Optical systems, lens modules and terminal equipment

Abstract

The embodiments of the present application disclose an optical system, a lens module and a terminal device. The optical system includes a first lens with positive refractive power, a third lens with negative refractive power, a second lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens with refractive power, which are arranged in sequence from the object side to the image side. The object side of the first lens is convex at the optical axis, the image side of the third lens is concave at the optical axis, and the image side of the fourth lens is convex at the optical axis; the optical system satisfies the following condition: TTL / f<1.1, TTL is the distance from the object side of the first lens to the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system. The present application reasonably configures the refractive power and surface shape of the first lens to the eighth lens in the optical system and limits TTL / f<1.1, so that the optical system has the characteristics of long focal length and good imaging quality while satisfying the miniature design.

Description

Technical Field

[0001] The present application belongs to the field of optical imaging technology, and in particular, relates to an optical system, a lens module and a terminal device. Background Art

[0002] With the widespread use of electronic products such as mobile phones, tablet computers, drones, and computers in our lives, various technological improvements have been introduced. Among them, the improvement and innovation of the shooting effect of camera lenses in new electronic products has become the focus of people's attention.

[0003] Current camera lenses are usually required to have miniaturized features. As the demand for long-range photography increases, camera lenses need to have long focal lengths, but they are prone to problems such as insufficient clarity and poor image quality, resulting in unsatisfactory long-range photography effects.

[0004] Therefore, how to increase the focal length and improve the image quality while satisfying the miniature design so that the scene at a distant object can be clearly imaged on the imaging surface should be the research and development direction of the industry. Summary of the invention

[0005] The embodiments of the present application provide an optical system, a lens module and a terminal device. The optical system increases the focal length of the system and improves the image quality while meeting the requirements of miniature design, and can take clear pictures even under low-light conditions.

[0006] In the first aspect, an embodiment of the present application provides an optical system, the optical system includes a plurality of lenses, the plurality of lenses include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from the object side (the object side refers to the side where light enters) to the image side (the image side refers to the side where light exits), wherein the first lens has a positive refractive power, the third lens has a negative refractive power, and the remaining lenses have a refractive power; the object side surface of the first lens is a convex surface at the optical axis, the image side surface of the third lens is a concave surface at the optical axis, and the image side surface of the fourth lens is a convex surface at the optical axis. The refractive power is the optical focal length, which characterizes the ability of the optical system to deflect light, and the second lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens have a refractive power, which means that the second lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens can have a positive refractive power or a negative refractive power, and a positive refractive power indicates that the lens has a converging effect on the light beam, and a negative refractive power indicates that the lens has a diverging effect on the light beam. For example, in a preferred embodiment, the refractive power of the eight lenses can be that the first lens has a positive refractive power, the second lens has a negative refractive power, the third lens has a negative refractive power, the fourth lens has a positive refractive power, the fifth lens has a negative refractive power, the sixth lens has a negative refractive power, the seventh lens has a negative refractive power, and the eighth lens L8 has a positive refractive power. The refractive power of the eight lenses can also be other preferred combinations. When the lens has no refractive power, that is, when the optical power is zero, it is a plane refraction. At this time, the parallel light beam along the axis is still a parallel light beam along the axis after refraction, and no refraction phenomenon occurs. The optical system satisfies the following conditional formula: TTL / f<1.1, TTL is the distance from the object side of the first lens to the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system.

[0007] The present application reasonably configures the refractive power of the first lens to the eighth lens in the optical system and the surface shapes of the first lens, the third lens and the fourth lens and limits TTL / f<1.1, so that the optical system has the characteristics of a long focal length and good imaging quality while meeting the requirements of miniature design, so that the captured images have high image quality, high resolution and high definition.

[0008] In one embodiment, the object side surfaces and image side surfaces of all the lenses are aspherical surfaces, which is beneficial for correcting the spherical aberration of the optical system and improving the imaging quality of the optical system.

[0009] In one embodiment, the optical system satisfies the conditional formula: -1.8 < f1 / f28 < -0.5, where f1 is the focal length of the first lens and f28 is the combined focal length of the second lens to the eighth lens. By defining a reasonable range of f1 / f28, it is beneficial to the reasonable distribution of the optical power of the first lens to the eighth lens of the optical system, and can better correct the chromatic aberration of the system and improve the imaging performance of the system.

[0010] In one embodiment, the optical system satisfies the conditional formula: TTL / ct56 > 4, where TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the optical system, and ct56 is the distance on the optical axis from the object side of the fifth lens to the image side of the sixth lens. By reasonably restricting the range of TTL / ct56, the multiple lenses of the optical system can be arranged compactly. Only a thick spacer needs to be provided between the fifth lens and the sixth lens, which can reduce the number of accessories and thus reduce the system tolerance.

[0011] In one embodiment, the optical system satisfies the conditional formula: (L81 - L82) / 2 * L83 > 0.7. A beam of light is incident on the farthest point from the optical axis of the imaging surface of the optical system, and the light has a first intersection point with the image side of the eighth lens. L81 is the maximum distance from the first intersection point to the vertical projection point of the first intersection point on the optical axis. L82 is the minimum distance from the first intersection point to the vertical projection point of the first intersection point on the optical axis. A beam of light is incident on the center point of the imaging surface of the optical system, and the light has a second intersection point with the image side of the eighth lens. L83 is the maximum distance from the second intersection point to the vertical projection point of the second intersection point on the optical axis. By restricting the appropriate range of (L81 - L82) / 2 * L83, it is beneficial to improve the relative brightness of the optical system, and clear imaging effects can also be achieved when shooting in a relatively dark environment.

[0012] In one embodiment, the optical system satisfies the conditional formula: TTL / Imgh < 2.5, where TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the optical system, and Imgh is the image height corresponding to half of the maximum field of view angle of the optical system. When the imaging surface is fixed, defining TTL / Imgh to be less than 2.5 can reduce the total length of the optical system and meet the requirement of miniaturization of the optical system.

[0013] In one embodiment, the optical system satisfies the conditional formula: FNO < 2.4, where FNO is the f-number of the optical system. By defining the f-number of the optical system, it is possible to obtain a large light flux even when the optical system has a long focal length, and clear imaging effects can also be achieved when shooting in a relatively dark environment.

[0014] In one embodiment, the optical system satisfies the conditional formula: Imgh / tan(HFOV)>5mm, where Imgh is the image height corresponding to half of the maximum field of view of the optical system, and tan(HFOV) is the tangent value of half of the maximum field of view of the optical system. By limiting the range of Imgh / tan(HFOV), the system can have the characteristics of a long focal length, increase the imaging magnification, and facilitate long-range shooting.

[0015] In a second aspect, the present application provides a lens module, comprising a photosensitive element and the optical system described in any one of the aforementioned embodiments, wherein the photosensitive element is located on the image side of the optical system.

[0016] In a third aspect, the present application provides a terminal device, comprising the lens module.

[0017] By rationally configuring the refractive power of the first to eighth lenses in the optical system and the surface shapes of the first, third and fourth lenses and limiting TTL / f<1.1, the optical system has the characteristics of a long focal length and good imaging quality while meeting the requirements of miniature design. Clear pictures can be taken even under dark conditions, and the captured images have high image quality, high resolution and high definition. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0019] Figure 1 is a schematic structural diagram of an optical system provided in the first embodiment of the present application;

[0020] Figure 2 are the longitudinal spherical aberration curve, astigmatism curve and distortion curve of the optical system of the first embodiment;

[0021] Figure 3 is a schematic structural diagram of an optical system provided in a second embodiment of the present application;

[0022] Figure 4 are the longitudinal spherical aberration curve, astigmatism curve and distortion curve of the optical system of the second embodiment;

[0023] Figure 5 is a schematic structural diagram of an optical system provided in the third embodiment of the present application;

[0024] Figure 6 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the third embodiment;

[0025] Figure 7 is a schematic structural diagram of an optical system provided in a fourth embodiment of the present application;

[0026] Figure 8 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fourth embodiment;

[0027] Fig. 9 is a schematic structural diagram of an optical system provided in a fifth embodiment of the present application;

[0028] Fig.10 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fifth embodiment;

[0029] Fig.11 is a schematic structural diagram of an optical system provided in a sixth embodiment of the present application;

[0030] Fig.12 are the longitudinal spherical aberration curve, astigmatism curve and distortion curve of the optical system of the sixth embodiment;

[0031] Fig.13 is a schematic structural diagram of an optical system provided in the seventh embodiment of the present application;

[0032] Fig.14 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the seventh embodiment;

[0033] Fig.15 is a schematic structural diagram of an optical system provided in an eighth embodiment of the present application;

[0034] Fig.16 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the eighth embodiment;

[0035] Fig.17 is a schematic structural diagram of an optical system provided in a ninth embodiment of the present application;

[0036] Fig.18 are a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the ninth embodiment;

[0037] Fig.19 It is a schematic diagram of the optical system provided by the present application applied in a terminal device. DETAILED DESCRIPTION

[0038] The embodiments of the present application are described below in conjunction with the drawings in the present application.

[0039] The present application provides an optical system including eight lenses, which are arranged in sequence from the object side to the image side as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens.

[0040] Specifically, the surface shape and refractive power of the eight lenses are as follows:

[0041] The first lens has a positive refractive power, the third lens has a negative refractive power, and the remaining lenses have refractive powers; the object side surface of the first lens is convex at the optical axis, the image side surface of the third lens is concave at the optical axis, and the image side surface of the fourth lens is convex at the optical axis.

[0042] The optical system satisfies the following conditional formula: TTL / f < 1.1, where TTL is the distance from the object side surface of the first lens to the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system.

[0043] By reasonably configuring the refractive powers of the first lens to the eighth lens in the optical system, the surface shapes of the first lens, the third lens, and the fourth lens, and limiting TTL / f < 1.1, while meeting the miniaturized design, the optical system has the characteristics of a long focal length and good imaging quality, making the captured image have high picture quality, high resolution, and high clarity.

[0044] In one embodiment, the object side surfaces and the image side surfaces of all the lenses are aspherical surfaces, which is beneficial to correcting the spherical aberration of the optical system and improving the imaging quality of the optical system.

[0045] In one embodiment, the optical system satisfies the conditional formula: -1.8 < f1 / f28 < -0.5, where f1 is the focal length of the first lens and f28 is the combined focal length of the second lens to the eighth lens. By limiting the reasonable range of f1 / f28, it is beneficial to the reasonable distribution of the optical powers of the first lens to the eighth lens of the optical system, can better correct the chromatic aberration of the system, and improve the imaging performance of the system.

[0046] In one embodiment, the optical system satisfies the conditional formula: TTL / ct56 > 4, where TTL is the distance from the object side surface of the first lens to the imaging surface of the optical system on the optical axis, and ct56 is the distance from the object side surface of the fifth lens to the image side surface of the sixth lens on the optical axis. By reasonably restricting the range of TTL / ct56, the multiple lenses of the optical system can be compactly arranged, and only a thick spacer needs to be set between the fifth lens and the sixth lens, which can reduce the number of accessories and thus reduce the system tolerance.

[0047] In one embodiment, the optical system satisfies the conditional formula: (L81-L82) / 2*L83>0.7, a beam of light is incident on the imaging surface of the optical system at the farthest point from the optical axis, the light has a first intersection with the image side surface of the eighth lens, L81 is the maximum distance from the first intersection to the vertical projection point of the first intersection on the optical axis, L82 is the minimum distance from the first intersection to the vertical projection point of the first intersection on the optical axis, a beam of light is incident on the center point of the imaging surface of the optical system, the light has a second intersection with the image side surface of the eighth lens, and L83 is the maximum distance from the second intersection to the vertical projection point of the second intersection on the optical axis. By limiting the appropriate range of (L81-L82) / 2*L83, it is beneficial to improve the relative brightness of the optical system, and a clear imaging effect can be achieved even when shooting in a darker environment.

[0048] In one embodiment, the optical system satisfies the conditional formula: TTL / Imgh<2.5, where TTL is the distance from the object side of the first lens to the imaging surface of the optical system on the optical axis, and Imgh is the image height corresponding to half of the maximum field angle of the optical system. When the imaging surface is fixed, limiting TTL / Imgh to less than 2.5 can reduce the total length of the optical system and achieve the requirement of miniaturization of the optical system.

[0049] In one embodiment, the optical system satisfies the condition: FNO<2.4, where FNO is the aperture number of the optical system. By limiting the aperture number of the optical system, a large light flux can be obtained when the optical system has a long focal length, and a clear imaging effect can be achieved even when shooting in a dark environment.

[0050] In one embodiment, the optical system satisfies the conditional formula: Imgh / tan(HFOV)>5mm, where Imgh is the image height corresponding to half of the maximum field of view of the optical system, and tan(HFOV) is the tangent value of half of the maximum field of view of the optical system. By limiting the range of Imgh / tan(HFOV), the system can have the characteristics of a long focal length, increase the imaging magnification, and facilitate long-range shooting.

[0051] The present application is described in detail below through nine specific embodiments.

[0052] Embodiment 1

[0053] like Figure 1As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0054] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0055] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0056] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and at the circumference, and its image-side surface S6 is concave at the optical axis and at the circumference, and both are aspherical.

[0057] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and at the circumference, and its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0058] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0059] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and at the circumference and is aspherical.

[0060] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is convex at the optical axis and concave at the circumference. Its image-side surface S14 is concave at the optical axis and at the circumference and is aspherical.

[0061] The eighth lens L8 has positive refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and concave at the circumference. Its image-side surface S16 is concave at the optical axis and convex at the circumference, and both are aspherical.

[0062] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0063] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0064] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0065] Table 1a shows the characteristics of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0066] Table 1a

[0067]

[0068] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0069] In this embodiment, the object side surface and the image side surface of any lens of the first lens L1 to the eighth lens L8 are aspherical surfaces, and the surface shape of each aspherical lens can be defined by but not limited to the following aspherical surface formula:

[0070]

[0071] Among them, Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the aspherical vertex, k is the cone constant, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface shape formula.

[0072] Table 1b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the first embodiment.

[0073] Table 1b

[0074]

[0075]

[0076] Figure 2 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the first embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Figure 2 It can be seen that the optical system provided in the first embodiment can achieve good imaging quality.

[0077] Embodiment 2

[0078] like Figure 3 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0079] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0080] The second lens L2 has positive refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0081] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0082] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and at the circumference, and its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0083] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0084] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0085] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is concave at the optical axis and at the circumference, its image-side surface S14 is convex at the optical axis, and its image-side surface S14 is concave at the circumference, and both are aspherical.

[0086] The eighth lens L8 has negative refractive power and is made of plastic. Its object-side surface S15 is concave at the optical axis and at the circumference, and its image-side surface S16 is convex at the optical axis and at the circumference, and both are aspherical.

[0087] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0088] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0089] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0090] Table 2a shows the characteristic table of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0091] Table 2a

[0092]

[0093] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0094] Table 2b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the second embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0095] Table 2b

[0096]

[0097]

[0098] Figure 4 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the second embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the focal point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Figure 4 It can be seen that the optical system provided in the second embodiment can achieve good imaging quality.

[0099] Embodiment 3

[0100] like Figure 5 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0101] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0102] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0103] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0104] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and at the circumference, and its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0105] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and at the circumference, and its image-side surface S10 is concave at the optical axis and at the circumference, and both are aspherical.

[0106] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0107] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is concave at the optical axis and at the circumference, and its image-side surface S14 is convex at the optical axis and at the circumference, and both are aspherical.

[0108] The eighth lens L8 has positive refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and concave at the circumference. Its image-side surface S16 is concave at the optical axis and at the circumference and is aspherical.

[0109] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0110] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0111] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0112] Table 3a shows a characteristic table of the optical system of this embodiment, wherein the radius of curvature in this embodiment is the radius of curvature of each lens at the optical axis.

[0113] Table 3a

[0114]

[0115] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0116] Table 3b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the third embodiment, wherein the surface shape of each aspherical surface can be defined by the formula given in the first embodiment.

[0117] Table 3b

[0118] Surface number K A4 A6 A8 A10 S1 -1.5927 0.0383 0.0058 -0.0150 0.0374 S2 -0.5411 0.0728 -0.0943 0.0780 0.0068 S3 -54.0522 -0.0228 0.0443 -0.2186 0.4926 S4 -52.8856 -0.1064 0.5556 -1.4723 1.9014 S5 -50.3669 -0.0536 0.4573 -0.8476 -1.0347 S6 -5.3633 -0.0628 0.6052 -1.9371 3.4718 S7 97.1066 0.1124 -0.0865 0.7395 -3.5234 S8 -26.4300 0.2440 -0.5512 2.2389 -6.4464 S9 89.0000 0.0871 -0.6040 1.9220 -3.8201 S10 -78.4730 -0.0499 -0.0998 0.3176 -0.3732 S11 -5.6393 0.0002 -0.2762 0.4536 -0.4762 S12 -0.4504 0.1226 -0.4444 0.6009 -0.5452 S13 -13.2306 0.1168 -0.2188 0.0977 0.0475 S14 -42.9930 -0.0504 0.1287 -0.2262 0.2036 S15 -1.3708 -0.1396 0.1671 -0.1518 0.1022 S16 -17.6617 -0.1058 0.0483 -0.0270 0.0214 Surface number A12 A14 A16 A18 A20 S1 -0.0497 0.0401 -0.0194 0.0052 -0.0006 S2 -0.0913 0.1070 -0.0636 0.0196 -0.0024 S3 -0.5896 0.4458 -0.2197 0.0644 -0.0083 S4 -1.0027 -0.2168 0.5265 -0.2325 0.0337 S5 5.6308 -8.6056 6.6739 -2.6768 0.4410 S6 -5.3002 7.6411 -8.1037 4.9782 -1.2817 S7 8.7537 -13.5185 12.4727 -6.1117 1.2047 S8 13.9810 -20.5251 18.2451 -8.7741 1.7471 S9 6.1392 -7.1828 5.2685 -2.1178 0.3542 S10 0.3081 -0.1594 0.0260 0.0174 -0.0071 S11 0.2617 -0.0256 -0.0437 0.0204 -0.0028 S12 0.3297 -0.1293 0.0317 -0.0045 0.0003 S13 -0.0734 0.0361 -0.0091 0.0012 -0.0001 S14 -0.1062 0.0336 -0.0064 0.0007 0.0000 S15 -0.0503 0.0166 -0.0034 0.0004 0.0000 S16 -0.0130 0.0045 -0.0009 0.0001 0.0000

[0119] Figure 6 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the third embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Figure 6 It can be seen that the optical system provided in the third embodiment can achieve good imaging quality.

[0120] Embodiment 4

[0121] like Figure 7 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0122] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0123] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and convex at the circumference, and both are aspherical.

[0124] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0125] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and at the circumference, and its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0126] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0127] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0128] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is concave at the optical axis and convex at the circumference. Its image-side surface S14 is convex at the optical axis and concave at the circumference, and both are aspherical.

[0129] The eighth lens L8 has positive refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and concave at the circumference. Its image-side surface S16 is concave at the optical axis and at the circumference and is aspherical.

[0130] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0131] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0132] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0133] Table 4a shows a characteristic table of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0134] Table 4a

[0135]

[0136]

[0137] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0138] Table 4b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the fourth embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0139] Table 4b

[0140]

[0141]

[0142] Figure 8 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the fourth embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Figure 8 It can be seen that the optical system provided in the fourth embodiment can achieve good imaging quality.

[0143] Embodiment 5

[0144] like Fig. 9 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0145] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0146] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is concave at the optical axis and convex at the circumference. Its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0147] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0148] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and at the circumference, and its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0149] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is concave at the optical axis and at the circumference, and its image-side surface S10 is concave at the optical axis and at the circumference, and both are aspherical.

[0150] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0151] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is concave at the optical axis and is convex at the circumference. Its image-side surface S14 is concave at the optical axis and is convex at the circumference. Both are aspherical surfaces.

[0152] The eighth lens L8 has positive refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and concave at the circumference. Its image-side surface S16 is concave at the optical axis and at the circumference and is aspherical.

[0153] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0154] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0155] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0156] Table 5a shows a characteristic table of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0157] Table 5a

[0158]

[0159] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0160] Table 5b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the fifth embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0161] Table 5b

[0162]

[0163]

[0164] Fig.10 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the fifth embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Fig.10 It can be seen that the optical system provided in the fifth embodiment can achieve good imaging quality.

[0165] Embodiment 6

[0166] like Fig.11 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0167] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0168] The second lens L2 has positive refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0169] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0170] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is convex at the optical axis and concave at the circumference. Its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0171] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0172] The sixth lens L6 has positive refractive power and is made of plastic. Its object-side surface S11 is convex at the optical axis and at the circumference, its image-side surface S12 is concave at the optical axis, and its image-side surface S12 is convex at the circumference, and both are aspherical.

[0173] The seventh lens L7 has positive refractive power and is made of plastic. Its object-side surface S13 is convex at the optical axis and at the circumference, its image-side surface S14 is concave at the optical axis, and its image-side surface S14 is convex at the circumference, and both are aspherical.

[0174] The eighth lens L8 has negative refractive power and is made of plastic. Its object-side surface S15 is concave at the optical axis and at the circumference, its image-side surface S16 is convex at the optical axis, and its image-side surface S16 is concave at the circumference, and both are aspherical.

[0175] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0176] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0177] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0178] Table 6a shows a characteristic table of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0179] Table 6a

[0180]

[0181]

[0182] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0183] Table 6b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the sixth embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0184] Table 6b

[0185]

[0186]

[0187] Fig.12 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the sixth embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Fig.12 It can be seen that the optical system provided in the sixth embodiment can achieve good imaging quality.

[0188] Embodiment 7

[0189] like Fig.13 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0190] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0191] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0192] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and at the circumference, and its image-side surface S6 is concave at the optical axis and at the circumference, and both are aspherical.

[0193] The fourth lens L4 has negative refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and convex at the circumference. Its image-side surface S8 is convex at the optical axis and at the circumference and is aspherical.

[0194] The fifth lens L5 has positive refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0195] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is concave at the optical axis and convex at the circumference. Both are aspherical surfaces.

[0196] The seventh lens L7 has positive refractive power and is made of plastic. Its object-side surface S13 is convex at the optical axis and concave at the circumference. Its image-side surface S14 is concave at the optical axis and at the circumference and is aspherical.

[0197] The eighth lens L8 has negative refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and concave at the circumference. Its image-side surface S16 is concave at the optical axis and convex at the circumference, and both are aspherical.

[0198] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0199] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0200] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0201] Table 7a shows a characteristic table of the optical system of this embodiment, wherein the radius of curvature in this embodiment is the radius of curvature of each lens at the optical axis.

[0202] Table 7a

[0203]

[0204]

[0205] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0206] Table 7b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the seventh embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0207] Table 7b

[0208]

[0209]

[0210] Fig.14 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the seventh embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Fig.14 It can be seen that the optical system provided in the seventh embodiment can achieve good imaging quality.

[0211] Embodiment 8

[0212] like Fig.15 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0213] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0214] The second lens L2 has positive refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is convex at the optical axis and concave at the circumference, and both are aspherical.

[0215] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is concave at the optical axis and at the circumference, and its image-side surface S6 is concave at the optical axis and at the circumference, and both are aspherical.

[0216] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is convex at the optical axis and concave at the circumference. Its image-side surface S8 is convex at the optical axis and at the circumference, and both are aspherical.

[0217] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is convex at the optical axis and concave at the circumference. Its image-side surface S10 is concave at the optical axis and at the circumference and is aspherical.

[0218] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is convex at the optical axis and at the circumference and is aspherical.

[0219] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is convex at the optical axis and at the circumference, and its image-side surface S14 is concave at the optical axis and at the circumference, and both are aspherical.

[0220] The eighth lens L8 has negative refractive power and is made of plastic. Its object-side surface S15 is concave at the optical axis and is convex at the circumference. Its image-side surface S16 is convex at the optical axis and is concave at the circumference. Both are aspherical surfaces.

[0221] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0222] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0223] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0224] Table 8a shows a characteristic table of the optical system of this embodiment, wherein the curvature radius in this embodiment is the curvature radius of each lens at the optical axis.

[0225] Table 8a

[0226]

[0227] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0228] Table 8b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the eighth embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0229] Table 8b

[0230] Surface number K A4 A6 A8 A10 S1 -1.9598 0.0490 0.0008 -0.0056 0.0285 S2 0.0000 0.0458 -0.0173 0.0302 -0.1152 S3 -49.6866 -0.0330 0.0136 0.1699 -0.6833 S4 -57.0050 -0.1849 0.9705 -2.6363 3.9094 S5 -57.0050 -0.2023 1.3246 -4.3385 8.2137 S6 -4.8729 -0.0313 0.4411 -2.0219 4.8284 S7 86.9060 0.1621 -0.0567 0.2286 -2.1164 S8 -49.7195 0.3297 -0.4951 1.1111 -1.1350 S9 89.0000 0.0721 -0.5393 1.0971 0.6424 S10 -78.4730 -0.0582 -0.0529 0.0593 0.5863 S11 -10.9160 -0.0588 0.0776 -0.1700 0.1468 S12 -35.5530 0.0017 0.1125 -0.2868 0.2929 S13 0.0000 0.0729 -0.1379 0.0370 0.0709 S14 -42.9930 0.1424 -0.3037 0.2888 -0.1870 S15 -26.3451 0.0424 -0.1011 0.0816 -0.0504 S16 0.0000 -0.0454 -0.0175 0.0210 -0.0139 Surface number A12 A14 A16 A18 A20 S1 -0.0504 0.0503 -0.0291 0.0092 -0.0013 S2 0.2084 -0.1851 0.0839 -0.0184 0.0015 S3 1.2850 -1.3247 0.7743 -0.2430 0.0323 S4 -2.8932 0.3720 0.9859 -0.6770 0.1420 S5 -9.5260 6.7535 -2.7366 0.5223 -0.0219 S6 -6.9851 5.8839 -2.1462 -0.2782 0.3365 S7 6.9561 -13.2247 14.1647 -7.8153 1.7349 S8 -0.3130 2.9986 -5.1346 4.0317 -1.2165 S9 -7.0954 16.8312 -20.2904 12.3777 -3.0301 S10 -1.9332 3.1732 -3.0005 1.5845 -0.3642 S11 -0.0948 0.0593 -0.0290 0.0084 -0.0010 S12 -0.1676 0.0568 -0.0111 0.0011 0.0000 S13 -0.0741 0.0328 -0.0078 0.0010 -0.0001 S14 0.0862 -0.0270 0.0054 -0.0006 0.0000 S15 0.0255 -0.0092 0.0021 -0.0003 0.0000 S16 0.0079 -0.0031 0.0007 -0.0001 0.0000

[0231] Fig.16 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the eighth embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Fig.16 It can be seen that the optical system provided in the eighth embodiment can achieve good imaging quality.

[0232] Embodiment 9

[0233] like Fig.17 As shown, the straight line 11 represents the optical axis, the side of the first lens L1 away from the second lens L2 is the object side 12, and the side of the sixth lens L6 away from the fifth lens L5 is the image side 13. In the optical system provided by this embodiment, from the object side 12 to the image side 13 are the aperture STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF.

[0234] The first lens L1 has positive refractive power and is made of plastic. Its object-side surface S1 is convex at the optical axis and concave at the circumference. Its image-side surface S2 is convex at the optical axis and at the circumference and is aspherical.

[0235] The second lens L2 has positive refractive power and is made of plastic. Its object-side surface S3 is convex at the optical axis and at the circumference, and its image-side surface S4 is concave at the optical axis and at the circumference, and both are aspherical.

[0236] The third lens L3 has negative refractive power and is made of plastic. Its object-side surface S5 is convex at the optical axis and concave at the circumference. Its image-side surface S6 is concave at the optical axis and at the circumference and is aspherical.

[0237] The fourth lens L4 has positive refractive power and is made of plastic. Its object-side surface S7 is concave at the optical axis and convex at the circumference. Its image-side surface S8 is convex at the optical axis and at the circumference and is aspherical.

[0238] The fifth lens L5 has negative refractive power and is made of plastic. Its object-side surface S9 is concave at the optical axis and at the circumference, its image-side surface S10 is convex at the optical axis, and its image-side surface S10 is concave at the circumference, and both are aspherical.

[0239] The sixth lens L6 has negative refractive power and is made of plastic. Its object-side surface S11 is concave at the optical axis and convex at the circumference. Its image-side surface S12 is convex at the optical axis and at the circumference and is aspherical.

[0240] The seventh lens L7 has negative refractive power and is made of plastic. Its object-side surface S13 is concave at the optical axis and convex at the circumference. Its image-side surface S14 is concave at the optical axis and at the circumference and is aspherical.

[0241] The eighth lens L8 has negative refractive power and is made of plastic. Its object-side surface S15 is convex at the optical axis and at the circumference, and its image-side surface S16 is concave at the optical axis and at the circumference, and both are aspherical.

[0242] The aperture STO may be located between the object plane of the optical system and the eighth lens. In the present embodiment, the aperture STO is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

[0243] The infrared filter element IRCF is arranged after the eighth lens L8, and includes an object-side surface S17 and an image-side surface S18. The infrared filter element IRCF is used to filter out infrared light so that the light incident on the imaging surface is visible light. The wavelength of visible light is 380nm-780nm. The material of the infrared filter element IRCF is glass.

[0244] The imaging plane S19 is the plane where the image of the object is formed after the light passes through the optical system.

[0245] Table 9a shows a characteristic table of the optical system of this embodiment, wherein the radius of curvature in this embodiment is the radius of curvature of each lens at the optical axis.

[0246] Table 9a

[0247]

[0248]

[0249] Wherein, f is the focal length of the optical system, FNO is the aperture number of the optical system, FOV is the maximum field angle of the optical system, and TTL is the distance from the object side of the first lens to the imaging plane of the optical system on the optical axis.

[0250] Table 9b gives the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the aspheric mirror surfaces S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 that can be used in the ninth embodiment, wherein the surface shape of each aspheric surface can be defined by the formula given in the first embodiment.

[0251] Table 9b

[0252]

[0253]

[0254] Fig.18 The longitudinal spherical aberration curve, astigmatism curve, and distortion curve of the optical system of the ninth embodiment are shown. The longitudinal spherical aberration curve indicates the deviation of the convergence point of light of different wavelengths after passing through each lens of the optical system; the astigmatism curve indicates the meridional image curvature and the sagittal image curvature, where S indicates the sagittal direction and T indicates the meridional direction; the distortion curve indicates the distortion magnitude value corresponding to different field angles. Fig.18 It can be seen that the optical system provided in the ninth embodiment can achieve good imaging quality.

[0255] Table 10 shows the values ​​of TTL / Imgh, TTL / f, f1 / f28, FNO, (L81-L82) / 2*L83, TTL / ct56, and Imgh / tan(HFOV) of the optical systems of the first to ninth embodiments.

[0256] Table 10

[0257]

[0258] It can be seen from Table 10 that all embodiments can meet the following requirements: TTL / Imgh<2.5, TTL / f<1.1, -1.8 <f1 / f28<-0.5,FNO<2.4,(L81-L82) / 2*L83>0.7,TTL / ct56> 4.Imgh / tan(HFOV)>5mm.

[0259] See also Fig.19 The optical system involved in the present application is applied to a lens module 20 in a terminal device 30. The terminal device 30 may be a mobile phone, a tablet computer, a drone, a computer, etc. The photosensitive element of the lens module 20 is located on the image side of the optical system, and the lens module 20 is assembled inside the terminal device 30.

[0260] The present application provides a lens module, including a photosensitive element and an optical system provided by the present application, wherein the photosensitive element is located on the image side of the optical system, and is used to convert light passing through the first lens to the eighth lens and incident on the electronic photosensitive element into an electrical signal of an image. The electronic photosensitive element can be a complementary metal oxide semiconductor (CMOS) or a charge-coupled device (CCD). By installing the optical system in the lens module, the lens module has the characteristics of a long focal length while meeting the miniature design, and has good imaging quality, so that the captured picture has high image quality, high resolution and high definition.

[0261] The present application also provides a terminal device, which includes the lens module provided by the present application. The terminal device can be a mobile phone, a tablet computer, a drone, a computer, etc. By installing the lens module in the terminal device, the terminal device has the characteristics of a long focal length while meeting the requirements of a miniature design, and has good imaging quality, so that the captured picture has high image quality, high resolution, and high definition.

[0262] The above is a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. An optical system, characterized in that: There are eight lenses with refractive power, which are respectively a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from the object side to the image side, wherein the first lens has positive refractive power, the third lens has negative refractive power, and the remaining lenses have refractive power; the object side surface of the first lens is convex at the optical axis, the image side surface of the third lens is concave at the optical axis, the image side surface of the fourth lens is convex at the optical axis, and the material of the eighth lens is plastic; The optical system satisfies the following conditional formula: TTL / f<1.1, -1.8 <f1 / f28<-0.5, TTL is the distance from the object side of the first lens to the imaging surface of the optical system on the optical axis, f is the focal length of the optical system, f1 is the focal length of the first lens, and f28 is the combined focal length of the second lens to the eighth lens.

2. The optical system according to claim 1, characterized in that The object side surfaces and image side surfaces of all the lenses are aspherical.

3. The optical system according to claim 1 or 2, characterized in that: The optical system satisfies the condition: 7.27≥TTL / ct56>4, TTL is the distance from the object side surface of the first lens to the imaging surface of the optical system on the optical axis, and ct56 is the distance from the object side surface of the fifth lens to the image side surface of the sixth lens on the optical axis.

4. The optical system according to claim 1 or 2, characterized in that: The optical system satisfies the condition: (L81-L82) / 2*L83>0.7, A beam of light is incident on the farthest point from the optical axis of the imaging surface of the optical system, the light has a first intersection with the image side surface of the eighth lens, L81 is the maximum distance from the first intersection to the vertical projection point of the first intersection on the optical axis, L82 is the minimum distance from the first intersection to the vertical projection point of the first intersection on the optical axis, a beam of light is incident on the center point of the imaging surface of the optical system, the light has a second intersection with the image side surface of the eighth lens, L83 is the maximum distance from the second intersection to the vertical projection point of the second intersection on the optical axis.

5. The optical system according to claim 1 or 2, characterized in that: The optical system satisfies the condition: 2.09≤TTL / Imgh<2.5, TTL is the distance from the object side of the first lens to the imaging surface of the optical system on the optical axis, and Imgh is the image height corresponding to half of the maximum field of view of the optical system.

6. The optical system according to claim 1 or 2, characterized in that: The optical system satisfies the condition: 1.88≤FNO<2.4, FNO is the aperture number of the optical system.

7. The optical system according to claim 1 or 2, characterized in that: The optical system satisfies the condition: Imgh / tan(HFOV)>5mm, Imgh is the image height corresponding to half of the maximum field of view of the optical system, and tan(HFOV) is the tangent value of half of the maximum field of view of the optical system.

8. A lens module, characterized in that: The optical system comprises a photosensitive element and the optical system as claimed in any one of claims 1 to 7, wherein the photosensitive element is located on the image side of the optical system.

9. A terminal device, characterized in that: Comprising the lens module as described in claim 8.

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