5 <TTL / f1 <3.3 An imaging lens that satisfies the conditional expression of.

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