Optical system and camera module comprising the same

Abstract

A zoom optical system according to an embodiment of the present application includes, arranged in order from an object side to an image side, a first lens group, a second lens group, a third lens group, and a fourth lens group, wherein each of the first lens group to the fourth lens group includes at least two lenses, the second lens group and the third lens group are movable, and an effective focal length (EFL) at a wide angle is defined by the following expression: EFL = H / 2 tan (A / 2) where EFL wide refers to the effective focal length of the zoom optical system at the wide angle, and H imageD refers to half of the diagonal length of an image sensor pixel area.

Description

Technical Field

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

[0002] With the advancement of camera module performance embedded in portable devices, even camera modules in portable devices now require autofocus functionality.

[0003] In the process of converting external light into digital images or digital video, the magnification can be increased digitally to enable autofocus in the camera module of a portable terminal. Therefore, zooming is only possible at predetermined magnification levels (such as 1x, 3x, and 5x), and as the magnification increases, the resolution decreases and digital degradation occurs.

[0004] Meanwhile, to enable autofocus in the camera module of a portable device, a technique has been attempted to move the lens to adjust the distance between the lens and the image sensor. However, designing a movable optical system within the limited space of a portable device is not easy. Summary of the Invention

[0005] Technical issues

[0006] The technical objective of this invention is to provide a zoom optical system and a camera module including the zoom optical system.

[0007] The objectives to be addressed by the embodiments are not limited thereto, and will include purposes or effects that can be understood from the technical solutions or specific implementations described below.

[0008] Technical solution

[0009] One aspect of the present invention provides a zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially in a direction from the subject side to the image side, wherein each of the first to fourth lens groups comprises at least two lenses, the second and third lens groups are movable, and the effective focal length (EFL) in wide-angle mode is defined by the following expression.

[0010]

[0011] Here, EFL wide It is the EFL of the zoom optical system in wide-angle mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

[0012] 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.

[0013] In telephoto mode, the EFL can be defined by the following expression.

[0014]

[0015] Here, EFL tele It is the EFL of the zoom optical system in telephoto mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

[0016] When zooming from wide-angle mode to telephoto mode, the travel distance of the second lens group can be defined by the following expression.

[0017]

[0018] Here, TTL (Total Track Length) is the distance from the surface of the image sensor to the first surface of the zoom optical system, and STROKE2 is the travel distance of the second lens group.

[0019] When zooming from wide-angle mode to telephoto mode, the travel distance of the third lens group can be defined by the following expression.

[0020]

[0021] Here, TTL (Total Track Length) is the distance from the surface of the image sensor to the first surface of the zoom optical system, and STROKE3 is the travel distance of the third lens group.

[0022] The lens arranged on the image side of the two lenses included in the first lens group can have positive refractive power, and the lens arranged on the subject side of the two lenses included in the first lens group can have negative refractive power.

[0023] At least two lenses included in the second lens group may have Abbe numbers as defined by the following expression.

[0024] |ABBE3-ABBE4|>10

[0025] Here, ABBE3 is the Abbe number of the lens arranged on the subject side of the two lenses included in the second lens group, and ABBE4 is the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group.

[0026] The second lens group may include at least one of a glass lens and a plastic lens.

[0027] The maximum diameter of the plurality of lenses included in the first and fourth lens groups and the maximum diameter of the plurality of lenses included in the second and third lens groups are defined by the following expressions.

[0028]

[0029] Here, APER fix It refers to the maximum diameter of the lenses included in the first and fourth lens groups, which are fixed groups, and APER. mov It is the maximum diameter of the lenses included in the second and third lens groups, which are moving groups.

[0030] The principal ray angle (CRA) can be greater than -10° and less than 10°.

[0031] The zoom optical system may also include a right-angle prism positioned in front of the first lens group.

[0032] Another aspect of the present invention provides a zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially in a direction from the subject side to the image side, wherein each of the first to fourth lens groups comprises at least two lenses, the second and third lens groups are movable, and the EFL in telephoto mode is defined by the following expression.

[0033]

[0034] Here, EFL tele It is the EFL of the zoom optical system in telephoto mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

[0035] Another aspect of the present invention provides a zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially in a direction from the subject side to the image side, wherein the first lens group and the fourth lens group are fixed, the second lens group and the third lens group are movable, the second lens group provides a zoom function, the third lens group provides a focusing function, the second lens group includes a first lens and a second lens, and the difference in Abbe number between the first lens and the second lens is 10 or greater.

[0036] However, another aspect of the present invention provides a zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially in a direction from the subject side to the image side, wherein the first lens group and the fourth lens group are fixed, the second lens group and the third lens group are movable, the second lens group provides a zoom function, the third lens group provides a focusing function, the image-side surface of the first lens arranged closest to the image side in the first lens group is recessed, the subject-side surface of the second lens arranged closest to the subject side in the second lens group is convex, and when the distance between the first lens group and the second lens group is the minimum distance, the center of curvature of the subject-side surface of the second lens is positioned closer to the image side than the two ends of the image-side surface of the first lens.

[0037] Beneficial effects

[0038] According to embodiments of the present invention, an optical system capable of zooming not only at low magnification but also at high magnification, and a camera module including the optical system, can be obtained. In the optical system according to embodiments of the present invention, zoom can be continuously adjusted, and high resolution can be maintained even at high magnification. Attached Figure Description

[0039] Figure 1 This is a view illustrating a zoom optical system according to an embodiment of the present invention.

[0040] Figure 2a This is a cross-sectional view of a zoom optical system in wide-angle mode according to an embodiment of the present invention.

[0041] Figure 2b This is a cross-sectional view of a zoom optical system in intermediate mode according to an embodiment of the present invention.

[0042] Figure 2c This is a cross-sectional view of a zoom optical system in telephoto mode according to an embodiment of the present invention.

[0043] Figure 3a The graphs show the longitudinal spherical aberration, astigmatism curves, and distortion curves of light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in an optical system in wide-angle mode according to an embodiment.

[0044] Figure 3b The graphs show the longitudinal spherical aberration, astigmatism curves, and distortion curves of light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in an optical system in intermediate mode according to an embodiment.

[0045] Figure 3cThe graph shows the longitudinal spherical aberration, astigmatism curves, and distortion curves of light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in an optical system in telephoto mode according to an embodiment.

[0046] Figure 4a This is a graph showing the diffraction modulation transfer function (MTF) in an optical system in wide-angle mode according to an embodiment.

[0047] Figure 4b This is a graph showing the diffraction MTF in an optical system in intermediate mode according to an embodiment.

[0048] Figure 4c This is a graph showing the diffraction MTF in an optical system in telephoto mode according to an embodiment.

[0049] Figure 5 This is a graph showing the relative illumination of a zoom optical system according to an embodiment of the present invention.

[0050] Figure 6 This is a view of a portion of a portable terminal that uses a camera module according to an embodiment of the present invention. Detailed Implementation

[0051] In the following, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0052] However, the spirit of the present invention is not limited to the embodiments described, and various other embodiments may be used to implement it. Furthermore, within the scope of the spirit of the present invention, at least one component in the embodiments may be selectively coupled, replaced, and used.

[0053] Furthermore, unless the context explicitly and specifically defines otherwise, all terms used herein (including technical and scientific terms) are to be interpreted as having the conventional meanings of those skilled in the art, and the meanings of general terms, such as those defined in commonly used dictionaries, will be interpreted in light of the contextual meaning of the relevant art.

[0054] Furthermore, the terminology used in the embodiments of the present invention is considered to have a descriptive meaning and is not intended to limit the invention.

[0055] In this specification, unless the context clearly indicates otherwise, the singular form includes its plural form, and in the case of describing “at least one (or one or more) of A, B and C”, this may include at least one combination of all possible combinations of A, B and C.

[0056] Furthermore, in the description of the components of the present invention, terms such as "first", "second", "A", "B", "(a)" and "(b)" may be used.

[0057] These terms are only used to distinguish one element from another, and the nature, order, etc., of the elements are not limited by these terms.

[0058] Furthermore, it should be understood that when an element is referred to as being “connected or coupled” to another element, this description can include not only cases where the element is directly connected or coupled to another element, but also cases where the element is connected or coupled to another element by means of another element arranged between the element and the other element.

[0059] Furthermore, when any element is described as being formed or arranged "above or below" another element, this description includes not only cases where the two elements are formed or arranged in direct contact with each other, but also cases where one or more other elements are placed between the two elements. Additionally, when an element is described as being formed "above or below" another element, this description includes not only cases where the element is formed on the upper side, but also cases where the element is formed on the lower side relative to the other element. Figure 1 This is a view illustrating a zoom optical system according to an embodiment of the present invention.

[0060] refer to Figure 1 According to embodiments of the present invention, a zoom optical system may include a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400 arranged sequentially from the subject side to the image side. A right-angle prism may also be arranged in front of the first lens group 100. In this case, the zoom optical system may include a right-angle prism, a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400 arranged sequentially from the subject side to the image side.

[0061] According to an embodiment of the present invention, the first lens group 100 includes a plurality of lenses. The first lens group 100 may include at least two lenses. When the first lens group 100 includes one lens, it may be difficult to correct the resolution at maximum magnification, and when the first lens group 100 includes three or more lenses, the overall size of the zoom optical system may increase, and therefore, the first lens group 100 may preferably include two lenses.

[0062] The first lens group 100 is fixed relative to the image side. The first lens group 100 is fixed relative to the surface of the sensor 10. That is, multiple lenses are fixed relative to the image side. When the first lens group 100 includes three lenses, two lenses can be fixed relative to the image side.

[0063] The second lens group 200 includes multiple lenses. The second lens group 200 may include at least two lenses. When the second lens group 200 includes one lens, it may be difficult to correct the resolution at maximum magnification, and when the second lens group 200 includes three or more lenses, the overall size of the zoom optical system may increase, and therefore, the second lens group 200 may preferably include two lenses.

[0064] The second lens group 200 is movable. All lenses included in the second lens group 200 can move along the central axis of the lens. Both lenses included in the second lens group 200 can move along the central axis of the lens. When the second lens group 200 includes three or more lenses, the size and weight of the second lens group 200 increase, and the driving force may increase when the second lens group 200 moves. Therefore, the second lens group 200 can include two lenses. The focal length can be continuously adjusted according to the movement of the second lens group 200. The magnification can be continuously adjusted as the second lens group 200 moves. Therefore, the second lens group 200 can be used as a zoom group.

[0065] The third lens group 300 includes multiple lenses. The third lens group 300 may include at least two lenses. When the third lens group 300 includes one lens, it may be difficult to correct the resolution at maximum magnification, and when the third lens group 300 includes three or more lenses, the overall size of the zoom optical system may increase, and therefore, the third lens group 300 may preferably include two lenses.

[0066] The third lens group 300 is movable. All lenses included in the plurality of lenses in the third lens group 300 are movable along the central axis of the lens. Both lenses included in the third lens group 300 are movable along the central axis of the lens. When the third lens group 300 includes three or more lenses, the size and weight of the third lens group 300 increase, and the driving force may increase when the third lens group 300 moves. Therefore, the third lens group 300 may include two lenses. As the third lens group 300 moves, the focus can be adjusted. The third lens group 300 can be used as a focusing group.

[0067] The fourth lens group 400 includes multiple lenses. The fourth lens group 400 includes at least two lenses. When the fourth lens group 400 includes one lens, it may be difficult to correct the resolution at maximum magnification, and when the fourth lens group 400 includes three or more lenses, the overall size of the zoom optical system may increase, and therefore, the fourth lens group 400 may preferably include two lenses.

[0068] The fourth lens group 400 is fixed relative to the image. The fourth lens group 400 is fixed relative to the surface of the sensor 10. That is, multiple lenses are fixed relative to the image side. When the fourth lens group 400 includes one lens, a lens 410 can be fixed relative to the image side.

[0069] According to an embodiment of the present invention, the filter 20 and the image sensor 10 may be arranged sequentially behind the fourth lens group 400. In this case, the filter 20 may be an infrared (IR) filter. Therefore, the filter 20 can block near-IR light, for example, light with wavelengths of 700 nm to 1100 nm, from incident on the camera module. Furthermore, the image sensor 10 may be connected to a printed circuit board via a wire.

[0070] The filter 20 may also include a foreign object blocking filter and an IR filter arranged sequentially in the direction from the subject side to the image side. When the filter 20 includes a foreign object blocking filter, it can prevent foreign objects generated while the third lens group 300 is moving from being introduced into the IR filter or the image sensor 10.

[0071] 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 continuously increase or decrease within the range of 5x to 10x depending on the movement of the second lens group 200 and the third lens group 300. According to this embodiment, the zoom optical system can have a magnification of 5x in wide-angle mode and 10x in telephoto mode. Furthermore, the continuous increase or decrease in magnification does not refer to an intermittent increase or decrease in magnification in a digital manner, but rather to a linear increase or decrease.

[0072] Each of the second lens group 200 and the third lens group 300 can move independently. For example, when the wide-angle mode is switched to the telephoto mode, the distance between the second lens group 200 and the third lens group 300 can increase in the direction from the starting point of the movement (the starting point of the wide-angle mode) to the predetermined point, and gradually decrease in the direction from the predetermined point to the ending point of the movement (the ending point of the telephoto mode).

[0073] The effective focal length (EFL) of a zoom optical system according to an embodiment of the present invention will be described.

[0074] The EFL of the zoom optical system in telephoto mode can be represented by the following expression 1.

[0075] [Expression 1]

[0076]

[0077] Here, EFL teleIt is the EFL of the zoom optical system in telephoto mode, and H imageD This is half the diagonal length of the pixel area of ​​the image sensor. The unit can be [mm]. The pixel area of ​​the image sensor can be the area in the image sensor where light-receiving pixels are arranged. The pixel area of ​​the image sensor can be the area in the total area of ​​the image sensor excluding the circuit area that converts the received light into electrical signals, the housing, etc.

[0078] The EFL of the zoom optical system in wide-angle mode can be represented by the following expression 2.

[0079] [Expression 2]

[0080]

[0081] Here, EFL wide It is the EFL of the zoom optical system in wide-angle mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

[0082] The travel distance of a zoom optical system according to an embodiment of the present invention will be described. The travel distance can refer to the distance that the lens group can move via the drive section.

[0083] The travel distance of the second lens group 200 can be represented by the following expression 3.

[0084] [Expression 3]

[0085]

[0086] Here, TTL (Total Track Length) can be the distance from the surface of the image sensor to the first surface of the zoom optical system. For example, TTL can be the distance from the surface of the first lens group 100 closest to the subject to the upper surface of the image sensor 10 on which light is incident. In this specification, TTL can be used interchangeably with total length. STROKE2 can be the travel distance of the second lens group 200. The unit can be [mm].

[0087] The travel distance of the third lens group 300 can be represented by the following expression 4.

[0088] [Expression 4]

[0089]

[0090] Here, TTL can be the distance from the surface of the image sensor to the first surface of the zoom optical system. STROKE3 can be the travel distance of the third lens group 300. The unit can be [mm].

[0091] When the travel distance is large, the size of the drive section used to move the second lens group 200 and the third lens group 300 increases, and therefore, it becomes difficult to install in a portable terminal. However, since the travel distance is achieved in the range of about 1 / 5 to 1 / 3 of the TTL, the size of the drive section can be small, and therefore the camera module can be miniaturized.

[0092] The Abbe number of a zoom optical system according to an embodiment of the present invention will be described. The Abbe number can be a value obtained by quantizing the optical dispersion characteristics of the lens.

[0093] The Abbe numbers of the multiple lenses included in the second lens group 200 can be different. 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 as shown in the following expression 5.

[0094] [Expression 5]

[0095] |ABBE3-ABBE4 | >10

[0096] Here, ABBE3 can be the Abbe number of the lens arranged on the subject side of the two lenses included in the second lens group 200, and ABBE4 can be the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group 200. According to this embodiment, ABBE3 can be the Abbe number of the third lens 210, and ABBE4 can be the Abbe number of the fourth lens 220.

[0097] In a zoom optical system according to an embodiment of the present invention, chromatic aberration can be reduced by arranging two lenses in the second lens group 200 whose Abbe numbers differ by a predetermined value or greater.

[0098] The aperture of a lens in a zoom optical system according to an embodiment of the present invention will be described.

[0099] According to an embodiment of the present invention, the aperture of each of the second lens group 200 and the third lens group 300 may be smaller than the aperture of each of the first lens group 100 and the fourth lens group 400. This can be represented as shown in the following expression 6.

[0100] [Expression 6]

[0101]

[0102] Here, APER fix It can be 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 movThis can be the largest diameter of the lenses included in the second lens group 200 and the third lens group 300, which are movable groups. For example, when 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, APER fix It can be the diameter of the first lens 110. When the diameter of the third lens 210 is the largest among the lenses included in the second lens group 200 and the third lens group 300, which are moving groups, APER... mov It can be the diameter of the third lens 210.

[0103] By making the apertures of the second lens group 200 and the third lens group 300 smaller than those of the first lens group 100 and the fourth lens group 400, the weight of the second lens group 200 and the third lens group 300 can be reduced. Therefore, when the second lens group 200 and the third lens group 300, which are moving groups, move, power consumption can be reduced.

[0104] According to embodiments of the present invention, the plurality of lenses included in the first lens group 100 to the fourth lens group 400 may be lenses employing D-cut technology. Each of the plurality of lenses included in the first lens group 100 to the fourth lens group 400 may be a D-cut lens with a portion of its upper part and a portion of its lower part cut off. In this case, the ribs and portions of the upper and lower parts of the effective diameter of the plurality of lenses may be cut off, or only the ribs may be cut off without cutting the effective diameter. According to one embodiment, the second lens group 200 and the third lens group may include lenses whose value is 1 obtained by dividing the length of the major axis of the effective diameter by the length of the minor axis of the effective diameter. That is, the length of the major axis of the effective diameter and the length of the minor axis 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, only the upper and lower ribs may be cut off, and the effective diameter may not be cut off. In circular lenses, there is a problem that the lens volume increases due to its vertical height. However, since the D-cutting technique is applied to the upper and lower parts of multiple lenses according to an embodiment of the present invention, the vertical height can be reduced, thereby reducing the lens volume.

[0105] According to an embodiment of the present invention, the first lens group 100 may include a plurality of lenses with different refractive powers. Among the plurality of lenses included in the first lens group 100, the lens disposed on the image side may have positive (+) refractive power. Among the plurality of lenses included in the first lens group 100, the lens disposed on the subject side may have negative (-) refractive power. According to this embodiment, the first lens group 100 may include a first lens 110 and a second lens 120 arranged sequentially in the direction from the subject side to the image side. The first lens 110 may have positive refractive power, and the second lens 120 may have negative refractive power.

[0106] According to embodiments of the present invention, the first lens group 100 to the fourth lens group 400 may include plastic lenses. For example, all the plurality of lenses included in the fourth lens group 400 may be formed of plastic or glass material. The fourth lens group 400 may include glass lenses. For example, among the plurality of lenses included in the fourth lens group 400, the lens disposed on the subject side may be formed of glass material, and the lens disposed on the image side may be formed of plastic material. In this case, the glass lens may be a molded glass lens manufactured by a glass mold method.

[0107] According to embodiments of the present invention, in a zoom optical system, the principal ray angle (CRA) can be greater than -10° and less than 10°. The angle of incidence of light on the image sensor 10 (i.e., the upper surface) can be greater than -10° and less than 10°. That is, the CRA of the zoom optical system according to embodiments of the present invention can have any value between -10° and 10°. Because the angle of incidence of light on the image sensor 10 is small, the degree of freedom in selecting the sensor can be improved, and a zoom optical system with a compact size can be obtained.

[0108] Figure 2a This is a cross-sectional view of a zoom optical system in wide-angle mode according to an embodiment of the present invention. Figure 2b This is a cross-sectional view of a zoom optical system in intermediate mode according to an embodiment of the present invention, and Figure 2c This is a cross-sectional view of a zoom optical system in telephoto mode according to an embodiment of the present invention.

[0109] 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 Koenig constants and aspherical coefficients of the lenses included in the zoom optical system according to an embodiment of the present invention.

[0110] Table 1

[0111]

[0112] Table 2

[0113]

[0114] Table 3

[0115]

[0116] Table 4

[0117] 112 -2.15666E-10 1.6379E-10 0 0 0 114 8.9785E-09 -2.365E-10 0 0 0 122 1.92498E-08 -4.04404E-09 0 0 0 124 -9.87068E-09 9.44622E-10 0 0 0 212 1.88101E-07 -6.98355E-08 0 0 0 214 -6.59668E-08 -6.58479E-09 0 0 0 222 1.06861E-07 -5.29812E-10 0 0 0 224 7.79089E-07 -5.16153E-08 0 0 0 312 -6.77597E-07 5.2442E-08 0 0 0 314 1.30454E-06 -1.33203E-15 0 0 0 322 6.25312E-15 2.04106E-16 0 0 0 324 -6.71573E-14 -1.49767E-15 0 0 0 412 -1.33473E-07 -9.2372E-08 0 0 0 414 -5.97115E-08 -1.14911E-08 0 0 0 422 2.02276E-07 -1.34349E-08 0 0 0 424 -1.05608E-07 7.32181E-09 0 0 0

[0118] refer to Figures 2a to 2c As per Tables 1 to 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 arranged sequentially from the subject side to the image side. The first lens group 100 includes a first lens 110 and a second lens 120 arranged sequentially from the subject side to the image side. The second lens group 200 includes a third lens 210 and a fourth lens 220 arranged sequentially from the subject side to the image side. The third lens group 300 includes a fifth lens 310 and a sixth lens 320 arranged sequentially from the subject side to the image side. The fourth lens group 400 includes a seventh lens 410 and an eighth lens 420. In Table 1, thickness (mm) indicates the distance from the surface of one lens to the surface of the next lens.

[0119] For example, the thickness corresponding to the subject-side surface 112 of the first lens 110 is expressed as the distance from the subject-side surface 112 of the first lens 110 to the image-side surface 114. Specifically, the thickness corresponding to the subject-side surface 112 of the first lens 110 is expressed as the distance between the center of curvature of the subject-side surface 112 and the center of curvature of the image-side surface 114 in the first lens 110.

[0120] The thickness corresponding to the image-side surface 114 of the first lens 110 represents the distance from the image-side surface 114 of the first lens 110 to the subject-side surface 122 of the second lens 120. Specifically, the thickness corresponding to the image-side surface 114 of the first lens 110 represents 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 subject-side surface 122 of the second lens 120.

[0121] The thickness corresponding to the image-side surface 124 of the second lens 120 represents the distance from the image-side surface 124 of the second lens 120 to the subject-side surface 212 of the third lens 210. Specifically, the thickness corresponding to the image-side surface 124 of the second lens 120 represents 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 subject-side surface 212 of the third lens 210.

[0122] In this case, since the second lens group 200 moves during the zoom process from wide-angle mode to telephoto mode, the thickness of the image-side surface 124 corresponding to the second lens 120 can change. The thickness of the image-side surface 124 corresponding to the second lens 120 can have a value between the shortest and longest distance. Referring to Table 1, in wide-angle mode, the thickness of the image-side surface 124 corresponding to the second lens 120 can have the longest distance (5.710263206). In intermediate mode, the thickness of the image-side surface 124 corresponding to the second lens 120 can have a value between the shortest and longest distance (2.806912311). In telephoto mode, the thickness of the image-side surface 124 corresponding to the second lens 120 can have the shortest distance (0.20028764). The thickness of the image side surface 124 corresponding to the second lens 120 is the same as the thickness of the image side surface 224 corresponding to the fourth lens 220 and the thickness of the image side surface 324 corresponding to the sixth lens 320.

[0123] Referring to Table 1, it can be seen that the difference between the Abbe numbers of the third lens 210 and the fourth lens 220 included in the second lens group 200 is 10 or greater. Specifically, since the Abbe number of the third lens 210 is 56.17 and the Abbe number of the fourth lens 220 is 19.24, the difference between the Abbe numbers of the two lenses is approximately 37, and therefore it can be seen that the difference is 10 or greater.

[0124] 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 mold lens, and the eighth lens 420 is a plastic lens.

[0125] Referring to Table 2, each surface of the first lens 110 to the eighth lens 420 can be formed as convex or concave.

[0126] The first lens 110 may be a lens whose subject-side surface 112 protrudes towards the subject side. The first lens 110 may also be a lens whose image-side surface 114 protrudes towards the subject side. The second lens 120 may be a lens whose subject-side surface 122 is recessed towards the subject side. The second lens 120 may also be a lens whose image-side surface 124 protrudes towards the subject side.

[0127] The third lens 210 can be a lens whose subject-side surface 212 protrudes towards the subject side. The third lens 210 can also be a lens whose image-side surface 214 is recessed towards the subject side. The fourth lens 220 can be a lens whose subject-side surface 222 is recessed towards the subject side. The fourth lens 220 can also be a lens whose image-side surface 224 is recessed towards the subject side. Simultaneously, when the distance between the first lens group 100 and the second lens group 200 is at its minimum (i.e., in telephoto mode), the center of curvature of the subject-side surface 212 of the third lens 210 can be positioned closer to the image side than the two ends of the image-side surface 124 of the second lens 120.

[0128] The fifth lens 310 can be a lens whose subject-side surface 312 protrudes towards the subject side. The fifth lens 310 can also be a lens whose image-side surface 314 protrudes towards the subject side. The sixth lens 320 can be a lens whose subject-side surface 322 is recessed towards the subject side. The sixth lens 320 can also be a lens whose image-side surface 324 protrudes towards the subject side.

[0129] The seventh lens 410 can be a lens whose subject-side surface 412 is recessed towards the subject side. The seventh lens 410 can also be a lens whose image-side surface 414 protrudes towards the subject side. The eighth lens 420 can be a lens whose subject-side surface 422 protrudes towards the subject side. The eighth lens 420 can also be a lens whose image-side surface 424 is recessed towards the subject side.

[0130] refer to Figure 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 enter wide-angle mode (e.g., magnification of 5x). 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 subject-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 subject-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 subject-side surface 412 of the seventh lens 410 is d3a, the zoom optical system can enter wide-angle mode.

[0131] exist Figure 2bIn this system, the zoom optical system can enter an intermediate mode 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. Specifically, the zoom optical system can enter an intermediate mode 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 subject-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 subject-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 subject-side surface 412 of the seventh lens 410 is d3b.

[0132] exist Figure 2c In this zoom optical system, when the distance between the first lens group 100 and the second lens group 200 is d1c, 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 enter telephoto mode (e.g., magnification of 10x). 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 subject-side surface 212 of the third lens 210 is d1c, 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 subject-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 subject-side surface 412 of the seventh lens 410 is d3c, the zoom optical system can enter telephoto mode.

[0133] When changing the magnification from wide-angle mode to telephoto mode, the distance between adjacent lens groups can be changed.

[0134] The distance between the first lens group 100 and the second lens group 200 can be continuously changed from d1a to d1b and from d1b to d1c. Referring to Table 1, in wide-angle mode, the distance d1a between the first lens group 100 and the second lens group 200 is 5.710263206 [mm]. In intermediate mode, the distance d1b between the first lens group 100 and the second lens group 200 is 2.806912311 [mm]. In telephoto mode, the distance d1c between the first lens group 100 and the second lens group 200 is 0.20028764 [mm]. As described above, during the continuous change of magnification from wide-angle mode to intermediate mode and from intermediate mode to telephoto mode, the distance between the first lens group 100 and the second lens group 200 can continuously change from 5.710263206 [mm] to 2.806912311 [mm] and from 2.806912311 [mm] to 0.20028764 [mm]. That is, during the continuous change of magnification from wide-angle mode to telephoto mode, the distance between the first lens group 100 and the second lens group 200 can gradually decrease (d1a>d1b>d1c). In other words, during the continuous change of magnification from wide-angle mode to telephoto mode, the increase in the distance between the first lens group 100 and the second lens group 200 can gradually decrease.

[0135] The distance between the second lens group 200 and the third lens group 300 can be continuously changed from d2a to d2b and from d2b to d2c. Referring to Table 1, in wide-angle mode, the distance d2a between the second lens group 200 and the third lens group 300 is 0.674684273 [mm]. In intermediate mode, the distance d2b between the second lens group 200 and the third lens group 300 is 0.310740064 [mm]. In telephoto mode, the distance d1c between the second lens group 200 and the third lens group 300 is 0.2 [mm]. As described above, during the continuous change of magnification from wide-angle mode to intermediate mode and from intermediate mode to telephoto mode, the distance between the second lens group 200 and the third lens group 300 can be continuously changed from 0.674684273 [mm] to 0.310740064 [mm] and from 0.310740064 [mm] to 0.2 [mm]. That is, during the continuous change of magnification from wide-angle mode to telephoto mode, the distance between the second lens group 200 and the third lens group 300 can be reduced (d2a>d2b>d2c). In this case, the increase in the distance between the second lens group 200 and the third lens group 300 during the continuous change of magnification from wide-angle mode to telephoto mode can be reduced.

[0136] The distance between the third lens group 300 and the fourth lens group 400 can be continuously changed from d3a to d3b and from d3b to d3c. Referring to Table 1, in the wide-angle mode, the distance d3a between the third lens group 300 and the fourth lens group 400 is 1.237063216 [mm]. In the intermediate mode, the distance d3b between the third lens group 300 and the fourth lens group 400 is 4.50435832 [mm]. In the telephoto mode, the distance d3c between the third lens group 300 and the fourth lens group 400 is 7.221723054 [mm]. As described above, during the process of continuously changing magnification from the wide-angle mode to the intermediate mode and from the intermediate mode to the telephoto mode, the distance between the third lens group 300 and the fourth lens group 400 can be continuously changed from 1.237063216 [mm] to 4.50435832 [mm] and from 4.50435832 [mm] to 7.221723054 [mm]. That is, during the process of continuously changing magnification from the wide-angle mode to the telephoto mode, the distance between the third lens group 300 and the fourth lens group 400 can gradually increase (d3a<d3b<d3c). However, during the process of continuously changing magnification from the wide-angle mode to the telephoto mode, the increment of the distance between the third lens group 300 and the fourth lens group 400 can gradually decrease.

[0137] As described above, the moving speed of the second lens group 200 and the moving speed of the third lens group 300 can be different from each other.

[0138] By moving the second lens group 200 and the third lens group 300, the magnification of the zoom optical system can be continuously changed from 5x magnification to 10x magnification.

[0139] Next, reference will be made Figures 3a to 3c to describe simulation results of longitudinal spherical aberration, astigmatic field curves and distortion of the zoom optical system according to an embodiment of the present invention. Longitudinal spherical aberration refers to longitudinal spherical aberration for each wavelength, astigmatic field curves refer to aberration characteristics of tangential and sagittal planes according to the height of the image surface, and distortion refers to the degree of distortion according to the height of the image surface.

[0140] Figure 3a is a graph showing longitudinal spherical aberration, astigmatic field curves and distortion of light with wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm in the optical system in the wide-angle mode according to the embodiment.

[0141] Figure 3b is a graph showing longitudinal spherical aberration, astigmatic field curves and distortion of light with wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm in the optical system in the intermediate mode according to the embodiment.

[0142] Figure 3c The graph shows the longitudinal spherical aberration, astigmatism curves, and distortion curves of light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm in an optical system in telephoto mode according to an embodiment.

[0143] refer to Figures 3a to 3c As can be seen, regardless of wavelength, the longitudinal spherical aberration from the center to the edge of the image sensor ranges from -0.05 mm to 0.1 mm. Specifically, in wide-angle mode, the longitudinal spherical aberration is in the range of approximately -0.04 mm to 0.04 mm, and in intermediate mode, it is in the range of -0.03 mm to 1 mm. In telephoto mode, even when the wavelength of 435 nm is outside this range, the longitudinal spherical aberration remains in the range of -0.05 mm to 0.05 mm, except for the wavelength of 435 nm.

[0144] refer to Figures 3a to 3c It can be seen that, regardless of wavelength, the astigmatism curve from the center to the edge of the image sensor ranges from -0.04 mm to 0.01 mm. Specifically, it can be seen that in wide-angle mode, the astigmatism curve ranges from approximately -0.02 mm to 0 mm, and in intermediate mode, the astigmatism curve ranges from -0.02 mm to 0.01 mm. It can be seen that in telephoto mode, the astigmatism curve ranges from approximately -0.04 mm to 0 mm.

[0145] refer to Figures 3a to 3c It can be seen that, regardless of wavelength, the distortion from the center to the edge of the image sensor ranges from -2% to 0%. Specifically, it can be seen that in wide-angle mode, the distortion is in the range of approximately -1% to 0%, and in intermediate mode, the distortion is in the range of -1.5% to 0%. It can be seen that in telephoto mode, the distortion is in the range of -2% to 0%.

[0146] Then, refer to Figures 4a to 4c The simulation results of the modulation transfer function (MTF) of a zoom optical system according to an embodiment of the present invention are described. MTF is one of the methods for measuring the performance of an optical system.

[0147] Figure 4a This is a graph showing the diffraction MTF in an optical system in wide-angle mode according to an embodiment. Figure 4b This is a graph showing the diffraction MTF in an optical system in intermediate mode according to an embodiment. Figure 4cThis is a graph showing the diffraction MTF in an optical system in telephoto mode according to an embodiment.

[0148] refer to Figures 4a to 4c It can be seen that in each of the wide-angle, intermediate, and telephoto modes, the zoom optical system according to an embodiment of the present invention has a value close to the diffraction limit as a limiting value around the defocus position of 0 [mm].

[0149] Figure 5 This is a graph showing the relative illumination of a zoom optical system according to an embodiment of the present invention.

[0150] refer to Figure 5 It can be seen that, in the zoom optical system according to an embodiment of the present invention, the relative illumination value is 50% or higher in all areas of the wide-angle mode (zoom position 1), intermediate mode (zoom position 2), and telephoto mode (zoom position 3). It can also be seen that the relative illumination value is 80% or higher in all areas of the intermediate and telephoto modes, and in the case of the wide-angle mode, the relative illumination value is 80% or higher in the range of 0 to 1.6 [mm].

[0151] As can be seen from the embodiments described above, the optical system according to the present invention has high aberration characteristics.

[0152] Meanwhile, the zoom optical system according to an embodiment of the present invention can be applied to a camera module. A camera module including a zoom optical system according to an embodiment of the present invention can be installed in a portable terminal and applied thereto together with a main camera module. The camera module according to an embodiment of the present invention may include an image sensor, a filter arranged on the image sensor, and a zoom optical system arranged on the filter. 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. The portable terminal equipped with the camera module including the zoom optical system according to an embodiment of the present invention can be a smartphone, tablet computer (PC), laptop computer, personal digital assistant (PDA), etc. The optical system according to an embodiment of the present invention can be applied to a camera module.

[0153] Figure 6 This is a view of a portion of a portable terminal that uses a camera module according to an embodiment of the present invention.

[0154] refer to Figure 6 A camera module including a zoom optical system 1000 according to an embodiment of the present invention can be installed in a portable terminal and can be used thereon together with a main camera module 1100.

[0155] The zoom optical system 1000 according to an embodiment of the present invention may include a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400 as described above, and the first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400 may be arranged sequentially in the lateral direction of the portable terminal due to the thickness limitation of the portable terminal. For this purpose, as described above, a right-angle prism may be further arranged in front of the first lens group 100. When the zoom optical system is arranged in the thickness direction of the portable terminal, that is, when the lens surfaces of the lenses included in the zoom optical system are arranged in the thickness direction of the portable terminal, the diameter of the lenses included in the zoom optical system can be reduced to reduce the thickness of the portable terminal. Therefore, a zoom optical system capable of continuously adjusting the magnification by moving the lenses can even be installed in a portable terminal.

[0156] The portable terminal equipped with a camera module including a zoom optical system according to an embodiment of the present invention can be a smartphone, tablet computer, laptop computer, PDA, etc.

[0157] While the invention has been described above primarily with reference to embodiments, those skilled in the art will understand that the invention is not limited to the embodiments, but rather the embodiments are merely exemplary, and various modifications and applications not described above can be made within this scope without departing from the basic characteristics of the embodiments. For example, components specifically described in the embodiments can be modified and implemented. Furthermore, it should be interpreted that differences related to modifications and applications fall within the scope of the invention as defined by the appended claims.

Claims

1. A zoom optical system, the zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially in a direction from the subject side to the image side. in, Each of the first to fourth lens groups includes at least two lenses. The first lens group has negative refractive power, the second lens group has positive refractive power, the third lens group has negative refractive power, and the fourth lens group has positive refractive power. The second and third lens groups are movable, while the first and fourth lens groups are fixed. Specifically, when zooming from wide-angle mode to telephoto mode, the distance between the first lens group and the second lens group decreases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group increases. The effective focal length (EFL) in wide-angle mode is defined by the following expression: ， Here, EFL wide It is the EFL of the zoom optical system in wide-angle mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

2. The zoom optical system according to claim 1, wherein: 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; and The fourth lens group includes two or more lenses.

3. The zoom optical system according to claim 1, wherein, In telephoto mode, EFL is defined by the following expression. ， Here, EFL tele It is the EFL of the zoom optical system in the telephoto mode, and H imageD It is half the diagonal length of the pixel region of the image sensor.

4. The zoom optical system according to claim 1, wherein, When zooming from the wide-angle mode to the telephoto mode, the travel distance of the second lens group is defined by the following expression. ， Here, TTL (Total Track Length) is the distance from the surface of the image sensor to the first surface of the zoom optical system, and STROKE2 is the travel distance of the second lens group.

5. The zoom optical system according to claim 1, wherein, When zooming is performed from the wide-angle mode to the telephoto mode, the travel distance of the third lens group is defined by the following expression. ， Here, TTL (Total Track Length) is the distance from the surface of the image sensor to the first surface of the zoom optical system, and STROKE3 is the travel distance of the third lens group.

6. The zoom optical system according to claim 1, wherein: The lens arranged at the image side of the two lenses included in the first lens group has negative refractive power; and The lens arranged on the subject side of the two lenses included in the first lens group has positive refractive power.

7. The zoom optical system according to claim 6, wherein, The second lens group includes at least two lenses that have Abbe numbers defined by the following expression: ， Here, ABBE3 is the Abbe number of the lens arranged on the subject side of the two lenses included in the second lens group, and ABBE4 is the Abbe number of the lens arranged on the image side of the two lenses included in the second lens group.

8. The zoom optical system according to claim 7, wherein, The second lens group includes at least one of the following: Glass lenses; and Plastic lens.

9. The zoom optical system according to claim 1, wherein, The maximum diameter of the plurality of lenses included in the first lens group and the fourth lens group, and the maximum diameter of the plurality of lenses included in the second lens group and the third lens group, are defined by the following expressions. ， Here, APER fix It is the maximum diameter of the lenses included in the first lens group and the fourth lens group, which are fixed groups, and APER mov It is the maximum diameter of the lens included in the second lens group and the third lens group, which are moving groups.

10. The zoom optical system according to claim 1, wherein, The principal ray angle (CRA) is greater than -10° and less than 10°.

11. The zoom optical system according to claim 1, wherein, The second lens group and the third lens group have different moving speeds.

12. The zoom optical system according to claim 1, wherein, The filter and the image sensor are arranged sequentially at the rear end of the fourth lens group.

13. The zoom optical system according to claim 1, wherein, The first lens group includes a first lens and a second lens, the second lens group includes a third lens and a fourth lens, the third lens group includes a fifth lens and a sixth lens, and the fourth lens group includes a seventh lens and an eighth lens.

14. The zoom optical system according to claim 13, wherein, The first lens, the third lens, the seventh lens, and the eighth lens have positive refractive power, and the second lens, the fourth lens, the fifth lens, and the sixth lens have negative refractive power.

15. The zoom optical system according to claim 7, wherein, At least one of the lenses included in the first to fourth lens groups has an upper portion and a lower portion, the upper portion and the lower portion having partially cut ribs and an effective diameter, or having only cut ribs without cutting the effective diameter.

16. The zoom optical system according to claim 1, wherein, The second lens group and the third lens group include lenses in which a value of 1 is obtained by dividing the length of the major axis of the effective diameter by the length of the minor axis of the effective diameter.

17. The zoom optical system according to claim 1, wherein, At least one of the lenses included in the first to fourth lens groups is a D-cut lens.

18. The zoom optical system according to claim 1, wherein, Depending on the movement of the second and third lens groups, the magnification continuously increases or decreases within the range of 5x to 10x.

19. The zoom optical system according to claim 1, wherein, The aperture of each of the second and third lens groups is smaller than the aperture of each of the first and fourth lens groups.

20. The zoom optical system according to claim 13, wherein, The upper and lower ribs of the third, fourth, fifth, and sixth lenses are cut off, but the effective diameter is not cut off.

Images