Optical system

Abstract

Embodiments of the present application disclose 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 arranged in sequence from an object side to an image side along an optical axis, wherein the second lens has a positive refractive power, the third lens has a negative refractive power, the seventh lens has a positive refractive power, and the eighth lens has a negative refractive power, wherein the refractive index of the first lens, the third lens and the fifth lens is greater than the refractive index of the second lens, the fourth lens, the sixth lens and the eighth lens, and has a relationship of 1.2 < F / D1 < 2.4, wherein F is a total effective focal length of the optical system, and D1 can be an effective diameter of the first lens.

Description

Technical Field

[0001] The embodiments relate to an optical system for high resolution. Background Technology

[0002] Camera modules capture images of objects and store them as images or videos, which are then installed in various applications. In particular, camera modules are manufactured in very small sizes and are used not only in portable devices such as smartphones, tablets, and laptops, but also in drones and vehicles to provide a wide range of functions.

[0003] For example, the optical system of a camera module may include an imaging lens for forming an image and an image sensor for converting the formed image into an electrical signal. In this case, the camera module can perform autofocus (AF) by automatically adjusting the distance between the image sensor and the imaging lens, and can perform zoom functions by increasing or decreasing the magnification of distant objects using a zoom lens. Furthermore, the camera module employs image stabilization (IS) technology to correct or prevent image instability caused by unstable fixtures or camera movement due to user movement.

[0004] The most crucial component of a camera module for acquiring images is the image-forming lens. Recently, there has been a growing interest in high resolution, and research is underway using five or six lenses to achieve this. For example, research is being conducted on using multiple image-forming lenses with positive (+) and / or negative (-) diopters to achieve high resolution. However, when multiple lenses are included, a problem arises in obtaining excellent optical and aberration characteristics. Therefore, a new optical system capable of addressing these issues is needed. Summary of the Invention

[0005] Technical issues

[0006] One embodiment of the present invention provides an optical system with improved optical properties.

[0007] One embodiment of the present invention provides an optical system having at least eight lenses.

[0008] Technical solution

[0009] 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 the optical axis from the object side to the image side. The second lens has positive refractive power, the third lens has negative refractive power, the seventh lens has positive refractive power, and the eighth lens has negative refractive power. The refractive indices of the first, third, and fifth lenses are greater than those of the second, fourth, sixth, and eighth lenses, and they have a relationship of 1.2 < F / D1 < 2.4, where F is the total effective focal length of the optical system, and D1 may be the effective diameter of the first lens.

[0010] According to an embodiment of the present invention, the center thickness of the second lens may be greater than the center thickness of each of the first, third, to eighth lenses. The Abbe numbers of the second, fourth, sixth, and eighth lenses may be 50 or greater, and the Abbe numbers of the third and fifth lenses may be less than 30.

[0011] According to an embodiment of the present invention, the optical system includes an image sensor on the image side of an eighth lens; and a filter between the image sensor and the eighth lens, wherein the optical system satisfies the following equations 1 and 2:

[0012] [Equation 1] 0 < BFL / TTL < 0.5,

[0013] [Equation 2] 0 < BFL / Img < 0.5,

[0014] Wherein, BFL is the distance from the vertex of the image-side surface of the eighth lens to the image sensor, TTL is the distance from the vertex of the object-side first surface of the first lens to the image sensor, and Img can be the vertical distance from the optical axis to the diagonal end, i.e., 1.0F, in the image sensor.

[0015] According to an embodiment of the present invention, the optical system includes an image sensor on the image side of the eighth lens and a filter between the image sensor and the eighth lens, and the optical system satisfies the following equation 5:

[0016] [Equation 5] 0.5 < TTL / D8 < 1.5,

[0017] Where TTL is the distance from the vertex of the first surface on the object side of the first lens to the image sensor, and D8 can be the effective diameter of the eighth lens.

[0018] According to an embodiment of the present invention, the optical system satisfies the following equation:

[0019] [Equation] 0.5 < f² / F < 1.5,

[0020] [Equation] -5 < f2 / f3 < 0,

[0021] F is the total effective focal length of the optical system, f2 can be the focal length of the second lens, and f3 can be the focal length of the third lens.

[0022] 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 the optical axis from the object side to the image side. The center thickness of the second lens is greater than the center thickness of each of the first, third, to eighth lenses, and the Abbe number of the second lens is greater than the Abbe numbers of the third and fifth lenses. The optical system satisfies the following equation:

[0023] 0.5 < TTL / D8 < 1.5 and 0 < |f2 / f3| < 5

[0024] TTL is the distance from the vertex of the first surface on the object side of the first lens to the image sensor, D8 is the effective diameter of the eighth lens, f2 is the focal length of the second lens, and f3 can be the focal length of the third lens.

[0025] According to an embodiment of the present invention, the radius of curvature of the object-side surface of the second lens is L2R1 and the absolute value of the radius of curvature of the image-side surface of the second lens is |L2R2|, which can satisfy the following equation:

[0026] 0 < L2R1 / |L2R2| < 1.

[0027] According to an embodiment of the present invention, when the absolute value of the radius of curvature of the object-side surface of the third lens is |L3R1| and the radius of curvature of the image-side surface of the second lens is L3R2, the following equation can be satisfied:

[0028] 0 < L3R2 / |L3R1| < 1.

[0029] According to an embodiment of the present invention, when the refractive index of the second lens at 587 nm is G2 and the refractive index of the third lens at 587 nm is G3, the following relationship can be satisfied:

[0030] 0.7 < G2 / G3 < 1.2.

[0031] The center thickness of the second lens is T2, and the center thickness of the third lens is T3. The following relationship can be satisfied:

[0032] 1 < T2 / T3 < 5.

[0033] 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 the optical axis from the object side to the image side, and can satisfy the following formula:

[0034] [Equation 4] 1.2 < F / D1 < 2.4

[0035] [Equation 5] 0.5 < TTL / D8 < 1.5

[0036] [Equation 7] 0 < |f2 / f3| < 5

[0037] Here, F is the total effective focal length of the optical system, D1 is the effective diameter of the first lens, TTL is the distance from the vertex of the first surface on the object side of the first lens to the image sensor, D8 is the effective diameter of the eighth lens, f2 can be the focal length of the second lens, and f3 can be the focal length of the third lens.

[0038] According to an embodiment of the present invention, the first distance between the seventh and eighth lenses along the optical axis can be greater than the second distance between the first and second lenses. The first and second distances can be greater than or equal to 0.4 mm. The center thickness of the second lens can be in the range of 2 to 4 times the center thickness of the third lens.

[0039] Beneficial effects

[0040] The optical system according to the embodiment can correct aberration characteristics and achieve a thin optical system. Therefore, the optical system can be miniaturized and can achieve high image quality and high resolution.

[0041] Furthermore, the optical system according to the embodiment can block unwanted light from entering the optical system. Therefore, the performance of the optical system can be improved by reducing aberrations. Attached Figure Description

[0042] Figure 1 This is a configuration diagram of an optical system according to a first embodiment of the present invention.

[0043] Figure 2 This is a configuration diagram of an optical system according to a second embodiment of the present invention.

[0044] Figure 3 This is a configuration diagram of an optical system according to a third embodiment of the present invention.

[0045] Figure 4 This is a perspective view of a mobile terminal having an optical system according to an embodiment of the present invention. Detailed Implementation

[0046] Preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. The spirit of the invention is not limited to the embodiments described, and it can be implemented in various other forms. One or more components can be selectively combined and substituted within the scope of the spirit of the invention. Furthermore, the terminology used in the embodiments of the invention (including technical and scientific terms) is to be interpreted in a meaning that is generally understood by one of ordinary skill in the art to which this invention pertains, unless specifically defined and explicitly described. General terms, such as those defined in a dictionary, should be interpretable in the context of the relevant art. Moreover, the terminology used in the embodiments of the invention is for explaining the embodiments and not for limiting the invention. In this specification, the singular form may also include the plural form, unless otherwise specifically stated in the phrase, and where at least one (or more) of A and / or B, C is stated, it may include one or more of all combinations that can be combined with A, B, and C. In describing components of embodiments of the invention, terms such as first, second, A, B, (a), and (b) may be used. Such terms are only used to distinguish one component from another, and the nature, order, or procedure of the corresponding constituent elements may not be determined by the term. Furthermore, when a component is described as being "connected," "joined," or "engaged" to another component, this description includes not only direct connection, joining, or engagement to another component, but also connection, joining, or engagement through another component between the component and the other component. Additionally, when described as being formed or disposed "above" or "below" each component, this description includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or disposed between the two components. Moreover, when expressed as "above" or "below," it can refer to both the downward and upward directions relative to a single element.

[0047] In the description of this invention, the first lens refers to the lens closest to the object side, and the last lens refers to the lens closest to the image side (or sensor surface). Unless otherwise stated in the description of this invention, all units for the radius, effective diameter, thickness, distance, BFL (back focal length), and TTL (total trajectory length or total top length) of the lens are in mm. In this specification, the shape of the lens is shown based on its optical axis. For example, if the object side of the lens is convex, it means that the object side of the lens is convex near the optical axis, not convex around the optical axis. Therefore, even when the object side of the lens is described as convex, the portion of the object side of the lens around the optical axis can be concave. In this specification, it is noted that the thickness and radius of curvature of the lens are measured based on the optical axis of the lens. Furthermore, "object side surface" can refer to the surface of the lens facing the object side based on its optical axis, and "image side surface" can refer to the surface of the lens facing the image side based on its optical axis.

[0048] An optical system according to embodiments of the present invention may include a plurality of lenses. Specifically, an optical system according to the first to third embodiments may include at least eight lenses. As resolution increases, the size of the image sensor also increases, and the number of lenses gradually increases according to the resolution of the image sensor. One embodiment of the present invention provides a high-resolution optical system using at least eight lenses.

[0049] Reference Figure 1 For example, the optical system of the first embodiment may include 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 a filter 192 and an image sensor 190. An optical system having multiple lenses 111 to 118 can be defined as a lens optical system. In addition to lenses 111 to 118, an optical system further including a filter 192 and an image sensor 190 can be defined as a camera module.

[0050] The first lens 111 to the eighth lens 118 can be arranged sequentially along the optical axis Lx of the optical system.

[0051] Light corresponding to the image information of the object can be incident through the first lens 111, the second lens 112, the third lens 113, the fourth lens 114, the fifth lens 115, the sixth lens 116, the seventh lens 117 and the eighth lens 118, and the image sensor 190 can obtain electrical signals through the filter 192.

[0052] Each of the first lens 111 to the eighth lens 118 may include an effective region and an ineffective region. The effective region can be the area through which light incident on each lens passes. That is, the effective region can be the area where incident light is refracted to achieve optical properties. The ineffective region may be arranged around the effective region. The ineffective region can be the area where light is not incident. That is, the ineffective region can be the area unrelated to optical properties. Additionally, the ineffective region can be the area fixed to a lens barrel (not shown) housing the lens, or the area where light is blocked by light-blocking parts or spacers.

[0053] The optical system according to an embodiment may include an aperture stop ST for adjusting the amount of incident light. The aperture stop ST may be disposed between two lenses selected from 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. For example, the aperture stop ST may be disposed on the outer periphery between the first lens 111 and the second lens 112, or on the outer periphery between the second lens 112 and the third lens 113. The aperture stop ST may be disposed closer to the exit side of the first lens 111 than the fourth lens 114. As another example, at least one of the first lens 111, the second lens 112, the third lens 113, the fourth lens 114, the fifth lens 115, the sixth lens 116, the seventh lens 117, and the eighth lens 118 may serve as an aperture stop. For example, one of the lens surfaces selected from the first lens 111, the second lens 112, the third lens 113, the fourth lens 114, the fifth lens 115, the sixth lens 116, the seventh lens 117, and the eighth lens 118 can serve as an aperture stop for adjusting the amount of light. For example, the outer periphery of the image side of the first lens 111 or the outer periphery of the object side of the second lens 112 can serve as an aperture stop.

[0054] The first lens 111 may have a positive (+) or negative (-) refractive power. The first lens 111 may comprise a plastic material. The first lens 111 may comprise a first surface S1 defined as an object-side surface and a second surface S2 defined as an image-side surface. The first surface S1 may convex in the optical axis Lx direction, and the second surface S2 may be concave in the optical axis Lx direction. That is, the first lens 111 may have a meniscus shape convex toward the object side.

[0055] At least one of the first surface S1 and the second surface S2 of the first lens 111 can be aspherical. For example, both the first surface S1 and the second surface S2 can be aspherical. At least one of the first surface S1 and the second surface S2 can have an inflection point. Specifically, the first surface S1 can include a first inflection point defined as an inflection point. When the optical axis Lx is the starting point and the edge of the first lens 111 is the ending point, the first inflection point can be located at a position between approximately 80% and approximately 99% of the optical axis. Here, the position of the first inflection point can be a position set based on the vertical direction of the optical axis Lx. The second surface S2 can include a second inflection point defined as an inflection point. When the optical axis Lx is the starting point and the edge of the first lens 111 is the ending point, the second inflection point can be located at a position between approximately 60% and approximately 80% of the optical axis Lx. Here, the position of the second inflection point can be a position set based on the vertical direction of the optical axis Lx.

[0056] The second lens 112 may have a positive (+) refractive power. The second lens 112 may comprise a plastic or glass material. The second lens 112 may comprise a third surface S3 defined as an object-side surface and a fourth surface S4 defined as an image-side surface. The third surface S3 may convex in the optical axis Lx direction, and the fourth surface S4 may convex in the optical axis Lx direction. That is, the second lens 112 may have a convex shape on both sides. As another example, the third surface S3 may be convex and the fourth surface S4 may be infinitely large or concave. At least one of the third surface S3 and the fourth surface S4 may be spherical or aspherical. For example, both the third surface S3 and the fourth surface S4 may be aspherical. The effective diameter of the first lens 111 and / or the second lens 112 may be larger than that of the third lens 113. Here, the effective diameter may be the diameter of the region where light is incident.

[0057] The third lens 113 may have a negative (-) refractive power. The third lens 113 may comprise a plastic or glass material. The third lens 113 may comprise a fifth surface S5 defined as an object-side surface and a sixth surface S6 defined as an image-side surface. The fifth surface S5 may convex in the optical axis Lx direction, and the sixth surface S6 may be concave in the optical axis Lx direction. That is, the third lens 113 may have a meniscus shape convex toward the object side. As another example, the fifth surface S5 may be flat or concave, and the second lens 112 may have concave shapes on both sides. At least one of the fifth surface S5 and the sixth surface S6 may be spherical or aspherical. For example, both the fifth surface S5 and the sixth surface S6 may be aspherical.

[0058] The fourth lens 114 may have a positive (+) or negative (-) refractive power. The fourth lens 114 may comprise a plastic material. The fourth lens 114 may comprise a seventh surface S7 defined as the object-side surface and an eighth surface S8 defined as the image-side surface. The seventh surface S7 may be concave in the optical axis Lx direction, and the eighth surface S8 may be convex in the optical axis Lx direction. That is, the fourth lens 114 may have a meniscus shape convex on the image side. Alternatively, the seventh surface S7 may be flat. At least one of the seventh surface S7 and the eighth surface S8 may be aspherical. For example, both the seventh surface S7 and the eighth surface S8 may be aspherical.

[0059] The fifth lens 115 may have a positive (+) or negative (-) refractive power. The fifth lens 115 may comprise a plastic material. The fifth lens 115 may comprise a ninth surface S9 defined as the object-side surface and a tenth surface S10 defined as the image-side surface. The ninth surface S9 may be concave in the optical axis Lx direction, and the tenth surface S10 may be convex in the optical axis Lx direction. That is, the fifth lens 115 may have a meniscus shape convex towards the image side. Alternatively, the ninth surface S9 may be flat. At least one of the ninth surface S9 and the tenth surface S10 may be aspherical. For example, the ninth surface S9 and the tenth surface S10 may be aspherical.

[0060] The sixth lens 116 may have a positive (+) or negative (-) refractive power. The sixth lens 116 may comprise a plastic or glass material. The sixth lens 116 may comprise an eleventh surface S11 defined as an object-side surface and a twelfth surface S12 defined as an image-side surface. The eleventh surface S11 may be concave in the optical axis Lx direction, and the twelfth surface S12 may be convex in the optical axis Lx direction. That is, the sixth lens 116 may have a meniscus shape convex on the image side. At least one of the eleventh surface S11 and the twelfth surface S12 may be aspherical. For example, both the eleventh surface S11 and the twelfth surface may be aspherical.

[0061] At least one of the eleventh surface S11 and the twelfth surface S12 may have an inflection point. The radius of curvature at the center of the eleventh surface S11 of the sixth lens 116 may be smaller than the radius of curvature at the center of the seventh surface S7 of the fourth lens 114 and the ninth surface S9 of the fifth lens 115. Here, the effective diameters of the third lens 113, the fourth lens 114, the fifth lens 115, and the sixth lens 116 may be larger than the effective diameters of the lenses adjacent to the image side from the object side.

[0062] The seventh lens 117 may have a positive (+) diopter. The seventh lens 117 may comprise a plastic material. The seventh lens 117 may comprise a thirteenth surface S13, defined as an object-side surface, and a fourteenth surface S14, defined as an image-side surface. The thirteenth surface S13 may convex in the optical axis Lx direction, and the fourteenth surface S14 may be concave in the optical axis Lx direction. Both the thirteenth and fourteenth surfaces S13 may be aspherical. At least one or both of the thirteenth and fourteenth surfaces S14 may have at least one inflection point. Specifically, the thirteenth surface S13 may have an inflection point around its center, and when the starting point is the optical axis Lx and the ending point is the edge of the seventh lens 117, this inflection point may be located at a position between approximately 40% and approximately 60% of the optical axis. Here, the location of the inflection point on the thirteenth surface S13 may be a position set based on the vertical direction of the optical axis Lx. The inflection point of the fourteenth surface S14 may be set closer to the edge than the inflection point of the thirteenth surface S13.

[0063] The eighth lens 118 may have a negative (-) refractive power. The eighth lens 118 may comprise a plastic material. The eighth lens 118 may comprise a fifteenth surface S15, defined as an object-side surface, and a sixteenth surface S16, defined as an image-side surface. The fifteenth surface S15 may convex in the direction of the optical axis Lx, and the sixteenth surface S16 may be concave in the direction of the optical axis Lx. Both the fifteenth and sixteenth surfaces S15 may be aspherical. Each of the fifteenth and sixteenth surfaces S16 may have at least one inflection point. Specifically, the fifteenth surface S15 may have an inflection point around its center, and when the starting point is the optical axis Lx and the ending point is the edge of the eighth lens 118, the inflection point may be located at a position between approximately 15% and approximately 50% of the optical axis. Here, the position of the inflection point on the fifteenth surface S15 may be a position set based on the vertical direction of the optical axis Lx. The inflection point of the sixteenth surface S16 can be set to be closer to the edge than the inflection point of the fifteenth surface S15.

[0064] Filter 192 may include at least one of an infrared filter and a filter such as a cover glass. Light of a specific wavelength band can pass through filter 192, while light of other wavelength bands is filtered out. When filter 192 includes an infrared filter, it prevents radiant heat emitted from external light from being transferred to the image sensor. Furthermore, filter 192 may transmit visible light and reflect infrared light. Image sensor 190 can detect light. Image sensor 190 may include a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) sensor.

[0065] In the optical system of the first embodiment, the first surfaces S1 to the sixteenth surfaces S16 of the first lens 111 to the eighth lens 118 can all be aspherical. Among the radii of curvature (in absolute value) of the first surfaces S1 to the sixteenth surfaces S16, the radius of curvature of the seventh surface S7 can be the largest. The thirteenth surface S13 can have a radius of curvature of 2.5 mm or less, which is smaller than the radii of curvature of the other surfaces. Among the Abbe numbers of the first lenses 111 to the eighth lenses 118, the Abbe numbers of the second lens 112, the fourth lens 114, the sixth lens 116, and the eighth lens 118 are 50 or more, and the Abbe numbers of the first lens 111, the third lens 113, the fifth lens 115, and the seventh lens 117 can be less than or equal to 30. Among the refractive indices of the first lens 111 to the eighth lens 118, the refractive indices of the first lens 111, the third lens 113, the fifth lens 115, and the seventh lens 117 are 1.6 or higher, and the refractive indices of the second lens 112, the fourth lens 114, the sixth lens 116, and the eighth lens 118 may be less than 1.6. The third lens 113 and the fifth lens 115 may have the highest refractive index and may be 1.65 or higher.

[0066] Table 1 shows data on the radius of curvature, thickness, distance, refractive index, and Abbe number of the surface of each lens in the first embodiment.

[0067] Table 1

[0068]

[0069]

[0070] In Table 1, thickness refers to the center thickness (mm) of each lens, and distance refers to the distance (mm) between two adjacent lenses. S17 is the incident surface of the filter, and S18 is the exit surface of the filter. Comparing the radii of curvature as absolute values, the radius of curvature of the seventh surface S7 of the fourth lens 114 can be the largest among the lenses, and can be more than twice the radii of curvature of the ninth surface S9 and the tenth surface S10 of the fifth lens 115. The radius of curvature of the tenth surface S10 can be greater than the radius of curvature of the ninth surface S9. Among the first lenses 111 to the fifth lenses 115, the second lens has the thickest center thickness, and the distance between the third lens 113 and the fourth lens 114 can be greater than the distance between the first lens 111 and the second lens 112, and can be less than the center thickness of the seventh lens 117 and the eighth lens 118. The center thickness of the second lens 112 can be the thickest among the lenses.

[0071] Table 2 shows Figure 1 The aspheric coefficient values ​​of the surfaces of each lens.

[0072] Table 2

[0073]

[0074]

[0075]

[0076] Reference Figure 2 For example, the optical system of the second embodiment may include a first lens 121, a second lens 122, a third lens 123, a fourth lens 124, a fifth lens 125, a sixth lens 126, a seventh lens 127, and an eighth lens 128 arranged sequentially from the object side to the image side. The optical system may include a filter 192 and an image sensor 190. The first lens 121 to the eighth lens 128 may be arranged sequentially along the optical axis Lx of the optical system. Light corresponding to the image information of the object is incident through the first lens 121 to the eighth lens 128, passes through the filter 192, and can be obtained as an electrical signal by the image sensor 190. Each of the first lens 121 to the eighth lens 128 may include an effective region and an ineffective region. The effective region may be the area through which light incident on each lens passes. That is, the effective region may be the area where incident light is refracted to achieve optical properties. The ineffective region may be arranged around the effective region. The ineffective region may be the area where light is not incident. That is, the ineffective region may be the area unrelated to optical properties. In addition, the invalid area can be the area fixed to the lens barrel (not shown) that houses the lens, or the area where light is blocked by light blocking parts or spacers.

[0077] An aperture stop ST can be disposed between two lenses selected from the first lens 121 to the eighth lens 128. For example, the aperture stop ST can be disposed on the outer periphery between the first lens 121 and the second lens 122, or on the outer periphery between the second lens 122 and the third lens 123. The aperture stop ST can be disposed closer to the exit-side surface of the first lens 121 than the fourth lens 124. As another example, at least one of the first lenses 121 to the eighth lens 128 can serve as an aperture stop. For example, one of the lens surfaces selected from the first lens 121 to the eighth lens 128 can serve as an aperture stop for adjusting the amount of light. For example, the outer periphery of the image side of the first lens 121 or the outer periphery of the object side of the second lens 122 can serve as an aperture stop. In the optical system of the second embodiment, each lens may have differences in curvature of the object-side surface and the image-side surface of each lens in the first embodiment, differences in thickness or refractive index at the center of each lens, and differences in distances between other lenses, which will be described below.

[0078] Reference Figure 2In the optical system of the second embodiment, the first surfaces S1 to the sixteenth surface S16 of the first lens 121 to the eighth lens 128 can all be aspherical. Among the radii of curvature (including absolute values) of the first surfaces S1 to the sixteenth surface S16, the seventh surface S7 can have the largest radius of curvature, and the third surface S3 and the thirteenth surface S13 can have radii of curvature of 2.5 mm or less, which are smaller than the radii of curvature of the other surfaces. Among the Abbe numbers of the first lenses 121 to the eighth lens 128, the Abbe numbers of the first lens 121, the second lens 122, the fourth lens 124, the sixth lens 126, and the eighth lens 128 are 50 or more, and the Abbe numbers of the third lens 123, the fifth lens 125, and the seventh lens 127 can be 30 or less. Among the refractive indices of the first lens 121 to the eighth lens 128, the refractive indices of the first lens 121, the third lens 123, the fifth lens 125, and the seventh lens 127 are 1.6 or higher, and the refractive indices of the second lens 122, the fourth lens 124, the sixth lens 126, and the eighth lens 128 can be less than 1.6. The third lens 123 and the fifth lens 125 can have the highest refractive index and can be 1.65 or higher.

[0079] Table 3 shows the data for the radius of curvature, thickness, distance, refractive index, and Abbe number of the surface of each lens in the second embodiment.

[0080] Table 3

[0081]

[0082]

[0083] In Table 3, thickness refers to the center thickness (mm) of each lens, and distance refers to the distance (mm) between two adjacent lenses. S17 is the incident surface of the filter, and S18 is the exit surface of the filter. Comparing the radii of curvature as absolute values, the radius of curvature of the seventh surface S7 of the fourth lens 124 can be the largest among the lenses, and can be more than 40 times the radius of curvature of the ninth surface S9 of the fifth lens 125. The radius of curvature of the tenth surface S10 can be greater than the radius of curvature of the ninth surface S9. Among the first lenses 121 to the fifth lenses 125, the second lens has the thickest center thickness, and the distance between the third lens 123 and the fourth lens 124 can be greater than the distance between the first lens 121 and the second lens 122, and can be less than the center thickness of the seventh lens 127 and the eighth lens 128. The center thickness of the second lens 122 can be the thickest among the lenses.

[0084] Table 4 shows Figure 2 The aspheric coefficient values ​​of the surfaces of each lens.

[0085] Table 4

[0086]

[0087]

[0088]

[0089]

[0090] Reference Figure 3 For example, the optical system of the third embodiment may include a first lens 131, a second lens 132, a third lens 133, a fourth lens 134, a fifth lens 135, a sixth lens 136, a seventh lens 137, and an eighth lens 138 arranged sequentially from the object side to the image side. The optical system may include a filter 192 and an image sensor 190. The first lens 131 to the eighth lens 138 may be arranged sequentially along the optical axis Lx of the optical system. Light corresponding to the image information of the object is incident through the first lens 131 to the eighth lens 138, passes through the filter 192, and can be obtained as an electrical signal by the image sensor 190. Each of the first lens 131 to the eighth lens 138 may include an effective region and an ineffective region. The effective region may be the area through which light incident on each lens passes. That is, the effective region may be the area where incident light is refracted to achieve optical properties. The ineffective region may be arranged around the effective region. The ineffective region may be the area where light is not incident. That is, the ineffective region may be the area unrelated to optical properties. In addition, the invalid area can be the area fixed to the lens barrel (not shown) that houses the lens, or the area where light is blocked by light blocking parts or spacers.

[0091] An aperture stop ST can be disposed between two lenses selected from the first lens 131 to the eighth lens 138. For example, the aperture stop can be disposed on the outer periphery between the first lens 131 and the second lens 132, or on the outer periphery between the second lens 132 and the third lens 133. The aperture stop ST can be disposed closer to the exit side of the first lens 131 than the fourth lens 134. As another example, at least one lens among the first lens 131 to the eighth lens 138 can serve as an aperture stop. For example, a surface of a lens selected from the first lens 131 to the eighth lens 138 can serve as an aperture stop for adjusting the amount of light. For example, the outer periphery of the image-side surface of the first lens 131 or the outer periphery of the object-side surface of the second lens 132 can serve as an aperture stop. In the optical system of the third embodiment, each lens may have the differences in curvature of the object-side surface and the image-side surface of each lens disclosed in the optical system of the first embodiment, the differences in thickness or refractive index at the center of each lens, and the differences in distances between other lenses, which will be described below.

[0092] exist Figure 3 In the optical system, the first surfaces S1 to the sixteenth surfaces S16 of the first lens 131 to the eighth lens 138 can all be aspherical. Among the radii of curvature (absolute value variation) of the first surfaces S1 to the sixteenth surfaces S16, the radius of curvature of the seventh surface S7 can be the largest, and when the absolute value changes, the radius of curvature of the third surface can be the smallest. Among the Abbe numbers of the first lenses 131 to the eighth lenses 138, the Abbe numbers of the second lens 132, the fourth lens 134, the sixth lens 136, the seventh lens 137, and the eighth lens 138 can be 50 or higher, and the Abbe numbers of the first lens 131, the third lens 133, and the fifth lens 135 can be 30 or lower. Regarding the refractive indices of the first lens 131 to the eighth lens 138, the refractive indices of the first lens 131, the third lens 133, and the fifth lens 135 are 1.6 or higher; the refractive indices of the second lens 132 and the fourth lens 132 are 1.6 or higher; and the refractive indices of the lens 134, the sixth lens 136, the seventh lens 137, and the eighth lens 138 may be less than 1.6. The third lens 133 and the fifth lens 135 have the highest refractive indices and may be 1.65 or higher.

[0093] Table 5 shows the data for the radius of curvature, thickness, distance, refractive index, and Abbe number of the surface of each lens in the third embodiment.

[0094] Table 5

[0095]

[0096]

[0097] In Table 5, thickness refers to the center thickness (mm) of each lens, and distance refers to the distance (mm) between two adjacent lenses. S17 is the incident surface of the filter, and S18 is the exit surface of the filter. Comparing the radii of curvature as absolute values, the radius of curvature of the seventh surface S7 of the fourth lens 134 can be the largest among the lenses, and can be more than 7 times the radii of curvature of the ninth surface S9 and the tenth surface S10 of the fifth lens 135. The radius of curvature of the tenth surface S10 can be greater than the radius of curvature of the ninth surface S9. Among the first lenses 131 to the fifth lenses 135, the second lens 132 has the thickest center thickness, and the distance between the third lens 133 and the fourth lens 134 can be greater than the distance between the first lens 131 and the second lens 132, and can be less than the center thickness of the seventh lens 137 and the eighth lens 138. The center thickness of the second lens 132 can be the thickest among the lenses.

[0098] Table 6 shows Figure 3 The aspheric coefficient values ​​of the surfaces of each lens.

[0099] Table 6

[0100]

[0101]

[0102]

[0103] As can be seen in the above embodiments, each lens can be made of plastic, and all surfaces of each lens have an aspherical surface coefficient. In the first to third embodiments of the present invention, the second lenses 112, 122, and 132 have the thickest center thickness, and can be, for example, 0.7 mm or more. The distances along the optical axis between the third lenses 113, 123, and 133 and the fourth lenses 114, 124, and 134, and between the seventh lenses 117, 127, and 137 and the eighth lenses 118, 128, and 138 can be greater than the distances between the first lenses 111, 121, and 131 and the second lenses 112, 122, and 132, or between the second lenses 112, 122, and 132 and the third lenses 113, 123, and 133, or can be greater than the distances between the fourth to sixth lenses, and can be, for example, 0.4 mm or more.

[0104] The optical systems according to the first to third embodiments of the present invention can satisfy at least one or more of the formulas described below. Therefore, the optical systems according to the first to third embodiments can have the effect of optical improvement.

[0105] [Formula 1]

[0106] 0 < BFL / TTL < 0.5

[0107] In Equation 1, BFL represents the distance from the vertex of the sixteenth image-side surface S16 of the eighth lenses 118, 128, and 138 to the image sensor 190, and TTL represents the distance from the vertex of the object-side first surface S1 of the first lenses 111, 121, and 131 to the image sensor 190. Equation 1 can provide a high-resolution optical system by providing a TTL that is longer than that due to BFL.

[0108] [Equation 2]

[0109] 0 < BFL / Img < 0.5

[0110] In Equation 2, Img represents the vertical distance from the optical axis Lx to 1.0F, which is the diagonal end, in the image sensor 190. Equation 2 shows the relationship between the distance from the vertex of the sixteenth image-side surface S16 of the eighth lenses 118, 128, and 138 to the image sensor 190 and the distance from the optical axis Lx to 1.0F.

[0111] [Formula 3]

[0112] 0.5 < F / TTL < 1.2

[0113] In Equation 3, F represents the total effective focal length of the optical system.

[0114] [Formula 4]

[0115] 1.2 < F / D1 < 2.4

[0116] In Equation 4, D1 represents the effective diameter of the first lenses 111, 121, and 131. The effective diameter of the first lenses 111, 121, and 131 can be less than the total effective focal length F.

[0117] [Formula 5]

[0118] 0.5 < TTL / D8 < 1.5

[0119] In Equation 5, D8 represents the effective diameter of the eighth lenses 118, 128, and 138. The effective diameter of the eighth lenses 118, 128, and 138 can be greater than or less than the total effective focal length F.

[0120] [Formula 6]

[0121] 0.5 < f² / F < 1.5

[0122] In Equation 6, f2 represents the focal length of the second lenses 112, 122, and 132.

[0123] [Formula 7]

[0124] -5 < f2 / f3 < 0

[0125] In Equation 7, f3 represents the focal length of the third lenses 113, 123, and 133.

[0126] [Formula 8]

[0127] 0.5 < f2 / f28 < 1.5

[0128] In Equation 8, f28 is the combined focal length of the second to eighth lenses in the optical systems of the first to third embodiments.

[0129] [Formula 9]

[0130] 0.5 < f2 / f12 < 1.5

[0131] In Equation 9, f12 represents the combined focal length of the first lenses 111, 121 and 131 and the second lenses 112, 122 and 132.

[0132] [Formula 10]

[0133] 0.5 < f28 / F < 1.5

[0134] As shown in Equation 10, the combined focal length f28 of the second to eighth lenses in the optical system can be less than or greater than the total focal length F.

[0135] [Equation 11]

[0136] 0.5 < f12 / F < 1.5

[0137] As shown in Equation 11, the combined focal length f12 of the first lens and the second lens in the optical system can be less than or greater than the total focal length F.

[0138] [Equation 12]

[0139] 0 < L2R1 / |L2R2| < 1

[0140] In Equation 12, L2R1 represents the radius of curvature of the third object-side surface S3 of the second lenses 112, 122, and 132, and |L2R2| represents the absolute value of the radius of curvature of the fourth image surface S4. The radius of curvature of the third surface S3 can be smaller than the absolute value of the radius of curvature of the fourth surface S4.

[0141] [Equation 13]

[0142] 0 < L3R2 / |L3R1| < 1

[0143] In Equation 13, |L3R1| represents the absolute value of the radius of curvature of the object-side fifth surface S5 of the third lenses 113, 123, and 133, and L3R2 represents the radius of curvature of the sixth image surface S6. The radius of curvature of the fifth surface S5 can be greater than the absolute value of the radius of curvature of the sixth surface S6.

[0144] [Formula 14]

[0145] 0.7 < G2 / G3 < 1.2

[0146] In Equation 14, G2 represents the refractive index of the second lenses 112, 122 and 132 at 587 nm, and G3 represents the refractive index of the third lenses 113, 123 and 133 at 587 nm.

[0147] [Formula 15]

[0148] 1 < T2 / T3 < 5

[0149] In Equation 15, T2 represents the center thickness (thickness along the optical axis) of the second lenses 112, 122, and 132, and T3 represents the center thickness (thickness along the optical axis) of the third lenses 113, 123, and 133. The center thickness T2 of the second lenses 112, 122, and 132 can be greater than 1 times and less than or equal to 5 times the center thickness T3 of the third lenses 113, 123, and 133, for example, in the range of 2 to 4 times the thickness T3, and the optical performance can be improved by the difference between the thickness T2 of the second lens and the thickness T3 of the third lens.

[0150] The optical systems according to the first to third embodiments of the present invention can satisfy at least one, two or more, or all of Equations 1 to 15. In this case, the optical system can realize a high-definition and high-resolution imaging lens system. In addition, by using at least one of Equations 1 to 15, unwanted light entering the optical system can be blocked, aberrations can be corrected, and the performance of the optical system can be improved.

[0151] Table 7 provides examples of preferred values ​​for the items disclosed in Formulas 1 to 15 of the first to third embodiments.

[0152] Table 7

[0153]

[0154] Table 8 shows the preferred values ​​obtained using Equations 1 to 15 with the values ​​in Table 1.

[0155] Table 8

[0156]

[0157]

[0158] As shown in Tables 1 to 8 above, it can be confirmed that the first to third embodiments of the present invention satisfy Equations 1 to 15.

[0159] Figure 4 This is a perspective view illustrating an example of a mobile device employing an optical system according to an embodiment of the present invention. Figure 4As shown, the mobile terminal 1500 may include a camera module 1520, a flash module 1530, and an autofocus device 1510 disposed on one side or the rear side. Here, the autofocus device 1510 may include a surface-emitting laser device as a light-emitting layer and a light receiver. The flash module 1530 may include a light emitter. The flash module 1530 can operate by operating the camera of the mobile terminal or by user control. The camera module 1520 may include image capture and autofocus functions. For example, the camera module 1520 may include an autofocus function using an image. The autofocus device 1510 may include an autofocus function using a laser. The autofocus device 1510 can be used primarily when the autofocus function using the image from the camera module 1520 is degraded (e.g., near 10m or in dark environments).

[0160] The features, structures, effects, etc., described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, those skilled in the art to which the embodiments pertain can combine or modify the features, structures, effects, etc., shown in each embodiment for other embodiments. Therefore, anything relating to such combinations and modifications should be interpreted as being included within the scope of the present invention. Moreover, although embodiments have been described above, they are merely examples and do not limit the present invention, and those skilled in the art to which the present invention pertain can illustrate them by way of example without departing from the essential characteristics of the embodiments. It can be seen that various modifications and applications are possible. For example, the components specifically shown in the embodiments can be implemented by modification. Furthermore, differences relating to such modifications and applications should be interpreted as being included within the scope of the present invention as defined in the appended claims.

Claims

1. An optical system comprising a lens assembly, said lens assembly consisting of 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 the optical axis from the object side to the image side. in, The second lens has positive diopter. The third lens has a negative refractive power. The seventh lens has positive diopter. The eighth lens has negative refractive power. The refractive indices of the first lens, the third lens, and the fifth lens are greater than those of the second lens, the fourth lens, the sixth lens, and the eighth lens. Wherein, the following equation is satisfied: 1.2 < F / D1 < 2.4 Where F is the total effective focal length of the optical system, and D1 is the effective diameter of the first lens. The center thickness of the second lens is greater than the center thickness of each of the first lens, the third lens, and the eighth lens. The Abbe number of the second lens is greater than that of the third and fifth lenses. The optical system satisfies the following equation: 0 < |f2 / f3| < 5 Where f2 is the focal length of the second lens and f3 is the focal length of the third lens. The second lens includes an object-side surface protruding along the optical axis and an image-side surface protruding along the optical axis, and Wherein, when the radius of curvature of the object-side surface of the second lens is L2R1 and the absolute value of the radius of curvature of the image-side surface of the second lens is |L2R2|, the following equation is satisfied: 0 < L2R1 / |L2R2| < 1.

2. The optical system according to claim 1, wherein, The center thickness of the second lens is greater than the center thickness of each of the first lens, the third lens, and the eighth lens.

3. The optical system according to claim 1, wherein, The second lens, the fourth lens, the sixth lens, and the eighth lens have an Abbe number of 50 or higher, and the third lens and the fifth lens have an Abbe number of less than 30.

4. The optical system according to any one of claims 1 to 3, comprising: An image sensor is disposed on the image side of the eighth lens; and the filter between the image sensor and the eighth lens, The optical system satisfies the following equation: 0 < BFL / TTL < 0.5 0 < BFL / Img < 0.5 Wherein, BFL is the distance from the vertex of the image-side surface of the eighth lens to the image sensor, TTL is the distance from the vertex of the object-side first surface of the first lens to the image sensor, and Img is the vertical distance from the optical axis to the diagonal end, i.e., 1.0F, in the image sensor.

5. The optical system according to any one of claims 1 to 3, comprising: An image sensor located on the image side of the eighth lens; and the filter between the image sensor and the eighth lens, The optical system satisfies the following equation: 0.5 < TTL / D8 < 1.5 Wherein, TTL is the distance from the vertex of the first surface on the object side of the first lens to the image sensor, and D8 is the effective diameter of the eighth lens.

6. The optical system according to any one of claims 1 to 3, wherein, The optical system satisfies the following equation: 0.5 < f² / F < 1.5 -5 < f2 / f3 < 0 Where F is the total effective focal length of the optical system. Where f2 is the focal length of the second lens, and Where f3 is the focal length of the third lens.

7. The optical system according to claim 1, wherein, When the absolute value of the radius of curvature of the object-side surface of the third lens is |L3R1| and the radius of curvature of the image-side surface of the third lens is L3R2, the following relationship is satisfied: 0 < L3R2 / |L3R1| < 1.

8. The optical system according to claim 7, wherein, When the refractive index of the second lens at 587 nm is G2 and the refractive index of the third lens at 587 nm is G3, the following relationship is satisfied: 0.7 < G2 / G3 < 1.

2.

9. The optical system according to claim 7, wherein, When the center thickness of the second lens is T2 and the center thickness of the third lens is T3, the following relationship is satisfied: 1 < T2 / T3 < 5.

10. The optical system according to claim 1, wherein, Satisfy the following formula: 0 < |f2 / f3| < 5 Where f2 is the focal length of the second lens, f3 is the focal length of the third lens, and The seventh lens includes an object-side surface that protrudes along the optical axis and an image-side surface that is recessed along the optical axis.

11. The optical system according to claim 10, wherein, The first distance between the seventh lens and the eighth lens along the optical axis is greater than the second distance between the first lens and the second lens.

12. The optical system according to claim 11, wherein, The first distance is greater than or equal to 0.4 mm.

13. The optical system according to any one of claims 10 to 12, wherein, The center thickness of the second lens is in the range of 2 to 4 times the center thickness of the third lens, and The center thickness of the second lens is the thickest among the center thicknesses of the first lens to the eighth lens.

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