Optical system, lens module and terminal device

Abstract

Embodiments of the present application disclose optical systems, lens modules and terminal devices. The optical system comprises, along the optical axis direction from the object side to the image side, a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power, the object side surface of the fourth lens near the optical axis being a convex surface, the image side surface of the fourth lens near the optical axis being a concave surface; and a fifth lens having positive refractive power, the image side surface of the fifth lens near the optical axis being a convex surface; the image side surface of the fourth lens and the object side surface of the fifth lens are in contact, and the optical system satisfies the following conditional expression: 4 < TTL / (ImgH*2) < 6; wherein TTL is the distance on the optical axis from the object side surface of the first lens to the imaging surface of the optical system, and ImgH is the half image height in the horizontal direction of the optical system. Reasonably configuring the surface shape and refractive power of the first to fifth lenses and the ratio of TTL / (ImgH*2) enables the optical system to have a wide viewing angle and high imaging resolution, which is beneficial to correcting system aberration.

Description

TECHNICAL FIELD

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

[0002] In recent years, in order to meet the growing market demand, ultra-wide-angle lenses are widely used in mobile phones, monitoring, vehicle-mounted terminal devices and the like to obtain a larger field of view.

[0003] At present, an ultra-wide-angle lens is generally composed of glass lenses and plastic lenses. In order to obtain a larger field of view, multiple glass lenses or multiple plastic lenses are often required. However, such an ultra-wide-angle lens has a large size and a high price, and cannot meet the requirements of customers for small size, low price and high performance.

[0004] How to solve the problems of wide viewing angle, miniaturization and poor optical performance of the ultra-wide-angle lens and improve the imaging resolution of the ultra-wide-angle lens should be the direction of research and development in the industry. SUMMARY

[0005] The embodiments of the present application provide an optical system, a lens module and a terminal device. The optical system is an ultra-wide-angle lens. The optical system has good optical performance and high imaging resolution, and meets the development requirements of lens miniaturization.

[0006] In a first aspect, the embodiments of the present application provide an optical system, which comprises, in order from the object side to the image side along the optical axis direction: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power, the object side surface of the fourth lens near the optical axis being a convex surface, and the image side surface of the fourth lens near the optical axis being a concave surface; and a fifth lens having positive refractive power, the object side surface of the fifth lens near the optical axis being a convex surface, and the image side surface of the fifth lens near the optical axis being a convex surface; the image side surface of the fourth lens and the object side surface of the fifth lens are bonded, the fourth lens and the fifth lens form a cemented lens, the cemented lens has positive refractive power, the cemented lens is formed by bonding the fourth lens and the fifth lens through photosensitive glue or the like, the optical system further comprises a diaphragm, the diaphragm is located between the object side and the fourth lens, and the optical system satisfies the following conditional expression: 4 < TTL / (ImgH*2) < 6; wherein TTL is the distance on the optical axis from the object side surface of the first lens to the imaging surface of the optical system, and ImgH is the horizontal half image height of the optical system.

[0007] The application limits the ratio of the surface type and the refractive power of the first to fifth lenses and TTL / (ImgH*2) in the optical system, and sets the fourth and fifth lenses to be bonded to form a cemented lens, so that the optical system has a wide viewing angle and high imaging resolution, which is beneficial to correcting system aberration and miniaturization of the ultra-wide-angle lens, ensuring the stability of the optical system and the high-pixel imaging system, and providing users with a good experience.

[0008] In an embodiment, the optical system satisfies the condition formula: 11.8<FOV / CRA<21; wherein FOV is the horizontal field of view of the optical system, and CRA is the chief ray incidence angle, that is, the angle between the chief ray at the maximum image height and the normal direction of the imaging surface. By limiting the ratio of the field of view and the chief ray incidence angle, the optical system has a larger field of view to meet the demand of large field of view of terminal devices such as mobile phones, monitoring, vehicle-mounted, etc., while reducing the angle of the chief ray incident to the imaging surface, which can improve the photosensitive performance of the photosensitive element and is beneficial to improve the imaging quality of the optical system.

[0009] In an embodiment, the optical system satisfies the condition formula: 3.5<f45 / f<7; wherein f45 is the combined focal length of the fourth and fifth lenses. By limiting the range of the ratio of the combined focal length of the fourth and fifth lenses to the effective focal length of the optical system, the refractive power of the optical system is reasonably distributed, which is beneficial to reduce the assembly sensitivity of the optical system, solve the process manufacturing and assembly problems of the fourth and fifth lenses, improve the yield, and at the same time, is beneficial to reduce the eccentricity sensitivity, correct the system aberration, improve the imaging resolution, and achieve better imaging effect.

[0010] In an embodiment, the optical system satisfies the condition formula: 1≤CT5 / CT4<5; wherein CT4 is the thickness of the fourth lens on the optical axis, and CT5 is the thickness of the fifth lens on the optical axis. By reasonably configuring the thickness of the fourth and fifth lenses on the optical axis, the cementing process of the fourth and fifth lenses is facilitated, the system aberration is corrected, and the imaging resolution is improved.

[0011] By limiting the range of the ratio of the combined focal length of the fourth and fifth lenses to the effective focal length of the optical system, and limiting the thickness of the fourth and fifth lenses on the optical axis, the fourth and fifth lenses are better bonded to form a cemented lens, so as to correct the aberration of the optical system and improve the imaging resolution.

[0012] In an embodiment, the optical system satisfies the condition formula: nd4-nd5>0; wherein nd4 is the refractive index of the fourth lens, and nd5 is the refractive index of the fifth lens. nd4-nd5>0 is beneficial to correct the off-axis chromatic aberration and improve the resolution of the optical system.

[0013] In one embodiment, the optical system satisfies the condition: -6 < f1 / f < 0; wherein f1 is the focal length of the first lens, and f is the effective focal length of the optical system. The present embodiment adjusts the optical performance of the optical system by limiting the range of the ratio of the focal length of the first lens to the effective focal length of the optical system, while making the optical system have the characteristics of wide viewing angle, low sensitivity and miniaturization.

[0014] In one embodiment, the optical system satisfies the condition: -78 < RDYS3 / RDYS2 < -15; wherein RDYS2 is the curvature radius of the image side surface of the first lens, and RDYS3 is the curvature radius of the object side surface of the second lens. The size of RDYS2 affects the bending degree of the first lens and the position of the ghost image, and the greater the RDYS2, the smaller the bending degree of the first lens, i.e. the smoother the first lens, and the closer the position of the ghost image to the edge, which is beneficial to reducing the influence on the imaging quality of the optical system. The size of RDYS3 affects the brightness of the ghost image, and the greater the RDYS3, the darker the ghost image, and the smaller the bending degree of the third lens, which is beneficial to reducing the influence on the imaging quality.

[0015] By limiting the range of the ratio of the focal length of the first lens to the effective focal length of the optical system, and limiting the curvature radius of the image side surface of the first lens and the curvature radius of the object side surface of the second lens, it is beneficial to reduce the brightness of the ghost image and make the position of the ghost image closer to the edge on the basis of ensuring wide viewing angle, low sensitivity and miniaturization, and improve the imaging quality.

[0016] In one embodiment, the optical system satisfies the condition: -5 < f2 / f < -1.5; wherein f2 is the focal length of the second lens, and f is the effective focal length of the optical system. The present embodiment strengthens the wide viewing angle capability of the optical system by limiting the range of the ratio of the focal length of the second lens to the effective focal length of the optical system, so that the optical system has the characteristics of wide viewing angle, low sensitivity and miniaturization.

[0017] In one embodiment, the optical system satisfies the condition: RDYS4 / f < 1.69; wherein RDYS4 is the curvature radius of the image side surface of the second lens. By limiting the ratio of the curvature radius of the image side surface of the second lens to the effective focal length of the optical system, the second lens has a smaller bending degree, and the generation rate of the ghost image is reduced.

[0018] In one embodiment, the optical system satisfies the condition: ET2 / CT2≤3.3; wherein ET2 is the edge thickness of the second lens at the maximum effective diameter, and CT2 is the thickness of the second lens at the optical axis. By limiting the ratio of the edge thickness of the second lens at the maximum effective diameter to the thickness at the optical axis, the difficulty of forming the second lens is reduced, the manufacturability of the second lens is ensured, and the yield is improved.

[0019] In one embodiment, the optical system satisfies the condition: 3<f3 / f<6; wherein f3 is the focal length of the third lens. By limiting the range of the ratio of the focal length of the third lens to the effective focal length of the optical system, the optical system has the characteristics of wide viewing angle, low sensitivity and miniaturization, which is beneficial to correcting system aberration and improving imaging resolution.

[0020] In one embodiment, the optical system satisfies the condition: 3mm<CT3<4.5mm; wherein CT3 is the thickness of the third lens at the optical axis. By limiting the thickness of the third lens at the optical axis, the system aberration is corrected, and the imaging resolution is improved.

[0021] In one embodiment, the optical system satisfies the condition: 0.6<ΣCT / L<0.8; wherein ΣCT is the sum of the thicknesses of the first lens, the second lens, the third lens, the fourth lens and the fifth lens of the optical system at the optical axis, and L is the distance from the object side of the first lens to the image side of the fifth lens of the optical system at the optical axis. By limiting ΣCT / L, the total length of the optical system can be effectively shortened, the structure between the lenses is compact, the sensitivity is reduced, and the service life of the lens is prolonged.

[0022] In a second aspect, the application provides a lens module, comprising a lens barrel and the optical system of any one of the preceding embodiments, wherein the optical system is installed in the lens barrel.

[0023] In a third aspect, the application provides a terminal device comprising the lens module.

[0024] By limiting the surface shape, the vergence and TTL / (ImgH*2) of the first to fifth lenses in the optical system, and by forming a cemented lens by bonding the fourth lens and the fifth lens, the lens module has good optical performance, improves user experience, and can obtain excellent optical quality. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the background art, the drawings needed to be used in the embodiments of the application or the background art will be described below.

[0026] Figure 1 is a schematic diagram of the optical system provided by the present application applied in a terminal device;

[0027] Figure 2 is a structural schematic diagram of the optical system provided by the first embodiment of the present application;

[0028] Figure 3 is the spherical aberration curve of the optical system of the first embodiment;

[0029] Figure 4 is the astigmatism curve of the optical system of the first embodiment;

[0030] Figure 5 is the distortion curve of the optical system of the first embodiment;

[0031] Figure 6 is a structural schematic diagram of the optical system provided by the second embodiment of the present application;

[0032] Figure 7 is the spherical aberration curve of the optical system of the second embodiment;

[0033] Figure 8 is the astigmatism curve of the optical system of the second embodiment;

[0034] Figure 9 is the distortion curve of the optical system of the second embodiment;

[0035] Figure 10 is a structural schematic diagram of the optical system provided by the third embodiment of the present application;

[0036] Figure 11 is the spherical aberration curve of the optical system of the third embodiment;

[0037] Figure 12 is the astigmatism curve of the optical system of the third embodiment;

[0038] Figure 13 is the distortion curve of the optical system of the third embodiment;

[0039] Figure 14 is a structural schematic diagram of the optical system provided by the fourth embodiment of the present application;

[0040] Figure 15 is the spherical aberration curve of the optical system of the fourth embodiment;

[0041] Figure 16 is the astigmatism curve of the optical system of the fourth embodiment;

[0042] Figure 17 is the distortion curve of the optical system of the fourth embodiment. DETAILED DESCRIPTION

[0043] Embodiments of the present application will be described below with reference to the accompanying drawings.

[0044] Referring to Figure 1 The optical system 10 provided by the present application is applied to a lens module 20 in a terminal device 30. The terminal device 30 can be a mobile phone, a monitoring device, a vehicle-mounted device, or the like. The optical system 10 can be a super-wide-angle lens. The optical system 10 is installed in a lens barrel of the lens module 20, and the lens module 20 is assembled inside the terminal device 30.

[0045] In an embodiment, the optical system provided by the present application includes five lenses. The five lenses are sequentially arranged along the optical axis direction from the object side to the image side as a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The fourth lens and the fifth lens form a cemented lens, and the cemented lens has positive refractive power.

[0046] Specifically, the surface shape and the refractive power of the five lenses are as follows:

[0047] The first lens has negative refractive power; the second lens has negative refractive power; the third lens has positive refractive power; the fourth lens has negative refractive power, and the object side surface of the fourth lens near the optical axis is a convex surface, and the image side surface of the fourth lens near the optical axis is a concave surface; and the fifth lens has positive refractive power, and the object side surface of the fifth lens near the optical axis is a convex surface, and the image side surface of the fifth lens near the optical axis is a convex surface.

[0048] The optical system further includes a diaphragm, which is located between the object side and the fourth lens.

[0049] The optical system satisfies the following condition formula: 4 < TTL / (ImgH*2) < 6; wherein TTL is the distance on the optical axis from the object side surface of the first lens to the imaging surface of the optical system, and ImgH is the half image height in the horizontal direction of the optical system.

[0050] Reasonable configuration of the surface shape and the refractive power of the first lens to the fifth lens, and the formation of the cemented lens by the fourth lens and the fifth lens are conducive to meeting the requirements of miniaturization and high imaging resolution of the optical system. At the same time, the appropriate ratio of TTL / (ImgH*2) is limited to achieve a shorter TTL, which is conducive to the compact structure of the optical system and ensures the stability of the optical system, and a high-pixel imaging system is obtained.

[0051] The aspherical surface curve equation of the second lens to the fifth lens is as follows:

[0052]

[0053] wherein Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the surface vertex, r is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the aspherical surface vertex, k is the conic constant, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface shape formula.

[0054] The present application will be described in detail below through four specific embodiments.

[0055] Example 1

[0056] like Figure 2 As shown, the straight line in the middle represents the optical axis. The left side of the optical system is the object side, and the right side is the image side. In the optical system provided in this embodiment, along the optical axis from the object side to the image side, the components are, in sequence: first lens L1, second lens L2, third lens L3, aperture stop STO, fourth lens L4, fifth lens L5, infrared filter element IRCF, and protective glass CG. The fourth lens L4 and the fifth lens L5 are cemented lenses, which helps reduce the assembly sensitivity of the optical system, solves lens manufacturing and assembly problems, and improves yield.

[0057] The first lens L1 has negative refractive power and is made of glass. Its object-side surface S1 is convex near the optical axis, and its image-side surface S2 is concave near the optical axis. Both are spherical.

[0058] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is concave near the optical axis, and its image-side surface S4 is concave near the optical axis. Both are aspherical.

[0059] The third lens L3 has positive refractive power and is made of plastic. Its object-side surface S5 is convex near the optical axis, and its image-side surface S6 is convex near the optical axis. Both are aspherical.

[0060] The fourth lens L4 has negative refractive power and is made of plastic. Its object-side surface S7 is convex near the optical axis, and its image-side surface S8 is concave near the optical axis. Both are aspherical.

[0061] The fifth lens L5 has positive refractive power and is made of plastic. Its object-side surface S9 is convex near the optical axis, and its image-side surface S10 is convex near the optical axis. Both are aspherical.

[0062] The aperture stop STO can be located between the object side of the optical system and the fourth lens L4. In this embodiment, the aperture stop STO is located after the third lens L3, tending to the middle position of the optical system, which is beneficial for balancing the aberrations of the optical system.

[0063] The infrared filter element IRCF is located after the fifth lens L5 and includes the object side S11 and the image side S12. The infrared filter element IRCF is used to filter out infrared light so that the light entering the imaging surface is visible light with a wavelength of 380nm-780nm. The infrared filter element IRCF is made of glass.

[0064] The protective glass CG is located after the infrared filter element IRCF and includes the object side S13 and the image side S14. The protective glass CG is used to protect the photosensitive element, preventing it from being exposed to the outside and protecting it from dust and other factors, thus ensuring image quality. The imaging surface S15 is the effective pixel area of ​​the electronic photosensitive element.

[0065] Table 1a shows the characteristics of the optical system in this embodiment, where the Y-radius (i.e., radius of curvature), thickness, and focal length are all in millimeters (mm).

[0066] Table 1a

[0067]

[0068] Where f is the effective focal length of the optical system, FNO is the aperture number of the optical system, and FOV is the horizontal field of view of the optical system.

[0069] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0070] Table 1b gives the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror S3, S4, S5, S6, S7, S8 / S9, S10 in the first embodiment.

[0071] Table 1b

[0072]

[0073]

[0074] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as one surface in the data.

[0075] Figure 3 The spherical aberration curve of the optical system of the first embodiment is shown, which represents the deviation of the focal point of light of different wavelengths after passing through each lens of the optical system;

[0076] Figure 4 The astigmatism curves of the optical system of the first embodiment are shown, which represent the meridional image plane curvature and the sagittal image plane curvature;

[0077] Figure 5 The distortion curve of the optical system of the first embodiment is shown, which represents the distortion magnitude value corresponding to different field of view angles;

[0078] according toFigure 3 , Figure 4 and Figure 5 It can be seen that the optical system given in the first embodiment can achieve good imaging quality.

[0079] Example 2

[0080] like Figure 6 As shown, the straight line in the middle represents the optical axis. The left side of the optical system is the object side, and the right side is the image side. In the optical system provided in this embodiment, along the optical axis from the object side to the image side, the components are, in sequence: first lens L1, second lens L2, third lens L3, aperture stop STO, fourth lens L4, fifth lens L5, infrared filter element IRCF, and protective glass CG. The fourth lens L4 and the fifth lens L5 are cemented lenses, which helps reduce the assembly sensitivity of the optical system, solves lens manufacturing and assembly problems, and improves yield.

[0081] The first lens L1 has negative refractive power and is made of glass. Its object-side surface S1 is convex near the optical axis, and its image-side surface S2 is concave near the optical axis. Both are spherical.

[0082] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is concave near the optical axis, and its image-side surface S4 is concave near the optical axis. Both are aspherical.

[0083] The third lens L3 has positive refractive power and is made of plastic. Its object-side surface S5 is convex near the optical axis, and its image-side surface S6 is convex near the optical axis. Both are aspherical.

[0084] The fourth lens L4 has negative refractive power and is made of plastic. Its object-side surface S7 is convex near the optical axis, and its image-side surface S8 is concave near the optical axis. Both are aspherical.

[0085] The fifth lens L5 has positive refractive power and is made of plastic. Its object-side surface S9 is convex near the optical axis, and its image-side surface S10 is convex near the optical axis. Both are aspherical.

[0086] The other structures of Embodiment 2 are the same as those of Embodiment 1, and can be referred to accordingly.

[0087] Table 2a shows the characteristics of the optical system in this embodiment, where the Y-radius (i.e., radius of curvature), thickness, and focal length are all in millimeters (mm).

[0088] Table 2a

[0089]

[0090]

[0091] Where f is the effective focal length of the optical system, FNO is the aperture number of the optical system, and FOV is the horizontal field of view of the optical system.

[0092] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0093] Table 2b gives the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror S3, S4, S5, S6, S7, S8 / S9, S10 in the second embodiment.

[0094] Table 2b

[0095]

[0096] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0097] Figure 7 The spherical aberration curve of the optical system of the second embodiment is shown, which represents the deviation of the focal point of light of different wavelengths after passing through each lens of the optical system;

[0098] Figure 8 The astigmatism curves of the optical system of the second embodiment are shown, which represent the meridional image plane curvature and the sagittal image plane curvature.

[0099] Figure 9 The distortion curves of the optical system of the second embodiment are shown, which represent the distortion magnitude values ​​corresponding to different field of view angles;

[0100] according to Figure 7 , Figure 8 and Figure 9 It can be seen that the optical system given in the second embodiment can achieve good imaging quality.

[0101] Example 3

[0102] like Figure 10 As shown, the straight line in the middle represents the optical axis. The left side of the optical system is the object side, and the right side is the image side. In the optical system provided in this embodiment, along the optical axis from the object side to the image side, the components are, in sequence: first lens L1, second lens L2, third lens L3, aperture stop STO, fourth lens L4, fifth lens L5, infrared filter element IRCF, and protective glass CG. The fourth lens L4 and the fifth lens L5 are cemented lenses, which helps reduce the assembly sensitivity of the optical system, solves lens manufacturing and assembly problems, and improves yield.

[0103] The first lens L1 has negative refractive power and is made of glass. Its object-side surface S1 is convex near the optical axis, and its image-side surface S2 is concave near the optical axis. Both are spherical.

[0104] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is concave near the optical axis, and its image-side surface S4 is concave near the optical axis. Both are aspherical.

[0105] The third lens L3 has positive refractive power and is made of plastic. Its object-side surface S5 is convex near the optical axis, and its image-side surface S6 is convex near the optical axis. Both are aspherical.

[0106] The fourth lens L4 has negative refractive power and is made of plastic. Its object-side surface S7 is convex near the optical axis, and its image-side surface S8 is concave near the optical axis. Both are aspherical.

[0107] The fifth lens L5 has positive refractive power and is made of plastic. Its object-side surface S9 is convex near the optical axis, and its image-side surface S10 is convex near the optical axis. Both are aspherical.

[0108] The other structures of Embodiment 3 are the same as those of Embodiment 1, and can be referred to accordingly.

[0109] Table 3a shows the characteristics of the optical system in this embodiment, where the Y-radius (i.e., radius of curvature), thickness, and focal length are all in millimeters (mm).

[0110] Table 3a

[0111]

[0112] Where f is the effective focal length of the optical system, FNO is the aperture number of the optical system, and FOV is the horizontal field of view of the optical system.

[0113] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0114] Table 3b gives the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror S3, S4, S5, S6, S7, S8 / S9, S10 in the third embodiment.

[0115] Table 3b

[0116]

[0117]

[0118] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0119] Figure 11 The spherical aberration curve of the optical system of the third embodiment is shown, which represents the deviation of the focal point of light of different wavelengths after passing through each lens of the optical system;

[0120] Figure 12 The astigmatism curves of the optical system of the third embodiment are shown, which represent the meridional image plane curvature and the sagittal image plane curvature.

[0121] Figure 13 The distortion curve of the optical system of the third embodiment is shown, which represents the distortion magnitude value corresponding to different field of view angles;

[0122] according to Figure 11 , Figure 12 and Figure 13 It can be seen that the optical system given in the third embodiment can achieve good imaging quality.

[0123] Example 4

[0124] like Figure 14 As shown, the straight line in the middle represents the optical axis. The left side of the optical system is the object side, and the right side is the image side. In the optical system provided in this embodiment, along the optical axis from the object side to the image side, the components are, in sequence: first lens L1, second lens L2, third lens L3, aperture stop STO, fourth lens L4, fifth lens L5, infrared filter element IRCF, and protective glass CG. The fourth lens L4 and the fifth lens L5 are cemented lenses, which helps reduce the assembly sensitivity of the optical system, solves lens manufacturing and assembly problems, and improves yield.

[0125] The first lens L1 has negative refractive power and is made of glass. Its object-side surface S1 is convex near the optical axis, and its image-side surface S2 is concave near the optical axis. Both are spherical.

[0126] The second lens L2 has negative refractive power and is made of plastic. Its object-side surface S3 is concave near the optical axis, and its image-side surface S4 is concave near the optical axis. Both are aspherical.

[0127] The third lens L3 has positive refractive power and is made of plastic. Its object-side surface S5 is convex near the optical axis, and its image-side surface S6 is convex near the optical axis. Both are aspherical.

[0128] The fourth lens L4 has negative refractive power and is made of plastic. Its object-side surface S7 is convex near the optical axis, and its image-side surface S8 is concave near the optical axis. Both are aspherical.

[0129] The fifth lens L5 has positive refractive power and is made of plastic. Its object-side surface S9 is convex near the optical axis, and its image-side surface S10 is convex near the optical axis. Both are aspherical.

[0130] The other structures of Embodiment 4 are the same as those of Embodiment 1, and can be referred to accordingly.

[0131] Table 4a shows the characteristics of the optical system in this embodiment, where the Y-radius (i.e., radius of curvature), thickness, and focal length are all in millimeters (mm).

[0132] Table 4a

[0133]

[0134]

[0135] Where f is the effective focal length of the optical system, FNO is the aperture number of the optical system, and FOV is the horizontal field of view of the optical system.

[0136] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0137] Table 4b gives the higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each aspherical mirror S3, S4, S5, S6, S7, S8 / S9, S10 in the fourth embodiment.

[0138] Table 4b

[0139]

[0140] S8 / S9 refers to the image-side surface of the fourth lens and the object-side surface of the fifth lens. The image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are glued together, so they are represented as a single surface in the data.

[0141] Figure 15 The spherical aberration curve of the optical system of the fourth embodiment is shown, which represents the deviation of the focal point of light of different wavelengths after passing through each lens of the optical system;

[0142] Figure 16 The astigmatism curves of the optical system of the fourth embodiment are shown, which represent the meridional image plane curvature and the sagittal image plane curvature.

[0143] Figure 17 The distortion curves of the optical system of the fourth embodiment are shown, which represent the distortion magnitude values ​​corresponding to different field of view angles;

[0144] according toFigure 15 , Figure 16 and Figure 17 It can be seen that the optical system given in the fourth embodiment can achieve good imaging quality.

[0145] Table 5 shows the TTL / (ImgH*2) values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 5, each embodiment satisfies the condition: 4 < TTL / (ImgH*2) < 6.

[0146] Table 5

[0147] TTL / (ImgH*2) First embodiment 4.54 Second embodiment 4.54 Third embodiment 4.54 Fourth embodiment 4.54

[0148] Table 6 shows the FOV / CRA values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 6, each embodiment satisfies the condition: 11.8 < FOV / CRA < 21.

[0149] Table 6

[0150] FOV / CRA First embodiment 12.19 Second embodiment 12.27 Third embodiment 12.04 Fourth embodiment 11.96

[0151] Table 7 shows the f1 / f values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 7, all embodiments satisfy the condition: -6 <f1 / f<0。

[0152] Table 7

[0153] f1 / f First embodiment -5.92 Second embodiment -5.71 Third embodiment -5.50 Fourth embodiment -5.45

[0154] Table 8 shows the RDY S3 / RDY S2 values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 8, each embodiment satisfies the condition: -78 < RDY S3 / RDY S2 < -15.

[0155] Table 8

[0156] RDY S3 / RDY S2 First embodiment -45.87 Second embodiment -49.23 Third embodiment -65.63 Fourth embodiment -48.90

[0157] Table 9 shows the f2 / f values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 9, all embodiments satisfy the condition: -5 <f2 / f<-1.5。

[0158] Table 9

[0159] f2 / f First embodiment -2.77 Second embodiment -2.65 Third embodiment -2.86 Fourth embodiment -2.88

[0160] Table 10 shows the RDY S4 / f values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 10, each embodiment satisfies the condition: RDY S4 / f < 1.69.

[0161] Table 10

[0162] RDY S4 / f First embodiment 1.53 Second embodiment 1.47 Third embodiment 1.58 Fourth embodiment 1.59

[0163] Table 11 shows the ET2 / CT2 values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 11, each embodiment satisfies the condition: ET2 / CT2≤3.3.

[0164] Table 11

[0165]

[0166]

[0167] Table 12 shows the f3 / f values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 12, all embodiments satisfy the condition: 3 <f3 / f<6。

[0168] Table 12

[0169] f3 / f First embodiment 4.30 Second embodiment 4.23 Third embodiment 4.41 Fourth embodiment 4.41

[0170] Table 13 shows the CT3 values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 13, all embodiments satisfy the condition: 3 <CT3<4.5。

[0171] Table 13

[0172] CT3 First embodiment 3.50 Second embodiment 3.50 Third embodiment 3.80 Fourth embodiment 4.00

[0173] Table 14 shows the f45 / f values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 14, all embodiments satisfy the condition: 3.5. <f45 / f<7。

[0174] Table 14

[0175] f45 / f First embodiment 4.01 Second embodiment 3.78 Third embodiment 3.96 Fourth embodiment 4.02

[0176] Table 15 shows the CT5 / CT4 values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 15, each embodiment satisfies the condition: 1≤CT5 / CT4<5.

[0177] Table 15

[0178] CT5 / CT4 First embodiment 3.91 Second embodiment 4.43 Third embodiment 4.23 Fourth embodiment 4.23

[0179] Table 16 shows the ΣCT / L values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 16, each embodiment satisfies the condition: 0.6 < ΣCT / L < 0.8.

[0180] Table 16

[0181] ΣCT / L First embodiment 0.63 Second embodiment 0.63 Third embodiment 0.66 Fourth embodiment 0.68

[0182] Table 17 shows the nd4-nd5 values ​​of the optical systems in the first to fourth embodiments. As can be seen from Table 17, each embodiment satisfies the condition: nd4-nd5 > 0.

[0183] Table 17

[0184] nd4-nd5 First embodiment 0.12 Second embodiment 0.12 Third embodiment 0.12 Third embodiment 0.12

[0185] The above description is the preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. An optical system, characterized in that, Along the optical axis from the object side to the image side, the order is as follows: The first lens has negative refractive power; The second lens has negative refractive power; The third lens has positive refractive power; The fourth lens has negative refractive power. The object-side surface of the fourth lens near the optical axis is convex, and the image-side surface of the fourth lens near the optical axis is concave. The fifth lens has positive refractive power, and the image-side surface of the fifth lens near the optical axis is convex. The image-side surface of the fourth lens is in contact with the object-side surface of the fifth lens, and the optical system satisfies the following condition: 4 < TTL / (ImgH*2) < 6, and 1 ≤ CT5 / CT4 < 5; Wherein, TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the optical system, ImgH is the horizontal half-image height of the optical system, CT4 is the thickness of the fourth lens on the optical axis, and CT5 is the thickness of the fifth lens on the optical axis.

2. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: 11.8 < FOV / CRA < 21; Wherein, FOV is the horizontal field of view of the optical system, and CRA is the incident angle of the principal ray.

3. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: 3.5 <f45 / f<7; Where f45 is the combined focal length of the fourth lens and the fifth lens, and f is the effective focal length of the optical system.

4. The optical system according to claim 1, characterized in that, The object-side surface of the first lens near the optical axis is convex, and the image-side surface of the first lens near the optical axis is concave. The object-side surface of the second lens near the optical axis is concave, and the image-side surface of the second lens near the optical axis is also concave. The object-side surface of the third lens near the optical axis is convex, and the image-side surface of the third lens near the optical axis is also convex.

5. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: nd4-nd5>0; Wherein, nd4 is the refractive index of the fourth lens, and nd5 is the refractive index of the fifth lens.

6. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: -6 <f1 / f<0; Where f1 is the focal length of the first lens, and f is the effective focal length of the optical system.

7. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: -78 < RDY S3 / RDY S2 < -15; Wherein, RDY S2 is the radius of curvature of the image side of the first lens, and RDY S3 is the radius of curvature of the object side of the second lens.

8. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: -5 <f2 / f<-1.5; Where f2 is the focal length of the second lens, and f is the effective focal length of the optical system.

9. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: RDY S4 / f < 1.69; Wherein, RDY S4 is the radius of curvature of the image-side surface of the second lens, and f is the effective focal length of the optical system.

10. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: ET2 / CT2≤3.3; Wherein, ET2 is the thickness at the maximum effective diameter of the second lens, and CT2 is the thickness of the second lens at the optical axis.

11. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: 3 <f3 / f<6; Where f3 is the focal length of the third lens, and f is the effective focal length of the optical system.

12. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: 3mm <CT3<4.5mm; Wherein, CT3 is the thickness of the third lens at the optical axis.

13. The optical system according to claim 1, characterized in that, The optical system satisfies the following condition: 0.6 < ΣCT / L < 0.8; Wherein, ΣCT is the total thickness of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens of the optical system on the optical axis, and L is the distance on the optical axis from the object side of the first lens to the image side of the fifth lens.

14. A lens module, characterized in that, It includes a lens barrel and an optical system as described in any one of claims 1 to 13, wherein the optical system is mounted within the lens barrel.

15. A terminal device, characterized in that, Includes the lens module as described in claim 14.

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