KR102599615B1 - Image pickup lens, camera module and digital device including the same - Google Patents

Abstract

The embodiment includes a first lens group including first to third lenses arranged in order from the object side to the image forming side, and a second lens group including fourth to seventh lenses, wherein the first lens and the second lens and the sixth lens have negative refractive power, and the third to fifth lenses and the seventh lens have positive refractive power, providing an imaging lens that satisfies Equation 1.
<Equation 1>
0.45 < L2CT/L2ET < 0.7, where L2CT is the center thickness of the second lens, and L2ET is the thickness at the effective diameter of the edge of the second lens.

Description

Imaging lens, camera module and digital device including the same {IMAGE PICKUP LENS, CAMERA MODULE AND DIGITAL DEVICE INCLUDING THE SAME}

The embodiment relates to an imaging lens.

Conventional film cameras are being replaced by camera modules for portable terminals that use small solid-state imaging elements such as CCD and CMOS, digital still cameras (DSC), camcorders, and PC cameras (imaging devices attached to personal computers). These imaging devices are becoming smaller and thinner.

In this trend, miniaturization of light-receiving elements such as CCD (Charge Coupled Device) mounted on miniaturized imaging devices is progressing, but the part that occupies the most volume in the imaging device is the imaging lens.

Therefore, the most important component in the imaging device for miniaturization and thinness is the imaging lens that forms an image of an object.

Here, the problem is not only to implement a small imaging lens, but also to correspond to the increased performance of the light receiving element, the imaging lens is also required to be high performance. However, a miniaturized imaging lens inevitably becomes closer to the light-receiving element, which causes the problem that the angle of incidence of light is slanted with respect to the imaging surface of the imaging device, so that the light-gathering performance of the imaging lens is not sufficiently exercised. This causes the problem that the brightness of the image can change dramatically from the center of the image to the periphery.

In consideration of these problems, it is necessary to increase the number of lenses, which may increase the volume of the imaging device.

The embodiment seeks to provide an imaging lens with high performance and an ultra-thin size.

The embodiment includes a first lens group including first to third lenses arranged in order from the object side to the image forming side, and a second lens group including fourth to seventh lenses, wherein the first lens and the second lens and the sixth lens have negative refractive power, and the third to fifth lenses and the seventh lens have positive refractive power, providing an imaging lens that satisfies Equation 1.

<Equation 1>

0.45 < L2CT/L2ET < 0.7, where L2CT is the center thickness of the second lens, and L2ET is the thickness at the effective diameter of the edge of the second lens.

In an embodiment, the first lens and the second lens may have the shape of a meniscus convex toward the object.

Additionally, the first lens group and the second lens group may each include at least one aspherical lens.

In addition, it may further include an aperture disposed between the first lens group and the second lens group.

Additionally, the fifth lens and the sixth lens may be bonded to each other.

Meanwhile, Equation 2 can be satisfied.

<Equation 2>

0.5 < [ FO / FI ] < 1.5, where FO is the focal length of the first lens group and FI is the focal length of the second lens group.

And, Equation 3 can be satisfied.

<Equation 3>

1 < [ FO / EFL ] < 3, where FO is the focal length of the first lens group, and EFL is the entire focal length of the optical system.

In addition, Equation 4 can be satisfied.

<Equation 4>

0.09 < [ F1F2 / F3 ] < 0.3, where F1F2 is the combined focal length between the first lens and the second lens, and F3 is the focal length of the third lens.

Another embodiment includes the imaging lens described above; a filter that selectively transmits light that has passed through the imaging lens according to its wavelength; and a light-receiving element that receives light passing through the filter.

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

The imaging lens according to the embodiment includes seven lenses and is ultra-thin, so it can capture moving objects without image distortion.

1 is a diagram showing a first embodiment of an imaging lens.
Figure 2 is a diagram showing a second embodiment of an imaging lens.
Figure 3 is a graph showing the aberration diagram of the first embodiment of the imaging lens, showing longitudinal spherical aberration, astigmatic field curves, and distortion in that order from the left.
Figure 4 is a graph showing the aberration diagram of the second embodiment of the imaging lens, and is a graph showing spherical aberration, astigmatism, and distortion aberration in that order from the left.

Hereinafter, embodiments of the present invention that can specifically realize the above object will be described with reference to the attached drawings.

In the description of the embodiment according to the present invention, 'target surface' refers to the surface of the lens facing the object side based on the optical axis, and 'image forming surface' refers to the surface of the lens facing the object side based on the optical axis. This refers to the side of the lens facing the image side.

Additionally, in the present invention, the “+ power” of a lens represents a converging lens that converges parallel light, and the “-power” of a lens represents a diverging lens that diverges parallel light.

FIG. 1 is a diagram showing a first embodiment of an imaging lens, and FIG. 2 is a diagram showing a second embodiment of an imaging lens.

Referring to Figures 1 and 2, the first and second embodiments of the imaging lens include a first lens 110, a second lens 120, and a third lens 130 arranged in order from the object side to the image forming side. ) a first lens group (I) including, and a second lens group (II) including the fourth lens 140, the fifth lens 150, the sixth lens 160, and the seventh lens 170. Includes.

A shutter may be included on the front of the first lens 110, and an aperture (AS) may be placed between the first lens group (I) and the second lens group (II). It may be a variable aperture. In addition, the filter 180 and the light-receiving element 190 may be included in that order to form an imaging lens within the camera module, and a cover glass may be included between the filter 180 and the light-receiving element 190. .

And, the light receiving element 190 may be an image sensor. The above-described embodiment and the embodiments described below can provide an imaging lens that can be applied to a camera module with a high number of pixels and/or pixels, and the above-described camera module includes an image sensor or light-receiving element with a high number of pixels and/or pixels. can do.

1 and 2, 'S11' is the target surface of the first lens 110, 'S12' is the imaging surface of the first lens 110, and 'S21' is the target surface of the second lens 120, 'S22' is the imaging plane of the second lens 120, 'S31' is the object plane of the third lens 130, 'S32' is the imaging plane of the third lens 130, and 'S41' is the fourth lens 130. The target surface of the lens 140, 'S42' is the imaging surface of the fourth lens 140, 'S51' is the target surface of the fifth lens 150, and 'S52' is the imaging surface of the fifth lens 150. , 'S61' is the target surface of the sixth lens 160, 'S62' is the imaging surface of the sixth lens 160, 'S71' is the target surface of the seventh lens 170, and 'S72' is the seventh lens 160. This is the imaging surface of the lens 170.

The filter 180 is disposed with a flat optical member such as an infrared ray filter, the cover glass may be an optical member, for example, a cover glass for protecting the imaging surface, and the light receiving element 190 is a printed circuit board ( It may be an image sensor stacked on top (not shown).

In this embodiment, the first lens 110 and the second lens 120 of the first lens group (I) may have the shape of a meniscus convex toward the object. The lens 120 has convex target surfaces S11 and S21 and may have negative refractive power. In addition, the third lens 130 may have both the target surface (S31) and the image forming surface (S32) convex, or the target surface (S31) may be convex and the image forming surface (S32) may be flat or concave, and may have positive refractive power. You can have it.

In addition, in the second lens group (II), the fourth lens 140 has both the target surface S41 and the image forming surface S42 convex, or the target surface S41 is flat or concave and the image forming surface S42 is convex. and can have positive refractive power. In addition, the fifth lens 150 may have both the target surface S51 and the image forming surface S52 convex, or the target surface S51 may be flat or concave and the image forming surface S52 may be convex, and may have positive refractive power. there is. In addition, the sixth lens 160 may have both the target surface (S61) and the image forming surface (S62) concave, or the target surface (S61) may be concave and the image forming surface (S62) may be flat or convex, and have a negative refractive index. You can.

Here, the fifth lens 150 and the sixth lens 160 can be implemented as bonded lenses by bonding the imaging surface (S52) of the fifth lens and the target surface (S61) of the sixth lens to each other, and low dispersion ( Low Dispersion) performance can be improved and aberrations can be minimized.

In addition, the seventh lens 170 may have both the target surface (S71) and the image forming surface (S72) convex, or the image forming surface (S72) may be convex and the target surface (S71) may be flat or concave, and may have positive refractive power. You can have it. Here, in the case of the second embodiment, the seventh lens 170 may be disposed at a distance of 0.1 mm from the sixth lens 160.

Some of the target surfaces and imaging surfaces of the above-described first to seventh lenses 110 to 170 may be aspherical, and when the aspherical surface is formed on at least one surface of the lenses, various aberrations, such as spherical aberration and coma, may occur. It can be excellent for correcting aberrations and distortion aberrations.

In addition, at least one of the first to seventh lenses 110 to 170 may be a glass lens, and in the embodiment, the first lens 110, the fourth lens 140, and the seventh lens 170 may be made of glass. Because glass lenses have a relatively high transition point, they can minimize changes in refractive index and focal length despite changes over time due to temperature changes.

In addition, the surface of the lens according to the embodiment may be coated to prevent reflection or improve surface hardness.

Meanwhile, the first and second embodiments can satisfy Equation 1 below.

<Equation 1>

0.45 < L2CT/L2ET < 0.7

Here, L2CT represents the center thickness of the second lens, and L2ET represents the thickness at the effective diameter of the edge of the second lens.

Equation 1 relates to the ratio of the thickness on the optical axis of the second lens and the thickness at the peripheral effective diameter, which affects distortion correction. And, as shown in FIG. 1, the thickness (ET: Edge Thickness) at the effective diameter of the edge of the second lens 120 is a vertical line extending from the effective diameter of the target surface S21 of the second lens 120 and the second lens 120. ) can be measured as the distance between the vertical lines drawn from the effective diameter of the imaging surface (S22).

If the value of L2CT/L2ET is less than 0.45, the difference between the lens thickness on the optical axis and the thickness at the peripheral effective diameter becomes large, making it difficult to correct distortion of the entire optical system. As a result, distortion aberration increases.

Also, if the value of L2CT/L2ET is greater than 0.7, the difference between the thickness on the optical axis and the thickness at the peripheral effective diameter decreases, but manufacturability becomes disadvantageous.

The first and second embodiments can satisfy Equation 2 below.

<Equation 2>

0.5 < [ FO / FI ] < 1.5

Here, FO represents the focal length of the first lens group, and FI represents the focal length of the second lens group.

Equation 2 is a condition regarding the ratio of the focal lengths of the lens group on the object side and the lens group on the image side, and is used to obtain a wide angle of view by setting the refractive power of the lens group on the object side to be relatively weak. .

If the value of [ FO / FI ] is less than 0.5, the back focal distance increases, making wide-angle implementation difficult and spherical aberration increasing.

And, if the value of [ FO / FI ] is greater than 1.5, the refractive power of the lens group on the target side becomes weak, which makes it advantageous to implement a wide angle of view, but the aperture of the lens becomes large and the optical system becomes heavy.

The first and second embodiments can satisfy Equation 3 below.

<Equation 3>

1 < [ FO / EFL ] < 3

Here, FO represents the focal length of the first lens group, and EFL represents the entire focal length of the optical system.

Equation 3 relates to the ratio of the total focal length of the optical system and the focal distance of the target side. If the value of [ FO / EFL ] is less than 1, the size of the optical system can be implemented small, but the effective diameter becomes small, making aberration correction difficult. You lose.

And, if the value of [ FO / EFL ] is greater than 3, the refractive power of sound on the target side becomes smaller, making it easier to implement a wide angle, but there is a disadvantage in that distortion increases.

Meanwhile, the first and second embodiments can satisfy Equation 4 below.

<Equation 4>

0.09 < [ F1F2 / F3 ] < 0.3

Here, F1F2 represents the combined focal length between the first lens and the second lens, and F3 represents the focal length of the third lens.

Equation 4 relates to the ratio of the combined focal length between the first lens and the second lens of the target lens group divided by the focal length of the third lens. If the value of [ F1F2 / F3 ] is less than 0.09, the target lens group As the focal length of the group becomes longer, it becomes difficult to realize a large angle of view. And, if the value of [ F1F2 / F3 ] is greater than 0.3, the refractive power of the lens group on the target side decreases and the aperture of the first lens located first on the target side increases.

Table 1 shows the radius of curvature, thickness or distance, refractive index, and Abbe number of each lens of the first embodiment of the imaging lens. When the radius of curvature is large, the size of the absolute value of the radius of curvature is taken into consideration without considering the case where the surface on the target side is concave or convex, that is, the radius of curvature is - or +.

radius of curvature Thickness or distance (mm) refractive index Abesu Object Infinity Infinity Target surface (S11) of the first lens 11.11 1.00 1.7725 49.6 Imaging surface (S12) of the first lens 5.00 1.95 Target surface (S21) of the second lens 31.12 1.10 1.531 55.8 Imaging surface of the second lens (S22) 3.99 2.49 Target surface of the third lens (S31) 16.23 3.00 1.632 23.4 Imaging surface of the third lens (S32) -25.67 3.56 Aperture (AS) Infinity 0.10 Target surface of the fourth lens (S41) 66.32 3.79 1.589 61.2 Imaging surface of the fourth lens (S42) -4.90 0.38 Target surface of the fifth lens (S51) -337.20 2.50 1.531 55.8 Imaging surface of the fifth lens (S52) -4.90 0.07 Target surface of the sixth lens (S61) -4.90 1.84 1.632 23.4 Imaging surface of the sixth lens (S62) 107.19 1.10 Target surface of the 7th lens (S71) 30.50 1.62 1.493 69.8 Imaging surface of the 7th lens (S72) -9.18 1.00 filter Infinity 0.70 1.523 55.0 cover glass Infinity 3.79

In Table 1, the object, the first to third lenses (110 to 130), the aperture, the fourth to seventh lenses (140 to 170), the filter 180, the target surface of the cover glass 190, and The curvature of the imaging surface is described in order. If the curvature is positive (+), it is bent toward the object, and if it is negative (-), it is bent toward the light receiving element. When the curvature is infinite, it is flat, and the thickness is described corresponding to each target surface, and the distance to adjacent lenses, etc. is described corresponding to the image forming surface.

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

Table 2 shows the Conic constant (k) and aspheric coefficients (A to F) of each lens surface in the first embodiment.

k A B C D E F S21 0.00 2.26E-03 -3.65E-05 1.11E-07 1.79E-08 -4.81E-10 -5.82E-12 S22 0.00 -1.50E-04 1.17E-05 -3.98E-07 -6.39E-07 8.16E-09 -3.88E-10 S31 0.00 -8.71E-04 6.12E-05 2.02E-06 -1.27E-07 8.74E-09 5.98E-10 S32 0.00 1.25E-06 1.17E-06 4.10E-06 5.25E-08 -8.28E-09 1.16E-09 S41 -2189.13 -1.11E-03 -2.83E-04 2.68E-05 -7.60E-06 0.00E+00 0.00E+00 S42 0.10 -8.11E-05 -4.51E-05 -6.50E-06 -6.53E-08 0.00E+00 0.00E+00 S51 -51230.91 -1.78E-04 -3.72E-05 -6.70E-06 -1.99E-07 2.02E-09 2.74E-10 S62 401.96 1.07E-03 -5.42E-06 -1.09E-06 -4.53E-08 -2.49E-09 2.13E-10

Figure 3 is a graph showing the aberration diagram of the first embodiment of the imaging lens, showing longitudinal spherical aberration, astigmatic field curves, and distortion in that order from the left.

In Figure 3, the Y-axis represents the size of the image, the Additionally, the graph regarding spherical aberration in Figure 3 represents the longitudinal spherical aberration for light with wavelengths of 656.27nm, 587.56nm, 546.07nm, 486.13nm, and 435.84nm, and the graph for astigmatism represents light with a wavelength of 546.07nm. Indicates the aberrations on the spherical surface (S: Sagittal surface) and the meridional surface (T: Tangential surface). Additionally, the graph regarding distortion aberration shows the distortion for light with a wavelength of 546.07 nm.

Table 3 shows the radius of curvature, thickness or distance, refractive index, and Abbe number of the second embodiment of the imaging lens. When the radius of curvature is large, the size of the absolute value of the radius of curvature is taken into consideration without considering the case where the surface on the target side is concave or convex, that is, the radius of curvature is - or +.

radius of curvature Thickness or distance (mm) refractive index Abesu Object Infinity Infinity Target surface (S11) of the first lens 12.00 1.00 1.7725 49.6 Imaging surface (S12) of the first lens 5.00 1.19 Target surface (S21) of the second lens 10.00 1.00 1.531 55.8 Imaging surface of the second lens (S22) 3.47 1.00 Target surface of the third lens (S31) 4.63 3.04 1.632 23.4 Imaging surface of the third lens (S32) 4.01 3.05 Aperture (AS) Infinity 0.10 Target surface of the fourth lens (S41) -85.86 2.50 1.531 55.8 Imaging surface of the fourth lens (S42) -3.21 2.39 Target surface of the fifth lens (S51) -19.53 3.00 1.531 55.8 Imaging surface of the fifth lens (S52) -4.16 0.06 Target surface of the sixth lens (S61) -4.16 0.60 1.632 23.4 Imaging surface of the sixth lens (S62) -110.88 0.08 Target surface of the 7th lens (S71) 15.00 2.00 1.531 55.8 Imaging surface of the 7th lens (S72) -6.03 1.30 filter Infinity 0.70 1.523 55.0 cover glass Infinity 3.98

In Table 3, the target surface of the object, the first to third lenses 110 to 130, the aperture, the fourth to seventh lenses 140 to 170, the filter 180, and the cover glass 190, and The curvature of the imaging surface is described in order. If the curvature is positive (+), it is bent toward the object, and if it is negative (-), it is bent toward the light receiving element. When the curvature is infinite, it is flat, and the thickness is described corresponding to each target surface, and the distance to adjacent lenses, etc. is described corresponding to the image forming surface.

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

Table 4 shows the Conic constant (k) and aspheric coefficients (A to D) of each lens surface in the second embodiment.

k A B C D S21 2.10 7.15E-04 -5.44E-06 7.76E-07 -1.47E-09 S22 -0.20 -1.44E-03 -2.27E-05 -3.04E-06 -1.72E-07 S31 0.00 2.12E-03 -9.06E-05 1.79E-06 -3.39E-07 S32 0.00 9.75E-03 -4.61E-04 1.33E-04 -2.45E-05 S41 0.00 9.75E-03 -4.61E-04 1.33E-04 -2.45E-05 S42 0.00 9.75E-03 -4.61E-04 1.33E-04 -2.45E-05 S51 0.00 9.75E-03 -4.61E-04 1.33E-04 -2.45E-05 S62 0.00 8.25E-04 -8.61E-05 -4.74E-06 2.14E-07 S71 -7.04 3.77E-05 2.18E-05 -1.01E-06 3.72E-08 S72 -3.18 0.000606 2.71E-05 1.66E-06 -8.39E-08

Figure 4 is a graph showing the aberration diagram of the second embodiment of the imaging lens, showing longitudinal spherical aberration, astigmatic field curves, and distortion in that order from the left. Additionally, the graph regarding spherical aberration in FIG. 4 represents the longitudinal spherical aberration for light with wavelengths of 656.27nm, 587.56nm, 546.07nm, 486.13nm, and 435.84nm, and the graph for astigmatism represents light with a wavelength of 546.07nm. Indicates the aberrations on the spherical surface (S: Sagittal surface) and the meridional surface (T: Tangential surface). Additionally, the graph regarding distortion aberration shows the distortion for light with a wavelength of 546.07 nm.

In Figure 4, the Y-axis represents the size of the image, the

The camera module including the above-described imaging lens can be built into various digital devices such as digital cameras, smartphones, laptops, and tablet PCs. In particular, it can be built into digital devices such as drones to capture images from above by implementing a wide angle, thereby minimizing distortion of images taken from above.

Although the above description focuses on the examples, this is only an example and does not limit the present invention, and those skilled in the art will be able to You will see that various variations and applications are possible. For example, each component specifically shown in the examples can be modified and implemented. And these variations and differences in application should be construed as being included in the scope of the present invention as defined in the appended claims.

110: first lens 120: second lens
130: third lens 140: fourth lens
150: 5th lens 160: 6th lens
170: 7th lens 180: filter
190: Light receiving element AS: Aperture

Claims (12)

a first lens group including first to third lenses arranged in order from the object side to the image forming side, and a second lens group including fourth to seventh lenses; and
It includes an aperture disposed between the image forming surface of the third lens and the target surface of the fourth lens with respect to the optical axis,
The first lens, the second lens, and the sixth lens have negative refractive power, and the third to fifth lenses and the seventh lens have positive refractive power,
The aperture is disposed closer to the target surface of the fourth lens than the imaging surface of the third lens,
The first lens and the second lens have the shape of a meniscus convex toward the object,
The object surface (S31) of the third lens is convex and the image forming surface (S32) is convex,
The imaging surface (S42) of the fourth lens is convex,
The object surface (S51) of the fifth lens is concave and the image forming surface (S52) is convex,
Both sides (S61, S62) of the sixth lens are concave,
Both surfaces (S71, S72) of the seventh lens are convex,
The fourth lens closer to the aperture is the thickest imaging lens. delete According to claim 1,
An imaging lens wherein the first lens group and the second lens group each include at least one aspherical lens. According to claim 1,
An imaging lens that satisfies Equation 1.
<Equation 1>
0.45 < L2CT / L2ET < 0.7, where L2CT is the center thickness of the second lens, and L2ET is the thickness at the effective diameter of the edge of the second lens. According to claim 1,
The fifth lens and the sixth lens are bonded to each other. According to claim 1,
An imaging lens that satisfies Equation 2.
<Equation 2>
0.5 < | FO/FI | <1.5, where FO is the focal length of the first lens group and FI is the focal length of the second lens group. According to claim 1,
An imaging lens that satisfies Equation 3.
<Equation 3>
1 < | FO/EFL | < 3, where FO is the focal length of the first lens group, and EFL is the entire focal length of the optical system. According to claim 1,
An imaging lens that satisfies Equation 4.
<Equation 4>
0.09 < | F1F2/F3 | < 0.3, where F1F2 is the combined focal length between the first lens and the second lens, and F3 is the focal length of the third lens. According to claim 1,
An imaging lens in which the first lens, fourth lens, and seventh lens are made of glass. According to claim 1,
An imaging lens in which a filter is disposed between the seventh lens and a cover glass. The imaging lens of any one of claims 1, 3 to 10;
a filter that selectively transmits light that has passed through the imaging lens according to its wavelength; and
A camera module including a light-receiving element that receives light passing through the filter. A digital device including the camera module of claim 11.

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