Optical system

Abstract

An embodiment of the present invention discloses an optical system comprising: a first lens to an eighth lens, the lenses being sequentially arranged along an optical axis in a direction from an object side to a sensor side, wherein the first lens has positive refractive power and a convex surface on the object side, the second lens has negative refractive power and a concave surface on the sensor side, at least one of the object side surface and the sensor side surface of the sixth lens has a refractive point, the seventh lens has positive refractive power and a convex surface on the sensor side, the eighth lens has negative refractive power, and the object side surface and the sensor side surface of the eighth lens have at least one refractive point, and the center thickness of the seventh lens may be the thickest among the center thicknesses of the first lens to the eighth lens.

Description

Technical Field

[0001] This embodiment relates to an optical system for high resolution. Prior Art

[0002] A camera module captures an object and stores it as an image or video, and is installed in various applications. Specifically, camera modules are manufactured in extremely small sizes and are applied not only to portable devices such as smartphones, tablet PCs, and laptop computers, but also to drones and vehicles to provide various functions. For example, the optical system of a camera module may include an imaging lens for forming an image and an image sensor for converting the formed image into an electrical signal. In this case, the camera module can perform an autofocus (AF) function of aligning the focal length of the lens by automatically adjusting the distance between the image sensor and the imaging lens, and can perform a zoom function of magnifying or reducing by increasing or decreasing the magnification of a distal object via a zoom lens. In addition, the camera module employs an image stabilization (IS) technology to correct or prevent image stabilization problems caused by an unstable fixing device or camera movement caused by user movement. The most important component for this camera module to obtain an image is the imaging lens for forming the image. Recently, there has been an increasing concern for high performance such as high image quality and high resolution, and research is being conducted on optical systems including five or six lenses to achieve this. For example, research is being conducted on implementing a high-efficiency optical system using a plurality of imaging lenses having positive (+) and / or negative (-) refractive powers. However, when configuring a plurality of lenses, there is a problem in that it is difficult to derive excellent optical properties and aberration properties. Therefore, a new optical system capable of solving the problems described above is needed. Summary of the Invention Problems to be Solved by the Invention

[0003] Embodiments of the present invention provide an optical system with improved optical properties. Embodiments of the present invention provide a wide-angle optical system having at least eight lenses. Embodiments of the present invention provide an optical system in which the object-side surface and the sensor-side surface of at least eight lenses have aspherical surfaces. Embodiments of the present invention provide an optical system in which at least one lens having a positive (+) refractive power and at least four lenses having a negative (-) refractive power are aligned with respect to the optical axis among at least eight lenses. Means for Solving the Problems

[0004] An 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, a sixth lens, a seventh lens, and an eighth lens, which are arranged sequentially along the optical axis from the object side to the sensor side. The first lens has negative refractive power and has a concave object-side surface on the optical axis. The fourth lens has both a convex object-side surface and a sensor-side surface on the optical axis and has a low refractive index. The fifth lens has a concave sensor-side surface on the optical axis and has a high refractive index. The seventh lens has positive refractive power and has a convex sensor-side surface on the optical axis. The eighth lens has negative (-) refractive power and has a convex sensor-side surface on the optical axis. The optical system satisfies Equation 1: [Equation 1] 0.5>f4 / F<1.5, where f4 is the focal length of the fourth lens and F is the effective focal length of the optical system.

[0005] According to an embodiment of the present invention, at least one of equations 2, 3 and 4 satisfies: [Equation 2] 1.4>nd1<1.6, where nd1 is the refractive index of the first lens at 587nm; and [Equation 3] 10>vd5<30, where vd5 is the Abbe number of the fifth lens; [Equation 4] F / EPD>1, where EPD can be the diameter of the entrance pupil of the optical system.

[0006] According to an embodiment of the present invention, at least one of equations 5, 6 and 7 satisfies: [Equation 5] 1>T1 / T3<5, [Equation 6] 1>T4 / T5<5 and [Equation 7] 1>T7 / T8<5, where T1 is the center thickness of the first lens, T3 is the center thickness of the third lens, T4 is the center thickness of the fourth lens, T5 is the center thickness of the fifth lens, T7 is the center thickness of the seventh lens, and T8 may be the center thickness of the eighth lens.

[0007] According to an embodiment of the present invention, at least one of equations 8 and 9 satisfies: [Equation 8]|f5|>|f4|, [Equation 9]0.5>|f7| / |f8|<2, where f4 can be the focal length of the fourth lens, f5 can be the focal length of the fifth lens, f7 can be the focal length of the seventh lens, and f8 can be the focal length of the eighth lens.

[0008] According to an embodiment of the present invention, the center thickness of the first lens is thicker than the center thickness of each of the second to eighth lenses, and the optical axis spacing between the first and second lenses can be greater than the optical axis spacing between two adjacent lenses in the second to eighth lenses.

[0009] According to an embodiment of the present invention, the number of lenses among the first to eighth lenses having a convex object-side surface on the optical axis may be four or more, and the number of lenses having a concave object-side surface may be four or less.

[0010] According to an embodiment of the present invention, the number of lenses among the first to eighth lenses having a convex sensor-side surface on the optical axis may be four or more, and the number of lenses having a concave sensor-side surface may be four or less. The sensor-side surfaces of the first, fifth, sixth, and eighth lenses may be concave. Among the first to eighth lenses, the number of lenses having an Abbe number of 50 or more may be five or more, and the number of lenses having an Abbe number of 50 or more may be three or less.

[0011] According to an embodiment of the present invention, among the first to eighth lenses, the number of lenses having a refractive index of 1.6 or more may be three or more, and the number of lenses having a refractive index less than 1.6 may be five or less. The number of lenses among the first to eighth lenses having a center thickness of 0.5 mm or more is three or more, and the number of lenses having a thickness less than 0.5 mm is five or less. When the center thicknesses of the first, second, and third lenses are T1, T2, and T3, the following relationship may be satisfied: T3 < T2 < T1. When the center thicknesses of the third to sixth lenses are T3, T4, T5, and T6, the following relationship may be satisfied: T5 T3 < T6 < T4.

[0012] According to an embodiment of the present invention, the focal length of the second lens among the first to eighth lenses may be the largest. Relative to the third lens, the effective diameter of the object-side or sensor-side surface decreases in the order of the first lens, the second lens, and the third lens, and relative to the third lens, the effective diameter of the object-side or sensor-side surface increases in the order of the third lens, the fourth lens, the fifth lens, and the sixth lens.

[0013] An 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, a sixth lens, a seventh lens, and an eighth lens. These lenses are sequentially arranged along the optical axis in the direction from the object side to the sensor side. The first lens has a negative refractive power and has a concave object-side surface on the optical axis, and the fourth lens has both a convex object-side and a convex sensor-side surface on the optical axis and has a low refractive index. The fifth lens has a concave sensor-side surface on the optical axis and has a high refractive index. The seventh lens has a positive refractive power and has a convex sensor-side surface on the optical axis, and the eighth lens has a negative (-) refractive power and has a convex sensor-side surface on the optical axis. Among the first to eighth lenses, the number of lenses having a convex object-side surface on the optical axis is four or more, the number of lenses having a concave sensor-side surface is five or less, and the number of surfaces having a bending point among the object-side and sensor-side surfaces of the first to eighth lenses can be four or more.

[0014] According to an embodiment of the present invention, it includes an image sensor disposed on the sensor side of the eighth lens and an optical filter disposed between the image sensor and the eighth lens, and may include at least one of the above equations 1 to 4. Effect of the Invention

[0015] The optical system according to an embodiment of the present invention can correct aberration characteristics and achieve a thin optical system. Therefore, the optical system can be miniaturized and high quality and high resolution can be achieved. The optical system according to an embodiment of the present invention can prevent unnecessary light from entering the optical system. Therefore, it is possible to improve the performance of the optical system by reducing aberration. Brief Explanation of Drawings

[0016] FIG. 1 is a block diagram of an optical system according to a first embodiment of the present invention.

[0017] FIG. 2 is a graph showing longitudinal spherical aberration, astigmatism field curvature, and distortion aberration in the optical system of FIG. 1.

[0018] FIG. 3 is a block diagram of an optical system according to a second embodiment of the present invention.

[0019] FIG. 4 is a diagram showing spherical aberration, astigmatism field curvature, and distortion aberration in the optical system of FIG. 3.

[0020] FIG. 5 is a block diagram of an optical system according to a third embodiment of the present invention.

[0021] Figure 6 shows the spherical aberration, astigmatism curves, and distortion aberrations in the optical system of Figure 5.

[0022] Figure 7 is a perspective view of a mobile terminal having an optical system according to an embodiment of the present invention. Implementation

[0023] In the following description, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. The spirit of the invention is not limited to the embodiments described, and may be implemented in various other forms, with one or more components selectively combined and substituted for use within the scope of the spirit of the invention. Furthermore, unless specifically defined and explicitly described, the terminology (including technical and scientific terms) used in the embodiments of the invention can be interpreted in the meaning commonly understood by those skilled in the art to which this invention pertains, and the meaning of commonly used terms, such as those defined in dictionaries, should be interpreted taking into account the contextual meaning of the relevant art. Moreover, the terminology used in the embodiments of the invention is for explaining these embodiments and is not intended to limit the invention. In this specification, unless otherwise specifically stated in a phrase, the singular form may also include the plural form, and where at least one (or more) of A and / or B, C is stated, it may include one or more of all combinations that can be combined with A, B, and C. In describing the components of embodiments of the invention, terms such as first, second, A, B, (a), and (b) may be used. Such terms are used only to distinguish one component from another, and can be determined without relying on the nature, sequence, or process of the corresponding constituent elements. Furthermore, when describing a component as "connected," "coupled," or "joined" to another component, the description may include not only direct connection, coupling, or joining to another component, but also connection, coupling, or joining to another component via a link between the two components. Additionally, when describing something as formed or placed "above" or "below" each component, the description includes not only when the two components are in direct contact with each other, but also when one or more other components are formed or placed between the two components. Moreover, when expressed as "above" or "below," it can refer to the downward and upward directions relative to a component.

[0024] In the description of this invention, the first lens refers to the lens closest to the object side among a plurality of lenses aligned with the optical axis, and the last lens refers to the lens closest to the image side (or sensor side) among a plurality of lenses aligned with the optical axis. In the description of this invention, unless otherwise specified, all measurements of the lens, such as radius, effective diameter, thickness, distance, back focal length (BFL), total track length, or total top length (TTL), are in mm. In this invention, the shape of the lens is shown based on its optical axis. For example, a convex surface on the object side or sensor side of the lens means a convex surface near the optical axis on the object side or sensor side of the lens, but not necessarily a convex surface around the optical axis. Therefore, even when describing a convex surface on the object side of the lens, the portion of the lens on the object side surrounding the optical axis may be concave. It should be noted in this specification that the thickness and radius of curvature of the lens are measured based on the optical axis of the lens. In addition, "object-side surface" can refer to the surface of the lens facing the object side relative to the optical axis, and "image side" refers to the surface of the lens facing the imaging surface relative to the optical axis.

[0025] An optical system according to embodiments of the present invention may include a plurality of lenses. Specifically, the optical system according to the first to third embodiments may include at least eight lenses. As resolution increases, the size of the image sensor also increases, and the number of lenses gradually increases according to the resolution of the image sensor. Embodiments of the present invention are intended to provide a high-resolution optical system using at least eight lenses.

[0026] Referring to FIG1, the optical system according to the first embodiment may include, for example, a first lens 111, a second lens 112, a third lens 113, a fourth lens 114, a fifth lens 115, a sixth lens 116, a seventh lens 117, and an eighth lens 118, which are arranged sequentially from the object side to the image side. The optical system may include an optical filter 192 and an image sensor 190. An optical system having a plurality of lenses 111 to 118 may be defined as a lens optical system, and an optical system further including lenses 111 to 118, an optical filter 192, and an image sensor 190 may be defined as a camera module. A camera module may include at least one of the following: a circuit board, at least one lens holder supporting at least one lens or two or more lenses, and one or more drive components for moving the lens holder in the optical axis direction and / or in a direction perpendicular to the optical axis.

[0027] The first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 can be arranged sequentially along the optical axis Lx of the optical system. The light corresponding to the image information of the object is the first lens 111, the second lens 112, the third lens 113, the fourth lens 114, the fifth lens 115, the sixth lens 116, the seventh lens 117, and the eighth lens 118, which passes through the optical filter 192 and is focused on the image sensor 190, and can be obtained as an electrical signal.

[0028] Each of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 may include an effective region and an ineffective region. The effective region may be the area where light is effectively incident or emitted for each lens. That is, the effective region may be the area where incident light is refracted to achieve optical properties. The ineffective region may be located around the effective region. The ineffective region may be the area where light is not incident. That is, the ineffective region may be the area with optical properties independent of the optical system. Furthermore, the ineffective region may be the area fixed to a housing (not shown) for the lens, or the area where light is blocked by light-blocking units or spacers. Here, the object-side surface may be the incident surface, and the sensor-side surface may be the image-side surface or the exit-side surface.

[0029] At least one or more of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118, or at least one or more of the fifth to eighth lenses 115, 116, 117, 118, may have an effective diameter in a first direction orthogonal to the optical axis Lx, which is smaller than the effective diameter in a second direction orthogonal to the first direction. Such lenses may be provided in a non-circular shape, having a diameter in the second direction and a distance smaller than the diameter in the first direction.

[0030] The optical system according to Figure 1 may include an aperture ST for adjusting the amount of incident light. The aperture ST may be disposed between two lenses selected from the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118. For example, the aperture ST may be disposed on the outer periphery between the third lens 113 and the fourth lens 114, or on the outer periphery between the second lens 112 and the third lens 113. The aperture ST may be disposed around the sensor-side surface of the third lens 113 or the object-side surface of the fourth lens 114. As another example, at least one of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 may serve as the aperture. For example, one of the lens surfaces selected from the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 may serve as the aperture for controlling the amount of light. For example, the periphery of the sensor-side surface of the third lens 113 or the periphery of the object-side surface of the fourth lens 114 can serve as an aperture.

[0031] Referring to Figure 1, in the optical system, the first lens 111 may have negative (-) refractive power. The first lens 111 may include a plastic material. The first lens 111 may include a first surface S1 defined as an object-side surface and a second surface S2 defined as a sensor-side surface. Along the optical axis Lx, the first surface S1 may be concave and the second surface S2 may be concave. At least one or both of the first surface S1 and the second surface S2 of the first lens 111 may be aspherical. At least one of the first surface S1 and the second surface S2 may have a reversal point; for example, the first surface S1 may have a reversal point between the periphery of the optical axis and the edge of the first surface S1. The effective diameter of the object-side surface or sensor-side surface of the first lens 111 may be larger than the effective diameter of the object-side surface or sensor-side surface of the second lens 112 or the third lens 113. Here, the effective diameter may be the diameter of the effective area of ​​the object-side surface or sensor-side surface on which light is incident.

[0032] The second lens 112 may have positive (+) refractive power. The second lens 112 may comprise a plastic or glass material. The second lens 112 may include a third surface S3 defined as the object-side surface and a fourth surface S4 defined as the sensor-side surface. Along the optical axis Lx, the third surface S3 may be concave and the fourth surface S4 may be convex. At least one of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 112 may have negative refractive power, the third surface S3 may be convex or planar, and the fourth surface S4 may be concave or planar.

[0033] Here, the center thickness of the first lens 111 may be greater than the center thickness of each of the second lens 112 and the third lens 113. The center thickness of the first lens 111 may be 1.5 times or greater than the center thickness of the second lens 112, for example, in the range of 1.5 to 2.5 times. The center thickness of the first lens 111 may be at least twice the center thickness of the third lens 113, for example, in the range of 2 to 4 times, or in the range of 2.5 to 3.5 times. Here, the center thickness of the first lens 111 may be the largest among the center thicknesses of the lenses in the optical system, and may be 0.7 mm or greater, for example, in the range of 0.7 mm to 1 mm. The center thickness of the first lens 111 may be greater than the sum of the center thicknesses of the second lens 112 and the third lens 113.

[0034] The optical axis spacing between the first lens 111 and the second lens 112 can be the largest among the spacings between two adjacent lenses, and can be, for example, 80% or more of the center thickness of the second lens 112, for example, in the range of 80% to 120%. The difference between the optical axis spacing between the first lens 111 and the second lens 112 and the center thickness of the second lens 112 can be 0.1 mm or less. The optical axis spacing between the first lens 111 and the second lens 112 can be 0.35 mm or more, for example, in the range of 0.35 to 0.55 mm.

[0035] The third lens 113 may have positive (+) refractive power. The third lens 113 may be made of plastic or glass. The third lens 113 may include a fifth surface S5 defined as the object-side surface and a sixth surface S6 defined as the sensor-side surface. The fifth surface S5 may be concave and the sixth surface S6 may be convex. That is, the third lens 113 may have a meniscus shape convex toward the image side. At least one or both of the fifth surface S5 and the sixth surface S6 may be aspherical. As another example, the third lens 113 may have negative refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0036] The optical axis spacing between the second lens 112 and the third lens 113 may be smaller than the optical axis spacing between the first lens 111 and the second lens 112 and larger than the optical axis spacing between the third lens 113 and the fourth lens 114. The optical axis spacing between the second lens 112 and the third lens 113 may be smaller than the optical axis spacing between the fifth lens 115 and the sixth lens 116 and smaller than the optical axis spacing between the sixth lens 116 and the seventh lens 117, but may be larger than the optical axis spacing between the seventh lens 117 and the eighth lens 118.

[0037] The fourth lens 114 may have positive (+) refractive power. The fourth lens 114 may comprise a plastic or glass material. The fourth lens 114 may comprise a seventh surface S7 defined as an object-side surface and an eighth surface S8 defined as a sensor-side surface. On the optical axis, the seventh surface S7 may be convex, and the eighth surface S8 may be convex. At least one or both of the seventh surface S7 and the eighth surface S8 may be aspherical. Both surfaces of the fourth lens 114 may be convex, and when expressed in absolute value, the radius of curvature of the seventh surface S7 at its center may be greater than the radius of curvature of the eighth surface S8, and may be 5.5 mm or greater, for example, in the range of 5.5 mm to 8 mm. The radius of curvature of the seventh surface S7 at its center may be smaller than the radius of curvature of the third surface S3, and the difference between the radius of curvature of the seventh surface S7 and the radius of curvature of the second surface S7 may be 2 mm or less. Here, the center thickness of the fourth lens 114 may be greater than the center thickness of the second lens 112, and may be 0.45 mm or greater, for example, in the range of 0.45 mm to 0.7 mm. The difference between the center thickness of the fourth lens 114 and the center thickness of the seventh lens 117 may be 0.1 mm or less, for example, in the range of 0.005 mm to 0.1 mm. The center thickness of the fourth lens 114 may be greater than the sum of the center thicknesses of the third lens 113 and the fifth lens 115.

[0038] The fifth lens 115 may have negative (-) refractive power. The fifth lens 115 may comprise a plastic or glass material. The fifth lens 115 may comprise a ninth surface S9 defined as the object-side surface and a tenth surface S10 defined as the sensor-side surface. The ninth surface S9 may be convex, and the tenth surface S10 may be concave. The ninth surface S9 may have at least one recurved point around a center. At least one or both of the ninth surface S9 and the tenth surface S10 may be aspherical. As another example, the ninth surface S9 of the fifth lens 115 may be flat or concave.

[0039] Here, based on the third lens 113, the effective diameter of the object-side or sensor-side surface can decrease in the order of the first lens 111, the second lens 112, and the third lens 113. Relative to the third lens 113, the effective diameter of the object-side or sensor-side surface can increase in the order of the third lens 113, the fourth lens 114, the fifth lens 115, and the sixth lens 116. Furthermore, the effective diameter of the object-side or sensor-side surface of the seventh lens 117 can be greater than the effective diameter of each surface of the sixth lens 116 and less than the effective diameter of each surface of the eighth lens 118.

[0040] The sixth lens 116 may have positive (+) refractive power. The sixth lens 116 may comprise a plastic or glass material. The sixth lens 116 may include an eleventh surface S11 defined as the object-side surface and a twelfth surface S12 defined as the sensor-side surface. On the optical axis, the eleventh surface S11 may be convex and the twelfth surface S12 may be concave. The eleventh and twelfth surfaces S11 and S12 may be aspherical. The twelfth surface S12 may have at least one refractive point around a center. The refractive point may be positioned closer to the edge than the optical axis or the center. As another example, the sixth lens 116 may have negative refractive power, the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0041] The center thickness of the sixth lens 116 may be thicker than the center thickness of the fifth lens 115, and thinner than the center thickness of the seventh lens 117. In absolute values, the radius of curvature at the center of the eleventh surface S11 is greater than the radius of curvature of the tenth surface S10 of the fifth lens 115, and may be greater than the radius of curvature of the fourteenth surface S14 of the seventh lens 117. In absolute values, the radius of curvature at the center of the twelfth surface S12 may be greater than the respective radii of curvature of the tenth surface S10 and the eleventh surface S11, and may be less than the radius of curvature of the thirteenth surface S13 of the seventh lens 117.

[0042] The seventh lens 117 may have negative (-) refractive power. The seventh lens 117 may comprise a plastic or glass material. The seventh lens 117 may include a thirteenth surface S13 defined as the object-side surface and a fourteenth surface S14 defined as the sensor-side surface. Along the optical axis Lx, the thirteenth surface S13 may be concave and the fourteenth surface S14 may be convex. That is, the seventh lens 117 may have a meniscus shape convex toward the sensor side. At least one or both of the thirteenth surface S13 and the fourteenth surface S14 may be aspherical. As another example, the thirteenth surface S13 may be flat or convex.

[0043] The center thickness of the seventh lens 117 may be greater than the center thickness of the sixth lens 116, and may be 1.5 times thicker than the center thickness of the eighth lens 118. When expressed in absolute values, the radius of curvature at the center of the thirteenth surface S13 may be 4 times or greater than the radius of curvature of the fourteenth surface S14, for example, in the range of 4 to 6 times. The center thickness of the seventh lens 117 may be 1.5 times or greater than the center thickness of each of the third lens 113 and the fifth lens 115, for example, in the range of 1.5 to 3 times.

[0044] The optical axis spacing between the seventh lens 117 and the sixth lens 116 on the optical axis Lx can be greater than the optical axis spacing between the seventh lens 117 and the eighth lens 118, and can be less than the center thickness of the seventh lens 117.

[0045] The eighth lens 118 may have negative (-) refractive power. The eighth lens 118 may include a plastic material. The eighth lens 118 may include a fifteenth surface S15 defined as the object-side surface and a sixteenth surface S16 defined as the sensor-side surface. On the optical axis, the fifteenth surface S15 may be convex and the sixteenth surface S16 may be concave. Both the fifteenth and sixteenth surfaces S15 may be aspherical. Each of the fifteenth and sixteenth surfaces S16 may have at least one recurve point. Specifically, the fifteenth surface S15 may have a recurve point around a center, and the recurve point of the sixteenth surface S16 relative to the optical axis may be positioned further outward than the recurve point of the fifteenth surface S15. Here, a straight line connecting the edge of the object-side fifteenth surface S15 of the eighth lens 118 may be positioned between the vertex of the sensor-side sixteenth surface S16 and the vertex of the fifteenth surface S15 of the seventh lens 117 placed on the optical axis. Therefore, light incident from the eighth lens 118 can be further refracted outward relative to the optical axis Lx. In the optical system of the present invention, the number of surfaces with reversal points among the first surface S1 to the sixteenth surface S16 can be four, five, or more.

[0046] Optical filter 192 may include at least one of an infrared filter and an optical filter such as a protective glass cover. Optical filter 192 allows light of a defined wavelength band to pass through and filters light of different wavelength bands. When optical filter 192 includes an infrared filter, it can prevent radiative heat emitted from external light from being transferred to the image sensor. Furthermore, optical filter 192 can transmit visible light and reflect infrared light. Image sensor 190 can detect light. Image sensor 190 may include a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) sensor.

[0047] A reflective element may be disposed on the incident side of the first lens 111 according to an embodiment of the present invention. The reflective element may reflect light incident on the first lens 111 through an optical axis perpendicular to the optical axis Lx of the first lens 111 to the eighth lens 118. The reflective element may include a prism, i.e., a triangular or right-angled prism.

[0048] The total length (TTL) of the optical system according to the first embodiment can be set to a range of 4 mm or greater, for example, from 4 mm to 12 mm or from 4 mm to 8 mm. TTL is the distance from the vertex of the object-side first surface S1 of the first lens 111 to the image sensor 190. The distance BFL from the vertex of the sensor-side sixteenth surface S16 of the eighth lens 118 to the image sensor 190 can be 3 mm or less, for example, from 0.2 mm to 3 mm or from 0.2 mm to 2 mm. The vertical distance Img from the optical axis of the image sensor 190 to the 1.0 field can be 0.8 mm or greater, for example, from 0.8 mm to 2.0 mm or from 0.8 mm to 1.5 mm. The total focal length F of the optical system can be in the range of 1 mm or greater, for example, from 1 mm to 5 mm or from 1 mm to 3 mm.

[0049] The effective focal length (EFL) of the optical system can be 1 mm or greater, for example, in the range of 1 mm to 3 mm or in the range of 1 mm to 2 mm. The total F-number of the optical system can be 2 or greater, for example, in the range of 2 to 3 or in the range of 2 to 2.80. In the optical system, the half field of view (HFOV) can be 30 degrees or greater, for example, in the range of 30 degrees to 80 degrees or in the range of 40 degrees to 75 degrees. The object-side entrance pupil (EPD) diameter of the optical system can be 1 mm or less, for example, in the range of 0.2 mm to 1 mm.

[0050] In the optical system of the first embodiment, all first surfaces S1 to sixteenth surfaces S16 of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117 and 118 may be aspherical. Among each radius of curvature (in absolute terms) around the optical axis of the first to sixteenth surfaces S16, the number of surfaces having a radius of curvature of 5.5 mm or less may be 12 or less, and the number of surfaces having a radius of curvature exceeding 5.5 mm may be 4 or more.

[0051] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117 and 118, the number of lenses having a protruding object-side surface on the optical axis is 4 or more, the number of lenses having a concave object-side surface is 4 or less, and the number of lenses having a protruding sensor-side surface is 4 or more, and the number of lenses having a concave sensor-side surface may be 4 or less.

[0052] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, the number of lenses having an Abbe number of 50 or greater is 5 or greater, and the number of lenses having an Abbe number less than 50 is 3 or less. For example, the Abbe numbers of the first lens 111, the third lens 113, the fourth lens 114, the sixth lens 116, and the seventh lens 117 are 50 or greater, the Abbe numbers of the second lens 112, the fifth lens 115, and the eighth lens 118 can be 35 or less, and the Abbe number of the fifth lens 115 can be the smallest among the lenses of the optical system and can be less than 25.

[0053] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, the number of lenses made of a high-refractive-index material having a refractive index of 1.6 or higher at 587 nm (d-line) can be 3 or greater, and the number of lenses made of a low-refractive-index material having a refractive index less than 1.6 can be 5 or less. For example, at 587 nm, the second lens 112, the fifth lens 115, and the eighth lens 118 have a high refractive index of 1.6 or higher, and the first lens 111, the third lens 113, the fourth lens 114, the sixth lens 116, and the seventh lens 117 have a low refractive index less than 1.6.

[0054] When observing the center thicknesses of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, the number of lenses having a center thickness of 0.5 mm or greater can be 3 or greater, and the number of lenses having a center thickness less than 0.5 mm can be 5 or less. For example, the center thicknesses T1, T2, and T3 of the first to third lenses 111, 112, and 113 can satisfy the following relationship: T3 < T2 < T1, and the center thicknesses T3, T4, T5, and T6 of the third to sixth lenses 113, 114, 115, and 116 satisfy the following relationship: T5 T3 < T6 < T4, and the center thicknesses T3 and T4 of the third lens 113 and the fourth lens 114 satisfy the following relationship: T3 < T4, and the center thicknesses T7 and T8 of the seventh lens 117 and the eighth lens 118 can satisfy the following relationship: T8 < T7 < T1. Here, T1 to T8 are the respective center thicknesses of the first lens 111 to the eighth lens 118.

[0055] Among the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, when observing the intervals on the optical axis between two adjacent lenses, the following relationship is satisfied: T78 < T23 < T67 < T12, where T67 is the interval on the optical axis between the adjacent sixth lens 116 and seventh lens 117, T23 is the interval on the optical axis between the second lens 112 and third lens 113, T78 is the interval on the optical axis between the adjacent seventh lens 117 and eighth lens 118, and T12 is the interval on the optical axis between the first lens 111 and second lens 112. Here, T12 is 0.35 mm or greater and can be greater than the thicknesses at the centers of the third lens 113 and fifth lens 115, and T23 can be 0.12 mm or less, and T67 can be greater than the interval on the optical axis between the fifth lens 115 and sixth lens 116. When observing the interval between the seventh lens 117 and eighth lens 118, the interval on the optical axis between two adjacent vertices can be less than the interval between two adjacent peripheral portions.

[0056] When the refractive powers of each of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 are P1 to P9, when their refractive powers are expressed as absolute values, the following relationship can be satisfied: P2 < P6 < P3 or / and P3 < P1 < P5 < P7 < P8 P4.

[0057] When observing the respective focal lengths of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, the focal length of the second lens 112 can be the largest and can be 25 mm or greater, for example, within the range of 25 mm to 45 mm or 25 mm to 35 mm. The focal length of the sixth lens 116 can be less than the focal length of the second lens 112 and greater than the focal length of the third lens 113. The combined focal length of the first lens 111 and second lens 112 can be -3 mm or greater, and the combined focal length of the third lens 113 and fourth lens 114 can be 2 mm or less. When expressed as an absolute value, the combined focal length of the first lens 111 and second lens 112 can be greater than the combined focal length of the third lens 113 and fourth lens 114.

[0058] Among the edge thicknesses of each of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, the number of lenses having an edge thickness of 0.55 mm or greater can be 2 or greater, the number of lenses having an edge thickness less than 0.55 mm can be 6 or less, and the number of lenses having an edge thickness less than 0.3 mm can be 3 or less.

[0059] Table 1 shows the values ​​of the radius of curvature, thickness, spacing, refractive index, and Abbe number of the surface of each lens in the first embodiment.

[0060] [Table 1]

[0061] In Table 1, the thickness is the center thickness of each lens (mm), and the interval is the distance between two adjacent lenses (mm). S17 indicates the incident side surface of the optical filter, and S18 indicates the exit surface of the optical filter.

[0062] Table 2 shows the effective radius (half-aperture), edge thickness, power value, and focal length of each lens in Figure 1.

[0063] [Table 2]

[0064] Figure 2 is an analytical diagram illustrating the longitudinal spherical aberration, astigmatism, and distortion aberration of the optical system of Figure 1. According to the optical system of the first embodiment, spherical aberration can be the phenomenon of changes in the focusing position of light passing through different parts of the lens (e.g., the central part and the peripheral part). The horizontal axis represents the degree of longitudinal spherical aberration, and the vertical axis represents the normalized distance from the center of the optical axis, showing the change in longitudinal spherical aberration according to the wavelength of light. For example, longitudinal spherical aberration can be exhibited for light with wavelengths of approximately 656.2725 nm, approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm. It can be seen that the longitudinal spherical aberration of the optical system is limited to +0.008 to -0.008, exhibiting stable optical properties.

[0065] Astigmatism in an optical system refers to the defocusing of light passing through the focal point in the vertical and horizontal directions when the meridional plane (or tangential plane) and sagittal plane of the lens have different radii. The astigmatism of an optical system is the result obtained at a wavelength of approximately 546.0740 nm. Solid lines indicate astigmatism in the tangential direction (e.g., meridional curvature), and dashed lines indicate astigmatism in the sagittal direction (e.g., spherical curvature). It is evident that astigmatism is limited to +0.025 to -0.025, demonstrating stable optical properties.

[0066] According to optical systems, distortion aberrations occur due to changes in optical magnification depending on the distance from the optical axis (OI), and the image formed on the actual imaging plane (e.g., 190 in Figure 1) may appear larger or smaller than the image formed on the theoretical imaging plane. The distortion of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured by the optical system may be slightly distorted at points deviating from the optical axis OI. However, such distortion is generally at a level visible in optical devices using lenses, and the distortion rate is less than about 3%, thus providing good optical properties.

[0067] <Second Embodiment>

[0068] The optical system according to the second embodiment will be referred to with reference to Figures 3 and 4. In the description of the second embodiment, configurations identical to those in the first embodiment will be referred to with reference to the description of the first embodiment, and repeated descriptions will be omitted.

[0069] Referring to Figure 3, in the optical system, the first lens 121 to the eighth lens 128 can be aligned along the optical axis Lx. The first lens 121 may have negative (-) refractive power. On the optical axis Lx, the first surface S1 of the first lens 121 may be concave and the second surface S2 may be concave. At least one or both of the first surface S1 and the second surface S2 of the first lens 121 may be aspherical. At least one of the first surface S1 and the second surface S2 may have a reversal point; for example, the first surface S1 may have a reversal point between the periphery of the optical axis and the edge of the first surface S1. The effective diameter of the object-side surface or sensor-side surface of the first lens 121 may be larger than the effective diameter of the object-side surface or sensor-side surface of the second lens 122 or the third lens 123. Here, the effective diameter may be the diameter of the effective area of ​​the object-side surface or sensor-side surface on which light is incident.

[0070] The second lens 122 may have positive (+) refractive power. Along the optical axis Lx, the third surface S3 of the second lens 122 may be convex and the fourth surface S4 may be concave. That is, the second lens 122 may have a meniscus shape convex toward the image side. At least one of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 122 may have negative refractive power, the third surface S3 may be concave or planar, and the fourth surface S4 may be convex or planar. At least one of the third surface S3 and the fourth surface S4 may have a reversal point; for example, the third surface S3 may have a reversal point between the edge and periphery of the optical axis of the third surface S3.

[0071] Here, the center thickness of the first lens 121 may be greater than the center thickness of each of the second lens 122 and the third lens 123. The center thickness of the first lens 121 may be 1.2 times or greater than the center thickness of the second lens 122, for example, in the range of 1.2 to 2.2 times. The center thickness of the first lens 121 may be 1.8 times or greater than the center thickness of the third lens 123, for example, in the range of 1.8 to 3 times or 2 to 3 times. Here, the center thickness of the first lens 121 may be the largest among the center thicknesses of the lenses in the optical system, and may be 0.7 mm or greater, for example, in the range of 0.7 mm to 1.2 mm. The center thickness of the first lens 121 may be equal to or less than the sum of the center thicknesses of the second lens 122 and the third lens 123.

[0072] The optical axis spacing between the first lens 121 and the second lens 122 can be the largest among the two adjacent lenses, and can be, for example, 40% or more of the center thickness of the second lens 122, for example, in the range of 40% to 80%. The difference between the optical axis spacing between the first lens 121 and the second lens 122 and the center thickness of the second lens 122 can be 0.2 mm or more. The optical axis spacing between the first lens 121 and the second lens 122 can be 0.40 mm or more, for example, in the range of 0.40 mm to 0.65 mm.

[0073] The third lens 123 may have positive (+) refractive power. Along the optical axis, the fifth surface S5 of the third lens 123 may be concave and the sixth surface S8 may be convex. That is, the third lens 123 may have a meniscus shape convex toward the image side. At least one or both of the fifth surface S5 and the sixth surface S6 may be aspherical. As another example, the third lens 123 may have negative refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0074] The optical axis spacing between the second lens 122 and the third lens 123 may be smaller than the optical axis spacing between the first lens 121 and the second lens 122 and may be larger than the optical axis spacing between the third lens 123 and the fourth lens 124. The optical axis spacing between the second lens 122 and the third lens 123 may be smaller than the optical axis spacing between the fifth lens 125 and the sixth lens 126, smaller than the optical axis spacing between the sixth lens 126 and the seventh lens 127, and larger than the optical axis spacing between the seventh lens 127 and the eighth lens 128.

[0075] The fourth lens 124 may have positive (+) refractive power. On the optical axis, the seventh surface S7 and the eighth surface S8 of the fourth lens 124 may be convex. At least one or both of the seventh surface S7 and the eighth surface S8 may be aspherical. Since both surfaces of the fourth lens 124 are convex, and in absolute terms, the radius of curvature of the seventh surface S7 at its center may be greater than the radius of curvature of the eighth surface S8, and may be 5.5 mm or greater, for example, in the range of 5.5 mm to 8 mm. The radius of curvature of the seventh surface S7 at its center may be less than the radius of curvature of the third surface S3, and the difference between the radius of curvature of the seventh surface S7 and the radius of curvature of the second surface S7 may be 3 mm or less. Here, the central thickness of the fourth lens 124 may be less than the central thickness of the second lens 122, and may be 0.45 mm or greater, for example, in the range of 0.45 mm to 0.7 mm. The difference between the center thickness of the fourth lens 124 and the center thickness of the seventh lens 127 can be 0.1 mm or less, for example, in the range of 0.005 mm to 0.1 mm. The center thickness of the fourth lens 124 can be less than the sum of the center thicknesses of the third lens 123 and the fifth lens 125.

[0076] The fifth lens 125 may have negative (-) refractive power. Along the optical axis, the ninth surface S9 of the fifth lens 125 may be convex and the tenth surface S10 may be concave. The ninth surface S9 may have at least one refractive point around its center. At least one or both of the ninth surface S9 and the tenth surface S10 may be aspherical. As another example, the ninth surface S10 of the fifth lens 125 may be flat or concave.

[0077] Here, based on the third lens 123, the effective diameter of the object-side or sensor-side surface decreases in the order of the first lens 121, the second lens 122, and the third lens 123. Relative to the third lens 123, the effective diameter of the object-side or sensor-side surface can increase in the order of the third lens 123, the fourth lens 124, the fifth lens 125, and the sixth lens 126. Furthermore, the effective diameter of the object-side or sensor-side surface of the seventh lens 127 can be greater than the effective diameter of each surface of the sixth lens 126 and less than the effective diameter of each surface of the eighth lens 128.

[0078] The sixth lens 126 may have positive (+) refractive power. On the optical axis, the eleventh surface S11 of the sixth lens 126 may be convex and the twelfth surface S12 may be concave. Both the eleventh and twelfth surfaces S11 and S12 may be aspherical. The twelfth surface S12 may have at least one refractive point around its center. The refractive point may be positioned closer to the edge than to the optical axis or the center. As another example, the sixth lens 126 may have negative refractive power, the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0079] The center thickness of the sixth lens 126 may be thicker than the center thickness of the fifth lens 125, and thinner than the center thickness of the seventh lens 127. In absolute terms, the radius of curvature at the center of the eleventh surface S11 is greater than the radius of curvature of the tenth surface S10 of the fifth lens 125, and may be greater than the radius of curvature of the fourteenth surface S14. In absolute terms, the radius of curvature at the center of the twelfth surface S12 may be greater than the radii of curvature of both the tenth and eleventh surfaces S10, and may be less than the radius of curvature of the thirteenth surface S13 of the seventh lens 127.

[0080] The seventh lens 127 may have positive (+) refractive power. Along the optical axis Lx, the thirteenth surface S13 of the seventh lens 127 may be concave and the fourteenth surface S14 may be convex. That is, the seventh lens 127 may have a meniscus shape convex toward the sensor side. At least one or both of the thirteenth surface S13 and the fourteenth surface S14 may be aspherical. As another example, the thirteenth surface S13 may be flat or convex.

[0081] The center thickness of the seventh lens 127 may be greater than the center thickness of the sixth lens 126, and may be 1.3 times thicker than the center thickness of the eighth lens 128. When expressed in absolute values, the radius of curvature at the center of the thirteenth surface S13 may be 4 times or greater than the radius of curvature of the fourteenth surface S14, for example, in the range of 4 to 6 times. The center thickness of the seventh lens 127 may be 1.5 times or greater than the center thickness of the fifth lens 125, for example, 1.5 to 3 times.

[0082] The optical axis spacing between the seventh lens 127 and the sixth lens 126 on the optical axis Lx can be greater than the optical axis spacing between the seventh lens 127 and the eighth lens 128, and can be less than the center thickness of the seventh lens 127.

[0083] The eighth lens 128 may have negative (-) refractive power. On the optical axis, the fifteenth surface S15 of the eighth lens 128 may be convex and the sixteenth surface S16 may be concave. Both the fifteenth and sixteenth surfaces S15 may be aspherical. Each of the fifteenth and sixteenth surfaces S16 may have at least one refractive point. Specifically, the fifteenth surface S15 may have a refractive point around its center, and the refractive point of the sixteenth surface S16 relative to the optical axis may be positioned further outward than the refractive point of the fifteenth surface S15. Here, the straight line connecting the edge of the object-side fifteenth surface S15 of the eighth lens 128 may be positioned between the vertex of the sensor-side sixteenth surface S16 and the vertex of the fifteenth surface S15 of the seventh lens 127 placed on the optical axis. Therefore, light incident from the eighth lens 128 may be further refracted outward relative to the optical axis Lx.

[0084] The optical filter 192 and image sensor 190 will be described with reference to the first embodiment. The total length (TTL) of the optical system according to the second embodiment can be set in the range of 4 mm or greater, for example, 4 mm to 12 mm or 4 mm to 8 mm. The distance BFL from the vertex of the sixteenth surface S16 on the sensor side of the eighth lens 128 to the image sensor 190 can be 3 mm or less, for example, in the range of 0.2 mm to 3 mm or 0.2 mm to 2 mm. The vertical distance Img from the optical axis of the image sensor 190 to the 1.0 field can be 0.8 mm or greater, for example, in the range of 0.8 mm to 2.0 mm or 0.8 mm to 1.5 mm. The total focal length F of the optical system can be in the range of 1 mm or greater, for example, 1 mm to 5 mm or 1 mm to 3 mm.

[0085] The effective focal length (EFL) of the optical system can be 1 mm or greater, for example, in the range of 1 mm to 3 mm or in the range of 1 mm to 2 mm. The total F-number of the optical system can be 2 or greater, for example, in the range of 2 to 3 or in the range of 2 to 2.80. In the optical system, the half field of view (HFOV) can be 30 degrees or greater, for example, in the range of 30 degrees to 80 degrees or 40 degrees to 75 degrees. The object-side entrance pupil (EPD) diameter of the optical system can be 1 mm or less, for example, in the range of 0.2 mm to 1 mm. The combined focal length of the first lens 121 and the second lens 122 can be -2.5 mm or greater, and the combined focal length of the third lens 123 and the fourth lens 124 can be 2 mm or less. When expressed as absolute values, the combined focal length of the first lens 121 and the second lens 122 can be greater than the combined focal length of the third lens 123 and the fourth lens 124.

[0086] In the optical system of the second embodiment, all first surfaces S1 to sixteenth surfaces S16 of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127 and 128 may be aspherical. Among each radius of curvature (in absolute terms) of the first to sixteenth surfaces S16 on the optical axis, the number of surfaces with a radius of curvature of 5.5 mm or less may be 12 or less, and the number of surfaces on the object side and sensor side with a radius of curvature exceeding 5.5 mm may be 4 or more.

[0087] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, 128 according to the second embodiment, the number of lenses having a protruding object-side surface on the optical axis is 5 or more, and the number of lenses having a concave object-side surface is 3 or less. The number of lenses having a protruding sensor-side surface may be 3 or more, and the number of lenses having a concave sensor-side surface may be 5 or less.

[0088] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127 and 128, the number of lenses with an Abbe number of 50 or greater may be 5 or greater, and the number of lenses with an Abbe number less than 50 may be 3 or less. For example, the Abbe number of the first lens 121, the third lens 123, the fourth lens 124, the sixth lens 126 and the seventh lens 127 is 50 or greater, the Abbe number of the second lens 122, the fifth lens 125 and the eighth lens 128 may be 35 or less, and the Abbe number of the fifth lens 125 may be the smallest among the lenses in the optical system and may be less than 25.

[0089] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, the number of lenses made of a high-refractive-index material with a refractive index of 1.6 or greater at 587 nm is three or greater, and the number of lenses made of a low-refractive-index material with a refractive index less than 1.6 may be five or fewer. For example, at 587 nm, the second lens 122, the fifth lens 125, and the eighth lens 128 have a high refractive index of 1.6 or greater, and the first lens 121, the third lens 123, the fourth lens 124, the sixth lens 126, and the seventh lens 127 have a low refractive index less than 1.6.

[0090] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, the number of lenses having a center thickness of 0.5 mm or more can be 4 or more, and the number of lenses having a center thickness of less than 0.5 mm can be 4 or less. For example, the center thicknesses T1, T2, and T3 of the first to third lenses 121, 122, and 123 can satisfy the following relationship: T3 < T2 < T1, and the center thicknesses T3, T4, T5, and T6 of the third to sixth lenses 123, 124, 125, and 126 can satisfy the following conditions: T5 < T3 T6 < T4, and the center thicknesses T3 and T4 of the third lens 123 and the fourth lens 124 satisfy the following relationship: T3 < T4, and the center thicknesses T7 and T8 of the seventh lens 127 and the eighth lens 128 can satisfy the following relationship: T8 < T7 < T1. Here, T1 to T8 are the respective center thicknesses of the first lens 121 to the eighth lens 128.

[0091] When observing the on-axis interval between two adjacent lenses among the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, the following relationship is satisfied: T78 < T23 < T67 < T12, where T67 is the on-axis interval between the adjacent sixth lens 126 and the seventh lens 127, T23 is the on-axis interval between the second lens 122 and the third lens 123, T78 is the on-axis interval between the adjacent seventh lens 127 and the eighth lens 128, and T12 is the on-axis interval between the first lens 121 and the second lens 122. Here, T12 can be 0.35 mm or more and can be greater than the center thickness of the fifth lens 125. T23 is 0.20 mm or less, and the on-axis interval T67 between the sixth lens 126 and the seventh lens 127 can be equal to or greater than the on-axis interval between the fifth lens 125 and the sixth lens 126. When observing the interval between the seventh lens 127 and the eighth lens 128, the on-axis interval between two adjacent vertices can be less than the interval between two adjacent peripheral portions.

[0092] When the refractive power of each of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128 is P1 to P9, when the refractive power is expressed as an absolute value, the following relationship can be satisfied: P2 P6 < P3 or / and P3 < P1 < P5 < P7 P8 P4.

[0093] Observing the individual focal lengths of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, the focal length of the second lens 122 can be the largest, and can be in the range of 12mm or greater, for example, in the range of 12mm to 30mm or 12mm to 20mm. The focal length of the sixth lens 126 can be less than the focal length of the second lens 122 and greater than the focal length of the third lens 123.

[0094] In each of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127 and 128, the number of lenses with an edge thickness of 0.50 mm or greater may be 3 or greater, the number of lenses with an edge thickness of less than 0.50 mm may be 6 or less, and the number of lenses with an edge thickness of less than 0.3 mm may be 2 or less.

[0095] Table 3 below shows the data on the radius of curvature, thickness, spacing, refractive index, and Abbe number of the surface of each lens in the second embodiment shown in Figure 3.

[0096] [Table 3]

[0097] In Table 3, the thickness is the center thickness (mm) of each lens in Figure 3, and the interval is the distance (mm) between two adjacent lenses. S17 indicates the incident side surface of the optical filter, and S18 indicates the exit surface of the optical filter.

[0098] Table 4 shows the effective radius (half-aperture), edge thickness, power value, and focal length of each lens in Figure 3.

[0099] [Table 4]

[0100] Figure 4 is an analytical diagram illustrating the longitudinal spherical aberration, astigmatism, and distortion aberration of the optical system of Figure 3. According to the optical system of the second embodiment, spherical aberration can be the phenomenon of changes in the focusing position of light passing through different parts of the lens (e.g., the central and peripheral parts). The horizontal axis represents the degree of longitudinal spherical aberration, and the vertical axis represents the normalized distance from the center of the optical axis, showing the change in longitudinal spherical aberration according to the wavelength of light. For example, longitudinal spherical aberration can be exhibited for light with wavelengths of approximately 656.2725 nm, approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm. It can be seen that the longitudinal spherical aberration of the optical system is limited to +0.025 to -0.025, exhibiting stable optical properties.

[0101] Astigmatism in an optical system refers to the defocusing of light passing through the focal point in the vertical and horizontal directions when the meridional plane (or tangential plane) and sagittal plane of the lens have different radii. The astigmatism of the optical system is the result obtained at a wavelength of approximately 546.0740 nm. Solid lines indicate astigmatism in the tangential direction (e.g., meridional curvature), and dashed lines indicate astigmatism in the sagittal direction (e.g., spherical curvature). As can be seen from Figure 4(B), astigmatism is confirmed to be limited to +0.050 to -0.050, demonstrating stable optical properties.

[0102] According to optical systems, distortion aberrations occur due to changes in optical magnification depending on the distance from the optical axis (OI), and the image formed on the actual imaging plane (e.g., 190 in Figure 1) may appear larger or smaller than the image formed on the theoretical imaging plane. The distortion of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured by the optical system may be slightly distorted at points deviating from the optical axis OI. However, such distortion is generally at a level visible in optical devices using lenses, and the distortion rate is less than about 3%, thus providing good optical properties.

[0103] <Third Embodiment>

[0104] The optical system according to the third embodiment will be referenced to Figures 5 and 6. In the description of the third embodiment, the configuration is the same as that of the first and second embodiments, and repeated descriptions will be omitted. Referring to Figure 5, in the optical system according to the third embodiment, the first lens 131 may have negative (-) refractive power. On the optical axis, the first surface S1 of the first lens 131 may be concave, and the second surface S2 may be concave. At least one or both of the first surface S1 and the second surface S2 of the first lens 131 may be aspherical. At least one of the first surface S1 and the second surface S2 may have a reversal point; for example, the first surface S1 may have a reversal point between the periphery of the optical axis and the edge of the first surface S1. The effective diameter of the object-side surface or sensor-side surface of the first lens 131 may be larger than the effective diameter of the object-side surface or sensor-side surface of the second lens 132 or the third lens 133. Here, the effective diameter may be the diameter of the effective area of ​​the object-side surface or sensor-side surface on which light is incident.

[0105] The second lens 132 may have positive (+) refractive power. Along the optical axis, the third surface S3 of the second lens 132 may be convex and the fourth surface S4 may be concave. That is, the second lens 132 may have a meniscus shape convex toward the image side. At least one of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 132 may have negative refractive power, the third surface S3 may be concave or planar, and the fourth surface S4 may be convex or planar.

[0106] Here, the center thickness of the first lens 131 may be greater than the center thickness of each of the second lens 132 and the third lens 133. The center thickness of the first lens 131 may be twice the center thickness of the second lens 132, for example, in the range of 1.2 to 2 times. The center thickness of the first lens 131 may be 1.5 times or greater than the center thickness of the third lens 133, for example, in the range of 1.5 to 2.5 times, or in the range of 1.5 to 2.2 times. Here, the center thickness of the first lens 131 may be the largest among the center thicknesses of the lenses in the optical system, and may be 0.7 mm or greater, for example, in the range of 0.7 mm to 1.2 mm. The center thickness of the first lens 131 may be less than the sum of the center thicknesses of the second lens 132 and the third lens 133.

[0107] The optical axis spacing between the first lens 131 and the second lens 132 can be the largest among the spacings between two adjacent lenses, and can be, for example, 50% or more of the center thickness of the second lens 132, for example, in the range of 50% to 90%. The difference between the optical axis spacing between the first lens 131 and the second lens 132 and the center thickness of the second lens 132 can be 0.4 mm or less. The optical axis spacing between the first lens 131 and the second lens 132 can be 0.35 mm or more, for example, in the range of 0.35 mm to 0.75 mm.

[0108] The third lens 133 may have positive (+) refractive power. Along the optical axis, the fifth surface S5 and the sixth surface S8 of the third lens 133 may be convex. At least one or both of the fifth surface S5 and the sixth surface S6 may be aspherical. As another example, the third lens 133 may have negative refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0109] The optical axis spacing between the second lens 132 and the third lens 133 can be smaller than the optical axis spacing between the first lens 131 and the second lens 132, and larger than the optical axis spacing between the third lens 133 and the fourth lens 134. The optical axis spacing between the second lens 132 and the third lens 133 is smaller than the optical axis spacing between the fifth lens 135 and the sixth lens 136, smaller than the optical axis spacing between the sixth lens 136 and the seventh lens 137, and the spacing between the seventh lens 137 and the eighth lens 138 can be larger than the optical axis spacing.

[0110] The fourth lens 134 may have positive (+) refractive power. On the optical axis, the seventh surface S7 and the eighth surface S8 of the fourth lens 134 may be convex. At least one or both of the seventh surface S7 and the eighth surface S8 may be aspherical. Since both surfaces of the fourth lens 134 are convex, and in absolute terms, the radius of curvature of the seventh surface S7 at its center may be greater than the radius of curvature of the eighth surface S8, and may be 5.5 mm or greater, for example, in the range of 5.5 mm to 8 mm. At its center, the radius of curvature of the seventh surface S7 may be greater than the radius of curvature of the third surface S3, and the difference between the radius of curvature of the seventh surface S7 and the radius of curvature of the second surface S7 may be 2 mm or greater. Here, the central thickness of the fourth lens 134 may be less than the central thickness of the second lens 132, and may be 0.45 mm or less, for example, in the range of 0.45 mm to 0.7 mm. The difference between the center thickness of the fourth lens 134 and the center thickness of the seventh lens 137 can be 0.1 mm or less, for example, in the range of 0.005 mm to 0.1 mm. The center thickness of the fourth lens 134 can be greater than the sum of the center thicknesses of the fifth lens 135 and the eighth lens 138.

[0111] The fifth lens 135 may have negative (-) refractive power. On the optical axis, the ninth surface S9 of the fifth lens 135 may be convex and the tenth surface S10 may be concave. The ninth surface S9 may have at least one refractive point around a center. At least one or both of the ninth surface S9 and the tenth surface S10 may be aspherical. As another example, the ninth surface S9 of the fifth lens 135 may be flat or concave.

[0112] Here, based on the third lens 133, the effective diameter of the object-side or sensor-side surface decreases in the order of the first lens 131, the second lens 132, and the third lens 133. Relative to the third lens 133, the effective diameter of the object-side or sensor-side surface can increase in the order of the third lens 133, the fourth lens 134, the fifth lens 135, and the sixth lens 136. Furthermore, the effective diameter of the object-side or sensor-side surface of the seventh lens 137 can be greater than the effective diameter of each surface of the sixth lens 136 and smaller than the effective diameter of each surface of the eighth lens 138.

[0113] The sixth lens 136 may have positive (+) refractive power. On the optical axis, the eleventh surface S11 of the sixth lens 136 may be convex and the twelfth surface S12 may be concave. Both the eleventh and twelfth surfaces S11 and S12 may be aspherical. The twelfth surface S12 may have at least one refractive point around its center. The refractive point may be positioned closer to the edge than to the optical axis or the center. As another example, the sixth lens 136 may have negative refractive power, the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0114] The center thickness of the sixth lens 136 may be thicker than the center thickness of the fifth lens 135, and thinner than the center thickness of the seventh lens 137. In absolute terms, the radius of curvature at the center of the eleventh surface S11 is greater than the radius of curvature of the tenth surface S10 of the fifth lens 125, and may be greater than the radius of curvature of the fourteenth surface S14 of the seventh lens 137. In absolute terms, the radius of curvature at the center of the twelfth surface S12 may be greater than the respective radii of curvature of the tenth surface S10 and the eleventh surface S11, and may be less than the radius of curvature of the thirteenth surface S13 of the seventh lens 137.

[0115] The seventh lens 137 may have positive (+) refractive power. Along the optical axis Lx, the thirteenth surface S13 of the seventh lens 137 may be concave and the fourteenth surface S14 may be convex. That is, the seventh lens 137 may have a meniscus shape convex toward the sensor side. At least one or both of the thirteenth surface S13 and the fourteenth surface S14 may be aspherical. As another example, the thirteenth surface S13 may be flat or convex.

[0116] The center thickness of the seventh lens 137 may be greater than the center thickness of the sixth lens 136, and 1.3 times thicker than the center thickness of the eighth lens 138. When expressed in absolute values, the radius of curvature at the center of the thirteenth surface S13 may be 4 times or greater than the radius of curvature of the fourteenth surface S14, for example, in the range of 4 to 6 times. The center thickness of the seventh lens 137 may be 1.5 times or greater than the center thickness of the fifth lens 135, for example, in the range of 1.5 to 3 times.

[0117] The optical axis spacing between the seventh lens 137 and the sixth lens 136 on the optical axis Lx can be greater than the optical axis spacing between the seventh lens 137 and the eighth lens 138, and can be less than the center thickness of the seventh lens 133.

[0118] The eighth lens 138 may have negative (-) refractive power. On the optical axis, the fifteenth surface S15 of the eighth lens 138 may be convex and the sixteenth surface S16 may be concave. Both the fifteenth and sixteenth surfaces S15 may be aspherical. Each of the fifteenth and sixteenth surfaces S16 may have at least one refractive point. Specifically, the fifteenth surface S15 may have a refractive point around its center, and the refractive point of the sixteenth surface S16 relative to the optical axis may be positioned further outward than the refractive point of the fifteenth surface S15. Here, the straight line connecting the edge of the object-side fifteenth surface S15 of the eighth lens 138 may be positioned between the vertex of the sensor-side sixteenth surface S16 and the vertex of the fifteenth surface S15 of the seventh lens 137 placed on the optical axis. Therefore, light incident from the eighth lens 138 may be further refracted outward relative to the optical axis Lx.

[0119] The optical filter 192 and image sensor 190 will be described with reference to the first embodiment. The total length (TTL) of the optical system according to the third embodiment can be set in the range of 4 mm or greater, for example, 4 mm to 12 mm or 4 mm to 8 mm. The distance BFL from the vertex of the sixteenth surface S16 on the sensor side of the eighth lens 138 to the image sensor 190 can be 3 mm or less, for example, in the range of 0.2 mm to 3 mm or 0.2 mm to 2 mm. The vertical distance Img from the optical axis of the image sensor 190 to the 1.0 field can be 0.8 mm or greater, for example, in the range of 0.8 mm to 2.0 mm or 0.8 mm to 1.5 mm. The total focal length F of the optical system can be in the range of 1 mm or greater, for example, 1 mm to 5 mm or 1 mm to 3 mm.

[0120] The effective focal length (EFL) of the optical system can be 1 mm or greater, for example, in the range of 1 mm to 3 mm or in the range of 1 mm to 2 mm. The total F-number of the optical system can be 2 or greater, for example, in the range of 2 to 3 or in the range of 2 to 2.80. In the optical system, the half field of view (HFOV) can be 30 degrees or greater, for example, in the range of 30 degrees to 80 degrees or 40 degrees to 75 degrees. The object-side entrance pupil (EPD) diameter of the optical system can be 1 mm or less, for example, in the range of 0.2 mm to 1 mm. The combined focal length of the first lens 121 and the second lens 122 can be -2 mm or greater, and the combined focal length of the third lens 123 and the fourth lens 124 can be less than 2 mm. When expressed as an absolute value, the combined focal length of the first lens 121 and the second lens 122 can be greater than the combined focal length of the third lens 123 and the fourth lens 124.

[0121] In the optical system of the third embodiment, all the first surfaces S1 to the sixteenth surface S16 of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137 and 138 may be aspherical. Among each radius of curvature (in absolute value) around the optical axis of the first surfaces S1 to the sixteenth surface S16, the number of surfaces having a radius of curvature of 5.5 mm or less may be 14 or less, and the number of surfaces having a curvature exceeding 5.5 mm may be 2 or more.

[0122] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137 and 138, the number of lenses having a protruding object-side surface on the optical axis may be 5 or more, the number of lenses having a concave object-side surface may be 3 or less, the number of lenses having a protruding sensor-side surface may be 4 or more, and the number of lenses having a concave sensor-side surface may be 4 or less.

[0123] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137 and 138, the number of lenses with an Abbe number of 50 or greater may be 5 or greater, and the number of lenses with an Abbe number less than 50 may be 3 or less. For example, the Abbe number of the first lens 131, the third lens 133, the fourth lens 134, the sixth lens 136 and the seventh lens 137 is 50 or greater, the Abbe number of the second lens 132, the fifth lens 135 and the eighth lens 138 may be 35 or less, and the Abbe number of the fifth lens 135 may be the smallest among the lenses in the optical system and may be less than 25.

[0124] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, the number of lenses having a refractive index of 1.6 or greater at 587 nm may be 3 or greater, and the number of lenses having a refractive index less than 1.6 may be 5 or less. For example, at 587 nm, the second lens 132, the fifth lens 135, and the eighth lens 138 may have a refractive index of 1.6 or greater, and the first lens 131, the third lens 133, the fourth lens 134, the sixth lens 136, and the seventh lens 137 may have a refractive index less than 1.6.

[0125] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, the number of lenses having a center thickness of 0.5 mm or greater can be 5 or greater, and the number of lenses having a center thickness less than 0.5 mm can be 3 or less. For example, the center thicknesses T1, T2, and T3 of the first to third lenses 131, 132, and 133 can satisfy the following relationship: T3 < T2 < T1, and the center thicknesses T3, T4, T5, and T6 of the third to sixth lenses 133, 134, 135, and 136 satisfy the following conditions: T5 < T6 < T4 T3, and the difference between the center thicknesses T3 and T4 of the third lens 133 and the fourth lens 134 can be 1 mm or less, and the thicknesses T7 and T8 of the seventh lens 137 and the eighth lens 138 can satisfy the following relationship: T8 << T6 < T7 < T1. Here, T1 to T8 are the respective center thicknesses of the first lens 131 to the eighth lens 138.

[0126] Observing the on-axis interval between two adjacent lenses among the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, it satisfies the following relationship: T78 < T23 < T67 < T12, where T67 is the on-axis interval between the adjacent sixth lens 136 and the seventh lens 137, T23 is the on-axis interval between the second lens 132 and the third lens 133, T78 is the on-axis interval between the adjacent seventh lens 137 and the eighth lens 138, and T12 is the on-axis interval between the first lens 131 and the second lens 132. Here, T12 can be 0.35 mm or greater and can be greater than the center thickness of the fifth lens 135. T23 is 0.20 mm or less, and the on-axis interval T67 between the sixth lens 136 and the seventh lens 137 can be equal to or greater than the on-axis interval between the fifth lens 135 and the sixth lens 136. Observing the interval between the seventh lens 137 and the eighth lens 138, the on-axis interval between two adjacent vertices can be less than the interval between two adjacent peripheral portions.

[0127] When the refractive power of each of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138 is P1 to P9, when the absolute value of its refractive power is expressed, it can satisfy the following relationship: P2 < P6 < P3 or / and P3 P5 < P1 < P7 P8 P4.

[0128] Observing the focal lengths of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, the focal length of the second lens 132 can be the largest, and can be in the range of 15mm or greater, for example, 15mm to 50mm or 20mm to 45mm. The focal length of the sixth lens 136 can be less than the focal length of the second lens 132 and greater than the focal length of the third lens 133.

[0129] In each of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137 and 138, the number of lenses with an edge thickness of 0.50 mm or greater may be 3 or greater, the number of lenses with an edge thickness of less than 0.50 mm may be 6 or less, and the number of lenses with an edge thickness of less than 0.3 mm may be 2 or less.

[0130] Table 5 below shows the values ​​of the radius of curvature, thickness, spacing, refractive index, and Abbe number of the surface of each lens in the third embodiment shown in Figure 5.

[0131] [Table 5]

[0132] In Table 5, the thickness is the center thickness (mm) of each lens in Figure 5, and the interval is the distance (mm) between two adjacent lenses. S17 indicates the incident side surface of the optical filter, and S18 indicates the exit surface of the optical filter.

[0133] Table 6 shows the effective radius (half-aperture), edge thickness, power value, and focal length of each lens in Figure 5.

[0134] [Table 6]

[0135] Figure 6 is an analytical diagram illustrating the longitudinal spherical aberration, astigmatism, and distortion aberration of the optical system of Figure 5. According to the optical system of the second embodiment, spherical aberration can be the phenomenon of changes in the focusing position of light passing through different parts of the lens (e.g., the central and peripheral parts). The horizontal axis represents the degree of longitudinal spherical aberration, and the vertical axis represents the normalized distance from the center of the optical axis, showing the change in longitudinal spherical aberration according to the wavelength of light. For example, longitudinal spherical aberration can be exhibited for light with wavelengths of approximately 656.2725 nm, approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm. It can be seen that the longitudinal spherical aberration of the optical system is limited to +0.025 to -0.025, exhibiting stable optical properties.

[0136] Astigmatism in an optical system refers to the defocusing of light passing through the focal point in the vertical and horizontal directions when the meridional plane (or tangential plane) and sagittal plane of the lens have different radii. The astigmatism of the optical system is the result obtained at a wavelength of approximately 546.0740 nm. Solid lines indicate astigmatism in the tangential direction (e.g., meridional curvature), and dashed lines indicate astigmatism in the sagittal direction (e.g., spherical curvature). As can be seen from Figure 6(B), astigmatism is confirmed to be limited to +0.050 to -0.050, demonstrating stable optical properties.

[0137] According to optical systems, distortion aberrations occur due to changes in optical magnification depending on the distance from the optical axis (OI), and the image formed on the actual imaging plane (e.g., 190 in Figure 1) may appear larger or smaller than the image formed on the theoretical imaging plane. The distortion of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured by the optical system may be slightly distorted at points deviating from the optical axis OI. However, such distortion is generally at a level visible in optical devices using lenses, and the distortion rate is less than approximately 3%, thus providing good optical properties.

[0138] As seen in the first to third embodiments, each lens can be formed of a plastic lens, and all surfaces of each lens have an aspherical coefficient. An aperture ST can be positioned around the third lenses 113, 123, and 133 and the fourth lenses 114, 124, and 134. In the first to third embodiments of the invention, the center thickness of the first lenses 111, 121, and 131 is the thickest among the lenses in the optical system, and the first interval along the optical axis between the first lenses 111, 121, and 131 and the second lenses 112, 122, and 132 can be greater than the second interval between the sixth lenses 116, 126, and 136 and the seventh lenses 117, 127, and 137, or greater than the optical axis interval between the fourth lenses 114, 124, and 134 and the sixth lenses 116, 126, and 136.

[0139] The optical systems according to the first to third embodiments of the present invention can satisfy at least one, two, or more of the following equations. Therefore, the optical systems according to the first to third embodiments can have the effect of optical improvement.

[0140] In the optical systems of the first to third embodiments, at least one, two or more, or both of the following equations can be satisfied.

[0141] [Equation 1]

[0142] 0.5 > f4 / F < 1.5

[0143] Here, F is the effective focal length of the optical system, and f4 is the focal length of the fourth lens. When the value of f4 / F exceeds the above range, it may affect the improvement of resolution, and may be, for example, 1.22.

[0144] [Equation 2]

[0145] 1.4 > nd1 < 1.6

[0146] nd1 is the refractive index of the first lens at 587 nm (d-line). When the refractive index value of the first lens exceeds the above range, it may affect the improvement of resolution; for example, it may be 1.53.

[0147] [Equation 3]

[0148] 10>vd5<30

[0149] Here, vd5 is the Abbe number of the fifth lens, and when the Abbe number of the fifth lens exceeds the above range, it may affect the improvement of resolution, and can be, for example, 21.49.

[0150] [Equation 4]

[0151] F / EPD>1

[0152] Here, EPD is the diameter of the entrance pupil of the optical system, and when the F / EPD value exceeds the above range, it may affect the brightness of the optical system.

[0153] [Equation 5]

[0154] 1>T1 / T3<5

[0155] Here, T1 is the center thickness of the first lens, and T3 is the center thickness of the third lens.

[0156] [Equation 6]

[0157] 1>T4 / T5<5

[0158] Here, T4 is the center thickness of the fourth lens, and T5 is the center thickness of the fifth lens.

[0159] [Equation 7]

[0160] 1>T7 / T8<5

[0161] Here, T7 is the center thickness of the first lens, and T8 is the center thickness of the third lens.

[0162] When it exceeds the range of equations 5 to 7, it may affect the reduction of distortion.

[0163] [Equation 8]

[0164] |f5|>|f4|

[0165] Here, f5 is the focal length of the fifth lens, and f4 is the focal length of the fourth lens.

[0166] [Equation 9]

[0167] 0.5>|f7| / |f8|<2

[0168] Here, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

[0169] In Equations 8 and 9, when they exceed the above range, they may affect the reduction of optical aberrations.

[0170] The optical system according to the first to third embodiments of the present invention can satisfy at least one, two or more, five or more, or all of the following equations 1 to 9. In this case, the optical system can implement a high-quality and high-resolution imaging lens system. Furthermore, unwanted light entering the optical system can be blocked by at least one of equations 1 to 9, aberrations can be corrected, and the performance of the optical system can be improved.

[0171] Figure 7 is a perspective view illustrating an example of an optical system according to an embodiment of the present invention applied to a mobile device.

[0172] As shown in Figure 7, the mobile terminal 1500 may include a camera module 1520, a flash module 1530, and an autofocus device 1510 disposed on one side or the back side. Here, the autofocus device 1510 may include a surface-emitting laser device and a light-receiving device as a light-emitting layer. The flash module 1530 may include an emitter that emits light therein. The flash module 1530 can be operated by the camera of the mobile terminal or by user control. The camera module 1520 may include image capture and autofocus functions. For example, the camera module 1520 may include an autofocus function using images. The autofocus device 1510 may include an autofocus function using lasers. The autofocus device 1510 may be primarily used in conditions where the autofocus function of the camera module 1520 is degraded, for example, at close range (10m or less) or in dark environments.

[0173] The features, structures, effects, etc., described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc., described in each embodiment can be combined or modified by those skilled in the art to be used in other embodiments. Therefore, content related to such combinations and modifications should be interpreted as being included within the scope of the present invention. Moreover, although embodiments have been described above, they are merely examples and do not limit the present invention; the examples described above are provided by those skilled in the art to be included without departing from the basic characteristics of the embodiments. It is evident that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be implemented by modification. Furthermore, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention as defined in the appended claims.

[0174] 111: First Lens 112: Second lens 113: Third Lens 114: Fourth Lens 115: Fifth Lens 116: Sixth Lens 117: The Seventh Lens 118: Eighth Lens 121: First Lens 122: Second Lens 123: Third Lens 124: Fourth Lens 125: Fifth Lens 126: The Sixth Lens 127: The Seventh Lens 128: The Eighth Lens 131: First Lens 132: Second Lens 133: Third Lens 134: Fourth Lens 135: Fifth Lens 136: The Sixth Lens 137: The Seventh Lens 138: The Eighth Lens 190: Image sensor 192: Optical Filter 1500: Mobile Terminal 1510: Autofocus device 1520: Camera Module 1530: Flash Module BFL: Distance Img: Vertical distance Lx: Optical axis S1: First surface S2: Second surface S3: Third Surface S4: Fourth Surface S5: Fifth Surface S6: Sixth Surface S7: Seventh Surface S8: Eighth Surface S9: Ninth Surface S10: Tenth Surface S11: Eleventh Surface S12: Twelfth Surface S13: The Thirteenth Surface S14: The Fourteenth Surface S15: The Fifteenth Surface S16: Sixteenth Surface ST: Aperture TTL: Total Length T1: Thickness T2: Thickness T3: Thickness T4: Thickness T5: Thickness T6: Thickness T7: Thickness T8: Thickness T12: Optical axis spacing T23: Optical axis spacing T67: Optical axis spacing T78: Optical axis spacing

Claims

1. An optical system, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens, said lenses being sequentially arranged along an optical axis in a direction from an object side to a sensor side, wherein the first lens has negative refractive power and has a concave object-side surface on the optical axis, wherein the fourth lens has both an object-side surface and a sensor-side surface that are convex on the optical axis, and has a refractive index lower than 1.6, wherein the fifth lens has a concave sensor-side surface on the optical axis and has a refractive index equal to or higher than 1.6, wherein the seventh lens has positive refractive power and has a convex sensor-side surface on the optical axis, wherein the eighth lens has negative (-) refractive power and has a concave sensor-side surface on the optical axis, when the central thicknesses of the first lens, the second lens and the third lens are T1, T2 and T3 respectively, the following relationship is satisfied: T3<T2<T1, and wherein the optical system satisfies Conditional Formula 1: [Conditional Formula 1] 0.5<f4 / F<1.5, wherein f4 is a focal length of the fourth lens and F is an effective focal length of the optical system;.

2. The optical system according to claim 1, wherein at least one of the following Conditional Formulas 2, 3 and 4 is satisfied: [Conditional Formula 2] 1.4<nd1<1.6, wherein nd1 is a refractive index of the first lens at 587 nm, [Conditional Formula 3] 10<vd5<30, wherein vd5 is an Abbe number of the fifth lens, [Conditional Formula 4] F / EPD>1, wherein EPD is an entrance pupil diameter of the optical system.

3. The optical system according to claim 1, wherein at least one of the following Conditional Formulas 5, 6 and 7 is satisfied: [Conditional Formula 5] 1<T1 / T3<5 [Conditional Formula 6] 1<T4 / T5<5 [Conditional Formula 7] 1<T7 / T8<5, wherein T1 is a central thickness of the first lens, T3 is a central thickness of the third lens, T4 is a central thickness of the fourth lens, T5 is a central thickness of the fifth lens, T7 is a central thickness of the seventh lens, and T8 is a central thickness of the eighth lens.

4. The optical system according to claim 1, comprising at least one of the following Conditional Formulas 8 and 9: [Conditional Formula 8] |f5|>|f4| [Conditional Formula 9] 0.5<|f7| / |f8|<2, wherein f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

5. The optical system according to any one of claims 1 to 4, wherein a thickness of a center of the first lens is thicker than a thickness of each of centers of the second lens to the eighth lens, and wherein an optical axis interval between the first lens and the second lens is larger than an optical axis interval between any two adjacent lenses from the second lens to the eighth lens.

6. An optical system as claimed in any one of claims 1 to 4, wherein the number of the first to eighth lenses having a convex object-side surface on the optical axis is four or more, and the number of the lenses having a concave object-side surface is four or less.

7. An optical system as claimed in any one of claims 1 to 4, wherein the number of lenses having a convex sensor-side surface on the optical axis among the first to eighth lenses is four or more, and the number of lenses having a concave sensor-side surface is four or less.

8. The optical system of claim 7, wherein the sensor-side surfaces of the first lens, the fifth lens, the sixth lens and the eighth lens are recessed.

9. An optical system according to any one of claims 1 to 4, wherein among the first to the eighth lenses, the number of lenses having an Abbe number of 50 or greater is five or greater, and the number of lenses having an Abbe number of less than 50 is three or less.

10. An optical system according to any one of claims 1 to 4, wherein among the first to the eighth lenses, the number of lenses having a refractive index of 1.6 or greater is three or greater, and the number of lenses having a refractive index of less than 1.6 is five or less.

11. An optical system according to any one of claims 1 to 4, wherein the number of lenses having a central thickness of 0.5 mm or greater among the first to eighth lenses is three or greater, and the number of lenses having a thickness of less than 0.5 mm is five or less.

12. An optical system according to any one of claims 1 to 4, wherein when the center thickness of one of the third to sixth lenses is T3, T4, T5 and T6, the following relationship is satisfied: T5T3 <T6<T4。 13. An optical system as claimed in any of claims 1 to 4, wherein the focal length of one of the second lenses is the largest among the first to the eighth lenses.

14. An optical system according to any one of claims 1 to 4, wherein the effective diameter of the object-side surface or the sensor-side surface decreases relative to the third lens in the order of the first lens, the second lens, and the third lens, and wherein the effective diameter of the object-side surface or the sensor-side surface increases relative to the third lens in the order of the third lens, the fourth lens, the fifth lens, and the sixth lens.

15. An optical system, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, said lenses being sequentially arranged along an optical axis in a direction from an object side to an image sensor side, wherein the first lens has negative refractive power and has an object-side surface concave on the optical axis, wherein the fourth lens has both an object-side surface and an image sensor side surface convex on the optical axis, and has a refractive index lower than 1.6, wherein the fifth lens has an image sensor side surface concave on the optical axis and has a refractive index equal to or higher than 1.6, wherein the seventh lens has positive refractive power and has an image sensor side surface convex on the optical axis, wherein the eighth lens has negative (-) refractive power and has an image sensor side surface concave on the optical axis, wherein the number of lenses from the first lens to the eighth lens having an object-side surface convex on the optical axis is four or more, wherein the number of lenses having an image sensor side surface concave on the optical axis is five or less, wherein the number of surfaces among the object-side surfaces and image sensor side surfaces of the first lens to the eighth lens that have an inflection point is four or more, and when the central thicknesses of the first lens, the second lens and the third lens are T1, T2 and T3 respectively, the following relationship is satisfied: T3<T2<T1.

16. The optical system according to claim 15, further comprising: an image sensor disposed on an image sensor side of the eighth lens; and an optical filter disposed between the image sensor and the eighth lens, wherein the optical system satisfies at least one of the following conditional expressions 1 to 4: [Conditional Expression 1] 0.5 < f4 / F < 1.5 where f4 is a focal length of the fourth lens, and F is an effective focal length of the optical system, [Conditional Expression 2] 1.4 < nd1 < 1.6 where nd1 is a refractive index of the first lens at 587 nm, [Conditional Expression 3] 10 < vd5 < 30 where vd5 is an Abbe number of the fifth lens, [Conditional Expression 4] F / EPD > 1 where EPD is an entrance pupil diameter of the optical system.

17. The optical system according to claim 15 or 16, comprising an aperture disposed between the third lens and the fourth lens.

Images