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 sequentially from an object side to an image side, the second lens group and the third lens group being movable, a total track length (TTL) being less than 20 mm, and an effective focal length (EFL) in telephoto mode being greater than 25 mm.

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 the camera modules in the mobile terminals to have an autofocusing function.

[0003] Since the camera module in the mobile device has an autofocus function, the magnification can be increased through digital processing in the process of converting external light into a digital image or video. However, zooming is only possible at a certain magnification such as 1x, 3x, 5x, etc., and as the magnification increases, the resolution decreases, which causes digital degradation.

[0004] Meanwhile, in order to provide the camera module in the mobile device with an autofocus function, a technology is being 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 the mobile device. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a zoom optical system and a camera module including the same.

[0006] The problems to be solved by the examples are not limited to those described above, and may also include the objectives and effects that can be grasped from the means for solving the problems and 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 sequentially from an object side to an image side, the second lens group and the third lens group are movable, a total track length (TTL) is less than 20 mm, and an effective focal length (EFL) in telephoto is greater than 25 mm.

[0008] The effective focal length at the telephoto position may be greater than 1.5 times the effective focal length at the wide angle position.

[0009] When zooming from a wide angle to a telephoto, the movement stroke of the second lens group may be less than 2.5.

[0010] The second lens group and the third lens group may include at least one glass lens.

[0011] The glass lens may have a refractive index greater than 1.7 or an Abbe number greater than 60.

[0012] The lenses included in the first to fourth lens groups may be D-cut lenses.

[0013] The second lens group and the third lens group may include a lens whose effective diameter major axis length divided by the effective diameter minor axis length is one.

[0014] The chief ray angle (CRA) may be less than 6 degrees.

[0015] The optical system may further include a right-angle prism disposed at a front end of the first lens group in the order from the object side to the image side.

[0016] In the telephoto, the effective focal length (EFL) divided by the F-number may be greater than six.

[0017] In the telephoto, the effective focal length (EFL) may be greater than 25 mm and the F-number may be less than 4.2.

[0018] 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 second lens group and the third lens group are movable, the zoom optical system is a telephoto system, the effective focal length (EFL) is greater than 25 mm, and the F-number is less than 4.2.

[0019] 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 second lens group and the third lens group are movable, and in a telephoto zoom optical system, the effective focal length (EFL) divided by the F-number is greater than 6. Effect of the Invention

[0020] According to the embodiment of the present invention, it is possible to obtain an optical system capable of zooming at not only low magnification but also high magnification, and a camera module including the same. The optical system according to the embodiment of the present invention is capable of continuous zoom adjustment, can maintain high resolution even at high magnification, can maintain a low F number even at a high focal length, and can maintain a low CRA, so it can be designed in a compact size. [Brief description of the drawings]

[0021] [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 a first embodiment of the present invention at a wide angle. [Figure 2b] 1 is a cross-sectional view of a zoom optical system according to a first embodiment of the present invention in an intermediate mode. [Figure 2c] 1 is a cross-sectional view of a telephoto of a zoom optical system according to a first embodiment of the present invention. [Figure 3a] 1 is a graph showing measurements of 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 the optical system of the first example. [Figure 3b] 11 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 first example. [Figure 3c] 11 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 in the optical system according to the first embodiment. [Figure 4a] FIG. 11 is a cross-sectional view of a zoom optical system according to a second embodiment of the present invention at a wide angle. [Figure 4b] FIG. 11 is a sectional view of a zoom optical system according to a second embodiment of the present invention in an intermediate mode. [Figure 4c] FIG. 11 is a sectional view of a telephoto zoom optical system according to a second embodiment of the present invention. [Figure 5a] 13 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 at a wide angle in the optical system according to the second example. [Figure 5b] 13 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 second example. [Figure 5c] 13 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 in the optical system according to the second embodiment. [Figure 6a] FIG. 11 is a cross-sectional view of a zoom optical system according to a third embodiment of the present invention at a wide angle. [Figure 6b] FIG. 11 is a sectional view of a zoom optical system according to a third embodiment of the present invention in an intermediate mode. [Figure 6c] FIG. 11 is a sectional view of a telephoto zoom optical system according to a third embodiment of the present invention. [Figure 7a] 13 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 at a wide angle in the optical system according to the third example. [Figure 7b] 13 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 third example. [Figure 7c] 13 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 in the optical system according to the third embodiment. [Figure 8] 1 shows a part of a mobile terminal to which a camera module according to an embodiment of the present invention is applied. [Figure 9] 1 is a diagram illustrating a camera module including a zoom optical system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] However, the technical concept of the present invention is not limited to the described embodiments, but 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.

[0024] Furthermore, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted in a manner that is commonly understood by a person having ordinary knowledge in the technical field to which the present invention belongs, unless otherwise clearly defined and described, and commonly used terms, such as terms defined in a dictionary, may be interpreted in light of the contextual meaning of the relevant art.

[0025] Furthermore, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0026] In this specification, the singular can also include the plural unless otherwise specified in the context, and when it is stated as "A 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.

[0027] Additionally, terms such as first, second, A, B, (a), (b), etc. may be used to describe components of embodiments of the present invention.

[0028] 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.

[0029] Furthermore, when a component is described as being "coupled," "coupled," or "connected" to another component, it includes 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.

[0030] In addition, when described as being formed or disposed "above or below" each component, "above" or "below" includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or disposed between the two components. In addition, when described as "above or below," it can include not only the upper direction but also the lower direction based on one component.

[0031] FIG. 1 shows a zoom optical system according to an embodiment of the present invention. Referring to FIG. 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 arranged in sequence from an object side to an image side.

[0032] According to an embodiment of the present invention, the first lens group 100 includes a plurality of lenses and is fixed. That is, the plurality of lenses 110, 120, and 130 are fixed. In this case, the first lens group 100 may include at least three lenses 110, 120, and 130. If the first lens group 100 includes two or fewer lenses, it may be difficult to correct the resolution at the maximum magnification, and if the first lens group 100 includes four or more lenses, the overall size of the zoom optical system may become large. Therefore, the first lens group 100 preferably includes three lenses.

[0033] The second lens group 200 includes a maximum of two lenses 210 and 220, and is movable. That is, the two lenses 210 and 220 are movable together along the central axis of the 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.

[0034] The third lens group 300 includes a maximum of two lenses 310 and 320, and is movable. That is, the two lenses 310 and 320 are movable together along the central axis of the lens. The focus can be adjusted by moving the third lens group 300. The third lens group 300 can function as a focusing group.

[0035] If the second lens group 200 includes three or more lenses or the third lens group 300 includes three or more lenses, the size and weight of the second lens group 200 or the third lens group 300 will increase, and the driving power during movement may become high.

[0036] The magnification of the zoom optical system can be increased or decreased continuously between 5x and 7.5x, for example, by moving the second lens group 200 and the third lens group 300. Here, the magnification increasing or decreasing continuously can mean that the magnification increases or decreases linearly, rather than increasing or decreasing digitally and intermittently.

[0037] 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, the distance between the second lens group 200 and the third lens group 300 may be far from the movement start point (wide angle) to a predetermined point, and may gradually become closer from the predetermined point to the movement end point (telephoto).

[0038] The fourth lens group 400 includes one lens 410, which is fixed.

[0039] 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 third lens group 300. In this case, the filter 20 may be an IR (infrared) filter. Accordingly, the filter 20 may block near-infrared light, for example, light having a wavelength of 700 nm to 1100 nm, from light entering the camera module. In addition, the image sensor 10 may be connected to a printed circuit board by a wire.

[0040] Alternatively, the filter 20 may include a foreign matter prevention filter and an IR filter arranged in sequence from the object side to the image side. When the filter 20 includes a foreign matter prevention filter, it is possible to prevent foreign matter generated in the process of the third lens group 300 moving from flowing into the IR filter or the image sensor 10.

[0041] According to an embodiment of the present invention, the zoom optical system may have a TTL of less than 20 mm. 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 total length.

[0042] According to an embodiment of the present invention, the zoom optical system may have an effective focal length (EFL, f) in telephoto mode greater than 25 mm. The zoom optical system may have an effective focal length in wide angle mode less than 17.5 mm. The zoom optical system may have an effective focal length in telephoto mode greater than 1.5 times the effective focal length in wide angle mode.

[0043] According to an embodiment of the present invention, the zoom optical system may have an F-number (Fno) in telephoto mode smaller than 4.2. Here, the F-number may refer to the ratio (f / D) of focal length (f) to the effective diameter (D) of the aperture. The smaller the F-number, the brighter the image may be since more light is collected, whereas the larger the F-number, the darker the image may be since less light is collected. Accordingly, since the zoom optical system according to the embodiment of the present invention has an F-number smaller than 4.2, a predetermined brightness may be maintained even at a long distance where the effective focal length in telephoto mode is greater than 25 mm.

[0044] According to an embodiment of the present invention, the zoom optical system may have a ratio of focal length to F-number (f / Fno) at maximum magnification that is greater than 6. That is, since it has a low F-number compared to the focal length, a certain brightness can be maintained even at high magnification.

[0045] According to an embodiment of the present invention, the movement stroke of the second lens group 200 may be less than 2.5 mm. Here, the movement stroke may refer to the distance that the lens group can be moved by the driving unit. Therefore, the second lens group 200 can move within a range of less than 2.5 mm when changing from telephoto to wide angle (or from wide angle to telephoto). If the movement stroke is more than 2.5 mm, the size of the driving unit for moving the lens group becomes large, which makes it difficult to install it in a mobile terminal. However, by implementing a movement stroke of less than 2.5 mm, it is possible to reduce the size.

[0046] According to an embodiment of the present invention, at least one of the lenses 210, 220, 310, 320 included in the second lens group 200 and the third lens group 300 may have a refractive index greater than 1.7 or an Abbe number greater than 60. That is, at least one of the lenses 210, 220 included in the second lens group 200 may have a refractive index greater than 1.7 or an Abbe number greater than 60, and at least one of the lenses 310, 320 included in the third lens group 300 may have a refractive index greater than 1.7 or an Abbe number greater than 60. At least one of the lenses 210, 220, 310, 320 included in the second lens group 200 and the third lens group 300 may be a glass lens. The lens having a refractive index greater than 1.7 or an Abbe number greater than 60 may be a glass lens. According to the embodiment of the present invention, the volume of the zoom optical system can be reduced by using glass lenses, and therefore the movable distance, i.e., the stroke, of the second lens group 200 and the third lens group 300 can be reduced. In addition, the use of glass lenses can reduce chromatic aberration and increase the refractive index, thereby improving performance.

[0047] According to an embodiment of the present invention, the lenses 110, 120, 130, 210, 220, 310, 320, 410 included in the first to fourth lens groups 100 to 400 may be lenses to which the D-cut technique is applied. The lenses 110, 120, 130, 210, 220, 310, 320, 410 included in the first to fourth lens groups 100 to 400 may be D-cut lenses in which a part of the upper and lower parts is cut. In this case, the lenses 110, 120, 130, 210, 220, 310, 320, 410 may have a rib and a part of the effective diameter cut in the upper and lower parts, or only the rib 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 length of the major axis of the effective diameter by the length of the minor axis of the effective diameter is 1. That is, the length of the effective diameter major axis and the length of the effective diameter minor axis may be the same. For example, in the case of the fifth lens 220, the sixth lens 310, and the seventh lens 320, only the ribs on the upper and lower sides may be cut, and the effective diameter may not be cut. In the case of a circular type lens, there is a problem that the volume of the lens increases depending on the vertical height, but as in the embodiment of the present invention, the vertical height can be reduced by applying D-cut to the upper and lower parts of the multiple lenses 110, 120, 130, 210, 220, 310, 320, and 410, and therefore the volume of the lens can be reduced.

[0048] The magnification can change depending on the distance between the first lens group 100 and the second lens group 200, the distance between the second lens group 200 and the third lens group 300, and the distance between the third lens group 300 and the fourth lens group 400.

[0049] According to an embodiment of the present invention, the zoom optical system may have a chief ray angle (CRA) of less than 6. Therefore, since 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.

[0050] The present invention will now be described in more detail with reference to various embodiments thereof.

[0051] FIG. 2a is a cross-sectional view of the zoom optical system according to the first embodiment of the present invention at a wide angle, FIG. 2b is a cross-sectional view of the zoom optical system according to the first embodiment of the present invention at a middle mode, and FIG. 2c is a cross-sectional view of the zoom optical system according to the first embodiment of the present invention at a telephoto mode.

[0052] The following Tables 1 and 2 show the optical characteristics of the lenses included in the zoom optical system according to the first embodiment of the present invention, and Tables 3 and 4 show the conic constants and aspheric coefficients of the lenses included in the zoom optical system according to the first embodiment of the present invention.

[0053] [Table 1]

[0054] [Table 2]

[0055] Here, the thickness (mm) represents the distance from each lens surface to the next lens surface. For example, the thickness written on the object side surface 112 of the first lens 110 represents the distance from the object side surface 112 of the first lens 110 to the image side surface 114. And the thickness written on 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 object side surface 122 of the second lens 120. Meanwhile, the thickness written on the image side surface 134 of the third lens 130 represents the distance from the image side surface 134 of the third lens 130 to the object side surface 212 of the fourth lens 210. At this time, the fourth lens 210 is a lens included in the second lens group 200 and moves during the process of zooming from a wide angle to a telephoto, so the thickness written on the image side surface 134 of the third lens 130 may have a value between the shortest distance (2.877) and the longest distance (0.4). The thickness described on the image side surface 134 of the fifth lens 130 and the thickness described on the image side surface 134 of the seventh lens 130 are also the same.

[0056] [Table 3]

[0057] [Table 4]

[0058] 2a to 2c and 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, which are arranged in sequence from the object side to the image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130, which are arranged in sequence from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220, which are arranged in sequence from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320, which are arranged in sequence from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. Here, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134. And the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

[0059] And the sixth lens 310 may include a convex object-side surface 312 and a convex image-side surface 314 , and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324 .

[0060] And the eighth lens 410 can include a convex object side surface 412 and a convex image side surface 414 .

[0061] The first lens 110 can have a positive refractive power, the second lens 120 can have a positive refractive power, and the third lens 130 can have a negative refractive power. The fourth lens 210 can have a positive refractive power, and the fifth lens 220 can have a negative refractive power. The sixth lens 310 can have a positive refractive power, and the seventh lens 320 can have a negative refractive power. The eighth lens 410 can have a positive refractive power.

[0062] The Abbe number of the fourth lens 210 is 49.5, which may be the highest Abbe number among the first lens 110 to the eighth lens 410. The focal length (f) of the seventh lens 320 is 1.772 mm, which may be the highest refractive index among the first lens 110 to the eighth lens 410. The fourth lens 210 and the seventh lens 320 may be glass lenses.

[0063] The fifth lens 220, sixth lens 310, and seventh lens 320 have the same length of the effective diameter major axis and the same length of the effective diameter minor axis. That is, the effective diameter does not need to be cut when D-cut is applied. In addition, the first lens 110 to the fourth lens 210 and the eighth lens 410 have different lengths of the effective diameter major axis and the effective diameter minor axis, and parts of the upper and lower parts of the effective diameter may be cut off.

[0064] In Fig. 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, a wide angle, for example a magnification of 5x, can be obtained. Then, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100 via Fig. 2b to reach Fig. 2c, 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 reduced to d3c, and a telephoto, for example a magnification of 7.5x can be obtained. In this way, 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 7.5x.

[0065] Accordingly, it can be seen that at the wide angle of FIG. 2a, the effective focal length (EFL) of the zoom optical system according to the first embodiment is 17.44 mm and Fno is 2.91, while at the telephoto of FIG. 2c, the effective focal length (EFL) of the zoom optical system according to the first embodiment is 26.33 mm and Fno is 4.02.

[0066] Here, it can be seen that the amount of movement of the third lens group 300 is greater than the amount of movement of the second lens group 200. In other words, the difference between d1a and d1b may be smaller than the difference between d2a and d2b, and the difference between d1b and d1c may be smaller than the difference between d2b and d2c.

[0067] FIG. 3a is a graph showing measurements of the spherical aberration, astigmatic field curves, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the first embodiment at a wide angle. FIG. 3b is a graph showing measurements of the spherical aberration, astigmatic field curves, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the first embodiment at an intermediate mode. FIG. 3c is a graph showing measurements of the spherical aberration, astigmatic field curves, and distortion for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the first embodiment at a telephoto mode.

[0068] Spherical aberration represents the spherical aberration for each wavelength, astigmatism represents the aberration characteristics of the tangential plane and sagittal plane depending on the height of the upper surface, and distortion represents the degree of distortion depending on the height of the upper surface. Referring to Figures 3a to 3c, it can be seen that the spherical aberration is within -0.05mm to 0.05mm regardless of the wavelength, the astigmatism is within -0.05mm to 0.05mm regardless of the wavelength, and the distortion is within -0.05mm to 0.05mm regardless of the wavelength.

[0069] FIG. 4a is a cross-sectional view of the zoom optical system according to the second embodiment of the present invention at a wide angle, FIG. 4b is a cross-sectional view of the zoom optical system according to the second embodiment of the present invention at a middle mode, and FIG. 4c is a cross-sectional view of the zoom optical system according to the second embodiment of the present invention at a telephoto mode.

[0070] Table 5 below shows the optical characteristics of the lenses included in the zoom optical system according to the second embodiment of the present invention, and Tables 6 and 7 show the conic constants and aspheric coefficients of the lenses included in the zoom optical system according to the second embodiment of the present invention.

[0071] [Table 5]

[0072] Here, the thickness (mm) represents the distance from each lens surface to the next lens surface. For example, the thickness recorded on the object-side surface 112 of the first lens 110 represents the distance from the object-side surface 112 to the image-side surface 114 of the first lens 110. And the thickness recorded on 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 object-side surface 122 of the second lens 120.

[0073] [Table 6]

[0074] [Table 7]

[0075] 4a to 4c and Tables 5 to 7, 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 sequentially arranged from the object side to the image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130, which are sequentially arranged from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220, which are sequentially arranged from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320, which are sequentially arranged from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. Here, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134. And the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

[0076] And the sixth lens 310 may include a concave object-side surface 312 and a convex image-side surface 314 , and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324 .

[0077] And the eighth lens 410 can include a convex object side surface 412 and a convex image side surface 414 .

[0078] In Fig. 4a, 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, a wide angle, for example a magnification of 5x, can be obtained. Then, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100 via Fig. 4b to reach Fig. 4c, 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 reduced to d3c, and a telephoto, for example a magnification of 7.5x can be obtained. In this way, 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 7.5x.

[0079] Here, it can be seen that the amount of movement of the third lens group 300 is greater than the amount of movement of the second lens group 200. In other words, the difference between d1a and d1b may be smaller than the difference between d2a and d2b, and the difference between d1b and d1c may be smaller than the difference between d2b and d2c.

[0080] FIG. 5a is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the second embodiment at a wide angle. FIG. 5b is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the second embodiment at an intermediate mode. FIG. 5c is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the second embodiment at a telephoto mode.

[0081] Spherical aberration represents the spherical aberration for each wavelength, astigmatism represents the aberration characteristics of the tangential plane and sagittal plane depending on the height of the upper surface, and distortion represents the degree of distortion depending on the height of the upper surface. Referring to Figures 5a to 5c, it can be seen that the spherical aberration is within -0.05mm to 0.05mm regardless of the wavelength, the astigmatism is within -0.05mm to 0.05mm regardless of the wavelength, and the distortion is within -0.05mm to 0.05mm regardless of the wavelength.

[0082] FIG. 6a is a cross-sectional view of a zoom optical system according to a third embodiment of the present invention in a wide angle mode, FIG. 6b is a cross-sectional view of a zoom optical system according to a third embodiment of the present invention in a middle mode, and FIG. 6c is a cross-sectional view of a zoom optical system according to a third embodiment of the present invention in a telephoto mode.

[0083] Table 8 below shows the optical characteristics of the lenses included in the zoom optical system according to the third embodiment of the present invention, and Tables 9 and 10 show the conic constants and aspheric coefficients of the lenses included in the zoom optical system according to the third embodiment of the present invention.

[0084] [Table 8]

[0085] Here, the thickness (mm) represents the distance from each lens surface to the next lens surface. For example, the thickness recorded on the object-side surface 112 of the first lens 110 represents the distance from the object-side surface 112 to the image-side surface 114 of the first lens 110. And the thickness recorded on 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 object-side surface 122 of the second lens 120.

[0086] [Table 9]

[0087] [Table 10]

[0088] 6a to 6c and Tables 8 to 10, 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 sequentially arranged from the object side to the image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130, which are sequentially arranged from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220, which are sequentially arranged from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320, which are sequentially arranged from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. Here, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134. And the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

[0089] And the sixth lens 310 may include a convex object-side surface 312 and a convex image-side surface 314 , and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324 .

[0090] And the eighth lens 410 can include a convex object side surface 412 and a convex image side surface 414 .

[0091] In Fig. 6a, 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, a wide angle, for example a magnification of 5x, can be obtained. Then, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100 via Fig. 6b to reach Fig. 6c, 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 reduced to d3c, and a telephoto, for example a magnification of 7.5x can be obtained. In this way, 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 7.5x.

[0092] Here, it can be seen that the amount of movement of the third lens group 300 is greater than the amount of movement of the second lens group 200. In other words, the difference between d1a and d1b may be smaller than the difference between d2a and d2b, and the difference between d1b and d1c may be smaller than the difference between d2b and d2c.

[0093] FIG. 7a is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the third embodiment at a wide angle. FIG. 7b is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the third embodiment at an intermediate mode. FIG. 7c is a graph showing measurements of spherical aberration, astigmatism, and distortion for light with wavelengths of 435 nm, 486 nm, 546 nm, 587 nm, and 656 nm of the optical system of the third embodiment at a telephoto mode.

[0094] The spherical aberration represents the spherical aberration for each wavelength, the astigmatism represents the aberration characteristics of the tangential plane and sagittal plane depending on the height of the upper surface, and the distortion aberration represents the degree of distortion depending on the height of the upper surface. Referring to Figures 7a to 7c, it can be seen that the spherical aberration is within -0.05mm to 0.05mm regardless of the wavelength, the astigmatism is within -0.05mm to 0.05mm regardless of the wavelength, and the distortion aberration is within -0.05mm to 0.05mm regardless of the wavelength.

[0095] As seen through the above examples, it can be seen that the optical system according to the embodiments of the present invention has excellent aberration characteristics.

[0096] Meanwhile, the zoom optical system according to the embodiment of the present invention may be applied to a camera module. The camera module including the zoom optical system according to the 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 the 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 the 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 mobile terminal in which the camera module including the zoom optical system according to the embodiment of the present invention is built may be a smartphone, a tablet PC, a laptop computer, a PDA, etc.

[0097] Meanwhile, the optical system according to the embodiment of the present invention can be applied to a camera module. Figure 8 shows a part of a mobile terminal to which a camera module according to an embodiment of the present invention is applied.

[0098] Referring to FIG. 8, 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.

[0099] The zoom optical system 1000 according to the 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, and 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 a lateral direction of the mobile terminal according to the thickness constraint of the mobile terminal. For this purpose, 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 terminal, that is, when the lens surface of the lens included in the zoom optical system is arranged in the thickness direction of the mobile terminal, the thickness of the mobile terminal can be reduced by reducing the diameter size of the lens included in the zoom optical system. Accordingly, a zoom optical system capable of continuously adjusting the magnification by moving the lens may be built into the mobile terminal.

[0100] A mobile terminal incorporating a camera module including a zoom optical system according to an embodiment of the present invention may be a smartphone, a tablet PC, a laptop computer, a PDA, or the like.

[0101] FIG. 9 is a diagram showing a camera module including a zoom optical system according to an embodiment of the present invention.

[0102] 9, the camera module 2000 including the zoom optical system according to the embodiment of the present invention may be embodied in a hexahedron shape. The width (w) of the camera module 2000 may be greater than 13.10 [mm] and less than 14.50 [mm]. The width (w) of the camera module 2000 may be 13.80 [mm]. The length (l) of the camera module 2000 may be greater than 27.00 [mm] and less than 30.00 [mm]. The length (l) of the camera module 2000 may be 28.5 [mm]. The height (h) of the camera module 2000 may be greater than 5.80 [mm] and less than 6.60 [mm]. The height (h) of the camera module 2000 may be 6.2 [mm].

[0103] The camera module 2000 including the zoom optical system according to the embodiment of the present invention may include an image sensor. The size of the image sensor may be greater than 0.30 [inch] and less than 0.34 [inch]. According to the embodiment, the size of the image sensor may be 1 / 3.14 [inch].

[0104] The camera module 2000 including the zoom optical system according to an embodiment of the present invention may include an actuator. The actuator may move at least one lens group included in the optical system combined with the zoom optical system. The actuator may also move a prism combined with the zoom optical system. The actuator may include at least one of a pin member and a ball member.

[0105] In addition, the camera module 2000 including the zoom optical system according to an embodiment of the present invention may include a driver IC and a printed circuit board.

[0106] The camera module 2000 including the zoom optical system according to the embodiment of the present invention may have a first field of view (FoV) at a wide angle and a second field of view at a telephoto angle. The first field of view may be greater than 17.70 degrees and less than 19.70 degrees. The first field of view may be 18.7 degrees. The second field of view may be greater than 11.80 degrees and less than 13.20 degrees. The first field of view may be 12.5 degrees.

[0107] The camera module 2000 including the zoom optical system according to the embodiment of the present invention may have a first F-number at wide angle and a second F-number at telephoto. The first F-number may be a value greater than 2.80 and less than 3.20. The first F-number may be 3.0. The second F-number may be a value greater than 4.20 and less than 4.80. The second F-number may be 4.5.

[0108] The above description focuses on the embodiments, but these are merely illustrative and do not limit the present invention. Those skilled in the art will appreciate that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the present embodiments. For example, each component specifically illustrated in the embodiments can be modified and implemented. Differences related to such modifications and applications should be interpreted as being included in the scope of the present invention as defined in the appended claims.

Claims

1. The optical system includes a first lens group, a second lens group, a third lens group, and a fourth lens group, which are arranged in this order from an object side to an image side, During zooming or focusing, the second lens group and the third lens group move, and the interval between adjacent lens groups changes; the first lens group and the fourth lens group are fixed; the first lens group includes a first lens having positive refractive power, a second lens having positive refractive power, and a third lens having negative refractive power, which are arranged in this order from the object side to the image side, the second lens group includes a fourth lens having positive refractive power and a fifth lens having negative refractive power, which are sequentially arranged from the object side to the image side, the third lens group includes a sixth lens having a positive refractive power and a seventh lens having a negative refractive power, which are sequentially arranged from the object side to the image side, the fourth lens group includes an eighth lens having a positive refractive power, TTL (total track length) is less than 20 mm, A zoom optical system in which the effective focal length (EFL) in telephoto is greater than 25 mm.

2. 2. The zoom optical system according to claim 1, wherein the effective focal length in telephoto mode is greater than 1.5 times the effective focal length in wide angle mode.

3. 3. The zoom optical system according to claim 1, wherein a stroke of movement of the second lens group is less than 2.5 mm when zooming from a wide angle to a telephoto angle.

4. 4. The zoom optical system according to claim 1, wherein the second lens group and the third lens group each include at least one glass lens.

5. 5. The zoom optical system according to claim 4, wherein the glass lens has a refractive index greater than 1.7 or an Abbe number greater than 60.

6. 6. The zoom optical system according to claim 1, wherein the lenses included in the first lens group to the fourth lens group are D-cut lenses.

7. 7. The zoom optical system according to claim 6, wherein the second lens group and the third lens group each include a lens whose effective diameter major axis length divided by the effective diameter minor axis length is 1.

8. 8. The zoom optical system according to claim 1, wherein a chief ray angle (CRA) is smaller than 6 degrees.

9. 9. The zoom optical system according to claim 1, further comprising a right-angle prism disposed at a front end of the first lens group in sequence from the object side to the image side.

10. 10. The zoom optical system according to claim 1, wherein a value obtained by dividing the effective focal length (EFL) by an F-number is greater than 6 in the telephoto zoom optical system.

11. 10. The zoom optical system according to claim 1, wherein the telephoto has an F-number smaller than 4.

2.

12. The optical system includes a first lens group, a second lens group, a third lens group, and a fourth lens group, which are arranged in this order from an object side to an image side, During zooming or focusing, the second lens group and the third lens group move, and the interval between adjacent lens groups changes; the first lens group and the fourth lens group are fixed; the first lens group includes a first lens having positive refractive power, a second lens having positive refractive power, and a third lens having negative refractive power, which are arranged in this order from the object side to the image side, the second lens group includes a fourth lens having positive refractive power and a fifth lens having negative refractive power, which are sequentially arranged from the object side to the image side, the third lens group includes a sixth lens having a positive refractive power and a seventh lens having a negative refractive power, which are sequentially arranged from the object side to the image side, the fourth lens group includes an eighth lens having a positive refractive power, A telephoto zoom optical system with an effective focal length (EFL) greater than 25 mm and an F-number less than 4.

2.

13. The optical system includes a first lens group, a second lens group, a third lens group, and a fourth lens group, which are arranged in this order from an object side to an image side, During zooming or focusing, the second lens group and the third lens group move, and the interval between adjacent lens groups changes; the first lens group and the fourth lens group are fixed; the first lens group includes a first lens having positive refractive power, a second lens having positive refractive power, and a third lens having negative refractive power, which are arranged in this order from the object side to the image side, the second lens group includes a fourth lens having positive refractive power and a fifth lens having negative refractive power, which are sequentially arranged from the object side to the image side, the third lens group includes a sixth lens having a positive refractive power and a seventh lens having a negative refractive power, which are sequentially arranged from the object side to the image side, the fourth lens group includes an eighth lens having a positive refractive power, A telephoto zoom optical system in which the effective focal length (EFL) divided by the F-number is greater than 6.

14. the first lens includes a convex object-side surface and a concave image-side surface, the second lens includes a convex object-side surface and a convex image-side surface, and the third lens includes a concave object-side surface and a concave image-side surface; the fourth lens includes a convex object-side surface and a convex image-side surface, the fifth lens includes a convex object-side surface and a concave image-side surface, the sixth lens includes a convex object-side surface and a convex image-side surface, and the seventh lens includes a concave object-side surface and a concave image-side surface; 12. The zoom optical system of claim 1, wherein the eighth lens includes a convex object side and a convex image side.

15. the first lens includes a convex object-side surface and a concave image-side surface, the second lens includes a convex object-side surface and a convex image-side surface, and the third lens includes a concave object-side surface and a concave image-side surface; the fourth lens includes a convex object-side surface and a convex image-side surface, the fifth lens includes a convex object-side surface and a concave image-side surface, the sixth lens includes a concave object-side surface and a convex image-side surface, the seventh lens includes a concave object-side surface and a concave image-side surface; 12. The zoom optical system of claim 1, wherein the eighth lens includes a convex object side and a convex image side.

16. 16. The zoom optical system according to claim 1, wherein the second lens group and the third lens group move independently of each other.

17. 17. The zoom optical system according to claim 1, wherein the second lens group is a zooming group, and the third lens group is a focusing group.

18. 18. The zoom optical system according to claim 1, wherein a movement amount of the third lens group is larger than a movement amount of the second lens group.

Images