KR20200052860A - Imaging lens - Google Patents

Abstract

An object of the present invention is to provide an imaging lens for providing an ultra-thin camera module. The imaging lens according to one embodiment of the present invention comprises in order from an object side: a first lens which is biconvex and has a positive (+) refractive power; a second lens having the positive refractive power; and a third lens having a negative refractive power. When a refractive index of the second lens is n2, a conditional expression of 1.5 < n2 < 1.6 is satisfied.

Description

Imaging lens {Imaging lens}

The present invention relates to an imaging lens.

2. Description of the Related Art In recent years, demands for a small camera module are increasing for various multimedia fields such as tablet computers, camera phones, PDAs, smart phones, and toys, and also for image input devices such as surveillance cameras or video tape recorder information terminals. In particular, smart phones are in a trend of developing small-sized camera modules according to an increase in demand from consumers who prefer a compact design.

Such a camera module is manufactured using an image sensor chip of CCD or CMOS, condensing an object through a lens on the image sensor chip, converting an optical signal into an electrical signal, and displaying the object on a display medium such as an LCD display device. So that the video is delivered.

The most important component for the camera module to obtain an image is a lens that forms an image. In recent years, the thinning of the thickness of the portable terminal is required, and parts for performing various functions are mounted on the portable terminal. Accordingly, various researches and technology developments have been made to pursue the thinning of the imaging lens optical system of the camera module for a mobile terminal. In particular, if the actuator performing the autofocusing function is changed to a single lens moving method instead of using a conventional voice coil motor, many studies have been conducted on this since it is advantageous for miniaturization of the camera module.

Republic of Korea Patent Publication No. 10-2012-0094729 (2012.08.27.) Republic of Korea Registered Patent No. 10-1171517 (2012.07.27.)

An object of the present invention is to provide an imaging lens for providing an ultra-thin camera module.

An imaging lens according to an embodiment of the present invention includes, in order from the object side, a first lens that is both convex with a positive (+) refractive power; A second lens having a positive refractive power; And a third lens having negative (−) refractive power. When the refractive index of the second lens is n2, a conditional expression of 1.5 <n2 <1.6 may be satisfied.

The refractive indices of the first to third lenses may all be the same.

The Abbe numbers of the first and second lenses may be formed in the same way.

The second lens may be provided in a meniscus shape having a convex surface toward the image side.

The second lens has a greater refractive power than the first and third lenses, and a stop surface may be formed between the first lens and the second lens.

The third lens may be provided in the form of a meniscus having a convex surface toward the object.

Both surfaces of the third lens may have an inflection point.

When the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3, the conditions of 50 <v1, v2, v3 <60 can be satisfied.

When the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3, the conditional expression of (v1-v2) / v3 <1 can be satisfied.

When the thickness of the entire optical system is Σd and the focal length of the entire optical system is f, the conditional expression of 0.5 <Σd / f <1.5 can be satisfied.

When the focal length of the entire optical system is f and the focal length of the first lens is f1, a conditional expression of 0.5 <f1 / f <1.5 can be satisfied.

When the center thickness of the first lens is d1 and the distance between the image side surface of the first lens and the object side surface of the second lens is d2, a conditional expression of 0.70 <d1 / d2 <0.95 can be satisfied.

When the distance from the object-side surface of the first lens to the imaging surface is ΣT, and the focal length of the entire optical system is f, the conditional expression of 0.5 <ΣT / f <1.5 can be satisfied.

When the object side curvature radius of the first lens is r1 and the focal length of the entire optical system is f, a conditional expression of 1> r1 / f> 0.5 can be satisfied.

When the object side curvature radius of the first lens is r1 and the focal length of the first lens is f1, the conditional expression r1 / f1> 0.5 can be satisfied.

When the focal length of the entire optical system is f and the focal length of the second lens is f2, a conditional expression of -0.2 <f / f2 <2 can be satisfied.

When the refractive index of the first lens is N1, the refractive index of the second lens is N2, and the refractive index of the third lens is N3, the conditional expressions of 1.5 <N1, N2, and N3 <1.6 may be satisfied.

FNO, a numerical value representing the brightness of the lens infinitely raw, can satisfy the conditional expressions FNO = f / D, 2.2 <FNO <3.0 when f is the focal length of the entire optical system and D is the thickness of the entire optical system.

It is possible to provide an imaging lens usable for an ultra-thin camera module using three lenses.

1 is a configuration diagram of an imaging lens according to an embodiment of the present invention, and
2 is a graph showing spherical aberration, astigmatism, and distortion of an imaging lens according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a configuration diagram of an imaging lens according to an embodiment of the present invention, and FIG. 2 is a graph showing spherical aberration, astigmatism and distortion of the imaging lens according to an embodiment of the present invention.

In the imaging lens of the camera module according to an embodiment of the present invention, an imaging lens including a plurality of lenses may be disposed around an optical axis. At this time, the thickness, size, and shape of the lenses shown in FIGS. 1 and 3 are exaggerated for explanation, and the spherical or aspherical shape is presented as an example and is not limited to this shape.

1 is a view showing the configuration of an imaging lens applied to a camera module according to an embodiment of the present invention.

Referring to FIG. 1, the camera lens module of the present invention may include an aperture, a first lens 10, a second lens 20, a third lens 30, and a filter 40 in order from the object side. have.

The light corresponding to the image information of the subject may pass through the first lens 10, the second lens 20, the third lens 30, and the filter 40, and enter the side of the image sensor, not shown.

In the following description of the configuration of each lens, the term “object side” refers to the surface of the lens facing the object side with respect to the optical axis, and the term “image side” refers to the lens facing the imaging surface based on the optical axis. It means the side of.

The feature of the present invention is to form the optical system of the ultra-thin camera module by configuring the three lenses described above.

The first lens 10 has a positive (+) refractive power, the second lens 20 has a positive (+) refractive power, and the third lens 30 has a negative (-) refractive power. Can be. Here, the first lens 10 may be formed in a convex shape, the second lens 20 may be formed in a meniscus shape having a convex surface toward the image side, the third lens 30 It may be formed in the form of a meniscus having a convex surface toward the object.

In this case, the first lens 10, the second lens 20, and the third lens 30 may all have the same refractive index.

In addition, the second lens 20 may have a greater refractive power than the first and third lenses 10 and 30, and a stop surface is formed between the first and second lenses 10 and 20. Apertures and the like are arranged to control the amount of light incident on the optical system.

The filter 40 is at least one of an optical filter such as an infrared cut filter and a cover glass. As the filter 40, when an infrared blocking filter is applied, infrared rays emitted from external light may be blocked from being transmitted to an image sensor (not shown). The infrared cut filter transmits visible light, but does not transmit light in the infrared wavelength band.

The conditional expressions and examples described below are preferred examples of increasing the effect of action, and it will be apparent to those skilled in the art that the present invention is not necessarily composed of the following conditions. For example, even if only some of the conditional expressions described below are satisfied, the lens configuration of the present invention may have an increased effect.

[Conditional Expression 1] 0.5 <Σd / f <1.5

[Conditional Expression 2] 0.5 <f1 / f <1.5

[Conditional Expression 3] 0.70 <d1 / d2 <0.95

here,

Σd is the total optical system thickness

f is the total optical system focal length

f1 is the focal length of the first lens

d1 is the center thickness of the first lens

d2 is the distance between the image side surface of the first lens and the object side surface of the second lens.

[Conditional Expression 4] 50 <v1, v2, v3 <60

[Conditional Expression 5] (v1-v2) / v3 <1

here,

v1 is the Abbe number of the first lens,

v2 is the Abbe number of the second lens,

v3 is the Abbe number of the third lens.

[Conditional Expression 6] 0.5 <ΣT / f <1.5

[Conditional Expression 7] 1> r1 / f> 0.5

[Conditional Expression 8] r1 / f1> 0.5

[Conditional Expression 10] -0.2 <f / f2 <2

[Conditional Expression 11] 1.5 <N1, N2, N3 <1.6

[Conditional Expression 12] 2.2 <FNO <3.0

here,

r1 is the radius of curvature of the object side of the first lens,

r2 is the radius of curvature of the object side of the second lens,

N1 is the refractive index of the first lens,

N2 is the refractive index of the second lens,

N3 is the refractive index of the third lens.

Table 1 shows an example that satisfies the above conditional expression.

value f 2 f1 2.37 f2 1.69 f3 -1.74 | f2 / f1 | 0.96 ∑T 2.92 ∑T / f 1.46

Where f is the focal length of the optical system,

f1, f2, and f3 are the first to third lens focal lengths,

ΣT is the distance from the first lens object side surface to the imaging surface.

Table 2 below shows the lens surface data of each lens surface.

R D N Material (reference) One* 1.26 0.45 1.53 Plastic (P) 2* -300 0.19 (Stop) 0.00 0.45 4* -0.89 0.52 1.53 Plastic (P) 5 * -0.54 0.1 6 * 5.38 0.56 1.53 Plastic (P) 7 * 0.79 0.26 8* 0 0.3 1.52 Plastic (P) 9 * 0 0.100 image 0.00 0.00

In Table 2 and Table 3, * in the table next to the surface number indicates an aspherical surface. The following Table 3 shows the value of the aspherical surface coefficient of each lens in the Example of Table 2 above.

k A B C D One* -0.420518 -.294747E-01 -.924352E-01 -.175545E + 00 -.195160E + 00 2* -0.169948e27 -.942088E-01 -.438920E + 00 0.101529E + 01 -.268995E + 01 4* 0.441273 -.607080E + 00 0.537315E + 00 -.990601E + 01 0.485091E + 02 5 * -0.909230 0.112051E + 00 0.275398E + 00 -.310644E + 01 0.538891E + 01 6 * -1176.976256 0.182918E-01 0.101451E + 00 -.644291E-01 0.155947E-01 7 * -6.580117 -.108027E + 00 0.791496E-01 -.325968E-01 0.383014E-02

2 is a graph showing aberration diagrams according to an embodiment of the present invention, and is a graph measuring longitudinal spherical aberration, astigmatic field curves, and distortion aberration in order from the left. In FIG. 2, it is interpreted that as the curves approach the Y-axis, the aberration correction function is good. In the illustrated aberration diagram, since the values of the images appear in the vicinity of the Y axis in almost all fields, spherical aberration, astigmatism, and distortion aberration all show excellent numerical values. Should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and a person having ordinary knowledge in the technical field of the present invention can improve and modify the technical spirit of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention as long as it is apparent to those skilled in the art.

10; First lens 20; 2nd lens
30; Third lens 40; Infrared cut filter

Claims (28)

They are arranged in order from the object side to the upper side,
A first lens having a positive refractive power;
A second lens having a positive refractive power; And
It includes a third lens having negative (-) refractive power,
An imaging lens having a center thickness of the second lens smaller than that of the third lens. According to claim 1,
It includes an aperture disposed between the first lens and the second lens,
An imaging lens having an optical axis distance between the image side surface of the first lens and the aperture is greater than an optical axis image distance between the image side surface of the second lens and the object side surface of the third lens. According to claim 1,
An imaging lens having a focal length of the first lens larger than a focal length of the second lens. According to claim 1,
The absolute value of the focal length of the first lens is greater than the absolute value of the focal length of the third lens. According to claim 1,
The absolute value of the focal length of the second lens is smaller than the absolute value of the focal length of the third lens. According to claim 1,
An imaging lens having a refractive power of the second lens greater than that of the first and third lenses. According to claim 1,
When the center thickness of the first lens is d1, and the distance between the image side surface of the first lens and the object side surface of the second lens is d2,
An imaging lens with 0.70 <d1 / d2 <0.95. According to claim 1,
The first to third lenses are all the same refractive index imaging lens. According to claim 1,
The Abbe number of the first and second lenses is the same imaging lens. According to claim 1,
An imaging lens in which the object side surface of the first lens is convex and the image side surface of the first lens is convex. According to claim 1,
An imaging lens in which the object side surface of the second lens is concave and the image side surface of the second lens is convex. According to claim 1,
The second lens is an imaging lens having a convex meniscus on the image side. According to claim 1,
An imaging lens in which the object side surface of the third lens is convex in the optical axis and the image side surface of the third lens is concave in the optical axis. According to claim 1,
The third lens is an imaging lens having a convex meniscus on the object side. According to claim 1,
The third lens is an imaging lens on both sides having an inflection point. According to claim 1,
When the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3,
50 <v1, v2, v3 <60
Imaging lens that satisfies the conditions of According to claim 1,
When the Abbe number of the first lens is v1, the Abbe number of the second lens is v2, and the Abbe number of the third lens is v3,
(v1-v2) / v3 <1
Imaging lens that satisfies the conditional expression of According to claim 1,
When the thickness of the entire optical system is Σd and the focal length of the entire optical system is f,
0.5 <Σd / f <1.5
Imaging lens that satisfies the conditional expression of According to claim 1,
When the focal length of the entire optical system is f and the focal length of the first lens is f1,
0.5 <f1 / f <1.5
Imaging lens that satisfies the conditional expression of According to claim 1,
When the distance from the object side to the imaging surface of the first lens is ΣT, and the focal length of the entire optical system is f,
0.5 <ΣT / f <1.5
Imaging lens that satisfies the conditional expression of According to claim 1,
When the radius of curvature of the object side of the first lens is r1 and the focal length of the entire optical system is f,
1> r1 / f> 0.5
Imaging lens that satisfies the conditional expression of According to claim 1,
When the radius of curvature of the object side of the first lens is r1 and the focal length of the first lens is f1,
r1 / f1> 0.5
Imaging lens that satisfies the conditional expression of According to claim 1,
The second lens has an index of refraction between 1.5 and 1.6. According to claim 1,
When the focal length of the entire optical system is f and the focal length of the second lens is f2,
-0.2 <f / f2 <2
Imaging lens that satisfies the conditional expression of According to claim 1,
When the refractive index of the first lens is N1, the refractive index of the second lens is N2, and the refractive index of the third lens is N3,
1.5 <N1, N2, N3 <1.6
Imaging lens that satisfies the conditional expression of According to claim 1,
FNO, a value representing the brightness of the lens in infinite distance, is defined as f for the focal length of the entire optical system and D for the thickness of the entire optical system.
FNO = f / D,
2.2 <FNO <3.0
Imaging lens that satisfies the conditional expression of According to claim 1,
The diameter of the second lens is an imaging lens larger than the diameter of the first lens. They are arranged in order from the object side to the upper side,
A first lens having a positive refractive power;
A second lens having a positive refractive power; And
An imaging lens including a third lens having negative (-) refractive power.

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