Patent ID: 12228794

Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be apparent to one of ordinary skill in the art. The sequences of operations described herein are merely examples, and are not limited to those set forth herein, but may be changed as will be apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Also, descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted for increased clarity and conciseness.

The features described herein may be embodied in different forms, and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will convey the full scope of the disclosure to one of ordinary skill in the art.

In the following description, a first lens refers to a lens closest to an object, while a sixth lens refers to a lens closest to an image sensor. In addition, a first surface of each lens refers to a surface thereof closest to an object side (or an object-side surface) and a second surface of each lens refers to a surface thereof closest to an image side (or an image-side surface). Further, all numerical values of radii of curvature, thicknesses, and the like, of lenses are expressed in millimeters (mm).

Further, a paraxial region refers to a very narrow region in the vicinity of an optical axis.

In addition, TTL is a distance from an object-side surface of the first lens to an image plane of the image sensor, SL is a distance from a stop limiting an amount of light incident to the optical system that is transmitted to the image plane of the image sensor, ImgH is half of a diagonal length of the image plane of the image sensor, BFL is a distance from an image-side surface of a lens closest to the image side to the image plane of the image sensor, and EFL is an entire focal length of the optical system.

An optical system according to example embodiments may include six lenses, for example. That is, the optical system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens.

However, the optical system is not limited to including only six lenses, and may include other components, if necessary. For example, the optical system may further include a stop configured to control an amount of light transmitted to the image sensor. In addition, the optical system may further include an infrared cut-off filter configured to filter infrared light. Further, the optical system may include an image sensor configured to convert an image of a subject incident thereon into electrical signals. Also, the optical system may further include a gap maintaining member configured to adjust a gap between lenses.

In the optical system according to example embodiments, the first to sixth lenses may be formed of plastic.

In addition, at least one of the first to sixth lenses may have an aspheric surface, and each of the first to sixth lenses may have at least one aspheric surface. That is, at least one of the first and second surfaces of the first to sixth lenses may be aspheric. Here, the aspheric surfaces of the first to sixth lenses may be represented by the following Equation 1:

Z=cY21+1-(1+K)⁢c2⁢Y2+AY4+BY6+CY8+DY10+EY12+FY14+….[Equation⁢1]

In Equation 1, c is a curvature (an inverse of a radius of curvature) at an apex of the lens, K is a conic constant, and Y is a distance from a certain point on the aspheric surface of the lens to an optical axis in a direction perpendicular to the optical axis. Constants A to F are aspheric coefficients. Z is a distance between the point on the aspheric surface at the distance Y and a tangential plane meeting the apex of the aspheric surface of the lens.

The first to sixth lenses may respectively have, in sequential order from the object side, negative refractive power, positive refractive power, negative refractive power, negative refractive power, positive refractive power, and negative refractive power.

The optical system configured as described above may improve optical performance through aberration improvement. Effects by respective configurations of lenses will be described below.

The optical system according to example embodiments may satisfy Conditional Expression 1.
TTL/(ImgH*2)≤0.75  [Conditional Expression 1]
In Conditional Expression 1, TTL is a distance from the object-side surface of the first lens to the image plane of the image sensor, and ImgH is half of a diagonal length of the image plane of the image sensor.

The optical system according to example embodiments may satisfy Conditional Expression 2.
TTL/(ImgH*2)≤0.68  [Conditional Expression 2]

The optical system according to example embodiments may satisfy Conditional Expression 3.
−5<f1/EFL<−4.6  [Conditional Expression 3]
In Conditional Expression 3, f1 is a focal length of the first lens, and EFL is an entire focal length of the optical system.

The optical system according to example embodiments may satisfy Conditional Expression 4.
2.3<f1/f3<2.6  [Conditional Expression 4]
In Conditional Expression 4, f1 is the focal length of the first lens, and f3 is a focal length of the third lens.

The optical system according to example embodiments may satisfy Conditional Expression 5.
BFL/EFL<0.31  [Conditional Expression 5]
In Conditional Expression 5, BFL is a distance from an image-side surface of the sixth lens to the image plane of the image sensor, and EFL is the entire focal length of the optical system.

The optical system according to example embodiments may satisfy Conditional Expression 6.
0.95<ER1/ER6<1.05  [Conditional Expression 6]
In Conditional Expression 6, ER1 is an effective radius of the object-side surface of the first lens, and ER6 is an effective radius of an image-side surface of the third lens.

The optical system according to example embodiments may satisfy Conditional Expression 7.
79<FOV<83  [Conditional Expression 7]
In Conditional Expression 7, FOV is a field of view of the optical system. Here, the field of view of the optical system is indicated by degrees.

Next, the first to sixth lenses configuring optical systems according to example embodiments will be described.

The first lens may have negative refractive power. In addition, the first lens may have a meniscus shape of which an object-side surface is convex. In detail, a first surface of the first lens may be convex in the paraxial region, and a second surface of the first lens may be concave in the paraxial region.

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

The second lens may have positive refractive power. In addition, the first and second surfaces of the second lens may be convex. In detail, the first and second surfaces of the second lens may be convex in the paraxial region.

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

The third lens may have negative refractive power. In addition, the third lens may have a meniscus shape of which an object-side surface is convex. In detail, a first surface of the third lens may be convex in the paraxial region, and a second surface of the third lens may be concave in the paraxial region.

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

The fourth lens may have negative refractive power. In addition, the fourth lens may have a meniscus shape of which an image-side surface is convex. In detail, a first surface of the fourth lens may be concave in the paraxial region, and a second surface of the fourth lens may be convex in the paraxial region.

At least one of the first and second surfaces of the fourth lens may be aspheric. For example, the first and second surfaces of the fourth lens may be aspheric.

The fifth lens may have positive refractive power. In addition, the fifth lens may have a meniscus shape of which an image-side surface is convex. In detail, a first surface of the fifth lens may be concave in the paraxial region, and a second surface of the fifth lens may be convex in the paraxial region.

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

The sixth lens may have negative refractive power. In addition, the sixth lens may have a meniscus shape of which an object-side surface is convex. In detail, a first surface of the sixth lens may be convex in the paraxial region, and a second surface of the sixth lens may be concave in the paraxial region.

In the optical system according to example embodiments, the first lens may have negative refractive power to realize a wide field of view, and the optical system may be designed using retro focus type lenses.

The wider the field of view is, the shorter the focal length is. In this case, a back focus, which is a distance between a lens closest to the image side and the image plane of the image sensor, may be shortened, and it may be difficult to secure a space in which the infrared cut-off filter may be disposed between the lens closest to the image side and the image plane of the image sensor.

Therefore, according to example embodiments, the optical system may be designed using the retro focus type lenses to make the back focus relatively long while realizing a wide field of view, whereby a space in which the infrared cut-off filter may be disposed may be secured between the sixth lens and the image sensor. Here, in order to prevent an increase in an entire length of the optical system due to a relative increase in the back focus, a synthetic focal length of the second and third lenses may be shorter than the entire focal length of the optical system.

The optical system according to example embodiments may easily correct chromatic aberration. Chromatic aberration is generated due to a difference in refractive indices depending on wavelengths, and chromatic aberration is generated because light having a long wavelength is focused on an area more distant from the lens as compared with light having a relatively short wavelength after it passes through the lens. Therefore, in a case in which chromatic aberration is large, light may be diffused depending on wavelengths, and thus, it is necessary to correct the chromatic aberration.

In the optical system according to example embodiments, the first to third lenses may have different refractive powers. For example, the first lens may have negative refractive power, the second lens may have positive refractive power, and the third lens may have negative refractive power. Therefore, the first to third lenses may have positive or negative refractive power in an alternating sequence toward the object side. Since the lenses adjacent to each other have refractive powers opposite to each other, light may diverge in any one of the lenses and converge in the other lenses. Therefore, light having different wavelengths may be collected on the same focus.

In the optical system according to example embodiments, gaps among the first to third lenses may be relatively narrow in order to significantly increase a chromatic aberration correction effect. For example, in the paraxial region, a gap between the first and second lenses and a gap between the second and third lenses may be narrower than a gap between other adjacent lenses. Further still, the gap between the first and second lenses and the gap between the second and third lenses may be narrower than each of the other gaps between lenses among the third to sixth lenses. According to a further embodiment, in the paraxial region, a sum of a gap between the first and second lenses and a gap between the second and third lenses may be narrower than a gap between other adjacent lenses. More specifically, the sum of the gap between the first and second lenses and the gap between the second and third lenses may be narrower than each of the other gaps between lenses among the third to sixth lenses. Therefore, an effect similar to that of a triply bonded lens in which the first to third lenses are bonded to each other may be achieved, and thus the chromatic aberration correction effect may be significantly increased.

In addition, since the gaps among the first to third lenses are narrow, the entire length of the optical system may be decreased. As a result, a slim optical system may be provided.

As described above, the second lens of the optical system, according to example embodiments, may have positive refractive power, and both surfaces thereof may be convex. Here, an absolute value of a radius of curvature of an object-side surface of the second lens may be less than that of a radius of curvature of an image-side surface of the second lens.

For example, when the radius of curvature of the object-side surface of the second lens is r3 and the radius of curvature of the image-side surface of the second lens is r4, |r4/r3|>20 may be satisfied. Therefore, a curvature of the object-side surface of the second lens may be relatively larger than that of the image-side surface of the second lens, and a curvature of the image-side surface of the second lens may be relatively smaller than that of the object-side surface of the second lens. According to the configuration as described above, spherical aberration may be easily corrected.

In the optical system according to example embodiments, the third lens may have the meniscus shape of which the object-side surface is convex, and the fourth and fifth lenses may have the meniscus shape of which the image-side surface is convex. As described above, the shapes of the third and fourth lenses may be symmetrical to each other or the shapes of the third and fifth lenses may be symmetrical to each other, thereby allowing light incident to the optical system to be vertically incident to the image plane of the image sensor. Therefore, in the optical system according to example embodiments, a difference between brightness of an image at a central portion of an image sensor and brightness of an image at edge portions of the image sensor may be decreased. Therefore, a lens shading phenomenon in which the image at the edge portions of the image sensor is relatively dark may be alleviated.

An optical system100according to a first example embodiment will be described with reference toFIGS.1through5. The optical system100includes a first lens110, a second lens120, a third lens130, a fourth lens140, a fifth lens150, and a sixth lens160, and further includes a stop (STOP), an infrared cut-off filter170, and an image sensor180.

Respective characteristics (radii of curvature, thicknesses, refractive indices, and Abbe numbers) of lenses110to160and the infrared cut-off filter170are illustrated inFIG.4. InFIG.4, Surfaces S1and S2indicate the first surface (object-side surface) and the second surface (image-side surface), respectively, of the first lens110, and Surfaces S3and S4indicate the first and second surfaces, respectively, of the second lens120. Similarly, Surfaces S5to S12indicate the first and second surfaces of the third to sixth lenses130-160, respectively. In addition, Surfaces S13and S14indicate first and second surfaces, respectively, of the infrared cut-off filter170.

The first lens110has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the first lens110is convex in the paraxial region, and a second surface of the first lens110is concave in the paraxial region.

The second lens120has positive refractive power and has a meniscus shape of which first and second surfaces are convex. For example, first and second surfaces of the second lens120are convex in the paraxial region.

The third lens130has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the third lens130is convex in the paraxial region, and a second surface of the third lens130is concave in the paraxial region.

The fourth lens140has negative refractive power and has a meniscus shape of which an image-side surface is convex. For example, a first surface of the fourth lens140is concave in the paraxial region, and a second surface of the fourth lens140is convex in the paraxial region.

The fifth lens150has positive refractive power and has a meniscus shape in which it is convex toward the image. For example, a first surface of the fifth lens150is concave in the paraxial region, and a second surface of the fifth lens150is convex in the paraxial region.

The sixth lens160has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the sixth lens160is convex in the paraxial region, and a second surface of the sixth lens160is concave in the paraxial region. In addition, the sixth lens160has at least one inflection point formed on at least one of the first or second surfaces thereof.

By way of example, the respective surfaces of the first to sixth lenses110to160have aspheric coefficients as illustrated inFIG.5.

The stop includes, for example, a first stop configured to limit an amount of light incident to the optical system that is transmitted through the first lens110and a second stop configured to block light at a portion at which excessive aberration is generated. The first stop is disposed in front of the object-side surface of the first lens110, and the second stop is disposed among the first to fourth lenses110to140.

In addition, by way of example, the optical system100has aberration characteristics as illustrated inFIGS.2and3.

An optical system200according to a second example embodiment will be described with reference toFIGS.6through10. The optical system200includes a first lens210, a second lens220, a third lens230, a fourth lens240, a fifth lens250, and a sixth lens260, and further includes the stop (STOP), an infrared cut-off filter270, and an image sensor280.

Respective characteristics (radii of curvature, thicknesses, refractive indices, and Abbe numbers) of lenses210to260and the infrared cut-off filter270are illustrated inFIG.9. InFIG.9, Surfaces S1and S2indicate the first surface (object-side surface) and the second surface (image-side surface), respectively, of the first lens210, and Surfaces S3and S4indicate the first and second surfaces, respectively, of the second lens220. Similarly, Surfaces S5to S12indicate the first and second surfaces of the third to sixth lenses230-260, respectively. In addition, Surfaces S13and S14indicate first and second surfaces, respectively, of the infrared cut-off filter270.

The first lens210has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the first lens210is convex in the paraxial region, and a second surface of the first lens210is concave in the paraxial region.

The second lens220has positive refractive power and has a meniscus shape of which first and second surfaces are convex. For example, the first and second surfaces of the second lens220are convex in the paraxial region.

The third lens230has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the third lens230is convex in the paraxial region, and a second surface of the third lens230is concave in the paraxial region.

The fourth lens240has negative refractive power and has a meniscus shape of which an image-side surface is convex. For example, a first surface of the fourth lens240is concave in the paraxial region, and a second surface of the fourth lens140is convex in the paraxial region.

The fifth lens150has positive refractive power and has a meniscus shape in which it is convex toward the image. For example, a first surface of the fifth lens150is concave in the paraxial region, and a second surface of the fifth lens250is convex in the paraxial region.

The sixth lens260has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the sixth lens260is convex in the paraxial region, and a second surface of the sixth lens260is concave in the paraxial region. In addition, the sixth lens260has at least one inflection point formed on at least one of the first or second surfaces thereof.

By way of example, the respective surfaces of the first to sixth lenses210to260have aspheric coefficients as illustrated inFIG.10.

The stop includes, for example, a first stop configured to limit an amount of light incident to the optical system that is transmitted through the first lens210and a second stop configured to block light at a portion at which excessive aberration is generated. For example, the first stop is disposed in front of the object-side surface of the first lens210, and the second stop is disposed among the first to fourth lenses210to240.

In addition, by way of example, the optical system200has aberration characteristics as illustrated inFIGS.7and8.

An optical system300according to a third example embodiment will be described with reference toFIGS.11through15. The optical system300includes a first lens310, a second lens320, a third lens330, a fourth lens340, a fifth lens350, and a sixth lens360, and further includes the stop (STOP), an infrared cut-off filter370, and an image sensor380.

Respective characteristics (radii of curvature, thicknesses, refractive indices, and Abbe numbers) of lenses310to360and the infrared cut-off filter370are illustrated inFIG.14. InFIG.14, Surfaces S1and S2indicate the first surface (object-side surface) and the second surface (image-side surface), respectively, of the first lens310, and Surfaces S3and S4indicate the first and second surfaces, respectively, of the second lens320. Similarly, Surfaces S5to S12indicate the first and second surfaces of the third to sixth lenses330-360, respectively. In addition, Surfaces S13and S14indicate first and second surfaces, respectively, of the infrared cut-off filter370.

The first lens310has negative refractive power and has a meniscus shape of which an image-side surface is convex. For example, a first surface of the first lens310is convex in the paraxial region, and a second surface of the first lens310is concave in the paraxial region.

The second lens320has positive refractive power and has a meniscus shape of which first and second surfaces are convex. For example, the first and second surfaces of the second lens320may be convex in the paraxial region.

The third lens330has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the third lens330is convex in the paraxial region, and a second surface of the third lens330is concave in the paraxial region.

The fourth lens340has negative refractive power and has a meniscus shape of which an image-side surface is convex. For example, a first surface of the fourth lens340is concave in the paraxial region, and a second surface of the fourth lens340is convex in the paraxial region.

The fifth lens350has positive refractive power and has a meniscus shape in which it is convex toward the image. For example, a first surface of the fifth lens350is concave in the paraxial region, and a second surface of the fifth lens is convex in the paraxial region.

The sixth lens360has negative refractive power and has a meniscus shape of which an object-side surface is convex. For example, a first surface of the sixth lens360is convex in the paraxial region, and a second surface of the sixth lens360is concave in the paraxial region. In addition, the sixth lens360has at least one inflection point formed on at least one of the first or second surfaces thereof. By way of example, the respective surfaces of the first to sixth lenses310to360have aspheric coefficients as illustrated inFIG.15.

The stop includes, for example, a first stop configured to limit an amount of light incident to the optical system that is transmitted through the first lens310and a second stop configured to block light at a portion at which excessive aberration is generated. For example, the first stop is disposed in front of the object-side surface of the first lens310, and the second stop is disposed among the first to fourth lenses310to340.

In addition, by way of example, the optical system300has aberration characteristics as illustrated inFIGS.12and13.

It can be appreciated from Table 1 that the optical systems100to300satisfy Conditional Expressions 1 to 7 described above. Therefore, optical performance of the lenses may be improved, and the optical system may be provided with a wide field of view and a slim construction.

TABLE 1OpticalOpticalOpticalSystem 100System 200System 300TTL5.305.303.21SL5.065.053.06EFL4.354.302.66BFL1.191.190.79f1−21.50−20.08−13.11f3−8.46−8.46−5.16IMGH3.683.682.39FOV79.3079.9382.07TTL/(IMGH*2)0.720.720.67f1/EFL−4.94−4.67−4.92f1/f32.542.372.54BFL/EFL0.270.280.30ER1/ER60.97885271.03662831.0098015

As set forth above, according to example embodiments, an optical system having a wide field of view and a slim construction may be provided. In addition, an aberration improvement effect may be increased, and high resolution may be achieved. Further, a difference between brightness of an image at a central portion of the image sensor and brightness of an image at edge portions of the image sensor may be decreased.

While this disclosure includes specific examples, it will be apparent to one of ordinary skill in the art that various changes in form and details may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only, and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.