KR20180059396A - Optical system - Google Patents

Abstract

The present invention relates to a photographing optical system capable of realizing high resolution. According to one embodiment of the present invention, the photographing optical system comprises first to sixth lenses disposed from an object side in order; and an image sensor to convert an image of a subject incident through the first to sixth lenses. An object side surface of any one from the first to sixth lenses has a spherical shape and the upper surface thereof has a non-spherical shape, and the object side and upper surfaces of the remaining lenses have a non-spherical shape. A refractive index of any one of the lenses disposed closer to the object side surface than the lens having the object surface of the spherical shape is greatest among the first to sixth lenses. Moreover, TTL/(2 X ImgH) < 0.75 is satisfied, wherein TTL represents a distance from the object side surface of the first lens to the upper surface of the image sensor and ImgH represents a half of the diagonal length of the upper surface of the image sensor.

Description

[0001]

The present invention relates to an imaging optical system.

BACKGROUND ART [0002] In recent years, a portable terminal has a camera so that a video call and a photograph can be taken. In addition, as the function of the camera in the portable terminal gradually increases, the demand for high resolution and high performance of the camera for the portable terminal is increasing.

In addition, aspheric surfaces are applied to all the lenses of a camera for a portable terminal in order to realize a high resolution with a small size according to recent miniaturization trends.

However, when an aspherical surface is applied to all the lenses, there is a problem that productivity is deteriorated because a performance change occurs due to manufacturing tolerance or assembly tolerance of each lens.

An object of an embodiment of the present invention is to provide an imaging optical system capable of improving the aberration improving effect, realizing a high resolution, and minimizing the influence of manufacturing tolerance or assembly tolerance.

An imaging optical system according to an embodiment of the present invention includes first to sixth lenses arranged in order from the object side; And an image sensor for converting an image of an object incident through the first lens to the sixth lens into an electric signal, wherein an object side surface of any one of the first lens to the sixth lens Side surface is an aspherical surface and the other lenses have refractive indexes of any one of lenses arranged on the object side and the image side closer to the object side than the spherical surface on the object side, Wherein the distance from the object side of the first lens to the image surface of the image sensor is TTL and the half of the diagonal length of the image sensor is ImgH, 2 * ImgH) < 0.75.

According to the imaging optical system according to an embodiment of the present invention, it is possible to improve the aberration improving effect, realize high resolution, minimize the influence of manufacturing tolerance or assembly tolerance, and improve productivity.

1 is a configuration diagram of an imaging optical system according to the first embodiment of the present invention,
Figs. 2 and 3 are curves showing the aberration characteristics of the imaging optical system shown in Fig. 1,
FIG. 4 is a table showing the lens characteristics of the imaging optical system shown in FIG. 1,
5 is a table showing the aspherical surface coefficients of the respective lenses of the imaging optical system shown in Fig. 1,
6 is a configuration diagram of an imaging optical system according to the second embodiment of the present invention,
Figs. 7 and 8 are curves showing the aberration characteristics of the imaging optical system shown in Fig. 6,
Fig. 9 is a table showing the lens characteristics of the imaging optical system shown in Fig. 6,
10 is a table showing the aspherical surface coefficients of the respective lenses of the imaging optical system shown in Fig. 6,
11 is a configuration diagram of an imaging optical system according to the third embodiment of the present invention,
Figs. 12 and 13 are curves showing the aberration characteristics of the imaging optical system shown in Fig. 11,
FIG. 14 is a table showing the lens characteristics of the imaging optical system shown in FIG. 11,
15 is a table showing the aspherical surface coefficients of the respective lenses of the imaging optical system shown in Fig.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the embodiments shown.

For example, those skilled in the art of the present invention will be able to easily suggest other embodiments included in the scope of the present invention by adding, changing or deleting components, etc., And the like.

In addition, throughout the specification, &quot; comprising &quot; means that other elements may be included, rather than excluding other elements, unless specifically stated otherwise.

In the following lens configuration diagrams, the thickness, size, and shape of the lens are shown somewhat exaggerated for explanatory purposes, and in particular, the shape of the spherical or aspherical surface presented in the lens configuration diagram is shown by way of example only and is not limited to this shape.

In the lens configuration diagrams of Figs. 1, 6, and 11, although one surface of each lens may be seen as convex, referring to the table showing the lens characteristics of Figs. 4, 9, and 14, It can be concave or flat. Likewise, although one side of the lens may appear to be concave, the actual shape of the side may be convex or planar.

The first lens means the lens closest to the object, and the sixth lens means the lens closest to the image sensor.

In each lens, the first surface means a surface close to the object side (or the object side surface), and the second surface means a surface (or an upper surface) close to the image side. In the present specification, the numerical values of the curvature radius (Radius), the thickness (Thickness), the ImgH (1/2 of the diagonal length of the upper surface of the image sensor) of the lens are all in mm and the unit of the FOV (angle of view of the imaging optical system) Degree is.

In addition, in the explanation of the shape of each lens, the convex shape of one surface means that the paraxial area of the surface is convex, and the concave shape of one surface means that the paraxial area of the surface is concave. Therefore, even if one surface of the lens is described as a convex shape, the edge portion of the lens can be concave. Similarly, even if one surface of the lens is described as a concave shape, the edge portion of the lens can be convex.

On the other hand, the paraxial region means a very narrow region near the optical axis.

An imaging optical system according to an embodiment of the present invention includes six lenses.

For example, an imaging optical system according to an embodiment of the present invention includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in order from the object side.

However, the imaging optical system according to one embodiment of the present invention is not limited to only six lenses, and may further include other components as needed.

For example, the imaging optical system may further include an image sensor for converting an image of an incident subject into an electrical signal.

Further, the imaging optical system may further include an infrared ray filter for blocking infrared rays. An infrared filter is disposed between the sixth lens and the image sensor.

Further, the imaging optical system may further include an iris for adjusting the amount of light. For example, the diaphragm may be disposed between the first lens and the second lens.

The first lens to the sixth lens constituting the imaging optical system according to an embodiment of the present invention may be made of a plastic material.

At least one of the first lens to the sixth lens has an aspherical surface. The first lens to the sixth lens may each have at least one aspherical surface.

That is, at least one of the first surface and the second surface of the first lens to the sixth lens may be an aspherical surface. Here, the aspherical surfaces of the first lens to the sixth lens are expressed by the following equation (1).

In Equation (1), c is the curvature of the lens (inverse of the curvature radius), K is the conic constant, and Y is the distance from the arbitrary point on the aspherical surface of the lens to the optical axis. In addition, the constants A to F mean aspheric coefficients. And Z represents the distance from an arbitrary point on the aspheric surface of the lens to the apex of the aspheric surface.

The imaging optical system composed of the first lens to the sixth lens has positive / negative / positive / negative / negative / negative refractive power in order from the object side.

The imaging optical system thus configured can improve the optical performance by improving the aberration.

The imaging optical system according to the embodiment of the present invention satisfies the conditional expression (1).

[Conditional expression 1]

2.0 < f3 / f1 < 6.0

In Conditional Expression 1, f1 is the focal length of the first lens, and f3 is the focal length of the third lens.

The imaging optical system according to the embodiment of the present invention satisfies the conditional expression (2).

[Conditional expression 2]

f / (CT3 + CT4 + CT5) < 4.0

CT3 is the thickness in the paraxial area of the third lens, CT4 is the thickness in the paraxial area of the fourth lens, CT5 is the paraxial area of the fifth lens, Lt; / RTI &gt;

The imaging optical system according to the embodiment of the present invention satisfies the conditional expression (3).

[Conditional expression 3]

| f / f5 | + | f / f6 | &Lt; 1.0

In the conditional expression 3, f is the total focal length of the imaging optical system, f5 is the focal length of the fifth lens, and f6 is the focal length of the sixth lens.

The imaging optical system according to the embodiment of the present invention satisfies the conditional expression (4).

[Conditional expression 4]

TTL / (2 x ImgH) < 0.75

In the conditional expression (4), TTL is the distance from the object side surface of the first lens to the image surface of the image sensor, and ImgH is half the diagonal length of the image sensor.

Referring to Table 1, the imaging optical system according to the embodiment of the present invention satisfies the conditional expressions 1 to 4.

Next, the first lens to the sixth lens constituting the imaging optical system according to the embodiment of the present invention will be described.

The first lens has a positive refractive power. Further, the first lens may have a convex meniscus shape toward the object side. In other words, the first surface of the first lens may be convex in the paraxial area, and the second surface may be concave in the paraxial area.

At least one of the first surface and the second surface of the first lens may be aspherical. For example, both surfaces of the first lens may be aspherical.

The second lens has a negative refractive power, and the second lens may have a convex meniscus shape toward the object side. In other words, the first surface of the second lens may be convex in the paraxial area, and the second surface may be concave in the paraxial area.

At least one of the first and second surfaces of the second lens may be aspherical. For example, both surfaces of the second lens may be aspherical. Further, the refractive index of the second lens among the first to sixth lenses may be the largest.

The third lens has a positive refractive power. In addition, the third lens may have a meniscus shape convex upward. In other words, the first surface of the third lens may be concave in the paraxial area, and the second surface may be convex in the paraxial area.

At least one of the first surface and the second surface of the third lens may be aspherical. For example, both surfaces of the third lens may be all aspherical.

The fourth lens has a negative refractive power. In addition, the fourth lens may have a concave shape on both sides. In other words, the first surface and the second surface of the fourth lens may be concave in the paraxial area.

In the fourth lens, either one of the first surface and the second surface may be an aspherical surface. For example, the first surface of the fourth lens may be a spherical surface, and the second surface may be an aspherical surface.

The fifth lens has a negative refractive power. In addition, the fifth lens may have a concave shape on both sides. In other words, the first and second surfaces of the fifth lens may be concave in the paraxial area.

At least one of the first surface and the second surface of the fifth lens may be an aspherical surface. For example, both surfaces of the fifth lens may be all aspherical.

The sixth lens has a negative refractive power. Further, the sixth lens may have a convex meniscus shape toward the object side. In other words, the first surface of the sixth lens may be convex in the paraxial area, and the second surface may be concave in the paraxial area.

The sixth lens may have at least one of the first surface and the second surface aspherical. For example, both surfaces of the sixth lens may be aspherical.

In addition, at least one inflection point is formed on at least one of the first surface and the second surface of the sixth lens. For example, the first surface of the sixth lens may be convex in the paraxial area and concave in the edge direction. The second surface of the sixth lens may be concave in the paraxial area and convex in the edge.

In the imaging optical system configured as described above, since a plurality of lenses perform the aberration correction function, the aberration improving performance can be improved.

In the case of downsizing the imaging optical system, there is a concern that the performance of the imaging optical system may change due to manufacturing tolerance or assembly tolerance of each lens. For example, as the imaging optical system is miniaturized, the sensitivity of the lens increases, and the performance variation due to manufacturing tolerance or assembly tolerance of each lens is increased.

In particular, when an aspherical surface is applied to all the lenses, the influence of the manufacturing tolerance or the assembly tolerance becomes large.

However, in the imaging optical system according to the embodiment of the present invention, one surface (for example, the object side surface of the fourth lens) of any one of the plurality of lenses is designed as a spherical surface, (For example, the refractive index of the second lens can be greater than 1.66) of any one of the arranged lenses (for example, the second lens) can be designed to be the largest Or variation in performance according to the assembly tolerance can be prevented.

An imaging optical system according to a first embodiment of the present invention will be described with reference to Figs. 1 to 5. Fig.

The imaging optical system according to the first embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, An infrared filter 170, and an image sensor 180. The image sensor 180 may be an infrared sensor.

As shown in FIG. 4, the focal length f1 of the first lens 110 is 2.6218 mm, the focal length f2 of the second lens 120 is -5.9743 mm, The focal length f4 of the fourth lens 140 is -12.4925 mm and the focal length f5 of the fifth lens 150 is -379.999 mm; 160 is -15.6656 mm, and the total focal length f of the imaging optical system is 3.5976 mm.

Here, the lens characteristics (radius of curvature, thickness of the lens or distance between lenses, index, Abbe number, effective radius) of each lens are as shown in Fig.

In the first embodiment of the present invention, the first lens 110 has a positive refractive power and a convex meniscus shape on the object side. For example, the first surface of the first lens 110 is convex in the paraxial area, and the second surface of the first lens 110 is concave in the paraxial area.

The second lens 120 has a meniscus shape having a negative refractive power and being convex on the object side. For example, the first surface of the second lens 120 is convex in the paraxial area, and the second surface of the second lens 120 is concave in the paraxial area.

The third lens 130 has a positive refractive power and a meniscus shape convex upward. For example, the first surface of the third lens 130 has a concave shape in the paraxial area, and the second surface of the third lens 130 has a convex shape in the paraxial area.

The fourth lens 140 has a negative refractive power and has a concave shape on both sides. For example, the first and second surfaces of the fourth lens 140 are concave in the paraxial area.

The fifth lens 150 has a negative refractive power and has a concave shape on both sides. For example, the first and second surfaces of the fifth lens 150 are concave in the paraxial area.

The sixth lens 160 has a negative refractive power and a convex meniscus shape on the object side. For example, the first surface of the sixth lens 160 is convex in the paraxial area, and the second surface of the sixth lens 160 is concave in the paraxial area.

In addition, at least one inflection point is formed on at least one of the first surface and the second surface of the sixth lens 160.

On the other hand, each surface of the first lens 110 to the sixth lens 160 has an aspheric surface coefficient as shown in FIG. For example, the first lens 110, the second lens 120, the third lens 130, the fifth lens 150, and the sixth lens 160 may have a first surface and a second surface, All sides are aspherical. The first surface of the fourth lens 140 is a spherical surface, and the second surface of the fourth lens 140 is an aspherical surface.

The diaphragm may be disposed between the first lens 110 and the second lens 120.

Further, the imaging optical system thus constructed can have the aberration characteristics shown in Figs. 2 and 3.

An imaging optical system according to a second embodiment of the present invention will be described with reference to Figs. 6 to 10. Fig.

The imaging optical system according to the second embodiment of the present invention includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, An infrared filter 270, and an image sensor 280. The image sensor 280 may be an infrared sensor.

9, the focal length f1 of the first lens 210 is 2.6207 mm, the focal length f2 of the second lens 220 is -5.9619 mm, The focal length f4 of the fourth lens 240 is -12.446 mm and the focal length f5 of the fifth lens 250 is -373.7857 mm; 260 is -16.0742 mm, and the total focal length f of the imaging optical system is 3.5947 mm.

The lens characteristics (radius of curvature, thickness of the lens, distance between lenses, index, Abbe number, effective radius) of each lens are shown in Fig.

In the second embodiment of the present invention, the first lens 210 has a positive refractive power and a convex meniscus shape toward the object side. For example, the first surface of the first lens 210 is convex in the paraxial area, and the second surface of the first lens 210 is concave in the paraxial area.

The second lens 220 has a negative refractive power and has a meniscus shape convex to the object side. For example, the first surface of the second lens 220 is convex in the paraxial area, and the second surface of the second lens 220 is concave in the paraxial area.

The third lens 230 has a positive refractive power and a meniscus shape convex upward. For example, the first surface of the third lens 230 is concave in the paraxial area, and the second surface of the third lens 230 is convex in the paraxial area.

The fourth lens 240 has a negative refractive power and has a concave shape on both sides. For example, the first and second surfaces of the fourth lens 240 are concave in a paraxial area.

The fifth lens 250 has a negative refracting power and has a concave shape on both sides. For example, the first and second surfaces of the fifth lens 250 are concave in the paraxial area.

The sixth lens 260 has a negative refractive power and a convex meniscus shape on the object side. For example, the first surface of the sixth lens 260 is convex in the paraxial area, and the second surface of the sixth lens 260 is concave in the paraxial area.

Also, at least one inflection point is formed on at least one of the first surface and the second surface of the sixth lens 260.

On the other hand, each surface of the first lens 210 to the sixth lens 260 has an aspheric surface coefficient as shown in FIG. For example, the first lens 210, the second lens 220, the third lens 230, the fifth lens 250, and the sixth lens 260 may have a first surface and a second surface, All sides are aspherical. The first surface of the fourth lens 240 is a spherical surface, and the second surface of the fourth lens 240 is an aspherical surface.

The diaphragm may be disposed between the first lens 210 and the second lens 220.

The imaging optical system thus configured can have the aberration characteristics shown in Figs. 7 and 8. Fig.

An imaging optical system according to a third embodiment of the present invention will be described with reference to Figs. 11 to 15. Fig.

The imaging optical system according to the third embodiment of the present invention includes a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, An infrared filter 370, and an image sensor 380, as shown in FIG.

14, the focal length f1 of the first lens 310 is 2.6206 mm, the focal length f2 of the second lens 320 is -5.9609 mm, The focal length f4 of the fourth lens 340 is -12.4783 mm, the focal length f5 of the fifth lens 350 is -362.3299 mm, the focal length f3 of the fifth lens 350 is 13.0307 mm, 360 is -16.1613 mm, and the total focal length f of the imaging optical system is 3.5943 mm.

Here, the lens characteristics (radius of curvature, thickness of the lens or distance between lenses, index, Abbe number, effective radius) of each lens are as shown in Fig.

In the third embodiment of the present invention, the first lens 310 has a positive refractive power and a convex meniscus shape toward the object side. For example, the first surface of the first lens 310 is convex in the paraxial area, and the second surface of the first lens 310 is concave in the paraxial area.

The second lens 320 has a meniscus shape having a negative refractive power and convex on the object side. For example, the first surface of the second lens 320 is convex in the paraxial area, and the second surface of the second lens 320 is concave in the paraxial area.

The third lens 330 has a positive refractive power and a meniscus shape convex upward. For example, the first surface of the third lens 330 is concave in the paraxial area, and the second surface of the third lens 330 is convex in the paraxial area.

The fourth lens 340 has a negative refractive power and has a concave shape on both sides. For example, the first and second surfaces of the fourth lens 340 are concave in the paraxial area.

The fifth lens 350 has a negative refractive power and has a concave shape on both sides. For example, the first and second surfaces of the fifth lens 350 are concave in a paraxial area.

The sixth lens 360 has a negative refractive power and a convex meniscus shape on the object side. For example, the first surface of the sixth lens 360 is convex in the paraxial area, and the second surface of the sixth lens 360 is concave in the paraxial area.

The sixth lens 360 has at least one inflection point formed on at least one of the first surface and the second surface.

On the other hand, each surface of the first lens 310 to the sixth lens 360 has an aspheric surface coefficient as shown in FIG. For example, the first lens 310, the second lens 320, the third lens 330, the fifth lens 350, and the sixth lens 360 may have a first surface and a second surface, All sides are aspherical. Also, the first surface of the fourth lens 340 is a spherical surface, and the second surface of the fourth lens 340 is an aspherical surface.

The diaphragm may be disposed between the first lens 310 and the second lens 320.

The imaging optical system thus constructed can have the aberration characteristics shown in Figs. 12 and 13. Fig.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be apparent to those skilled in the art that changes or modifications may fall within the scope of the appended claims.

110, 210, and 310: a first lens
120, 220, 320: a second lens
130, 230, 330: Third lens
140, 240, 340: fourth lens
150, 250, 350: fifth lens
160, 260, 360: Sixth lens
170, 270, 370: Infrared filter
180, 280, 380: image sensor

Claims (16)

A first lens to a sixth lens arranged in order from the object side; And
And an image sensor for converting an image of an object incident through the first lens to the sixth lens into an electric signal,
The object side surface of any one of the first lens to the sixth lens is a spherical surface, the upper surface is an aspherical surface,
The other lenses are aspherical surfaces on the object side and the upper side,
The refractive index of any one of the lenses disposed closer to the object side than the spherical surface of the object side is the largest among the first lens to the sixth lens,
A distance from the object side surface of the first lens to the image surface of the image sensor is TTL,
When half of the diagonal length of the image sensor is ImgH,
TTL / (2 * ImgH) < 0.75.
The method according to claim 1,
And said lens whose object side is a spherical surface is a fourth lens.
The method according to claim 1,
Wherein the lens having the largest refractive index among the first lens and the sixth lens is a second lens.
The method according to claim 1,
When the focal length of the first lens is f1 and the focal length of the third lens is f3,
2.0 < f3 / f1 < 6.0.
The method according to claim 1,
The total focal length of the imaging optical system is f, the thickness of the paraxial area of the third lens is CT3, the thickness of the paraxial area of the fourth lens is CT4, and the thickness of the paraxial area of the fifth lens is CT5 time,
f / (CT3 + CT4 + CT5) < 4.0.
The method according to claim 1,
When the total focal length of the imaging optical system is f, the focal length of the fifth lens is f5, and the focal length of the sixth lens is f6,
| f / f5 | + | f / f6 | &Lt; 1.0.
The method according to claim 1,
Wherein the first lens to the sixth lens have positive, negative, positive, negative, negative, and negative refractive powers in order.
The method according to claim 1,
Wherein the first lens has a positive refractive power, a convex meniscus shape toward the object side,
Wherein the second lens has a meniscus shape having a negative refractive power and being convex on the object side.
The method according to claim 1,
The second lens has a meniscus shape having a negative refractive power and convex on the object side,
Wherein the third lens has a positive refractive power and a meniscus shape convex upward.
The method according to claim 1,
And the fourth lens has a negative refractive power.
The method according to claim 1,
And the fourth lens is concave on both sides.
The method according to claim 1,
And the fifth lens has a negative refractive power.
The method according to claim 1,
And the fifth lens is concave on both sides.
The method according to claim 1,
Wherein the sixth lens has a meniscus shape having a negative refractive power and being convex on the object side.
The method according to claim 1,
And a diaphragm disposed between the first lens and the second lens.
A first lens to a sixth lens arranged in order from the object side; And
And an image sensor for converting an image of an object incident through the first lens to the sixth lens into an electric signal,
The object side surface of the fourth lens is a spherical surface, the upper surface is an aspherical surface,
The other lenses are aspherical surfaces on the object side and the upper side,
The refractive index of the second lens is greater than 1.66, the refractive index of the second lens is the largest among the first lens to the sixth lens,
A distance from the object side surface of the first lens to the image surface of the image sensor is TTL,
When half of the diagonal length of the image sensor is ImgH,
TTL / (2 * ImgH) < 0.75.

Images