Optical system and camera module including the same

Abstract

A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence from an object side to an image side, each of the first lens group to the fourth lens group including at least two lenses, the second lens group and the third lens group being movable, and an effective focal length (EFL) at a wide angle being defined by the following mathematical formula: TIFF2023522432000025.tif13156Here, EFL wide means the effective focal length of the zoom optical system at wide angle, and H imageD means half the diagonal length of the image sensor pixel area.

Description

[Technical Field]

[0001] The embodiments relate to an optical system and a camera module including the same. [Background technology]

[0002] As the performance of camera modules built into mobile terminals improves, there is a demand for autofocus functionality in camera modules built into mobile terminals.

[0003] Because the camera module in a mobile device has an autofocus function, it can increase the magnification through digital processing in the process of converting external light into a digital image or video. However, as the magnification increases, it is only possible to zoom to a predetermined magnification such as 1x, 3x, 5x, etc., and as the magnification increases, the resolution decreases, causing digital degradation.

[0004] Meanwhile, in order to provide the autofocus function for the camera module in a mobile device, a technology has been attempted to adjust the distance between the lens and the image sensor by moving the lens, but the reality is that it is not easy to design an optical system that can be moved within the narrow space inside a mobile device. Summary of the Invention [Problem to be solved by the invention]

[0005] The technical problem to be solved by the present invention is to provide a zoom optical system and a camera module including the same.

[0006] The problems to be solved by the examples are not limited to these, and may also include the means for solving the problems and the objectives and effects that can be grasped from the embodiments described below. [Means for solving the problem]

[0007] A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence from an object side to an image side, each of the first lens group to the fourth lens group including at least two lenses, the second lens group and the third lens group being movable, and an effective focal length (EFL) at a wide angle being defined by the following mathematical formula: TIFF0007742849000001.tif18151

[0008] Here, EFL wide means the effective focal length of the zoom optical system at wide angle, and H imageD means half the diagonal length of the image sensor pixel area.

[0009] The first lens group may include two or more lenses, the second lens group may include two or more lenses, the third lens group may include two or more lenses, and the fourth lens group may include two lenses.

[0010] The effective focal length (EFL) in a telephoto can be defined by the following mathematical formula: TIFF0007742849000002.tif15155

[0011] Here, EFL tele means the effective focal length of the zoom optical system in Telephoto, and H imageD means half the diagonal length of the image sensor pixel area.

[0012] When zooming from a wide angle to a telephoto, the movement stroke of the second lens group can be defined by the following mathematical formula: TIFF0007742849000003.tif15154

[0013] Here, TTL (Total Track Length) means the distance from the image sensor surface to the first surface of the zoom optical system, and STROKE2 means the movement stroke of the second lens group.

[0014] When zooming from a wide angle to a telephoto, the movement stroke of the third lens group can be defined by the following mathematical formula: TIFF0007742849000004.tif15162

[0015] Here, TTL (Total Track Length) means the distance from the image sensor surface to the first surface of the zoom optical system, and STROKE3 means the movement stroke of the third lens group.

[0016] Of the two lenses included in the first lens group, the lens located on the image side can have positive refractive power, and the lens located on the object side of the two lenses included in the first lens group can have negative refractive power.

[0017] At least two lenses included in the second lens group may have Abbe numbers defined by the following mathematical formula: TIFF0007742849000005.tif9167

[0018] Here, ABBE3 means the Abbe number of the lens arranged on the object side of the two lenses included in the second lens group, and ABBE4 means the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group.

[0019] The second lens group may include at least one of a glass lens and a plastic lens.

[0020] The maximum diameters of the lenses included in the first and fourth lens groups and the maximum diameters of the lenses included in the second and third lens groups may be defined by the following mathematical formulas. TIFF0007742849000006.tif14154

[0021] Here, APER fix means the maximum diameter of the lenses included in the first and fourth lens groups, which are fixed groups, and APER mov may refer to the maximum diameter of the lenses included in the second lens group and the third lens group, which are movable groups.

[0022] The CRA (chief ray angle) may be greater than -10 degrees and less than 10 degrees.

[0023] The optical system may further include a right-angle prism disposed at the front end of the first lens group.

[0024] A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence from an object side to an image side, each of the first lens group to the fourth lens group including at least two lenses, the second lens group and the third lens group being movable, and an effective focal length (EFL) in a telephoto lens is defined by the following mathematical formula: TIFF0007742849000007.tif15155

[0025] Here, EFL tele means the effective focal length of the zoom optical system in Telephoto, and H imageD means half the diagonal length of the image sensor pixel area.

[0026] A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence from an object side to an image side, the first lens group and the fourth lens group being fixed, and the second lens group and the third lens group being movable, the second lens group performing a zoom function, and the third lens group performing a focusing function, the second lens group including a first lens and a second lens, and a difference in Abbe number between the first lens and the second lens being 10 or more.

[0027] A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence from an object side to an image side, the first lens group and the fourth lens group being fixed, and the second lens group and the third lens group being movable, the second lens group performing a zoom function, and the third lens group performing a focusing function, the image-side surface of a first lens arranged closest to an image-side surface of the lenses included in the first lens group is concave, the object-side surface of a second lens arranged closest to an object-side surface of the lenses included in the second lens group is convex, and when the distance between the first lens group and the second lens group is minimum, the center of curvature of the object-side surface of the second lens is located closer to the image side than both ends of the image-side surface of the first lens. [Effects of the Invention]

[0028] According to an embodiment of the present invention, an optical system capable of zooming at both low and high magnifications and a camera module including the same can be obtained. The optical system according to the embodiment of the present invention is capable of continuous zoom adjustment and can maintain high resolution even at high magnifications. [Brief explanation of the drawings]

[0029] [Figure 1] 1 shows a zoom optical system according to an embodiment of the present invention. [Figure 2a] 1 is a cross-sectional view of a zoom optical system according to an embodiment of the present invention at a wide angle. [Figure 2b] 1 is a cross-sectional view of a zoom optical system according to an embodiment of the present invention in an intermediate mode. [Figure 2c] 1 is a cross-sectional view of a telephoto lens of a zoom optical system according to an embodiment of the present invention; [Figure 3a] 10 is a graph showing measurements of the spherical aberration (Longitudinal Spherical Aberration), astigmatic field curves, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm at a wide angle in an optical system according to an example. [Figure 3b] 10 is a graph showing measurements of spherical aberration, astigmatism, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in the intermediate mode of the optical system according to the example. [Figure 3c] 10 is a graph showing the results of measuring spherical aberration, astigmatism, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm using a telephoto lens of an optical system according to an example. [Figure 4a] 10 is a diffraction MTF graph at a wide angle of the optical system according to the example. [Figure 4b] 10 is a diffraction MTF graph in an intermediate mode of the optical system according to the example. [Figure 4c] 10 is a diffraction MTF graph in telephoto of an optical system according to an embodiment. [Figure 5] 4 is a graph showing the relative illumination of the zoom optical system according to the embodiment of the present invention; [Figure 6] 1 shows a part of a mobile terminal to which a camera module according to an embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0031] However, the technical concept of the present invention is not limited to the described embodiments and may be embodied in various different forms, and one or more of the components of the embodiments may be selectively combined or substituted within the scope of the technical concept of the present invention.

[0032] Furthermore, unless otherwise clearly defined and described, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted in a way that would be commonly understood by a person of ordinary skill in the art to which the present invention belongs, and commonly used terms, such as dictionary-defined terms, may be interpreted in light of the contextual meaning of the relevant art.

[0033] Furthermore, the terms used in the embodiments of the present invention are intended to explain the embodiments and are not intended to limit the present invention.

[0034] In this specification, the singular can also include the plural unless otherwise specified in the context, and when it is stated as "A and (and) at least one (or more) of B and C," it can include one or more of all possible combinations of A, B, and C.

[0035] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of embodiments of the present invention.

[0036] Such terms are merely used to distinguish a component from other components, and are not intended to limit the nature, order, or sequence of the components.

[0037] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it can include not only cases where the component is directly coupled, coupled, or connected to the other component, but also cases where the component is "coupled," "coupled," or "connected" by yet another component between the component and the other component.

[0038] Furthermore, when a component is described as being formed or disposed "above or below" another component, the above or below not only refers to the two components being in direct contact with each other, but also refers to the two components being formed or disposed between one or more other components. Furthermore, when the term "above or below" is used, it can refer to not only the upper direction but also the lower direction relative to one component. Figure 1 shows a zoom optical system according to an embodiment of the present invention.

[0039] 1, a zoom optical system according to an embodiment of the present invention includes a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400, which are sequentially arranged from the object side to the image side. A right-angle prism may be further disposed at the front end of the first lens group 100. In this case, the zoom optical system may include the right-angle prism, the first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400, which are sequentially arranged from the object side to the image side.

[0040] According to an embodiment of the present invention, the first lens group 100 includes multiple lenses. The first lens group 100 may include at least two lenses. If the first lens group 100 includes only one lens, it may be difficult to correct the resolution at maximum magnification, and if the first lens group 100 includes three or more lenses, the overall size of the zoom optical system may become large. Therefore, the first lens group 100 preferably includes two lenses.

[0041] The first lens group 100 is fixed relative to the image side. The first lens group 100 is fixed relative to the sensor 10 surface. That is, the lenses are fixed relative to the image side. If the first lens group 100 includes three lenses, two of the lenses may be fixed relative to the image side.

[0042] The second lens group 200 includes multiple lenses. The second lens group 200 may include at least two lenses. If the second lens group 200 includes only one lens, it may be difficult to correct the resolution at maximum magnification, and if the second lens group 200 includes three or more lenses, the overall size of the zoom optical system may become large. Therefore, the second lens group 200 preferably includes two lenses.

[0043] The second lens group 200 is movable. The lenses included in the second lens group 200 can move together along the central axis of the lens. Two lenses included in the second lens group 200 can move together along the central axis of the lens. If the second lens group 200 includes three or more lenses, the size and weight of the second lens group 200 will increase and the driving power required for movement may become high. Therefore, it is preferable that the second lens group 200 includes two lenses. The focal length can be continuously adjusted by moving the second lens group 200. The magnification can be continuously adjusted by moving the second lens group 200. Accordingly, the second lens group 200 can function as a zooming group.

[0044] The third lens group 300 includes multiple lenses. The third lens group 300 may include at least two lenses, as compared to the first lens group 300. If the third lens group 300 includes only one lens, it may be difficult to correct the resolution at maximum magnification, and if the third lens group 300 includes three or more lenses, the overall size of the zoom optical system may become large. Therefore, the third lens group 300 preferably includes two lenses.

[0045] The third lens group 300 is movable. The lenses included in the third lens group 300 can move together along the central axis of the lens. Two lenses included in the third lens group 300 can move together along the central axis of the lens. If the third lens group 300 includes three or more lenses, the size and weight of the third lens group 300 will increase and the driving power required for movement may become high. Therefore, it is preferable that the third lens group 300 includes two lenses. The focus can be adjusted by moving the third lens group 300. The third lens group 300 can function as a focusing group.

[0046] The fourth lens group 400 includes multiple lenses. The fourth lens group 400 includes at least two lenses. If the fourth lens group 400 includes only one lens, it may be difficult to correct the resolution at maximum magnification, and if the fourth lens group 400 includes three or more lenses, the overall size of the zoom optical system may become large. Therefore, the fourth lens group 400 preferably includes two lenses.

[0047] The fourth lens group 400 is fixed relative to the image side. The fourth lens group 400 is fixed relative to the sensor 10 surface. That is, the multiple lenses are fixed relative to the image side. When the fourth lens group 400 includes one lens, the single lens 410 may be fixed relative to the image side.

[0048] According to an embodiment of the present invention, a filter 20 and an image sensor 10 may be sequentially disposed at the rear end of the fourth lens group 400. In this case, the filter 20 may be an IR (infrared) filter. Accordingly, the filter 20 may block near-infrared light, for example, light with a wavelength of 700 nm to 1100 nm, from light entering the camera module. The image sensor 10 may be connected to a printed circuit board by a wire.

[0049] The filter 20 may include a foreign matter prevention filter and an IR filter arranged in order from the object side to the image side. When the filter 20 includes the foreign matter prevention filter, foreign matter generated during the movement of the third lens group 300 can be prevented from flowing into the IR filter or the image sensor 10.

[0050] The magnification of the zoom optical system can be changed by moving the second lens group 200 and the third lens group 300. For example, the magnification of the zoom optical system can be continuously increased or decreased between 5x and 10x by moving the second lens group 200 and the third lens group 300. According to an embodiment, the zoom optical system can have a magnification of 5x at a wide angle and a magnification of 10x at a telephoto angle. Meanwhile, the meaning of the magnification continuously increasing or decreasing may mean that the magnification increases or decreases linearly, rather than increasing or decreasing digitally and discontinuously.

[0051] The second lens group 200 and the third lens group 300 can move independently. For example, when moving from a wide angle to a telephoto position, the distance between the second lens group 200 and the third lens group 300 may increase from the start point (wide angle) to a predetermined point, and then gradually decrease from the predetermined point to the end point (telephoto position).

[0052] The effective focal length (EFL) of the zoom optical system according to the embodiment of the present invention will now be described in detail.

[0053] The effective focal length of a zoom optical system in telephoto can be expressed as follows: [Mathematical formula 1]

[0054]

number

[0055] Here, EFL telemeans the effective focal length of the zoom optical system in Telephoto, and H imageD means half the diagonal length of the image sensor pixel area. The unit may be [mm]. The image sensor pixel area may mean the area where pixels that receive light are arrayed in the image sensor. The image sensor pixel area may be the entire area of ​​the image sensor excluding the circuit area that converts received light into an electrical signal, the housing part due to packaging, etc.

[0056] The effective focal length of a zoom optical system at a wide angle can be expressed as the following mathematical formula 2. [Mathematical formula 2]

[0057]

number

[0058] Here, EFL wide means the effective focal length of the zoom optical system at wide angle, and H imageD means half the diagonal length of the image sensor pixel area.

[0059] The movement stroke of the zoom optical system according to the embodiment of the present invention will be described in detail below. The movement stroke may refer to a distance that a lens group can be moved by a driving unit.

[0060] The movement stroke of the second lens group 200 can be expressed as the following mathematical formula 3. [Mathematical formula 3]

[0061]

number

[0062] Here, TTL (Total Track Length) may refer to the distance from the image sensor surface to the first surface of the zoom optical system. For example, TTL may refer to the distance from the surface of the first lens group 100 closest to the object side to the top surface of the image sensor 10 where light is incident. In this specification, it may be used interchangeably with the total length. STROKE2 may refer to the movement stroke of the second lens group 200. The unit may be [mm].

[0063] The movement stroke of the third lens group 300 can be expressed as Equation 4 below. [Mathematical formula 4]

[0064]

number

[0065] Here, TTL may refer to the distance from the image sensor surface to the first surface of the zoom optical system, and STROKE3 may refer to the movement stroke of the third lens group 300. The unit may be [mm].

[0066] If the movement stroke is large, the size of the driving unit for moving the second lens group 200 and the third lens group 300 becomes large, which makes it difficult to install in a mobile terminal. However, by realizing a movement stroke that is approximately 1 / 5 to 1 / 3 of that of TTL, the size of the driving unit can be reduced, which makes it possible to miniaturize the camera module.

[0067] The Abbe number of the zoom optical system according to the embodiment of the present invention will be described in detail below. The Abbe number may refer to a numerical value that represents the properties of a lens related to the dispersion of light.

[0068] The Abbe numbers of the lenses included in the second lens group 200 may be different from each other. When the second lens group 200 includes two lenses, the Abbe numbers of the two lenses included in the second lens group 200 can be expressed by the following Equation 5. [Mathematical formula 5]

[0069]

number

[0070] Here, ABBE3 may refer to the Abbe number of the lens arranged on the object side of the two lenses included in the second lens group 200, and ABBE4 may refer to the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group 200. According to an embodiment, ABBE3 may refer to the Abbe number of the third lens 210, and ABBE4 may refer to the Abbe number of the fourth lens 220.

[0071] The zoom optical system according to the embodiment of the present invention can eliminate chromatic aberration by arranging two lenses in the second lens group 200 whose Abbe numbers differ by a certain value or more.

[0072] The lens aperture of the zoom optical system according to the embodiment of the present invention will now be described in detail.

[0073] According to an embodiment of the present invention, the apertures of the second lens group 200 and the third lens group 300 may be smaller than the apertures of the first lens group 100 and the fourth lens group 400. This can be expressed as in Equation 6 below. [Mathematical formula 6]

[0074]

number

[0075] Here, APER fix denotes the maximum diameter of the lenses included in the first lens group 100 and the fourth lens group 400, which are fixed groups, and APER mov APER may refer to the maximum diameter of the lenses included in the second lens group 200 and the third lens group 300, which are movable groups. For example, if the diameter of the first lens 110 is the largest among the lenses included in the first lens group 100 and the fourth lens group 400, which are fixed groups, then APER fixmay refer to the diameter of the first lens 110. When the third lens 210 has the largest diameter among the lenses included in the second lens group 200 and the third lens group 300, which are moving groups, APER mov may refer to the diameter of the third lens 210.

[0076] By implementing the apertures of the second lens group 200 and the third lens group 300 to be smaller than those of the first lens group 100 and the fourth lens group 400, it is possible to reduce the weight of the second lens group 200 and the third lens group 300. As a result, it is possible to reduce power consumption during movement of the second lens group 200 and the third lens group 300, which are moving groups.

[0077] According to an embodiment of the present invention, the lenses included in the first to fourth lens groups 100 to 400 may be lenses to which the D-cut technique is applied. The lenses included in the first to fourth lens groups 100 to 400 may be D-cut lenses in which portions of the upper and lower portions are cut. In this case, the upper and lower portions of the lenses may have ribs and portions of the effective diameter cut, or only the ribs may be cut without cutting the effective diameter. According to an embodiment, the second lens group 200 and the third lens group may include lenses in which the value obtained by dividing the major axis length of the effective diameter by the minor axis length of the effective diameter is 1. In other words, the major axis length and the minor axis length of the effective diameter may be the same. For example, in the case of the third lens 210, the fourth lens 220, the fifth lens 310, and the sixth lens 320, the ribs on the upper and lower portions may be cut, but the effective diameter may not be cut. In the case of circular lenses, there is a problem that the volume of the lens increases depending on the vertical height, but by applying D-cuts to the upper and lower parts of multiple lenses as in the embodiment of the present invention, the vertical height can be reduced, thereby reducing the volume of the lens.

[0078] According to an embodiment of the present invention, the first lens group 100 may include a plurality of lenses having different refractive powers. Of the plurality of lenses included in the first lens group 100, a lens arranged on the image side may have positive (+) refractive power. Of the plurality of lenses included in the first lens group 100, a lens arranged on the object side may have negative (-) refractive power. According to an embodiment, the first lens group 100 may include a first lens 110 and a second lens 120 arranged sequentially from the object side to the image side. Of these, the first lens 110 may have positive refractive power, and the second lens 120 may have negative refractive power.

[0079] According to an embodiment of the present invention, the first to fourth lens groups 100 to 400 may include plastic lenses. For example, the lenses included in the fourth lens group 400 may all be made of plastic or glass. The fourth lens group 400 may include glass lenses. For example, of the lenses included in the fourth lens group 400, the lens located on the object side may be made of glass, and the lens located on the image side may be made of plastic. In this case, the glass lenses may be glass molded lenses manufactured using a glass mold method.

[0080] According to an embodiment of the present invention, the zoom optical system may have a chief ray angle (CRA) greater than -10 degrees and less than 10 degrees. The angle of the light rays incident on the image sensor 10, i.e., the top surface, may be greater than -10 degrees and less than 10 degrees. That is, the CRA of the zoom optical system according to an embodiment of the present invention may have any one value between -10 degrees and 10 degrees. Because the angle of the light rays incident on the image sensor 10 is small, the degree of freedom in sensor selection may be increased, and a more compact zoom optical system may be obtained.

[0081] FIG. 2a is a cross-sectional view of a zoom optical system according to an embodiment of the present invention at a wide angle, FIG. 2b is a cross-sectional view of a zoom optical system according to an embodiment of the present invention at a middle mode, and FIG. 2c is a cross-sectional view of a zoom optical system according to an embodiment of the present invention at a telephoto mode.

[0082] Tables 1 and 2 below show the optical characteristics of the lenses included in the zoom optical system according to an embodiment of the present invention, and Tables 3 and 4 show the conic constants and aspherical coefficients of the lenses included in the zoom optical system according to an embodiment of the present invention.

[0083] [Table 1]

[0084] [Table 2]

[0085] [Table 3]

[0086] [Table 4]

[0087] 2a-2c and Tables 1-4, the zoom optical system includes a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400, which are arranged sequentially from the object side to the image side. The first lens group 100 includes a first lens 110 and a second lens 120, which are arranged sequentially from the object side to the image side. The second lens group 200 includes a third lens 210 and a fourth lens 220, which are arranged sequentially from the object side to the image side. The third lens group 300 includes a fifth lens 310 and a sixth lens 320, which are arranged sequentially from the object side to the image side. The fourth lens group 400 includes a seventh lens 410 and an eighth lens 420. In Table 1, the thickness (mm) indicates the distance from each lens surface to the next lens surface.

[0088] For example, the thickness written on the object-side surface 112 of the first lens 110 indicates the distance from the object-side surface 112 to the image-side surface 114 of the first lens 110. Specifically, the thickness written on the object-side surface 112 of the first lens 110 indicates the distance from the first lens 110 between the center of curvature of the object-side surface 112 and the center of curvature of the image-side surface 114.

[0089] The thickness written on the image-side surface 114 of the first lens 110 indicates the distance from the image-side surface 114 of the first lens 110 to the object-side surface 122 of the second lens 120. Specifically, the thickness written on the image-side surface 114 of the first lens 110 indicates the distance between the center of curvature of the image-side surface 114 of the first lens 110 and the center of curvature of the object-side surface 122 of the second lens 120.

[0090] The thickness described on the image-side surface 124 of the second lens 120 indicates the distance from the image-side surface 124 of the second lens 120 to the object-side surface 212 of the third lens 210. Specifically, the thickness described on the image-side surface 124 of the second lens 120 indicates the distance between the center of curvature of the image-side surface 124 of the second lens 120 and the center of curvature of the object-side surface 212 of the third lens 210.

[0091] As the second lens group 200 moves during zooming from wide angle to telephoto, the thickness recorded on the image side 124 of the second lens 120 may change. The thickness recorded on the image side 124 of the second lens 120 may have a value between the shortest and longest distances. Referring to Table 1, the thickness recorded on the image side 124 of the second lens 120 may have the longest distance (5.710263206) at wide angle. The thickness recorded on the image side 124 of the second lens 120 may have a value between the shortest and longest distances (2.806912311) at intermediate mode. The thickness recorded on the image side 124 of the second lens 120 may have the shortest distance (0.20028764) at telephoto. This is the same as the thickness recorded on the image side 224 of the fourth lens 220 and the thickness recorded on the image side 324 of the sixth lens 320.

[0092] Referring to Table 1, it can be seen that the difference in Abbe number between the third lens 210 and the fourth lens 220 included in the second lens group 200 is 10 or more. Specifically, the Abbe number of the third lens 210 is 56.17, and the Abbe number of the fourth lens 220 is 19.24, so the difference in Abbe number between the two lenses is approximately 37, which means there is a difference of 10 or more.

[0093] Referring to Table 1, it can be seen that either the seventh lens 410 or the eighth lens 420 included in the fourth lens group 400 is a glass lens. Specifically, it can be seen that the seventh lens 410 is a glass molded lens, and the eighth lens 420 is a plastic lens.

[0094] Referring to Table 2, each surface of the first to eighth lenses 110 to 420 may be embodied as a convex or concave shape.

[0095] The first lens 110 may be a lens whose object-side surface 112 bulges toward the object side. The first lens 110 may be a lens whose image-side surface 114 bulges toward the object side. The second lens 120 may be a lens whose object-side surface 122 is concave toward the object side. The second lens 120 may be a lens whose image-side surface 124 bulges toward the object side.

[0096] The third lens 210 may be a lens whose object-side surface 212 is convex toward the object side. The third lens 210 may be a lens whose image-side surface 214 is concave toward the object side. The fourth lens 220 may be a lens whose object-side surface 222 is concave toward the object side. The fourth lens 220 may be a lens whose image-side surface 224 is concave toward the object side. Meanwhile, when the distance between the first lens group 100 and the second lens group 200 is minimum (i.e., in telephoto), the center of curvature of the object-side surface 212 of the third lens 210 may be located closer to the image side than either end of the image-side surface 124 of the second lens 120.

[0097] The fifth lens 310 may be a lens whose object-side surface 312 bulges toward the object side. The fifth lens 310 may be a lens whose image-side surface 314 bulges toward the object side. The sixth lens 320 may be a lens whose object-side surface 322 is concave toward the object side. The sixth lens 320 may be a lens whose image-side surface 324 bulges toward the object side.

[0098] The seventh lens 410 may be a lens whose object-side surface 412 is concave toward the object side. The seventh lens 410 may be a lens whose image-side surface 414 is convex toward the object side. The eighth lens 420 may be a lens whose object-side surface 422 is convex toward the object side. The eighth lens 420 may be a lens whose image-side surface 424 is concave toward the object side.

[0099] 2a, when the distance between the first lens group 100 and the second lens group 200 is d1a, the distance between the second lens group 200 and the third lens group 300 is d2a, and the distance between the third lens group 300 and the fourth lens group 400 is d3a, the zoom optical system can have a wide angle (e.g., 5x magnification). That is, when the distance between the center of curvature of the image-side surface 124 of the second lens 120 and the center of curvature of the object-side surface 212 of the third lens 210 is d1a, the distance between the center of curvature of the image-side surface 224 of the fourth lens 220 and the center of curvature of the object-side surface 312 of the fifth lens 310 is d2a, and the distance between the center of curvature of the image-side surface 324 of the sixth lens 320 and the center of curvature of the object-side surface 412 of the seventh lens 410 is d3a, the zoom optical system can have a wide angle.

[0100] 2b, when the distance between the first lens group 100 and the second lens group 200 is d1b, the distance between the second lens group 200 and the third lens group 300 is d2b, and the distance between the third lens group 300 and the fourth lens group 400 is d3b, the zoom optical system can have an intermediate mode. That is, when the distance between the center of curvature of the image-side surface 124 of the second lens 120 and the center of curvature of the object-side surface 212 of the third lens 210 is d1b, the distance between the center of curvature of the image-side surface 224 of the fourth lens 220 and the center of curvature of the object-side surface 312 of the fifth lens 310 is d2b, and the distance between the center of curvature of the image-side surface 324 of the sixth lens 320 and the center of curvature of the object-side surface 412 of the seventh lens 410 is d3b, the zoom optical system can have an intermediate mode.

[0101] 2c, if the distance between the first lens group 100 and the second lens group 200 is dlc, the distance between the second lens group 200 and the third lens group 300 is d2c, and the distance between the third lens group 300 and the fourth lens group 400 is d3c, the zoom optical system can have a telephoto magnification (e.g., 10x magnification). That is, if the distance between the center of curvature of the image-side surface 124 of the second lens 120 and the center of curvature of the object-side surface 212 of the third lens 210 is dlc, the distance between the center of curvature of the image-side surface 224 of the fourth lens 220 and the center of curvature of the object-side surface 312 of the fifth lens 310 is d2c, and the distance between the center of curvature of the image-side surface 324 of the sixth lens 320 and the center of curvature of the object-side surface 412 of the seventh lens 410 is d3c, the zoom optical system can have a telephoto magnification.

[0102] In the process of changing magnification from wide angle to telephoto, the distance between adjacent lens groups can change.

[0103] The distance between the first lens group 100 and the second lens group 200 can change from d1a to d1b to d1c. Referring to Table 1, at wide angle, the distance d1a between the first lens group 100 and the second lens group 200 is 5.710263206 mm. At intermediate mode, the distance d1b between the first lens group 100 and the second lens group 200 is 2.806912311 mm. At telephoto, the distance d1c between the first lens group 100 and the second lens group 200 is 0.20028764 mm. Thus, as the magnification changes from wide angle to intermediate mode to telephoto, the distance between the first lens group 100 and the second lens group 200 can change from 5.710263206 mm to 2.806912311 mm to 0.20028764 mm. That is, in the process of changing the magnification from wide angle to telephoto, the distance between the first lens group 100 and the second lens group 200 may gradually decrease (d1a>d1b>d1c). That is, in the process of changing the magnification from wide angle to telephoto, the increase in the distance between the first lens group 100 and the second lens group 200 may gradually decrease.

[0104] The distance between the second lens group 200 and the third lens group 300 can change from d2a to d2b and then to d2c. Referring to Table 1, the distance d2a between the second lens group 200 and the third lens group 300 in the wide-angle mode is 0.674684273 [mm]. The distance d2b between the second lens group 200 and the third lens group 300 in the intermediate mode is 0.310740064 [mm]. The distance d1c between the second lens group 200 and the third lens group 300 in the telephoto mode is 0.2 [mm]. Thus, in the process of changing the magnification from the wide-angle to the intermediate mode and then to the telephoto, the distance between the second lens group 200 and the third lens group 300 can change from 0.674684273 [mm] to 0.310740064 [mm] and then to 0.2 [mm]. That is, in the process of changing the magnification from the wide-angle to the telephoto, the distance between the second lens group 200 and the third lens group 300 can decrease (d2a > d2b > d2c). At this time, in the process of changing the magnification from the wide-angle to the telephoto, the increase amount of the distance between the second lens group 200 and the third lens group 300 can decrease.

[0105] The distance between the third lens group 300 and the fourth lens group 400 can change from d3a to d3b and then to d3c. Referring to Table 1, the distance d3a between the third lens group 300 and the fourth lens group 400 in the wide-angle mode is 1.237063216 [mm]. The distance d3b between the third lens group 300 and the fourth lens group 400 in the intermediate mode is 4.50435832 [mm]. The distance d3c between the third lens group 300 and the fourth lens group 400 in the telephoto mode is 7.221723054 [mm]. Thus, in the process of changing the magnification from the wide-angle to the intermediate mode and then to the telephoto, the distance between the third lens group 300 and the fourth lens group 400 can change from 1.237063216 [mm] to 4.50435832 [mm] and then to 7.221723054 [mm]. That is, in the process of changing the magnification from the wide-angle to the telephoto, the distance between the third lens group 300 and the fourth lens group 400 can gradually increase (d3a < d3b < d3c). However, in the process of changing the magnification from the wide-angle to the telephoto, the increase amount of the distance between the third lens group 300 and the fourth lens group 400 can gradually decrease.

[0106] In this way, the second lens group 200 and the third lens group 300 can move at different speeds.

[0107] By moving the second lens group 200 and the third lens group 300, the magnification of the optical system can be continuously adjusted from 5x to 10x.

[0108] Next, we will explain in detail the results of simulating the spherical aberration, astigmatism, and distortion of the zoom optical system according to the embodiment of the present invention with reference to Figures 3a to 3c. The spherical aberration indicates the spherical aberration for each wavelength, the astigmatism indicates the aberration characteristics of the tangential plane and sagittal plane depending on the height of the upper surface, and the distortion indicates the degree of distortion depending on the height of the upper surface.

[0109] FIG. 3a is a graph showing the measured spherical aberration, astigmatic field curves, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm at a wide angle for the optical system according to the embodiment.

[0110] FIG. 3b is a graph showing the spherical aberration, astigmatism, and distortion measured for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in the intermediate mode of the optical system according to the example.

[0111] FIG. 3c is a graph showing the spherical aberration, astigmatism, and distortion measured for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm using a telephoto lens of the optical system according to the embodiment.

[0112] 3a to 3c, we can see that the spherical aberration is within -0.05 mm to 0.1 mm from the center to the end of the image sensor regardless of wavelength. Specifically, the spherical aberration is within approximately -0.04 mm to 0.04 mm in wide mode, and within -0.03 mm to 1 mm in medium mode. At Telephoto, the spherical aberration is outside the range at 435 nm, but is otherwise within -0.05 mm to 0.05 mm.

[0113] 3a to 3c, it can be seen that the astigmatism is within -0.04 mm to 0.01 mm from the center to the end of the image sensor regardless of wavelength. Specifically, in wide mode, the astigmatism is within approximately -0.02 mm to 0 mm, and in medium mode, the astigmatism is within -0.02 mm to 0.01 mm. In telephoto mode, the astigmatism is within approximately -0.04 mm to 0 mm.

[0114] 3a to 3c, we can see that distortion is within -2% to 0% from the center to the edge of the image sensor regardless of wavelength. Specifically, distortion is within approximately -1% to 0% in wide mode, and within -1.5% to 0% in medium mode. We can also see that distortion is within approximately -2% to 0% in telephoto mode.

[0115] Next, the MTF simulation results of the zoom optical system according to the embodiment of the present invention will be explained in detail with reference to Figures 4a to 4c. MTF (Modulation Transfer Function) means one of the methods for measuring the performance of an optical system.

[0116] 4a, 4b, and 4c are diffraction MTF graphs for the optical system according to the embodiment at wide angle, intermediate mode, and telephoto modes, respectively.

[0117] Referring to Figures 4a to 4c, it can be seen that the zoom optical system according to the embodiment of the present invention has values ​​close to the diffraction limit, which is the limit value, near the defocusing position of 0 [mm] in each of the wide angle, intermediate mode, and telephoto modes.

[0118] FIG. 5 is a graph showing the relative illumination of the zoom optical system according to the embodiment of the present invention.

[0119] 5, the zoom optical system according to the embodiment of the present invention exhibits a relative illumination value of 50% or more throughout the entire range of wide angle (zoom position 1), intermediate mode (zoom position 2), and telephoto (zoom position 3). In intermediate mode and telephoto, the relative illumination value is 80% or more throughout the entire range, and even in the wide angle range, the relative illumination value is 80% or more from 0 to 1.6 mm.

[0120] As explained in detail in the above embodiments, it can be seen that the optical system according to the embodiment of the present invention has excellent aberration characteristics.

[0121] Meanwhile, the zoom optical system according to an embodiment of the present invention may be applied to a camera module. A camera module including the zoom optical system according to an embodiment of the present invention may be built into a mobile terminal and applied together with a main camera module. The camera module according to an embodiment of the present invention may include an image sensor, a filter disposed on the image sensor, and a zoom optical system disposed on the filter, and the zoom optical system according to an embodiment of the present invention may include the first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400 described above. A mobile terminal incorporating a camera module including the zoom optical system according to an embodiment of the present invention may be a smartphone, a tablet PC, a laptop computer, a PDA, etc. The optical system according to an embodiment of the present invention may be applied to a camera module.

[0122] FIG. 6 shows a part of a mobile terminal to which a camera module according to an embodiment of the present invention is applied.

[0123] Referring to FIG. 6, a camera module including a zoom optical system 1000 according to an embodiment of the present invention can be built into a mobile terminal and applied together with a main camera module 1100.

[0124] The zoom optical system 1000 according to an embodiment of the present invention includes the first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400. The first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400 may be sequentially arranged in the lateral direction of the mobile device depending on the thickness constraints of the mobile device. To this end, as described above, a right-angle prism may be further arranged at the front end of the first lens group 100. When the zoom optical system is arranged in the thickness direction of the mobile device, i.e., when the lens surfaces of the lenses included in the zoom optical system are arranged in the thickness direction of the mobile device, the diameter size of the lenses included in the zoom optical system can be reduced, thereby reducing the thickness of the mobile device. Accordingly, a zoom optical system capable of continuously adjusting magnification by moving lenses may also be built into a mobile device.

[0125] The mobile terminal incorporating the camera module including the zoom optical system according to the embodiment of the present invention may be a smartphone, a tablet PC, a laptop computer, a PDA, or the like.

[0126] The above description focuses on the embodiments, but these are merely examples and are not intended to limit the present invention. Those skilled in the art will recognize that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the present invention. For example, each component specifically illustrated in the embodiments can be modified and implemented. Differences related to such modifications and applications should be construed as being included within the scope of the present invention as defined by the appended claims.

Claims

1. A zoom optical system comprising, arranged in order from an object side to an image side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, and a fourth lens group having positive refractive power, Each of the first to fourth lens groups includes at least two lenses, the second lens group and the third lens group are movable; During zooming, the spacing between adjacent lens groups changes, The effective focal length (EFL) at a wide angle is defined by the following mathematical formula: a zoom optical system, wherein a maximum diameter of a plurality of lenses included in the first lens group and the fourth lens group and a maximum diameter of a plurality of lenses included in the second lens group and the third lens group are defined by the following mathematical formula: Here, EFL wide means the effective focal length of the zoom optical system at wide angle, and H imageD may mean half the diagonal length of the image sensor pixel area, APER fix may mean the maximum diameter of the lenses included in the first lens group and the fourth lens group, which are fixed groups, and APER mov may mean the maximum diameter of the lenses included in the second lens group and the third lens group, which are movable groups.

2. the first lens group includes two or more lenses, the second lens group includes two or more lenses, the third lens group includes two or more lenses, The zoom optical system according to claim 1 , wherein the fourth lens group includes two or more lenses.

3. 2. The zoom optical system of claim 1, wherein the effective focal length (EFL) in telephoto is defined by the following mathematical formula: Here, EFL tele means the effective focal length of the zoom optical system in telephoto, and H imageD means half the diagonal length of the image sensor pixel area.

4. 2. The zoom optical system of claim 1, wherein when zooming from a wide angle to a telephoto, the movement stroke of the second lens group is defined by the following mathematical formula: Here, TTL (Total Track Length) means the distance from the image sensor surface to the first surface of the zoom optical system, and STROKE 2 means the movement stroke of the second lens group.

5. 2. The zoom optical system of claim 1, wherein when zooming from a wide angle to a telephoto, the movement stroke of the third lens group is defined by the following mathematical formula: Here, TTL (Total Track Length) means the distance from the image sensor surface to the first surface of the zoom optical system, and STROKE 3 means the movement stroke of the third lens group.

6. the lens disposed on the image side of the two lenses included in the first lens group has negative refractive power; 2. The zoom optical system according to claim 1, wherein the lens disposed on the object side of the two lenses included in the first lens group has positive refractive power.

7. 7. The zoom optical system of claim 6, wherein at least two lenses included in the second lens group have Abbe numbers defined by the following mathematical formula: Here, ABBE 3 means the Abbe number of the lens located on the object side of the two lenses included in the second lens group, and ABBE 4 means the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group.

8. The second lens group is 8. The zoom optical system of claim 7, comprising at least one of a glass lens and a plastic lens.

9. 2. The zoom optical system according to claim 1, wherein a chief ray angle (CRA) is greater than -10 degrees and smaller than 10 degrees.

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