KR20120033866A - Lens system - Google Patents

Abstract

PURPOSE: A lens system is provided to enable miniaturization and embody high definition. CONSTITUTION: A first lens(L1), a second lens(L2), a third lens(L3), a fourth lens(L4), and a fifth lens(L5) are successively placed on an image from an object. An infrared filter(F) is placed on a path from the lenses to an image sensor(I) and removes unnecessary noise among light sources flowing in the image sensor. The unnecessary noise is removed among the light sources flowing in the image sensor. The image sensor senses the light source incident through the lenses and converts the light source into the electric signals.

Description

Lens system {LENS SYSTEM}

The present invention relates to a lens system.

Cameras installed in mobile phones demand performance similar to those of electronic still cameras, but require miniaturization, light weight, and low cost for photographic lenses. Image sensors, such as CCD and CMOS, which are being used in recent years, are increasing in size while the pixel size is getting smaller, and the imaging optical system using such an image sensor requires high resolution.

In addition, in order to satisfy the miniaturization and cost reduction of the photographing lens mounted on a camera such as a mobile phone and a PC, the number of lenses needed to be reduced should be reduced. Becomes difficult.

Therefore, there is a need for a lens system capable of miniaturizing high resolution.

The present invention provides a lens system having a high resolution while being capable of miniaturization.

According to an aspect of the invention, the biconvex first lens having a positive refractive power; A second lens having negative refractive power and concave toward the object side; A third lens having negative refractive power; A fourth lens of a meniscus shape having positive refractive power and convex toward the image; A fifth lens having negative refractive power and concave toward the image; And an image sensor, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the image sensor are sequentially arranged from the object side toward the image side, and the first lens. The second lens, the third lens, the fourth lens, and the fifth lens are provided with a lens system satisfying the following Conditional Expression 1, Conditional Expression 2, Conditional Expression 3 and Conditional Expression 4.

[Condition 1]

TL / F < 1.5 where TL is the distance from the object side to the image surface of the first lens, and F is the focal length of the entire optical system.

[Condition Formula 2]

0.4 <F1 / F <1.2 where F1 is the focal length of the first lens.

[Condition 3]

R4 / F <-1.0

Where R4 is the object-side curvature radius of the second lens

[Condition 4]

-0.8 <F5 / F <-0.6

Here, F5 is a focal length of the fifth lens.

In addition, the first lens, the second lens, the third lens, the fourth lens and the fifth lens may be formed of a plastic material.

In addition, an aperture may be provided on the object side of the first lens.

In addition, an infrared filter may be further provided between the fifth lens and the image sensor.

According to the embodiment of the present invention, while the lens system is downsized, the resolution is high and may be suitable for a camera such as a mobile phone, a PC, and the like.

1 shows a lens system according to a first embodiment of the present invention;
2 is a diagram illustrating aberration diagrams of the lens system according to the first embodiment of the present invention;
3 shows a lens system according to a second embodiment of the invention;
4 shows aberration diagrams of a lens system according to a second embodiment of the present invention;
5 shows a lens system according to a third embodiment of the present invention;
6 illustrates aberration diagrams of a lens system according to a third embodiment of the present invention;
7 illustrates a lens system according to a fourth embodiment of the present invention.
8 illustrates aberration diagrams of a lens system according to a fourth exemplary embodiment of the present invention.
9 illustrates a lens system according to a first embodiment of the present invention.
10 is a diagram showing aberration diagrams of the lens system according to the first embodiment of the present invention;

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, an embodiment of a lens system according to the present invention will be described in detail with reference to the accompanying drawings, and in the following description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and redundant description thereof. Will be omitted.

1 is a view showing a lens system according to a first embodiment of the present invention. Referring to FIG. 1, an aperture, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an infrared filter, and an image sensor are illustrated. The drawings are exaggerated for convenience of explanation and understanding, and the shape of the spherical or aspherical surface shown in the schematic diagram of the lens system is provided as an example and is not limited thereto.

As shown in FIG. 1, the lens system according to the present exemplary embodiment includes a biconvex first lens L1 having positive refractive power, a second lens L2 having a negative refractive power and concave toward the object side, and a negative lens. A third lens L3 having refractive power, a fourth lens L4 of meniscus shape having positive refractive power and convex toward the image side, and a fifth lens L5 having a negative refractive power and concave toward the image side. It includes. The lens system according to the present exemplary embodiment includes a plurality of first, second, third, fourth, and fifth lenses L1, L2, L3, L4, and L5 having different dispersion characteristics, thereby improving chromatic aberration.

In particular, since the second lens L2 has a concave shape toward the object side, the second lens L2 has an aspherical surface having no inflection point, thereby making it insensitive to tolerances and improving productivity.

Here, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 are sequentially arranged from the object side toward the image side. The upper side means a surface on which an image sensor surface is formed. An aperture S may be provided on the front surface of the first lens L1, and an infrared filter F and an image sensor I may be sequentially provided on the opposite side of the object in the fifth lens L5. .

The infrared filter F may include the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the third lens so as to remove unnecessary noise among light sources flowing into the image sensor I. 5 is provided on the path from the lens L5 to the image sensor I. For example, the infrared filter F may be disposed between the fifth lens L5 and the image sensor I.

The image sensor I may be a CCD, a CMOS, or the like, and the image sensor I may include a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a third lens. 5 The light source incident through the lens L5 is sensed and converted into an electrical signal.

The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 satisfy the following conditional expression (1).

[Condition 1]

TL / F <1.5

Here, TL is the distance from the object side surface to the image surface of the first lens (L1), F is the focal length of the entire optical system.

Condition 1 is a ratio of the focal length of the first lens L1 to the focal length of the entire lens system, which is advantageous for obtaining optical performance when the condition is outside the upper limit of Condition 1, but the lens is long and compact. Is contrary to.

The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 satisfy the following Conditional Expression 2.

[Condition Formula 2]

0.4 <F1 / F <1.2

Here, F1 is a focal length of the first lens.

Condition 2 is a ratio of the focal length of the first lens L1 to the focal length of the entire lens system. By satisfying the condition 2, a compact lens system can be achieved.

Here, if the deviation from the lower limit of Conditional Expression 2 has the advantage that the size of the optical system is smaller, but the angle of view becomes larger, the shape of the lens can not actually be produced, the refractive power becomes larger, it is difficult to correct the spherical aberration. On the other hand, if it deviates from the upper limit of Conditional Expression 2, it is advantageous in terms of correction of spherical aberration, but it becomes difficult to miniaturize the lens system.

The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 satisfy the following conditional expression (3).

[Condition 3]

R4 / F <-1.0

Where R4 is the object-side curvature radius of the second lens

Condition 3 is a ratio of the curvature of the side of the second lens object to the focal length of the entire optical system. When the upper limit is exceeded, the aspheric coefficient becomes large, and the manufacturability decreases, and an inflection point occurs, thereby increasing sensitivity.

The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 satisfy the following conditional expression (4).

[Condition 4]

-0.8 <F5 / F <-0.6

Here, F5 is the focal length of the fifth lens.

Condition 4 is a ratio of the focal length of the fifth lens to the focal length of the entire optical system. When the upper limit is exceeded, the requirement for miniaturization cannot be satisfied. When the upper limit is exceeded, aberration correction becomes difficult.

For example, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 may be formed of a plastic material. Accordingly, the lens system is lower in price and easier to manufacture than the glass material.

As described above, all of the first to fifth embodiments below have a convex first lens L1 having positive refractive power and a negative concave power, concave toward the object side, sequentially from the object side to the image side. The second lens L2, the third lens L3 having negative refractive power, the fourth lens L4 of the meniscus shape having positive refractive power and convex upward and negative refractive power, and concave upward The fifth lens L5 is disposed.

The aspherical surface used in each of the following examples is obtained from a known equation (1), K is a Conic constant, and A, B, C, D, E, and F mean aspherical coefficients.

Equation 1

Where Z is the distance from the vertex of the lens in the optical axis direction, Y is the distance in the direction perpendicular to the optical axis, c is the inverse of the radius of curvature r at the vertex of the lens, and K is the Conic constant Where A, B, C, D, E, and F are aspheric coefficients.

Hereinafter will be described with reference to Tables 1 to 10. In Tables 1, 3, 5, 7, and 9, the aperture S, the first lens L1, the second lens L2, and the third lens L3 shown in FIGS. 1, 3, 5, 7, 9 are shown. ), The fourth lens L4, the fifth lens L5, the infrared filter F, and the image sensor I, respectively, a surface representing their surface and a radius representing their radius of curvature, The numerical values of the thickness indicating the distance and the thickness, the index indicating their refractive index, and the abbe number indicating their Abbe number are shown.

[First Embodiment]

Table 1 below shows numerical examples according to the first embodiment of the present invention.

1 is a view showing a lens system according to a first embodiment of the present invention, Figure 2 is a view showing aberration diagram of a lens system according to a first embodiment of the present invention.

Here, the conditions of the first embodiment are as follows.

TL is 4.836, f is 3.831, f1 is 2.584, f5 is -2.822, R4 is -27.063, TL / f is 1.262, f1 / f is 0.675, f5 / f is -0.737, R4 / f is -7.064.

Table 1 is a numerical example of the lens system according to the first embodiment.

The aspherical coefficients of Example 1 according to Equation 1 are shown in Table 2 below.

Through Example 1, as shown in Figure 2, it can be seen that the longitudinal spherical aberration is small in the range of -0.025 to +0.025, astigmatic field curves are -0.025 to + It turns out that it forms the shape near a straight line in the range of 0.025, and distortion appears small in the range of 0-1.

Second Embodiment

Table 3 below shows numerical examples according to the second embodiment of the present invention.

3 is a diagram illustrating a lens system according to a second embodiment of the present invention, and FIG. 4 is a diagram illustrating aberration diagrams of a lens system according to a second embodiment of the present invention.

The conditions of the second embodiment are as follows.

TL is 4.750, f is 3.761, f1 is 2.538, f5 is -2.830, R4 is -64.939, TL / f is 1.263, f1 / f is 0.675, f5 / f is -0.752, R4 / f is -17.266

Table 3 is a numerical example of the lens system according to the second embodiment.

The aspherical coefficients of Example 2 according to Equation 1 are shown in Table 4 below.

Through Example 2, as shown in Figure 4, it can be seen that the longitudinal spherical aberration is small in the range of -0.025 to +0.025, astigmatic field curves are -0.025 to + It turns out that it forms the shape near a straight line in the range of 0.025, and distortion appears small in the range of 0-1.

Third Embodiment

Table 5 below shows a numerical example according to the third embodiment of the present invention.

5 is a view showing a lens system according to a third embodiment of the present invention, Figure 6 is a view showing aberration diagram of the lens system according to a third embodiment of the present invention.

Here, the conditions of the third embodiment are as follows.

TL is 4.816, f is 3.900, f1 is 2.655, f5 is -2.689, R4 is -194.386, TL / f is 1.235, f1 / f is 0.681, f5 / f is -0.689, and R4 / f is -49.843.

Table 5 is a numerical example of the lens system according to the third embodiment.

The aspherical coefficients of Example 3 according to Equation 1 are shown in Table 6 below.

Through Example 3, as shown in Figure 6, it can be seen that the longitudinal spherical aberration is small in the range of -0.025 to +0.025, astigmatic field curves are -0.025 to + It turns out that it forms the shape near a straight line in the range of 0.025, and distortion appears small in the range of 0-1.

[Example 4]

Table 7 below shows numerical examples according to the fourth embodiment of the present invention.

7 is a diagram illustrating a lens system according to a fourth embodiment of the present invention, and FIG. 8 is a diagram illustrating aberration diagrams of a lens system according to a fourth embodiment of the present invention.

Here, the conditions of the fourth embodiment are as follows.

TL is 4.843, f is 3.900, f1 is 2.626, f5 is -2.689, R4 is -36.060, TL / f is 1.242, f1 / f is 0.673, f5 / f is -0.690, R4 / f is -9.246

Table 7 is a numerical example of the lens system according to the fourth embodiment.

The aspherical coefficients of Example 4 according to Equation 1 are shown in Table 8 below.

Through Example 4, as shown in FIG. 8, it can be seen that the longitudinal spherical aberration is small in the range of -0.025 to +0.025, and the astigmatic field curves are -0.025 to + It turns out that it forms the shape near a straight line in the range of 0.025, and distortion appears small in the range of 0-1.

[Fifth Embodiment]

Table 9 below shows a numerical example according to the fifth embodiment of the present invention.

9 is a diagram illustrating a lens system according to a fifth embodiment of the present invention, and FIG. 10 is a diagram illustrating aberration diagrams of a lens system according to a fifth embodiment of the present invention.

Here, the conditions of the fifth embodiment are as follows.

TL is 4.879, f is 3.900, f1 is 2.602, f5 is -2.721, R4 is -20.351, TL / f is 1.251, f1 / f is 0.667, f5 / f is -0.698, R4 / f is -5.218

Table 9 is a numerical example of the lens system according to the fifth embodiment.

The aspherical coefficients of Example 5 according to Equation 1 are shown in Table 10 below.

Through Example 5, as shown in FIG. 10, it can be seen that the longitudinal spherical aberration is small in the range of -0.025 to +0.025, and the astigmatic field curves are -0.025 to + It turns out that it forms the shape near a straight line in the range of 0.025, and distortion appears small in the range of 0-1.

Through the above embodiments, it can be seen that a lens system having excellent aberration degree can be obtained as shown in FIGS. 2, 4, 6, 8, and 10. By forming a lens system with excellent aberration degree, the resolution is high, so it can be suitable for cameras of mobile phones, PCs and the like.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

Many embodiments other than the above-described embodiments are within the scope of the claims of the present invention.

L1: first lens
L2: second lens
L3: third lens
L4: fourth lens
L5: fifth lens
F: infrared filter
I: image sensor

Claims (4)

A biconvex first lens having positive refractive power;
A second lens having negative refractive power and concave toward the object side;
A third lens having negative refractive power;
A fourth lens of a meniscus shape having positive refractive power and convex toward the image;
A fifth lens having negative refractive power and concave toward the image; And
Including an image sensor,
The first lens, the second lens, the third lens, the fourth lens, the fifth lens and the image sensor are sequentially disposed from the object side toward the image side,
And the first lens, the second lens, the third lens, the fourth lens, and the fifth lens satisfy the following conditional expressions 1, 2, 3, and 4.
[Condition 1]
TL / F <1.5
Here, TL is the distance from the object side surface to the image surface of the first lens,
F is the total optical focal length.
[Condition Formula 2]
0.4 <F1 / F <1.2
Here, F1 is a focal length of the first lens.
[Condition 3]
R4 / F <-1.0
Here, R4 is the radius of curvature of the object side of the second lens.
[Condition 4]
-0.8 <F5 / F <-0.6
Here, F5 is a focal length of the fifth lens.
The method of claim 1,
And the first lens, the second lens, the third lens, the fourth lens and the fifth lens are made of a plastic material.
The method of claim 1,
The lens system, characterized in that the aperture is provided on the object side of the first lens.
The method of claim 1,
And an infrared filter is further provided between the fifth lens and the image sensor.

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