Optical Department

Abstract

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 arranged sequentially 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 object side surface, the second lens has negative refractive power and a concave sensor side surface, at least one of the object side surface and the sensor side surface of the sixth lens has an inflection point, the seventh lens has positive refractive power and a convex sensor side surface, and the eighth lens has negative refractive power and at least one object side surface and the sensor side surface of the sixth lens has an inflection point, and among central thicknesses of the first to eighth lenses, the central thickness of the seventh lens may be the thickest.

Description

Technical Field

[0001] Embodiments of the present invention relate to an optical system for high resolution.

Background Art

[0002] A camera module performs a function of photographing an object and storing it as an image or video, and is mounted on various applications. In particular, the camera module is manufactured in a super-small size and is applied not only to portable devices such as smartphones, tablet PCs, and notebook computers, but also to drones, vehicles, etc., providing various functions. For example, the optical system of the camera module may include an imaging lens that forms an image and an image sensor that converts the formed image into an electrical signal. At this time, the camera module can perform an autofocus (AF) function of automatically adjusting the distance between the image sensor and the imaging lens to align the focal length of the lens, and can perform a zooming function of zooming in (zoom up) or zooming out (zoom out) by increasing or decreasing the magnification of a distant object through a zoom lens. Also, the camera module employs an image stabilization (IS) technology to correct or prevent image blurring caused by the movement of the camera due to an unstable fixing device or the movement of the user. The most important element for such a camera module to obtain an image is the imaging lens that forms the image. Recently, there has been an increasing interest in high resolution, and research using 5 or 6 lenses has been underway to realize this. Also, research using a plurality of imaging lenses having positive (+) or negative (-) refractive powers has been underway to realize high resolution. However, when arranging a plurality of lenses, there is a problem that it is difficult to derive excellent optical characteristics and aberration characteristics. Therefore, a new optical system that can solve the above problems is required.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Examples of the present invention aim to provide an optical system with improved optical characteristics. Examples of the present invention aim to provide an optical system having at least eight lenses. Examples of the present invention aim to provide an optical system in which at least the object side and the sensor side of at least eight lenses have aspherical surfaces. Examples of the present invention aim to 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 among at least eight lenses are aligned with respect to the optical axis.

Means for Solving the Problems

[0004] The optical system according to an example 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 sequentially arranged along the optical axis from the object side to the sensor side. The first lens has a negative refractive power, and the object side surface is concave on the optical axis. The fourth lens has convex surfaces on both the object side and the sensor side 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 the sensor side surface is concave on the optical axis. The eighth lens has a negative (-) refractive power, and the sensor side surface on the optical axis is concave such that the following formula 1 is satisfied: <Equation 1> 0.5 < f4 / F < 1.5, where f4 is the focal length of the fourth lens, and F can be the effective focal length of the optical system.

[0005] According to an example of the present invention, at least one of the following formulas 2, 3, and 4 is satisfied: <Equation 2> 1.4 < nd1 < 1.6, where nd1 is the refractive index of the first lens at 587 nm; <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 the following mathematical formulas 5, 6, and 7 is satisfied, <Equation 5> 1 < T1 / T3 < 5, <Equation 6> 1 < T4 / T5 < 5, <Equation 7> 1 < T7 / T8 < 5, where T1 is the central thickness of the first lens, T3 is the central thickness of the third lens, T4 is the central thickness of the fourth lens, T5 is the central thickness of the fifth lens, T7 is the central thickness of the seventh lens, and T8 may be the central thickness of the eighth lens.

[0007] According to an embodiment of the present invention, it includes at least one of the following mathematical formulas 8 and 9, <Equation 8> |f5| > |f4|, <Equation 9> 0.5 < |f7| / |f8| < 2, where 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 may be the focal length of the eighth lens.

[0008] According to an embodiment of the present invention, the central thickness of the first lens is thicker than the respective thicknesses of the centers of the second to eighth lenses, and the optical axis interval between the first lens and the second lens may be larger than the optical axis intervals between two adjacent lenses of the second to eighth lenses.

[0009] According to an embodiment of the present invention, among the first to eighth lenses on the optical axis, the number of lenses with a convex object side surface is 4 or more, and the number of lenses with a concave object side surface may be 4 or less.

[0010] According to an embodiment of the present invention, among the first to eighth lenses on the optical axis, the number of lenses with a convex sensor side surface is 4 or more, and the number of lenses with a concave sensor side surface may be 4 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 with an Abbe number of 50 or more is 5 or more, and the number of lenses with an Abbe number of less than 50 may be 3 or less.

[0011] According to an embodiment of the present invention, among the first to eighth lenses, there are three or more lenses with a refractive index of 1.6 or more, and there can be five or less lenses with a refractive index of less than 1.6. Among the first to eighth lenses, there are three or more lenses with a central thickness of 0.5 mm or more, and there are five or less lenses with a central thickness of less than 0.5 mm. When the central thicknesses of the first, second, and third lenses are T1, T2, and T3, T3 < T2 < T1 can be satisfied. When the central thicknesses of the third to sixth lenses are T3, T4, T5, and T6, T5 ≦ T3 < T6 < T4 can be satisfied.

[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. Based on the third lens, the effective diameters of the object side or the sensor side surface become smaller in the order of the first lens, the second lens, and the third lens. Based on the third lens, the effective diameters of the object side or the sensor side surface may become larger in the order of the third lens, the fourth lens, the fifth lens, and the sixth lens.

[0013] The 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 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 the object side surface is concave on the optical axis. The fourth lens has both the object side surface and the sensor side surface convex 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 the sensor side surface is convex on the optical axis. The eighth lens has a negative (-) refractive power, and the sensor side surface is concave on the optical axis. Among the first to eighth lenses, there are four or more lenses with a convex object side surface on the optical axis, and there are five or less lenses with a concave sensor side surface. Among the object side surface and the sensor side surface of the first to eighth lenses, there can be four or more surfaces having an inflection point.

[0014] According to an embodiment of the present invention, the present invention may include 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 formulas 1 to 4. [Effects of the Invention]

[0015] The optical system according to the embodiment can correct aberration characteristics and realize a slim optical system. This allows for miniaturization of the optical system and realizes high image quality and high resolution. The optical system according to the embodiment can block unwanted light entering the optical system. This reduces aberrations and improves the performance of the optical system. [Brief explanation of the drawing]

[0016] [Figure 1] This is a diagram showing the configuration of the optical system according to the first embodiment of the present invention. [Figure 2] Figure 1 shows graphs illustrating spherical aberration (longitudinal spherical aberration), astigmatic field curves, and distortion in the optical system. [Figure 3] This is a diagram showing the configuration of the optical system according to a second embodiment of the present invention. [Figure 4] Figure 3 shows graphs illustrating spherical aberration (longitudinal spherical aberration), astigmatic field curves, and distortion in the optical system. [Figure 5] This is a diagram showing the configuration of the optical system according to the third embodiment of the present invention. [Figure 6] Figure 5 shows graphs illustrating spherical aberration (longitudinal spherical aberration), astigmatic field curves, and distortion in the optical system. [Figure 7] This is a perspective view of a portable terminal having an optical system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0017] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described, but can be embodied in a variety of different forms, and within the scope of the technical concept of the present invention, one or more of its components can be selectively combined and substituted between embodiments. Furthermore, terms used in embodiments of the present invention (including technical and scientific terms) may be interpreted as having a meaning that can be generally understood by a person ordinary skill in the art to which the present invention belongs, unless they are clearly specifically defined and described, and commonly used terms, such as dictionary-defined terms, may be interpreted in consideration of their meaning in the context of the relevant technology. Also, terms used in embodiments of the present invention are for illustrative purposes only and are not intended to limit the present invention. In this specification, singular forms may also include plural forms unless otherwise specified in the text, and when it is written as "A and / or at least one (or more) of B and C", it may include one or more of all possible combinations of A, B, and C. Furthermore, terms such as 1st, 2nd, A, B, (a), (b), etc. may be used when describing the components of embodiments of the present invention. Such terminology is merely used to distinguish one component from another, and does not limit the nature, order, or sequence of the component in question. Furthermore, when it is stated that a component is “connected,” “joined,” or “connected” to another component, this can include not only cases where the component is directly connected, joined, or connected to the other component, but also cases where it is “connected,” “joined,” or “connected” by another component that lies between it and the other component. Also, when it is stated that something is formed or positioned “above or below” each component, “above or below” includes not only cases where two components are in direct contact with each other, but also cases where one or more other components are formed or positioned between the two components. Moreover, when expressed as “above or below,” it can include not only the upward direction but also the downward direction relative to one component.

[0018] In the description of the present invention, the first lens means the lens closest to the object side, and the last lens means the lens closest to the image side (or sensor surface). In the description of the present invention, unless otherwise specified, all units such as the radius, effective diameter, thickness, distance, BFL (Back Focal Length), TTL (Total track length or Total Top Length) of the lens are in mm. In this specification, the shape of the lens is shown based on the optical axis of the lens. As an example, the meaning that the object side surface of the lens is convex means that the vicinity of the optical axis on the object side surface of the corresponding lens is convex, not the meaning that the periphery of the optical axis is convex. Therefore, even when the object side surface of the lens is described as convex, the portion around the optical axis on the object side surface of the corresponding lens may be concave. In this specification, it is clarified that the thickness and radius of curvature of the lens are measured based on the optical axis of the corresponding lens. Also, the "object side surface" can mean the surface of the lens facing the object side with respect to the optical axis, and the "image side" can mean the surface of the lens facing the imaging surface with respect to the optical axis.

[0019] The optical system according to an embodiment of the present invention can include a plurality of lenses. Specifically, the optical systems according to the first to third embodiments can include at least eight lenses. As the resolution increases, the size of the image sensor also becomes larger, and the number of lenses gradually increases according to the resolution of the image sensor. The embodiments of the present invention attempt to provide a high-resolution optical system using at least eight lenses.

[0020] Referring to Figure 1, 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 arranged sequentially from the object side to the image side. The optical system may include an optical filter 192 and an image sensor 190. The optical system having the plurality of lenses 111 to 118 can be defined as a lens optical system, and the optical system further including the lenses 111 to 118, an optical filter 192, and an image sensor 190 can be defined as a camera module. The camera module may include a circuit board, at least one lens holder supporting at least one lens or two or more lenses, and at least one of one or more drive members that move the lens holder in the direction of the optical axis and / or perpendicular to the optical axis.

[0021] 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. Light corresponding to the image information of an object enters through the first lens 111, second lens 112, third lens 113, fourth lens 114, fifth lens 115, sixth lens 116, seventh lens 117, and eighth lens 118, passes through the optical filter 192, is focused on the image sensor 190, and can be acquired as an electrical signal.

[0022] Each of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118 may include an effective area and a non-effective area. The effective area may be an area where effective light is incident on or emitted from each lens. That is, the effective area may be an area where the incident light is refracted to embody optical characteristics. The non-effective area may be disposed around the effective area. The non-effective area may be an area where the light does not enter. That is, the non-effective area may be an area irrelevant to the optical characteristics of the optical system. Also, the non-effective area may be an area fixed to a barrel (not shown) that houses the lens or the like, or an area where light is blocked by a light-shielding portion or a spacer disposed around the object side or the sensor side of each lens. Here, the object side surface may be an incident side surface, and the sensor side surface may be an image side surface or an emission side surface.

[0023] At least one or two or more of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118, or at least one or two or more of the fifth to eighth lenses 115, 116, 117, 118 may have a length such that the effective diameter in a first direction orthogonal to the optical axis Lx is smaller than the effective diameter in a second direction orthogonal to the first direction. Such a lens may be provided in a non-circular shape having a diameter in the second direction and a distance smaller than the diameter in the second direction in the first direction.

[0024] The optical system shown in Figure 1 may include an aperture ST for adjusting the amount of incident light. The aperture ST may be positioned 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 positioned around the outside of the third lens 113 and the fourth lens 114, or around the outside of the second lens 112 and the third lens 113. The aperture ST may be positioned around the sensor side of the third lens 113 or around the object side 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 function as an aperture. For example, one surface selected from among the lens surfaces of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 can act as an aperture to adjust the amount of light. For example, the area around the sensor side of the third lens 113 or the area around the object side of the fourth lens 114 can act as an aperture.

[0025] Referring to Figure 1, the first lens 111 in the optical system may have a negative refractive power. The first lens 111 may be made of 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. The first surface S1 may be concave on the optical axis Lx, and the second surface S2 may be concave. At least one or both of the first surface S1 and the second surface S2 may be aspherical. At least one of the first surface S1 and the second surface S2 may contain an inflection point; for example, the first surface S1 may have an inflection point between the periphery of the optical axis and the edge of the first surface S1. The size of the effective diameter of the object side surface or sensor side surface of the first lens 111 may be larger than the size of 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 into which light is incident.

[0026] The second lens 112 may have a positive (+) refractive power. The second lens 112 may be made of plastic or glass material. The second lens 112 may have a third surface S3 defined as an object side and a fourth surface S4 defined as a sensor side. The third surface S3 may be concave on the optical axis Lx, and the fourth surface S4 may be convex. At least one or both of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 112 may have a negative (-) refractive power, the third surface S3 may be convex or planar, and the fourth surface S4 may be concave or planar.

[0027] Here, the central thickness of the first lens 111 may be greater than the central thicknesses of the second and third lenses 112 and 113, respectively. The central thickness of the first lens 111 may be 1.5 times or more the central thickness of the second lens 112, for example, in the range of 1.5 to 2.5 times. The central thickness of the first lens 111 may be 2 times or more the central 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 central thickness of the first lens 111 may be the largest among the central thicknesses of the lenses in the optical system, and may be 0.7 mm or more, for example, in the range of 0.7 mm to 1 mm. The central thickness of the first lens 111 may be greater than the sum of the central thicknesses of the second lens 112 and the third lens 113.

[0028] The optical axis spacing between the first lens 111 and the second lens 112 may be the largest among the spacings between two adjacent lenses, for example, 80% or more of the central 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 central thickness of the second lens 112 may be 0.1 mm or less. The optical axis spacing between the first lens 111 and the second lens 112 may be 0.35 mm or more, for example, in the range of 0.35 mm to 0.55 mm.

[0029] The third lens 113 may have a positive (+) refractive power. The third lens 113 may be made of plastic or glass material. The third lens 113 may include a fifth surface S5 defined as an object side and a sixth surface S6 defined as a sensor side. 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 that is convex on 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 a negative (-) refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0030] 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 and second lenses 111 and 112, and larger than the optical axis spacing between the third and fourth lenses 113 and 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 and sixth lenses 115 and 116, smaller than the optical axis spacing between the sixth and seventh lenses 116 and 117, and larger than the optical axis spacing between the seventh and eighth lenses 117 and 118.

[0031] The fourth lens 114 may have a positive (+) refractive power. The fourth lens 114 may be made of plastic or glass material. The fourth lens 114 may include a seventh surface S7 defined as an object side and an eighth surface S8 defined as a sensor side. The seventh surface S7 may be convex on the optical axis, 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 sides of the fourth lens 114 may be convex, and when expressed as an absolute value, the radius of curvature of the seventh surface S7 at the center may be greater than the radius of curvature of the eighth surface S8, and may be 5.5 mm or more, for example, in the range of 5.5 mm to 8 mm. The radius of curvature of the seventh surface S7 at the 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 S2 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 more, 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.

[0032] The fifth lens 115 may have a negative refractive power. The fifth lens 115 may be made of plastic or glass material. The fifth lens 115 may include a ninth surface S9 defined as an object side and a tenth surface S10 defined as a sensor side. The ninth surface S9 may be convex, and the tenth surface S10 may be concave. The ninth surface S9 may have at least one inflection 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 S9 of the fifth lens 115 may be planar or concave.

[0033] Here, with respect to the third lens 113, the effective diameter on the object side or sensor side may decrease in the order of the first lens 111, the second lens 112, and the third lens 113. With respect to the third lens 113, the effective diameter on the object side or sensor side may increase in the order of the third lens 113, the fourth lens 114, the fifth lens 115, and the sixth lens 116. Also, the effective diameter on the object side or sensor side of the seventh lens 117 may be larger than the effective diameter of each surface of the sixth lens 116 and smaller than the effective diameter of each surface of the eighth lens 118.

[0034] The sixth lens 116 may have a positive (+) refractive power. The sixth lens 116 may be made of a plastic material. The sixth lens 116 may include an eleventh surface S11 defined as an object side and a twelfth surface S12 defined as a sensor side. The eleventh surface S11 may be convex on the optical axis, and the twelfth surface S12 may be concave. The eleventh surface S11 and the twelfth surface S12 may be aspherical. The twelfth surface S12 may have at least one inflection point around its center. The inflection point may be located further adjacent to the edge than to the optical axis or center. As another example, the sixth lens 116 may have a negative (-) refractive power, or the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0035] The central thickness of the sixth lens 116 may be thicker than the central thickness of the fifth lens 115 and thinner than the central thickness of the seventh lens 117. When expressed as an absolute value, the radius of curvature of the eleventh surface S11 at the center may be greater than the radius of curvature of the tenth surface S10 of the fifth lens 115 and greater than the radius of curvature of the fourteenth surface S14 of the seventh lens 117. When expressed as an absolute value, the radius of curvature of the twelfth surface S12 at the center may be greater than the respective radii of curvature of the tenth surface S10 and the eleventh surface S11, and smaller than the radius of curvature of the thirteenth surface S13 of the seventh lens 117.

[0036] The seventh lens 117 may have a negative refractive power. The seventh lens 117 may be made of plastic or glass material. The seventh lens 117 may include a thirteenth surface S13 defined as an object side and a fourteenth surface S14 defined as a sensor side. The thirteenth surface S13 may be concave on the optical axis Lx, and the fourteenth surface S14 may be convex. That is, the seventh lens 117 may have a meniscus shape that is convex on 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 planar or convex.

[0037] The central thickness of the seventh lens 117 may be greater than the central thickness of the sixth lens 116 and 1.5 times thicker than the central thickness of the eighth lens 118. When expressed as an absolute value, the radius of curvature of the thirteenth surface S13 at the center may be four times or more the radius of curvature of the fourteenth surface S14, for example, in the range of 4 to 6 times. The central thickness of the seventh lens 117 may be 1.5 times or more the central thickness of the third and fifth lenses 113 and 115, for example, in the range of 1.5 to 3 times.

[0038] The optical axis distance between the seventh lens 117 and the sixth lens 116 on the optical axis Lx may be greater than the optical axis distance between the seventh lens 117 and the eighth lens 118, and may be less than the central thickness of the seventh lens 117.

[0039] The eighth lens 118 may have a negative refractive power. The eighth lens 118 may include a plastic material. The eighth lens 118 may include a 15th surface S15 defined as an object side and a 16th surface S16 defined as a sensor side. The 15th surface S15 may be convex on the optical axis, and the 16th surface S16 may be concave. The 15th surface S15 and the 16th surface S16 may be aspherical. Each of the 15th surface S15 and the 16th surface S16 may have at least one inflection point. In detail, the 15th surface S15 may have an inflection point around its center, and the position of the inflection point of the 16th surface S16 may be located further outward than the position of the inflection point of the 15th surface S15 with respect to the optical axis. Here, the straight line connecting the edges of the object-side 15th surface S15 of the 8th lens 118 can be positioned between the vertex of the sensor-side 16th surface S16 of the 7th lens 117 and the vertex of the 15th surface S15, which lie on the optical axis. As a result, the light incident from the 8th lens 118 can be refracted further outward with respect to the optical axis Lx. In the optical system of the present invention, the number of surfaces having inflection points among the 1st surface S1 to the 16th surface S16 may be 4 or 5 or more.

[0040] The optical filter 192 may include at least one of the following optical filters: an infrared filter, a cover glass, etc. The optical filter 192 can allow light in a set wavelength band to pass through and filter out light in a different wavelength band. If the optical filter 192 includes an infrared filter, it can block radiant heat emitted from external light from being transmitted to the image sensor. The optical filter 192 can also transmit visible light and reflect infrared light. The image sensor 190 can sense light. The image sensor 190 may include a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), etc.

[0041] A reflective member may be positioned on the incident side of the first lens 111 according to an embodiment of the present invention. The reflective member can reflect light incident through an optical axis perpendicular to the optical axis Lx of the first lenses 111 to the eighth lenses 118 back onto the first lens 111. The reflective member may include a prism, i.e., a triangular or right-angle prism.

[0042] The total length TTL of the optical system according to the first embodiment may be 4 mm or more, for example, in the range of 4 mm to 12 mm or 4 mm to 8 mm. The 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 16th surface S16 of the eighth lens 118 to the image sensor 190 may be 3 mm or more, 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 1.0 field may be 0.8 mm or more, 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 may be 1 mm or more, for example, in the range of 1 mm to 5 mm or 1 mm to 3 mm.

[0043] The effective focal length (EFL) of the optical system may be 1 mm or more, for example, in the range of 1 mm to 3 mm or 1 mm to 2 mm. The overall F-number of the optical system may be 2 or more, for example, in the range of 2 to 3 or 2 to 2.80. The half-field of view (HFOV) of the optical system may be 30 degrees or more, for example, in the range of 30 degrees to 80 degrees or 40 degrees to 75 degrees. The diameter of the object-side entrance pupil (EPD) of the optical system may be 1 mm or less, for example, in the range of 0.2 mm to 1 mm.

[0044] In the optical system of the first embodiment described above, the first to 16th surfaces S1 to S16 of the first to 8th lenses 111, 112, 113, 114, 115, 116, 117, and 118 can all be aspherical. With respect to the optical axis, the radius of curvature (converted to absolute value) of the first to 16th surfaces S1 to S16 is such that there are 12 or fewer surfaces with a radius of curvature of 5.5 mm or less among the object side surface and sensor side surface, and there may be 4 or more surfaces with a radius of curvature exceeding 5.5 mm.

[0045] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, there may be four or more lenses with a convex side facing the object on the optical axis, four or fewer lenses with a concave side facing the object, four or more lenses with a convex side facing the sensor, and four or fewer lenses with a concave side facing the sensor.

[0046] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, there may be five or more lenses with an Abbe number of 50 or more, and three or fewer lenses with an Abbe number less than 50. 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 may be 50 or more, the Abbe numbers of the second lens 112, the fifth lens 115, and the eighth lens 118 may be 35 or less, and the Abbe number of the fifth lens 115 may be the smallest among the lenses in the optical system and may be less than 25.

[0047] In the optical system or the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118, there may be three or more lenses made of high refractive index material with a refractive index of 1.6 or higher at 587 nm (d-line), and five or fewer lenses made of low refractive index material with a refractive index of less than 1.6. For example, the second, fifth, and eighth lenses 112, 115, and 118 at 587 nm may have a high refractive index of 1.6 or higher, while the first, third, fourth, sixth, and seventh lenses 111, 113, 114, 116, and 117 may have a low refractive index of less than 1.6.

[0048] Looking at the central thicknesses of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118, there can be three or more lenses with a central thickness of 0.5 mm or more, and five or more lenses with a central thickness of less than 0.5 mm. For example, the central thicknesses T1, T2, T3 of the first to third lenses 111, 112, 113 can satisfy the relationship T3 < T2 < T1, and the central thicknesses T3, T4, T5, T6 of the third to sixth lenses 113, 114, 115, 116 satisfy the relationship T5 ≤ T3 < T6 < T4, the central thicknesses T3, T4 of the third and fourth lenses 113, 114 satisfy the relationship T3 < T4, and the central thicknesses T7, T8 of the seventh and eighth lenses 117, 118 can satisfy the relationship T8 < T7 < T1. Here, T1 to T8 are the central thicknesses of the first to eighth lenses 111 to 118 respectively.

[0049] Looking at the intervals on the optical axis between two adjacent lenses among the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118, it satisfies T78 < T23 < T67 < T12. T67 is the optical axis interval between the adjacent sixth and seventh lenses 116, 117, T23 is the optical axis interval between the second and third lenses 112, 113, T78 is the optical axis interval between the adjacent seventh and eighth lenses 117, 118, and T12 is the optical axis interval between the first and second lenses 111, 112. Here, T12 is 0.35 mm or more and may be larger than the central thicknesses of the third and fifth lenses 113, 115. T23 is 0.12 mm or less, and T67 may be larger than the optical axis interval between the fifth and sixth lenses 115, 116. Looking at the interval between the seventh lens 117 and the eighth lens 118, the optical axis interval between two adjacent vertices on the optical axis may be smaller than the interval between two adjacent peripheral parts.

[0050] When the refractive powers of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, 118 are P1 to P9 respectively, when these refractive powers are expressed as absolute values, the relationships P2 < P6 < P3 or / and P3 < P1 < P5 < P7 < P8 ≤ P4 can be satisfied.

[0051] Looking at the 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 may be the largest, and could be 25mm or more, for example, in the range of 25mm to 45mm or 25mm to 35mm. The focal length of the sixth lens 116 may be smaller than the focal length of the second lens 112 and larger than the focal length of the third lens 113. The combined focal length of the first and second lenses 111 and 112 is -3mm or more, and the combined focal length of the third and fourth lenses 113 and 114 may be 2mm or less. When expressed as an absolute value, the combined focal length of the first and second lenses 111 and 112 may be larger than the combined focal length of the third and fourth lenses 113 and 114. The edge thickness of each of the first to eighth lenses 111, 112, 113, 114, 115, 116, 117, and 118 is such that there are two or more lenses with an edge thickness of 0.55 mm or more, six or fewer lenses with an edge thickness of less than 0.55 mm, and three or fewer lenses with an edge thickness of 0.3 mm or less.

[0052] Table 1 shows the values ​​for the radius of curvature, thickness, spacing, refractive index, and Abbe number of each lens surface in the first embodiment.

[0053] [Table 1]

[0054] In Table 1, Thickness is the center thickness of each lens (mm), and Spacing is the distance between two adjacent lenses (mm). S17 indicates the incident side of the optical filter, and S18 indicates the outgoing side of the optical filter.

[0055] Table 2 shows the effective radius (semi-aperture), edge thickness, refractive power value, and focal length for each lens in Figure 1.

[0056] [Table 2]

[0057] Figure 2 is an analysis graph showing the longitudinal spherical aberration, astigmatism, and distortion of the optical system in Figure 1. In the optical system according to the first embodiment, spherical aberration may be a phenomenon in which the focal point of light passing through different parts of the lens (e.g., the center and the periphery) changes. The horizontal axis shows the degree of longitudinal spherical aberration, and the vertical axis shows the normalized distance from the center of the optical axis, and can show the change in longitudinal spherical aberration with respect to the wavelength of light. Longitudinal spherical aberration can be shown, for example, for light with wavelengths of approximately 656.2725 nm (nanometer), approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm, respectively. The longitudinal spherical aberration of the optical system is limited to within +0.008 to ~0.008, confirming that it exhibits stable optical characteristics.

[0058] Astigmatism in an optical system can occur when the tangential plane (or meridian plane) and sagittal plane of a lens have different radii, resulting in misaligned focal points for light passing through the vertical and horizontal directions. The astigmatism of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, where the solid line represents tangential astigmatism (e.g., meridian curvature), and the dotted line represents sagittal astigmatism (e.g., sagittal curvature). It can be confirmed that the astigmatism is limited to +0.025 to -0.025, indicating stable optical characteristics.

[0059] Distortion in an optical system occurs because the optical magnification changes with distance from the optical axis OI. As a result, the image formed at the actual image plane (e.g., 190 in Figure 1) may appear larger or smaller than the image formed at the theoretical image plane. The distortion of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured through the optical system may exhibit some distortion at points deviated from the optical axis OI. However, such distortion is generally observed in optical devices using lenses, and the distortion rate is less than approximately 3%, providing good optical characteristics. <Second Example>

[0060] The optical system according to the second embodiment is shown in Figures 3 and 4. In the description of the second embodiment, for configurations identical to those of the first embodiment, refer to the description of the first embodiment, and redundant explanations will be omitted.

[0061] Referring to Figure 3, in the optical system, the first lenses 121 to the eighth lenses 128 can be aligned with the optical axis Lx. The first lens 121 can have a negative refractive power. The first surface S1 of the first lens 121 may be concave on the optical axis Lx, and the second surface S2 may also 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 contain an inflection point; for example, the first surface S1 may have an inflection point between the periphery of the optical axis and the edge of the first surface S1. The size of the effective diameter of the object side or sensor side of the first lens 121 may be larger than the size of the effective diameter of the object side or sensor side 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 or sensor side into which light is incident.

[0062] The second lens 122 may have a positive refractive power. The third surface S3 of the second lens 122 may be convex on the optical axis Lx, and the fourth surface S4 may be concave. That is, the second lens 122 may have a meniscus shape that is convex on the image side. At least one or both of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 122 may have a 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 contain an inflection point; for example, the third surface S3 may have an inflection point between the periphery of the optical axis and the edge of the third surface S3.

[0063] Here, the central thickness of the first lens 121 may be greater than the central thicknesses of the second and third lenses 122 and 123, respectively. The central thickness of the first lens 121 may be 1.2 times or more the central thickness of the second lens 122, for example, in the range of 1.2 to 2.2 times. The central thickness of the first lens 121 may be 1.8 times or more the central thickness of the third lens 123, for example, in the range of 1.8 to 3 times, or in the range of 2 to 3 times. Here, the central thickness of the first lens 121 may be the largest among the central thicknesses of the lenses in the optical system, and may be 0.7 mm or more, for example, in the range of 0.7 mm to 1.2 mm. The central thickness of the first lens 121 may be the same as or less than the sum of the central thicknesses of the second lens 122 and the third lens 123.

[0064] The optical axis spacing between the first lens 121 and the second lens 122 may be the largest among the spacings between two adjacent lenses, for example, 40% or more of the central 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 central thickness of the second lens 122 may be 0.2 mm or more. The optical axis spacing between the first lens 121 and the second lens 122 may be 0.40 mm or more, for example, in the range of 0.40 mm to 0.65 mm.

[0065] The third lens 123 may have a positive refractive power. On the optical axis, the fifth surface S5 of the third lens 123 may be concave, and the sixth surface S6 may be convex. That is, the third lens 123 may have a meniscus shape that is convex on 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 a negative refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0066] 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 and second lenses 121 and 122, and larger than the optical axis spacing between the third and fourth lenses 123 and 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 and sixth lenses 125 and 126, smaller than the optical axis spacing between the sixth and seventh lenses 126 and 127, and larger than the optical axis spacing between the seventh and eighth lenses 127 and 128.

[0067] The fourth lens 124 may have a positive refractive power. The seventh surface S7 of the fourth lens 124 may be convex on the optical axis, and the eighth surface S8 may also be convex. At least one or both of the seventh surface S7 and the eighth surface S8 may be aspherical. Both sides of the fourth lens 124 may be convex, and when expressed as an absolute value, the radius of curvature of the seventh surface S7 at the center may be larger than the radius of curvature of the eighth surface S8, and may be 5.5 mm or more, for example, in the range of 5.5 mm to 8 mm. The radius of curvature of the seventh surface S7 at the 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 S2 may be 3 mm or less. Here, the center thickness of the fourth lens 124 may be smaller than the center thickness of the second lens 122, and may be 0.45 mm or more, 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 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 124 may be smaller than the sum of the center thicknesses of the third lens 123 and the fifth lens 125.

[0068] The fifth lens 125 may have a negative refractive power. The ninth surface S9 of the fifth lens 125 may be convex on the optical axis, and the tenth surface S10 may be concave. The ninth surface S9 may have at least one inflection 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 S9 of the fifth lens 125 may be planar or concave.

[0069] Here, with respect to the third lens 123, the effective diameter on the object side or sensor side may decrease in the order of the first lens 121, the second lens 122, and the third lens 123. With respect to the third lens 123, the effective diameter on the object side or sensor side may increase in the order of the third lens 123, the fourth lens 124, the fifth lens 125, and the sixth lens 126. Also, the effective diameter on the object side or sensor side of the seventh lens 127 may be larger than the effective diameter of each surface of the sixth lens 126 and smaller than the effective diameter of each surface of the eighth lens 128.

[0070] The sixth lens 126 may have a positive (+) refractive power. The eleventh surface S11 of the sixth lens 126 may be convex on the optical axis, and the twelfth surface S12 may be concave. The eleventh surface S11 and the twelfth surface S12 may be aspherical. The twelfth surface S12 may have at least one inflection point around the center. The inflection point may be located further adjacent to the edge than to the optical axis or the center. As another example, the sixth lens 126 may have a negative (-) refractive power, or the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0071] The central thickness of the sixth lens 126 may be thicker than the central thickness of the fifth lens 125 and thinner than the central thickness of the seventh lens 127. When expressed as an absolute value, the radius of curvature of the eleventh surface S11 at the center may be greater than the radius of curvature of the tenth surface S10 of the fifth lens 125 and greater than the radius of curvature of the fourteenth surface S14 of the seventh lens 127. When expressed as an absolute value, the radius of curvature of the twelfth surface S12 at the center may be greater than the respective radii of curvature of the tenth surface S10 and the eleventh surface S11, and smaller than the radius of curvature of the thirteenth surface S13 of the seventh lens 127.

[0072] The seventh lens 127 may have a positive (+) refractive power. On the optical axis Lx, the 13th surface S13 of the seventh lens 127 may be concave, and the 14th surface S14 may be convex. That is, the seventh lens 127 may have a meniscus shape that is convex toward the sensor side. At least one or both of the 13th surface S13 and the 14th surface S14 may be aspherical. As another example, the 13th surface S13 may be planar or convex.

[0073] The central thickness of the seventh lens 127 may be greater than the central thickness of the sixth lens 126 and 1.3 times thicker than the central thickness of the eighth lens 128. When expressed as an absolute value, the radius of curvature of the thirteenth surface S13 at the center may be four times or more the radius of curvature of the fourteenth surface S14, for example, in the range of four to six times. The central thickness of the seventh lens 127 may be 1.5 times or more the central thickness of the fifth lens 125, for example, in the range of 1.5 to three times.

[0074] The optical axis distance between the seventh lens 127 and the sixth lens 126 on the optical axis Lx may be greater than the optical axis distance between the seventh lens 127 and the eighth lens 128, and may be less than the central thickness of the seventh lens 127.

[0075] The eighth lens 128 may have a negative refractive power. The 15th surface S15 of the eighth lens 128 may be convex on the optical axis, and the 16th surface S16 may be concave. The 15th surface S15 and the 16th surface S16 may be aspherical. Each of the 15th surface S15 and the 16th surface S16 may have at least one inflection point. In detail, the 15th surface S15 may have an inflection point around its center, and the position of the inflection point of the 16th surface S16 may be located further outward than the position of the inflection point of the 15th surface S15 with respect to the optical axis. Here, a straight line connecting the edges of the object-side 15th surface S15 of the eighth lens 128 may be located between the vertex of the sensor-side 16th surface S16 of the seventh lens 127 and the vertex of the 15th surface S15 on the optical axis. As a result, light entering from the eighth lens 128 can be refracted further outward with respect to the optical axis Lx.

[0076] The optical filter 192 and the image sensor 190 are described in reference to the description of the first embodiment. The total length TTL of the optical system according to the second embodiment may be 4 mm or more, for example, in the range of 4 mm to 12 mm or 4 mm to 8 mm. The distance BFL from the vertex of the sensor-side 16th surface S16 of the 8th lens 128 to the image sensor 190 may 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 1.0 field may be 0.8 mm or more, 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 may be 1 mm or more, for example, in the range of 1 mm to 5 mm or 1 mm to 3 mm.

[0077] The effective focal length (EFL) of the optical system may be 1 mm or more, for example, in the range of 1 mm to 3 mm or 1 mm to 2 mm. The overall F-number of the optical system may be 2 or more, for example, in the range of 2 to 3 or 2 to 2.80. The half-field of view (HFOV) of the optical system may be 30 degrees or more, for example, in the range of 30 degrees to 80 degrees or 40 degrees to 75 degrees. The diameter of the object-side entrance pupil (EPD) of the optical system may be 1 mm or less, for example, in the range of 0.2 mm to 1 mm. The combined focal length of the first and second lenses 121 and 122 is -2.5 mm or more, and the combined focal length of the third and fourth lenses 123 and 124 may be 2 mm or less. When expressed as an absolute value, the combined focal length of the first and second lenses 121 and 122 may be greater than the combined focal length of the third and fourth lenses 123 and 124.

[0078] In the optical system of the second embodiment described above, the first to 16th surfaces S1 to S16 of the first to 8th lenses 121, 122, 123, 124, 125, 126, 127, and 128 can all be aspherical. With respect to the optical axis, the radius of curvature (converted to absolute value) of the first to 16th surfaces S1 to S16 can be 12 or less for the object side surface and sensor side surface with a radius of curvature of 5.5 mm or less, and 4 or more for the radius of curvature exceeding 5.5 mm.

[0079] In the optical system according to the second embodiment or in the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, there may be five or more lenses with a convex object side on the optical axis, three or fewer lenses with a concave object side, three or more lenses with a convex sensor side, and five or fewer lenses with a concave sensor side.

[0080] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, there may be five or more lenses with an Abbe number of 50 or more, and three or fewer lenses with an Abbe number less than 50. For example, the Abbe numbers of the first lens 121, third lens 123, fourth lens 124, sixth lens 126, and seventh lens 127 are 50 or more, the Abbe numbers of the second lens 122, fifth lens 125, and 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.

[0081] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128, there may be three or more lenses made of high refractive index material with a refractive index of 1.6 or higher at 587 nm, and five or fewer lenses made of low refractive index material with a refractive index of less than 1.6. For example, the second, fifth, and eighth lenses 122, 125, and 128 at 587 nm may have a high refractive index of 1.6 or higher, while the first, third, fourth, sixth, and seventh lenses 121, 123, 124, 126, and 127 may have a low refractive index of less than 1.6.

[0082] In the optical system or the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, 128, there may be four or more lenses with a center thickness of 0.5 mm or more, and four or fewer lenses with a center thickness of less than 0.5 mm. For example, the center thicknesses T1, T2, T3 of the first to third lenses 121, 122, 123 can satisfy the relationship T3 < T2 < T1, and the center thicknesses T3, T4, T5, T6 of the third to sixth lenses 123, 124, 125, 126 satisfy the relationship T5 < T3 ≤ T6 < T4. The center thicknesses T3, T4 of the third and fourth lenses 123, 124 satisfy the relationship T3 < T4, and the center thicknesses T7, T8 of the seventh and eighth lenses 127, 128 can satisfy the relationship T8 < T7 < T1. Here, T1 to T8 are the center thicknesses of the first to eighth lenses 121 to 128.

[0083] In the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, 128, looking at the intervals on the optical axis between two adjacent lenses, T78 < T23 < T67 < T12 is satisfied, where T67 is the optical axis interval between the adjacent sixth and seventh lenses 126, 127, T23 is the optical axis interval between the second and third lenses 122, 123, T78 is the optical axis interval between the adjacent seventh and eighth lenses 127, 128, and T12 is the optical axis interval between the first and second lenses 121, 122. Here, T12 is 0.35 mm or more and may be larger than the center thickness of the fifth lens 125. T23 is 0.20 mm or less, and the optical axis interval T67 between the sixth and seventh lenses 126, 127 may be the same as or larger than the optical axis interval between the fifth and sixth lenses 125, 126. Looking at the interval between the seventh lens 127 and the eighth lens 128, the optical axis interval between two adjacent vertices on the optical axis may be smaller than the interval between two adjacent peripheral parts.

[0084] When the refractive powers of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, 128 are P1 to P9 respectively, when these refractive powers are represented by absolute values, the relationship P2 ≤ P6 < P3 or / and the relationship P3 < P1 < P5 < P7 ≤ P8 ≤ P4 can be satisfied.

[0085] Looking at the 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 may be the largest, and could be 12mm or more, for example, in the range of 12mm to 30mm or 12mm to 20mm. The focal length of the sixth lens 126 may be smaller than the focal length of the second lens 122 and larger than the focal length of the third lens 123.

[0086] The edge thickness of each of the first to eighth lenses 121, 122, 123, 124, 125, 126, 127, and 128 is such that there are three or more lenses with an edge thickness of 0.50 mm or more, six or fewer lenses with an edge thickness of less than 0.50 mm, and two or fewer lenses with an edge thickness of less than 0.3 mm.

[0087] Table 3 below shows the data for the radius of curvature, thickness, spacing, refractive index, and Abbe number of each lens surface in the second embodiment shown in Figure 3.

[0088] [Table 3]

[0089] In Table 3, the thickness is the center thickness (mm) of each lens in Figure 3, and the spacing is the distance (mm) between two adjacent lenses. S17 indicates the incident side of the optical filter, and S18 indicates the outgoing side of the optical filter.

[0090] Table 4 shows the effective radius (semi-aperture), edge thickness, refractive power value, and focal length for each lens in Figure 3.

[0091] [Table 4]

[0092] Figure 4 is an analysis graph showing the longitudinal spherical aberration, astigmatism, and distortion of the optical system in Figure 3. In the optical system according to the second embodiment, spherical aberration may be a phenomenon in which the focal point of light passing through different parts of the lens (e.g., the center and the periphery) changes. The horizontal axis shows the degree of longitudinal spherical aberration, and the vertical axis shows the normalized distance from the center of the optical axis, and the change in longitudinal spherical aberration with respect to the wavelength of light can be shown. Longitudinal spherical aberration can be shown, for example, for light with wavelengths of approximately 656.2725 nm (nanometer), approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm, respectively. The longitudinal spherical aberration of the optical system is limited to within +0.025 to -0.025, confirming that it exhibits stable optical characteristics.

[0093] Astigmatism in an optical system can occur when the tangential plane (or meridian plane) and sagittal plane of a lens have different radii, resulting in misaligned focal points for light passing through the vertical and horizontal directions. The astigmatism of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, where the solid line represents tangential astigmatism (e.g., meridian curvature), and the dotted line represents sagittal astigmatism (e.g., sagittal curvature). As can be seen through Figure 4, the astigmatism is limited to within +0.050 to -0.050, demonstrating stable optical characteristics.

[0094] Distortion in an optical system occurs because the optical magnification changes with distance from the optical axis OI. As a result, the image formed at the actual image plane (e.g., 190 in Figure 3) may appear larger or smaller than the image formed at the theoretical image plane. The distortion of the optical system described above is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured through the optical system may exhibit some distortion at points deviated from the optical axis OI. However, such distortion is generally observed in optical devices using lenses, and the distortion rate is less than approximately 3%, providing good optical characteristics. <Third Example>

[0095] The optical system according to the third embodiment is shown in Figures 5 and 6. In the description of the third embodiment, configurations identical to those of the first and second embodiments are described in the description, and redundant explanations are omitted. Referring to Figure 5, in the optical system according to the third embodiment, the first lens 131 can have a negative refractive power. The first surface S1 of the first lens 131 may be concave on the optical axis, and the second surface S2 may also 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 contain an inflection point; for example, the first surface S1 may have an inflection point between the periphery of the optical axis and the edge of the first surface S1. The size of the effective diameter of the object side or sensor side of the first lens 131 may be larger than the size of the effective diameter of the object side or sensor side of the second lens 132 or the third lens 133. Here, the effective diameter may be the diameter of the effective area on the side of the object or sensor into which the light is incident.

[0096] The second lens 132 may have a positive refractive power. The third surface S3 of the second lens 132 may be convex on the optical axis, and the fourth surface S4 may be concave. That is, the second lens 132 may have a meniscus shape that is convex on the image side. At least one or both of the third surface S3 and the fourth surface S4 may be aspherical. As another example, the second lens 132 may have a negative refractive power, the third surface S3 may be concave or planar, and the fourth surface S4 may be convex or planar.

[0097] Here, the central thickness of the first lens 131 may be greater than the central thicknesses of the second and third lenses 132 and 133, respectively. The central thickness of the first lens 131 may be more than 1 times the central thickness of the second lens 132, for example, in the range of 1.2 to 2 times. The central thickness of the first lens 131 may be 1.5 times or more the central 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 central thickness of the first lens 131 may be the largest among the central thicknesses of the lenses in the optical system, and may be 0.7 mm or more, for example, in the range of 0.7 mm to 1.2 mm. The central thickness of the first lens 131 may be less than the sum of the central thicknesses of the second lens 132 and the third lens 133.

[0098] The optical axis spacing between the first lens 131 and the second lens 132 may be the largest among the spacings between two adjacent lenses, for example, 50% or more of the central 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 central thickness of the second lens 132 may be 0.4 mm or less. The optical axis spacing between the first lens 131 and the second lens 132 may be 0.35 mm or more, for example, in the range of 0.35 mm to 0.75 mm.

[0099] The third lens 133 may have a positive refractive power. The fifth surface S5 of the third lens 133 may be convex on the optical axis, and the sixth surface S6 may also 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 a negative refractive power, the fifth surface S5 may be convex or planar, and the sixth surface S6 may be concave or planar.

[0100] The optical axis spacing between the second lens 132 and the third lens 133 may be smaller than the optical axis spacing between the first and second lenses 131 and 132, and larger than the optical axis spacing between the third and fourth lenses 133 and 134. The optical axis spacing between the second lens 132 and the third lens 133 may be smaller than the optical axis spacing between the fifth and sixth lenses 135 and 136, smaller than the optical axis spacing between the sixth and seventh lenses 136 and 137, and larger than the optical axis spacing between the seventh and eighth lenses 137 and 138.

[0101] The fourth lens 134 may have a positive refractive power. The seventh surface S7 of the fourth lens 134 may be convex on the optical axis, and the eighth surface S8 may also be convex. At least one or both of the seventh surface S7 and the eighth surface S8 may be aspherical. The fourth lens 124 may have convex sides, and when expressed as an absolute value, the radius of curvature of the seventh surface S7 at the center may be greater than the radius of curvature of the eighth surface S8, and may be 5.5 mm or more, for example, in the range of 5.5 mm to 8 mm. The radius of curvature of the seventh surface S7 at the 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 S2 may be 2 mm or more. Here, the center thickness of the fourth lens 134 may be smaller than the center thickness of the second lens 132, and may be 0.45 mm or more, 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 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 134 may be greater than the sum of the center thicknesses of the fifth lens 135 and the eighth lens 138.

[0102] The fifth lens 135 may have a negative refractive power. The ninth surface S9 of the fifth lens 135 may be convex on the optical axis, and the tenth surface S10 may be concave. The ninth surface S9 may have at least one inflection 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 S9 of the fifth lens 135 may be planar or concave.

[0103] Here, with respect to the third lens 133, the effective diameter on the object side or sensor side may decrease in the order of the first lens 131, the second lens 132, and the third lens 133. With respect to the third lens 133, the effective diameter on the object side or sensor side may increase in the order of the third lens 133, the fourth lens 134, the fifth lens 135, and the sixth lens 136. Also, the effective diameter on the object side or sensor side of the seventh lens 137 may be larger 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.

[0104] The sixth lens 136 may have a positive (+) refractive power. The eleventh surface S11 of the sixth lens 136 may be convex on the optical axis, and the twelfth surface S12 may be concave. The eleventh surface S11 and the twelfth surface S12 may be aspherical. The twelfth surface S12 may have at least one inflection point around the center. The inflection point may be located further adjacent to the edge than to the optical axis or the center. As another example, the sixth lens 136 may have a negative (-) refractive power, or the eleventh surface S11 may be planar or concave, and the twelfth surface S12 may be planar or convex.

[0105] The central thickness of the sixth lens 136 may be thicker than the central thickness of the fifth lens 135 and thinner than the central thickness of the seventh lens 137. When expressed as an absolute value, the radius of curvature of the eleventh surface S11 at the center may be greater than the radius of curvature of the tenth surface S10 of the fifth lens 135 and greater than the radius of curvature of the fourteenth surface S14 of the seventh lens 137. When expressed as an absolute value, the radius of curvature of the twelfth surface S12 at the center may be greater than the respective radii of curvature of the tenth surface S10 and the eleventh surface S11, and smaller than the radius of curvature of the thirteenth surface S13 of the seventh lens 137.

[0106] The seventh lens 137 may have a positive (+) refractive power. On the optical axis Lx, the 13th surface S13 of the seventh lens 137 may be concave, and the 14th surface S14 may be convex. That is, the seventh lens 137 may have a meniscus shape that is convex toward the sensor side. At least one or both of the 13th surface S13 and the 14th surface S14 may be aspherical. As another example, the 13th surface S13 may be planar or convex.

[0107] The central thickness of the seventh lens 137 may be greater than the central thickness of the sixth lens 136 and 1.3 times thicker than the central thickness of the eighth lens 138. When expressed as an absolute value, the radius of curvature of the thirteenth surface S13 at the center may be four times or more the radius of curvature of the fourteenth surface S14, for example, in the range of four to six times. The central thickness of the seventh lens 137 may be 1.5 times or more the central thickness of the fifth lens 135, for example, in the range of 1.5 to three times.

[0108] The optical axis spacing between the seventh lens 137 and the sixth lens 136 on the optical axis Lx may be greater than the optical axis spacing between the seventh lens 137 and the eighth lens 138, and may be less than the central thickness of the seventh lens 137.

[0109] The eighth lens 138 may have a negative refractive power. The 15th surface S15 of the eighth lens 138 may be convex on the optical axis, and the 16th surface S16 may be concave. The 15th surface S15 and the 16th surface S16 may be aspherical. Each of the 15th surface S15 and the 16th surface S16 may have at least one inflection point. In detail, the 15th surface S15 may have an inflection point around its center, and the position of the inflection point of the 16th surface S16 may be located further outward than the position of the inflection point of the 15th surface S15 with respect to the optical axis. Here, a straight line connecting the edges of the object-side 15th surface S15 of the eighth lens 138 may be located between the vertex of the sensor-side 16th surface S16 of the seventh lens 137 and the vertex of the 15th surface S15 on the optical axis. As a result, light entering from the eighth lens 138 can be refracted further outward with respect to the optical axis Lx.

[0110] The optical filter 192 and the image sensor 190 are described in reference to the description of the first embodiment. The total length TTL of the optical system according to the third embodiment may be 4 mm or more, for example, in the range of 4 mm to 12 mm or 4 mm to 8 mm. The distance BFL from the vertex of the sensor-side 16th surface S16 of the 8th lens 138 to the image sensor 190 may 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 1.0 field may be 0.8 mm or more, 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 may be 1 mm or more, for example, in the range of 1 mm to 5 mm or 1 mm to 3 mm.

[0111] The effective focal length (EFL) of the optical system may be 1 mm or more, for example, in the range of 1 mm to 3 mm or 1 mm to 2 mm. The overall F-number of the optical system may be 2 or more, for example, in the range of 2 to 3 or 2 to 2.80. The half-field of view (HFOV) of the optical system may be 30 degrees or more, for example, in the range of 30 degrees to 80 degrees or 40 degrees to 75 degrees. The diameter of the object-side entrance pupil (EPD) of the optical system may be 1 mm or less, for example, in the range of 0.2 mm to 1 mm. The combined focal length of the first and second lenses 131 and 132 is -2 mm or more, and the combined focal length of the third and fourth lenses 133 and 134 may be less than 2 mm. When expressed as an absolute value, the combined focal length of the first and second lenses 131 and 132 may be greater than the combined focal length of the third and fourth lenses 133 and 134.

[0112] In the optical system of the third embodiment, the first to 16th surfaces S1 to S16 of the first to 8th lenses 131, 132, 133, 134, 135, 136, 137, and 138 can all be aspherical. With respect to the optical axis, the radius of curvature (converted to absolute value) of the first to 16th surfaces S1 to S16 can be 14 or less for surfaces with a radius of curvature of 5.5 mm or less, and 2 or more for surfaces with a radius of curvature exceeding 5.5 mm.

[0113] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, there may be five or more lenses with a convex side facing the object on the optical axis, three or fewer lenses with a concave side facing the object, four or more lenses with a convex side facing the sensor, and four or fewer lenses with a concave side facing the sensor.

[0114] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, 138, there may be five or more lenses with an Abbe number of 50 or more, and three or fewer lenses with an Abbe number of less than 50. For example, the Abbe number is 50 or more for the Abbe numbers of the first lens 131, the third lens 133, the fourth lens 134, the sixth lens 136, and the seventh lens 137, and the Abbe numbers 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 of the optical system and may be less than 25.

[0115] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, 138, there may be three or more lenses with a refractive index of 1.6 or more at 587 nm, and five or fewer lenses with a refractive index of less than 1.6. For example, the second, fifth, and eighth lenses 132, 135, 138 at 587 nm may have a refractive index of 1.6 or more, and the first, third, fourth, sixth, and seventh lenses 131, 133, 134, 136, 137 may have a refractive index of less than 1.6.

[0116] In the optical system or the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, 138, there may be five or more lenses with a center thickness of 0.5 mm or more, and three or fewer lenses with a center thickness of less than 0.5 mm. For example, the thicknesses T1, T2, and T3 of the centers of the first to third lenses 131, 132, 133 can satisfy the relationship T3 < T2 < T1, and the center thicknesses T3, T4, T5, and T6 of the third to sixth lenses 133, 134, 135, 136 satisfy the relationship T5 < T6 < T4 ≤ T3, and the difference between the center thicknesses T3 and T4 of the third and fourth lenses 133 and 134 may be 1 mm or less, and the center thicknesses T7 and T8 of the seventh lens and the eighth lens 137 and 138 can satisfy the relationship T8 < T6 < T7 < T1. Here, T1 to T8 are the center thicknesses of the first to eighth lenses 131 to 138.

[0117] Among the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138, when looking at the intervals on the optical axis between two adjacent lenses, T78 < T23 < T67 < T12 is satisfied, where T67 is the optical axis interval between the adjacent sixth and seventh lenses 136 and 137, T23 is the optical axis interval between the second and third lenses 132 and 133, T78 is the optical axis interval between the adjacent seventh and eighth lenses 137 and 138, and T12 is the optical axis interval between the first and second lenses 131 and 132. Here, the T12 is 0.35 mm or more and may be larger than the central thickness of the fifth lens 135. The T23 is 0.20 mm or less, and the optical axis interval T67 between the sixth and seventh lenses 136 and 137 may be the same as or larger than the optical axis interval between the fifth and sixth lenses 135 and 136. When looking at the interval between the seventh lens 137 and the eighth lens 138, the optical axis interval between two adjacent vertices on the optical axis may be smaller than the interval between two adjacent peripheral portions.

[0118] When the refractive powers of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138 are P1 to P9 respectively, when these refractive powers are represented by absolute values, the relationship of P2 < P6 < P3 or / and the relationship of P3 ≤ P5 < P1 < P7 ≤ P8 ≤ P4 can be satisfied.

[0119] When looking at the focal lengths of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138 respectively, the focal length of the second lens 132 may be the largest and may be in the range of 15 mm or more, for example, 15 mm to 50 mm or 20 mm to 45 mm. The focal length of the sixth lens 136 may be smaller than the focal length of the second lens 132 and may be larger than the focal length of the third lens 133.

[0120] Regarding the edge thicknesses of the first to eighth lenses 131, 132, 133, 134, 135, 136, 137, and 138 respectively, there are three or more lenses having an edge thickness of 0.50 mm or more, there may be six or fewer lenses having an edge thickness of less than 0.50 mm, and there may be two or fewer lenses having an edge thickness of less than 0.3 mm.

[0121] Table 5 below shows the data for the radius of curvature, thickness, spacing, refractive index, and Abbe number of each lens surface in the third embodiment shown in Figure 5.

[0122] [Table 5]

[0123] In Table 5, the thickness is the center thickness (mm) of each lens in Figure 5, and the spacing is the distance (mm) between two adjacent lenses. S17 indicates the incident side of the optical filter, and S18 indicates the outgoing side of the optical filter.

[0124] Table 6 shows the effective radius (semi-aperture), edge thickness, refractive power value, and focal length for each lens in Figure 5. [Table 6]

[0125] Figure 6 is an analysis graph showing the longitudinal spherical aberration, astigmatism, and distortion of the optical system in Figure 5. In the optical system according to the second embodiment, spherical aberration may be a phenomenon in which the focal point of light passing through different parts of the lens (e.g., the center and the periphery) changes. The horizontal axis shows the degree of longitudinal spherical aberration, and the vertical axis shows the normalized distance from the center of the optical axis, and the change in longitudinal spherical aberration with respect to the wavelength of light can be shown. Longitudinal spherical aberration can be shown, for example, for light with wavelengths of approximately 656.2725 nm (nanometer), approximately 587.5618 nm, approximately 546.0740 nm, approximately 486.1327 nm, or approximately 435.8343 nm, respectively. The longitudinal spherical aberration of the optical system is limited to within +0.025 to -0.025, confirming that it exhibits stable optical characteristics.

[0126] Astigmatism in an optical system can occur when the tangential plane (or meridian plane) and sagittal plane of a lens have different radii, resulting in misaligned focal points for light passing through the vertical and horizontal directions. The astigmatism of the optical system is a result obtained at a wavelength of approximately 546.0740 nm, where the solid line represents tangential astigmatism (e.g., meridian curvature), and the dotted line represents sagittal astigmatism (e.g., sagittal curvature). As can be seen through Figure 6, the astigmatism is limited to within +0.050 to -0.050, demonstrating stable optical characteristics.

[0127] Distortion in an optical system occurs because the optical magnification changes with distance from the optical axis OI. As a result, the image formed at the actual image plane (e.g., 190 in Figure 5) may appear larger or smaller than the image formed at the theoretical image plane. The distortion of the optical system described above is a result obtained at a wavelength of approximately 546.0740 nm, and the image captured through the optical system may exhibit some distortion at points deviated from the optical axis OI. However, such distortion is generally observed in optical devices using lenses, and the distortion rate is less than approximately 3%, providing good optical characteristics.

[0128] As in the first to third embodiments described above, each lens may be composed entirely of plastic lenses, and each lens surface may have an aspherical coefficient. The aperture ST may be positioned around the third lenses 113, 123, 133 and the fourth lenses 114, 124, 134. In the first to third embodiments of the present invention, the central thickness of the first lenses 111, 121, 131 is the thickest among the lenses of the optical system, and the first spacing between the first lenses 111, 121, 131 and the second lenses 112, 122, 132 along the optical axis may be greater than the second spacing between the sixth lenses 116, 126, 136 and the seventh lenses 117, 127, 137, or greater than the optical axial spacing between the fourth lenses 114, 124, 134 and the sixth lenses 116, 126, 136.

[0129] The optical systems according to the first to third embodiments of the present invention can satisfy at least one or more of the mathematical formulas described below. As a result, the optical systems according to the first to third embodiments can have improved optical effects.

[0130] In the optical systems of the first to third embodiments, at least one, two or more, or all of the following formulas can be satisfied.

[0131] <Number 1> 0.5 <f4 / F<1.5

[0132] Here, F is the effective focal length of the optical system, and f4 is the focal length of the fourth lens. If such an f4 / F value falls outside the aforementioned range, it may affect the resolution improvement, and could be, for example, 1.22.

[0133] 1.4 <nd1<1.6

[0134] The aforementioned nd1 is the refractive index of the first lens at 587 nm (d-line). If the refractive index value of such a first lens falls outside the range, it may affect the resolution improvement, and could be, for example, 1.53.

[0135] 10 <vd5<30

[0136] Here, vd5 is the Abbe number of the fifth lens, and if the Abbe value of such a fifth lens falls outside the range, it may affect the resolution improvement, and could be, for example, 21.49.

[0137] F / EPD>1

[0138] Here, EPD is the diameter of the entrance pupil of the optical system, and if the F / EPD value falls outside the aforementioned range, it may affect the brightness of the optical system.

[0139] <Number 5> 1 <T1 / T3<5

[0140] Here, T1 is the central thickness of the first lens, and T3 is the central thickness of the third lens.

[0141] 1 <T4 / T5<5

[0142] Here, T4 is the center thickness of the fourth lens, and T5 is the center thickness of the fifth lens.

[0143] <Number 7> 1 <T7 / T8<5

[0144] Here, T7 is the center thickness of the 7th lens, and T8 is the center thickness of the 8th lens.

[0145] In equations 5-7, deviations from the aforementioned range may affect the reduction of distortion.

[0146] <Number 8> |f5|>|f4|

[0147] Here, f5 is the focal length of the fifth lens, and f4 is the focal length of the fourth lens.

[0148] <Number 9> 0.5<|f7| / |f8|<2

[0149] Here, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens. In equations 8 and 9, if the values ​​fall outside the specified range, it may affect the reduction of aberrations in the optical system.

[0150] The optical systems 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 equations 1 to 9. In this case, the optical system can embody a high-quality and high-resolution imaging lens system. Furthermore, at least one of the equations 1 to 9 can block unwanted light entering the optical system, correct aberrations, and improve the performance of the optical system.

[0151] Figure 7 is a perspective view showing an example of a mobile device to which the optical system according to an embodiment of the present invention is applied.

[0152] As shown in Figure 7, the mobile terminal 1500 may include a camera module 1520, a flash module 1530, and an autofocus device 1510, provided on one or the back of the device. Here, the autofocus device 1510 may include a surface-emitting laser element and a light-receiving unit as an emitting layer. The flash module 1530 may include an emitter that emits light internally. The flash module 1530 may be operated by the camera operation of the mobile terminal or by user control. The camera module 1520 may include an image capture function and an autofocus function. For example, the camera module 1520 may include an image-based autofocus function. The autofocus device 1510 may include a laser-based autofocus function. The autofocus device 1510 may be mainly used in conditions where the image-based autofocus function of the camera module 1520 is reduced, such as close proximity of 10m or less or in dark environments.

[0153] The features, structures, and effects described in the examples above are included in at least one embodiment of the present invention and are not necessarily limited to just one embodiment. Furthermore, the features, structures, and effects exemplified in each embodiment can be combined or modified and implemented in other embodiments by a person with ordinary skill in the art to which the embodiment belongs. Therefore, such combinations and modifications should be interpreted as being within the scope of the present invention. In addition, although the above description has focused on embodiments, these are merely examples and do not limit the present invention. A person with ordinary skill in the art to which the present invention belongs will understand that various modifications and applications not exemplified above are possible without departing from the essential characteristics of these embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. And the differences related to such modifications and applications should be interpreted as being within the scope of the present invention as defined in the attached claims.

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, which are sequentially arranged along the optical axis from the object side to the sensor side, The first lens has a negative refractive power, and the side surface of the object is concave along the optical axis. The second lens has a positive refractive power, The third lens has a positive refractive power, and the fourth lens has a positive refractive power, with both the object side and the sensor side being convex on the optical axis, and having a refractive index of less than 1.

6. The fifth lens has a concave sensor side on the optical axis and a refractive index of 1.6 or higher. The sixth lens has a positive (+) refractive power, and the side surface of the object is convex on the optical axis. The seventh lens has a positive (+) refractive power, and the sensor side is convex on the optical axis. The eighth lens has a negative refractive power, and the sensor side is concave on the optical axis. The center thickness of the first lens is thicker than the center thickness of each of the second to eighth lenses. The following equation 1 is satisfied, 0.5 < f4 / F < 1.5 The optical system wherein f4 is the focal length of the fourth lens, F is the effective focal length of the optical system, and the radius of curvature of the side surface of an object at the center of the fourth lens is smaller than the radius of curvature of the side surface of an object at the center of the second lens.

2. At least one of the following equations 2, 3, and 4 is satisfied, 1.4 < nd1 < 1.6 The aforementioned nd1 is the refractive index of the first lens at 587 nm, 10 < v d 5 < 30 The aforementioned vd5 is the Abbe number of the fifth lens, <Number 4> F / EPD>1 The optical system according to claim 1, wherein the EPD is the diameter of the entrance pupil of the optical system.

3. At least one of the following equations 5, 6, and 7 is satisfied, 1 < T1 / T3 < 5 <Number 6> 1<T4 / T5<5 <Number 7> 1 < T7 / T8 < 5 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 central thickness of the fifth lens, T7 is the central thickness of the seventh lens, The optical system according to claim 1 or claim 2, wherein T8 is the central thickness of the eighth lens.

4. The following formulas include at least one of formulas 8 and 9: <Number 8> |f5|> |f4| <Number 9> 0.5 < |f7| / |f8| < 2 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. The optical system according to any one of claims 1 to 3, wherein f8 is the focal length of the eighth lens.

5. The optical system according to any one of claims 1 to 4, wherein the optical axis spacing between the first lens and the second lens is greater than the optical axis spacing between two adjacent lenses of the second to eighth lenses.

6. There are four or more lenses whose object side is convex on the optical axis of the first to eighth lenses. The number of lenses with concave sides is four or less. The optical system according to any one of claims 1 to 5, wherein the object side surface of the fifth lens is convex on the optical axis.

7. There are four or more lenses whose sensor sides are convex on the optical axis of the first to eighth lenses. The sensor has four or fewer concave lenses. The sensor side of the sixth lens is concave on the optical axis, The optical system according to any one of claims 1 to 6, wherein the object side surface of the seventh lens is concave on the optical axis.

8. The optical system according to claim 7, wherein the sensor sides of the first, fifth, sixth, and eight lenses are concave.

9. The optical system according to any one of claims 1 to 8, wherein among the first to eighth lenses, there are five or more lenses with an Abbe number of 50 or more, and there are three or fewer lenses with an Abbe number of less than 50.

10. Of the first to eighth lenses mentioned above, there are three or more lenses with a refractive index of 1.6 or higher. The optical system according to any one of claims 1 to 9, wherein the number of lenses with a refractive index of less than 1.6 is five or less.

11. The number of lenses with a central thickness of 0.5 mm or more is 3 or more, and the number of lenses with a central thickness of less than 0.5 mm is 5 or less. The optical system according to any one of claims 1 to 10, wherein the central thicknesses of the first, second, and third lenses are T1, T2, and T3, and the condition T3 < T2 < T1 is satisfied.

12. The optical system according to any one of claims 1 to 11, wherein the central thicknesses of the third to sixth lenses are T3, T4, T5, and T6, and the condition T5 ≤ T3 < T6 < T4 is satisfied.

13. The optical system according to any one of claims 1 to 12, wherein the second lens has the largest focal length among the first to eighth lenses.

14. With respect to the third lens, the effective diameter on the object side or sensor side decreases in the order of the first lens, the second lens, and the third lens. The optical system according to any one of claims 1 to 13, wherein, with respect to the third lens, the effective diameter on the object side or sensor side increases 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, which are sequentially arranged along the optical axis from the object side to the sensor side, The first lens has a negative refractive power, and the side surface of the object is concave along the optical axis. The second lens has a positive refractive power, The third lens has a positive refractive power, The fourth lens has a positive refractive power, both the object side and the sensor side are convex on the optical axis, and has a refractive index of less than 1.

6. The fifth lens has a concave sensor side on the optical axis and a refractive index of 1.6 or higher. The sixth lens has a positive (+) refractive power, and the side surface of the object is convex on the optical axis. The seventh lens has a positive (+) refractive power, and the sensor side is convex on the optical axis. The eighth lens has a negative refractive power, and the sensor side is concave on the optical axis. The number of lenses with a convex side surface on the optical axis of the first to eighth lenses is four or more, and the number of lenses with a concave side surface on the sensor is five or less. The center thickness of the first lens is thicker than the center thickness of each of the second to eighth lenses. Of the object sides and sensor sides of the first to eighth lenses, there are four or more surfaces that have inflection points. An optical system in which the radius of curvature of the side surface of an object at the center of the fourth lens is smaller than the radius of curvature of the side surface of an object at the center of the second lens.

16. The image sensor located on the sensor side of the eighth lens, The optical filter is disposed between the image sensor and the eighth lens, The formula must include at least one of the following formulas 1 to 4: 0.5 < f4 / F < 1.5 The aforementioned f4 is the focal length of the fourth lens, and F is the effective focal length of the optical system. 1.4 < nd1 < 1.6 The aforementioned nd1 is the refractive index of the first lens at 587 nm, 10 < v d 5 < 30 The aforementioned vd5 is the Abbe number of the fifth lens, <Number 4> F / EPD>1 The optical system according to claim 15, wherein the EPD is the diameter of the entrance pupil of the optical system.

17. Includes an aperture arranged around the third lens and the fourth lens, The sensor side of the sixth lens is concave on the optical axis, The side surface of the seventh lens is concave on the optical axis, The optical system according to claim 15 or claim 16, wherein the optical axis spacing between the first lens and the second lens is greater than the optical axis spacing between two adjacent lenses among the second to eighth lenses.

Images