KR102424948B1 - Image pickup lens, camera module and digital device including the same - Google Patents

Abstract

The embodiment includes first to fourth lenses arranged in order from the object side to the imaging side and having refractive power, wherein the first lens and the fourth lens have negative refractive power, and the second lens and the third lens has a positive refractive power, and the sum of the radius of curvature R1 of the first surface in the object-side direction and the radius of curvature R2 of the second surface in the imaging-side direction of the first lens is greater than -40.0 and smaller than -20.0. to provide.

Description

An imaging lens, a camera module and a digital device including the same

Embodiments relate to imaging lenses.

The conventional film camera is replaced by a camera module for a portable terminal using a compact solid-state image sensor such as CCD and CMOS, a digital still camera (DSC), a camcorder, a PC camera (imaging device attached to a personal computer), etc. and such an imaging device has been reduced in size and thickness.

In this trend, miniaturization of a light receiving element such as a CCD (Charge Coupled Device) mounted in a miniaturized imaging device is progressing, but the portion of the imaging device that occupies the most volume is the imaging lens.

Accordingly, the most important component in the miniaturization and thinning of the imaging device is an imaging lens that forms an image of an object.

Here, the problem is not only to implement a small imaging lens, but also the imaging lens is required to have high performance in response to the improvement of the performance of the light receiving element. However, the miniaturized imaging lens inevitably becomes closer to the light-receiving element, which causes a problem that the incident angle of light is obliquely incident on the imaging plane of the imaging device, so that the light-collecting performance of the imaging lens is not sufficiently exhibited, It is accompanied by a problem that the brightness of the image can change dramatically from the center of the image to the periphery.

The conventional imaging lens may have a structure in which the surface of the first lens toward the object side is convex, and due to this structure, scratches or contamination by foreign substances may occur on the surface of the lens.

The embodiment is intended to provide an imaging lens that does not generate scratches or contamination by foreign substances on the surface.

The embodiment includes first to fourth lenses arranged in order from the object side to the imaging side and having refractive power, wherein the first lens and the fourth lens have negative refractive power, and the second lens and the third lens has a positive refractive power, and the sum of the radius of curvature R1 of the first surface in the object-side direction and the radius of curvature R2 of the second surface in the imaging-side direction of the first lens is greater than -40.0 and smaller than -20.0. to provide.

The refractive index n3 of the third lens may be greater than 1.61 and less than 1.63, and the Abbe's number may be greater than 57 and less than 63.

The refractive index n4 of the fourth lens may be greater than 1.63 and less than 1.65, and the Abbe's number may be greater than 20 and less than 24.

The first lens may be concave toward the object, and at least one surface of the first surface in the object-side direction and the second surface in the imaging-side direction may be an aspherical surface.

The second lens may be convex toward the object, and at least one of the first surface in the object-side direction and the second surface in the imaging-side direction may be an aspherical surface.

The imaging lens may further include a diaphragm disposed between the second lens and the third lens.

The third lens may be convex toward the object side and the imaging side.

The fourth lens may be concave toward the object side and the imaging side, and at least one surface of the first surface in the object-side direction and the second surface in the imaging-side direction may be an aspherical surface.

Another embodiment includes the above-described imaging lens; a filter that selectively transmits light passing through the imaging lens according to a wavelength; And it provides a camera module including a light receiving element for receiving the light transmitted through the filter.

The light receiving element is an image sensor, and a horizontal and/or vertical length of a unit pixel of the image sensor may be 4 micrometers or less, respectively.

Another embodiment provides a digital device including the above-described camera module.

In the imaging lens according to the embodiment, scratches may not occur on the surface of the lens and contamination by foreign substances may not occur.

1 is a view showing a first embodiment of an imaging lens,
FIG. 2 is a diagram illustrating a thickness and a separation distance of each lens in the imaging lens of FIG. 1 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention that can specifically realize the above objects will be described with reference to the accompanying drawings.

In the description of the embodiment according to the present invention, the term 'target surface' refers to the surface of the lens that faces the object side with respect to the optical axis, and the term 'image-forming surface' refers to the image formation based on the optical axis. The side of the lens that faces the image side.

Also, in the present invention, "+ power" of a lens indicates a converging lens that converges parallel light, and "-power" of a lens indicates a diverging lens that diverges parallel light.

1 is a diagram showing the configuration of a first embodiment of an imaging lens.

Referring to FIG. 1 , the first embodiment of the imaging lens includes a first lens 210 , a second lens 220 , a third lens 230 , and a fourth lens 240 sequentially from the object side to the imaging side. do. A stop may be included between the second lens 220 and the third lens 230 . In addition, the filter 250 , the cover glass 260 , and the light receiving element 270 may be included in this order to form an imaging lens in the camera module.

The light receiving element 270 may be an image sensor, and a horizontal and/or vertical length of a unit pixel of the image sensor may be 2um (micrometer) or less. The above-described embodiment and the embodiments described below may provide an imaging lens that can be applied to a camera module having a high pixel and/or pixel number, and the above-described camera module includes an image sensor or a light receiving element having a high pixel and/or pixel number. In this case, the horizontal and/or vertical length of the unit pixel may be 4 μm or less, specifically, 2 μm or less.

In FIG. 1 , 'S11' is the target surface of the first lens 210, 'S12' is the imaging plane of the first lens 210, 'S21' is the target surface of the second lens 220, and 'S22' is the imaging plane of the second lens 220 , 'S31' is the target plane of the third lens 230, 'S32' is the imaging plane of the third lens 230, and 'S41' is the fourth lens 240 ), 'S42' is the imaging plane of the fourth lens 240 .

The above-described 'Sxy' may be equally applied to other embodiments of an imaging lens to be described later.

In the filter 250, a flat optical member such as an infrared filter is disposed, the cover glass 260 may be an optical member, for example, a cover glass for protecting an imaging surface, and the light receiving element 270 is printed. It may be an image sensor stacked on a circuit board (not shown).

In this embodiment, the first lens 210 has a concave target surface S11, and a central region of the imaging surface S12 may be concave. At least one of the target surface S11 and the imaging surface S12 is It may be aspherical.

In the second lens 220 , the target surface S21 and the imaging surface S22 may be convex, and at least one of the target surface S21 and the imaging surface S22 may be aspherical.

The third lens 230 may have a target surface S31 and an imaging surface S32 convex, and the fourth lens 240 may have a concave target surface S41 and a concave imaging surface S42. However, at least one of the target surface S41 and the imaging surface 412 may be an aspherical surface.

When the aspherical surface is formed on at least one surface of the lenses, it can be excellent in correcting various aberrations, for example, spherical aberration, coma, and distortion aberration.

The shapes of the target surfaces of the lenses are as follows. The first lens 210 has a concave target surface S11, the second lens 220 has a convex target surface S21, and the third lens 230 has a convex target surface S31. , the fourth lens 240 may have a concave shape on the target surface S41 .

The shape of the imaging planes of the lenses is as follows. The first lens 210 may have a concave central region of the imaging plane S12 , the second lens 420 may have a convex imaging plane S22 , and the third lens 430 may have a convex shape. S32 may be a convex shape, and the fourth lens 440 may have a concave imaging surface S42.

Here, the shape of the target surface and the imaging plane of each lens indicates the shape in the vicinity of the optical axis, and when the target plane and the imaging plane of each lens have an inflection point, the shape of the target plane and the imaging plane in a region far from the optical axis is different from this. can

In the imaging lens according to the embodiments, the first lens 210 and the fourth lens 240 may have negative refractive power, and the second lens 220 and the third lens 230 may have positive refractive power. .

And, the sum of the radius of curvature R1 of the first surface of the first lens 210 in the target direction, that is, the target surface S11, and the radius of curvature R2 of the second surface in the imaging direction, that is, the imaging surface S12 is - It can be greater than 40.0 and less than -20.0.

The first lens 210 may be concave toward the object, and at least one of the object surface S11 in the object-side direction and the imaging surface S12 in the imaging-side direction may be an aspherical surface.

The second lens 220 may be convex toward the object, and at least one of the object surface S21 in the object-side direction and the imaging surface S22 in the imaging-side direction may be an aspherical surface.

In addition, the third lens 230 may be convex toward the object side and the imaging side, the fourth lens 240 is concave toward the object side and the imaging side, and at least one surface of the object surface S41 and the image forming surface S42 . This may be aspheric.

In addition, the refractive index n3 of the third lens 230 may be greater than 1.61 and less than 1.63, and the Abbe's number v3 may be greater than 57 and less than 63.

In addition, the refractive index n4 of the fourth lens 240 may be greater than 1.63 and less than 1.65, and the Abbe's number v4 may be greater than 20 and less than 24.

Table 1 shows the radius of curvature, thickness and distance, refractive index, and Abbe's number of each of the target and image planes of the first lens 210 to the fourth lens 240 of the first embodiment of the imaging lens.

When the radius of curvature is large, the magnitude of the absolute value of the radius of curvature is considered when the surface of the target side is concave or convex, that is, the absolute value of the radius of curvature is not considered - or the radius of curvature is positive.

Here, the overall focal length of the imaging lens in Table 1 may be f = 3.17 mm, the first lens 210 may have a focal length f1 = -5.10 mm, and the second lens 22 may have a focal length f2 = 8.697 mm. And, the focal length f3 of the third lens 230 may be 4.207 mm, and the focal length f4 of the fourth lens 240 may be -5.899 mm.

radius of curvature thickness or distance refractive index Abbesu note S11 -36.194 1.319 1.5311 56 aspheric S12 2.965 6.051 aspheric S21 16.364 2.8 1.5311 56 aspheric S22 -6.053 0 aspheric iris 3.090 S31 4.77 2.15 1.6204 60.3 S32 -4.77 0.05 S41 -5.323 0.46 1.642 22.4 aspheric S42 13.570 0.973 aspheric

FIG. 2 is a diagram illustrating a thickness and a separation distance of each lens in the imaging lens of FIG. 1 .

2 and Table 2, the thickness t1 of the first lens 210 is 1.319 millimeters (mm), the thickness t2 of the second lens 220 is 2.8 millimeters, and the thickness of the third lens 230 is (t3) is 2.15 millimeters, and the thickness t4 of the fourth lens 240 is 0.46 millimeters.

Further, on the optical axis, the distance d1 between the first lens 210 and the second lens 220 is 6.051 millimeters, and the distance d2 between the second lens 220 and the third lens 230 is 3.090 millimeters. Although not shown, the distance between the third lens 230 and the fourth lens 240 may be 0.05 millimeters, and the distance d4 between the fourth lens 230 and the filter 250 may be 0.973 millimeters. have. In addition, as the distance d4 between the aperture and the third lens 230 or the fourth lens 240 is smaller, it may be advantageous to improve the resolution of the imaging lens.

Table 2 shows the conic image k and the aspheric coefficients A to D of each lens surface of the first embodiment of the imaging lens.

S11 S12 S21 S22 S41 S42 K -38.998765 -0.0493508 -40.792050 -0.225426 -2.524008 -4.948423 A 0.212466E-03 0.813849E-03 -0.126510E-02 -0.192012E-02 -0.412303E-02 0.300605E-02 B -0.398223E-05 0.227856E-03 -0.408383E-03 -0.779158E-04 0.315975E-03 0.270693E-03 C 0.197458E-07 -0.203029E-04 0.476455E-04 0.115687E-04 -0.886968E-04 -0.389737E-04 D -0.706309E-11 0.235975E-05 -0.445578E-05 -0.126901E-05 0.799198E-05 0.264498E-05

Table 3 shows the radius of curvature, thickness and distance, refractive index, and Abbe's number of each of the target and image planes of the first lens 210 to the fourth lens 240 of the second embodiment of the imaging lens.

radius of curvature thickness or distance refractive index Abbesu note S11 -26.69 0.750 1.5311 56 aspheric S12 3.0825 5.993 aspheric S21 9.096 4.029 1.5311 56 aspheric S22 -7.406 0 aspheric iris 2.86 S31 4.77 1.84 1.6204 60.3 S32 -4.77 0.05 S41 -4.897 0.460 1.642 22.4 aspheric S42 17.37 0.906 aspheric

Here, the focal length f of the entire imaging lens of Table 3 is 3.169 mm, the focal length f1 of the first lens 210 may be −5.158 mm, and the focal length f2 of the second lens 22 may be 8.398 mm. And, the focal length f3 of the third lens 230 may be 4.151 mm, and the focal length f4 of the fourth lens 240 may be -5.903 mm.

Table 4 shows the conic image k and the aspheric coefficients A to D of each lens surface of the second embodiment of the imaging lens.

S11 S12 S21 S22 S41 S42 K -16.579379 -0.288786 -4.7878450 0.458052 -0.579987 -32.227894 A 0.487033E-03 0.126222E-03 -0.684325E-03 -0.101929E-02 -0.269175E-02 0.237005E-02 B -0.110966E-04 0.184202E-04 -0.138781E-03 -0.282426E-04 0.465361E-03 0.432981E-03 C 0.159277E-06 -0.153081E-05 0.119430E-04 0.917149E-05 -0.646831E-04 -0.388406E-04 D -0.126956E-08 0.390832E-06 -0.697457E-06 -0.615933E-06 0.288411E-05 0.977621E-06

Table 5 shows the radius of curvature, thickness and distance, refractive index, and Abbe's number of each of the target and image planes of the first lens 210 to the fourth lens 240 of the third embodiment of the imaging lens.

radius of curvature thickness or distance refractive index Abbesu note S11 -26.942 0.83 1.5311 56 aspheric S12 3.183 6.51 aspheric S21 8.944 3.36 1.5311 56 aspheric S22 -7.859 0 aspheric iris 2.935 S31 4.77 1.84 1.6204 60.3 S32 -4.77 0.05 S41 -4.967 0.46 1.642 22.4 aspheric S42 15.884 0.9 aspheric

Table 6 shows the conic image k and the aspheric coefficients A to D of each lens surface of the fourth embodiment of the imaging lens.

Here, the focal length f of the entire imaging lens of Table 5 is 3.168 mm, the focal length f1 of the first lens 210 may be -5.308 mm, and the focal length f2 of the second lens 22 may be 8.462 mm. And, the focal length f3 of the third lens 230 may be 4.150 mm, and the focal length f4 of the fourth lens 240 may be -5.843 mm.

S11 S12 S21 S22 S41 S42 K -20.000000 -0.251381 -3.573888 0.882868 0.345185 -50.000000 A 0.461869E-03 0.162653E-03 -0.946475E-03 -0.123154E-02 -0.220773E-02 0.318388E-02 B -0.110454E-04 0.262291E-04 -0.198982E-03 -0.490678E-04 0.528154E-03 0.225406E-03 C 0.170872E-06 -0.268774E-05 0.228271E-04 0.121194E-04 -0.737195E-04 -0.725676E-04 D -0.134801E-08 0.329714E-06 -0.159624E-05 -0.923869E-06 0.474332E-05 0.529929E-06

In order to correct chromatic aberration, the lenses are made of plastic, but one lens may be made of glass, and in embodiments, the third lens 230 or the fourth lens 24 may be made of glass.

In particular, the refractive indices of the first lens 210 and the second lens 220 may be 1.5 or more, and the Abbe's number may be 50 or more.

When the lenses are formed with a glass mold, the transition point is relatively high, so the press temperature for forming the lens must be set high, so that the mold is easily deformed, but there is a problem in that the manufacturing cost increases due to the increase in the number of exchanges of the mold. If the lens is made of plastic, it is easy to make the lens aspherical, and it is advantageous for the manufacture of a small lens.

Although not shown, each lens may be coated on the surface to prevent reflection or improve surface hardness.

The camera module including the above-described imaging lens may be embedded in various digital devices such as a digital camera, a smart phone, a notebook computer, and a tablet PC.

In the above, the embodiment has been mainly described, but this is only an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are not exemplified above in the range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

110, 210: first lens 120, 220: second lens
130, 230: third lens 140, 240: fourth lens
250: filter 260: cover glass
270: light receiving element

Claims (11)

first to fourth lenses arranged in order from the object side to the imaging side and having refractive power; and
and an iris disposed between the second lens and the third lens,
The first lens and the fourth lens have negative refractive power, and the second lens and the third lens have positive refractive power,
The first lens and the second lens have the same refractive index,
The first lens and the second lens have the same Abbe number,
The sum of the radius of curvature R1 of the first surface in the object-side direction and the radius of curvature R2 of the second surface in the imaging-side direction of the first lens is greater than -40.0 and less than -20.0,
The first lens, the second lens, and the fourth lens are made of plastic having an aspherical surface, and the third lens is made of glass,
The first lens and the second lens have a refractive index of 1.5 or more, and an Abbe's number of 50 or more. The method of claim 1,
The third lens has a refractive index n3 greater than 1.61 and less than 1.63 and an Abbe number greater than 57 and less than 63. The method of claim 1,
The fourth lens has a refractive index n4 greater than 1.63 and less than 1.65 and an Abbe number greater than 20 and less than 24. The method of claim 1,
The first lens is concave toward the object, and at least one surface of the first surface in the object-side direction and the second surface in the imaging-side direction is an aspherical surface. The method of claim 1,
The second lens is convex toward the object, and at least one of the first surface in the object-side direction and the second surface in the imaging-side direction is an aspherical surface. delete The method of claim 1,
The third lens is an imaging lens that is convex toward the object side and the imaging side. The method of claim 1,
The fourth lens is concave toward the object side and the imaging side, and at least one surface of the first surface in the object-side direction and the second surface in the imaging-side direction is an aspherical surface. The imaging lens of any one of claims 1 to 5, 7 and 8;
a filter that selectively transmits light passing through the imaging lens according to a wavelength; and
A camera module including a light receiving element for receiving the light passing through the filter. 10. The method of claim 9,
The light receiving element is an image sensor, and a horizontal and/or vertical length of a unit pixel of the image sensor is 4 micrometers or less, respectively. A digital device comprising the camera module of claim 9 .

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