Lens system, optical fingerprint device and electronic device

Abstract

Embodiments of the present application provide a lens system, an optical fingerprint device and an electronic device. The lens system comprises: a first lens, a second lens and a third lens arranged in sequence from an object side to an image side; the first lens is a negative lens, the first lens has a concave surface facing the object side and a concave surface facing the image side; the second lens is a positive lens, the second lens has a convex surface facing the object side and a convex surface facing the image side; the third lens is a positive lens, the third lens has a convex surface facing the object side; the maximum image height Y' of the lens system on the imaging surface, the focal length f and the optical length CTL satisfy 1.25<|Y' / (f*CTL)|<1.45, wherein the optical length CTL is the distance from the surface of the first lens facing the object side to the imaging surface. Through the technical scheme, the maximum image height Y' of the designed lens system on the imaging surface, the focal length f and the optical length CTL satisfy 1.25<|Y' / (f*CTL)|<1.45, while the overall thickness of the lens system is reduced, the lens system can have better imaging quality.

Description

Technical Field

[0001] This application relates to the field of optical imaging, and more specifically, to lens systems, optical fingerprint devices, and electronic devices. Background Technology

[0002] The emergence of optical under-display fingerprint recognition has enabled mobile phones to eliminate physical fingerprint buttons, increasing the freedom of mobile phone appearance design, increasing the screen-to-body ratio, and improving the aesthetic design. It has now become one of the best solutions for mobile phone fingerprint recognition.

[0003] The increasing diversity of mobile phone functions necessitates the inclusion of more functional modules within a slim and lightweight body. Simultaneously, the market demands greater specialization in various hardware modules. Currently, mobile phone bodies generally allocate more space to the battery and speaker enclosure to ensure long battery life and high-quality sound. The under-display optical fingerprint recognition module is located below the phone's mid-frame; reducing the thickness of the optical fingerprint recognition module effectively expands the installation space for other modules.

[0004] Therefore, how to provide a thin, high-performance optical imaging system and fingerprint device is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a lens system, an optical fingerprint device, and an electronic device, wherein the lens system has a low thickness and high imaging performance.

[0006] In a first aspect, a lens system is provided, comprising: a first lens, a second lens, and a third lens arranged sequentially from the object side to the image side; the first lens is a negative power lens, having a concave surface facing the object side and a concave surface facing the image side; the second lens is a positive power lens, having a convex surface facing the object side and a convex surface facing the image side; the third lens is a positive power lens, having a convex surface facing the object side; the maximum image height Y', focal length f, and optical length CTL of the lens system on the imaging plane satisfy 1.25 < |Y' / (f*CTL)| < 1.45, wherein the optical length CTL is the distance from the object-facing surface of the first lens to the imaging plane.

[0007] Through the technical solutions of this application embodiment, the maximum image height Y', focal length f, and optical length CTL of the lens system on the imaging plane have a high correlation, affecting not only the overall size of the lens system but also its optical imaging performance. In this application embodiment, Y' / f can be used to characterize the maximum field of view (FOV) of the lens system; the larger Y' / f is, the larger the FOV of the lens system. In the design of the ratio |Y' / (f*CTL)|, the larger Y' / f is and the smaller the CTL is, the larger the ratio value of |Y' / (f*CTL)| can be, which is greater than 1.25. In other words, when |Y' / (f*CTL)|>1.25, a lens system with a smaller optical length and a larger FOV can be designed, thereby balancing the overall thickness of the lens system and the imaging quality. In addition, in this application embodiment, when |Y' / (f*CTL)|<1.45, the optical length CTL of the lens system can be limited from being too small, thus preventing it from affecting the imaging performance of the lens system. Therefore, through the technical solution of the embodiments of this application, the maximum image height Y', focal length f and optical length CTL of the lens system on the imaging plane are designed to satisfy 1.25<|Y' / (f*CTL)|<1.45. While taking into account reducing the overall thickness of the lens system, the lens system can be guaranteed to have better imaging quality.

[0008] In some possible implementations, the focal length f1 of the first lens, the focal length f3 of the third lens, and the optical length CTL satisfy -1.1 < f1*f3 / CTL < -0.65.

[0009] In this technical solution, f1 represents the refractive power of the first lens, and f3 represents the refractive power of the third lens. A larger f1 for the first lens allows the lens system to have a larger field of view (FOV), increasing the detection area. Furthermore, a larger f3 for the third lens shortens the distance between the third lens and the imaging plane of the lens system, thereby reducing the optical length (CTL) of the lens system. In the design of the f1*f3 / CTL ratio, a larger f1*f3 and a smaller CTL result in a larger ratio greater than -1.1. In other words, when f1*f3 / CTL > -1.1, a lens system with a smaller optical length and a larger FOV can be designed, thus balancing the overall thickness of the lens system and image quality. Additionally, in this embodiment, when f1*f3 / CTL < -0.65, the optical length (CTL) of the lens system is limited from being too small, thus preventing it from affecting the imaging performance of the lens system. Therefore, through the technical solution of the embodiments of this application, the focal length f1 of the first lens, the focal length f3 of the third lens, and the optical length CTL of the lens system are designed to satisfy -1.1 < f1*f3 / CTL < -0.65. While taking into account reducing the overall thickness of the lens system, the lens system can be guaranteed to have better imaging quality.

[0010] In some possible implementations, the optical length CTL satisfies 1.5 mm < CTL < 1.7 mm.

[0011] In this implementation, the optical length (CTL) of the lens system is between 1.5mm and 1.7mm. Compared with the large optical length of over 1.9mm in traditional lens systems, the thickness space required by the lens system can be compressed by 0.2mm to 0.4mm, which is beneficial for the installation and promotion of the lens system in thin electronic devices.

[0012] In some possible implementations, the optical power distribution of each lens in the lens system satisfies at least one of the following relationships: -1.5 < f1 / f2 < -1.2; 0.26 < f2 / f3 < 0.39; -1.61 < f1 / f2 / f3 ... 12 <-1.45; 0.85 < f2 / f 12 <1.19; 1.3 < f2 / f 23 <1.45; 3.71 < f3 / f 23 <4.95; 1 ​​< f 12 / f 23 <1.29; 1.51 < f 12 / f<1.65; 1.2<f 23 / f<1.45; where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f12 f is the combined focal length of the first and second lenses. 23 denoted as f, where f is the combined focal length of the second and third lenses, and f is the focal length of the lens system.

[0013] By implementing this method, while reducing the overall thickness of the lens system, the optical power distribution of the lens system can be further optimized, resulting in a more reasonable optical group structure. This allows for the control of aberrations to be reasonably distributed among the first, second, and third lenses, thereby further improving the optical imaging quality of the lens system.

[0014] In some possible implementations, the surface shape of each lens in the lens system satisfies at least one of the following relationships: 1.1 < f1 / r1 < 1.39; -0.55 < f1 / r2 < -0.31; 0.51 < f2 / r3 < 0.69; -1.59 < f2 / r4 < -1.41; 3.1 < f3 / r5 < 5.2; 1.4 < f3 / r6 < 3.7; where f1 is the focal length of the first lens, r1 is the radius of curvature of the object-side surface of the first lens, r2 is the radius of curvature of the image-side surface of the first lens, f2 is the focal length of the second lens, r3 is the radius of curvature of the object-side surface of the second lens, r4 is the radius of curvature of the image-side surface of the second lens, f3 is the focal length of the third lens, r5 is the radius of curvature of the object-side surface of the third lens, and r6 is the radius of curvature of the image-side surface of the third lens.

[0015] In this embodiment, the surface design of each lens is achieved by designing the ratio of focal length to radius of curvature of each lens in the lens system. This allows the lenses to work together to form a lens system with a smaller thickness, larger FOV, smaller aberrations, and smaller distortion, thus ensuring the overall performance of the lens system.

[0016] In some possible implementations, the surface shape of each lens in the lens system also satisfies at least one of the following relationships: -0.45 < r1 / r2 < -0.21; -3.9 < r3 / r4 < -1.95; 0.6 < r5 / r6 < 0.8.

[0017] By designing the proportional relationship between the radii of curvature of the two surfaces of the first, second, and third lenses in this embodiment, the radii of curvature of the two surfaces of each lens can be mutually constrained, preventing large differences in the radii of curvature and surface shape of the two surfaces of each lens, which could lead to a decrease in the manufacturing precision of the lens surfaces. A reasonable design of the radii of curvature of the first, second, and third lenses can reduce the sensitivity of each lens; that is, even if there are certain production and assembly tolerances in the production and assembly process, the optical imaging performance of the first, second, and third lenses can be guaranteed. This embodiment can improve the manufacturing yield of the lens system.

[0018] In some possible implementations, the thickness of each lens in the lens system on the optical axis satisfies at least one of the following relationships: 0.45 < CT1 / CT2 < 0.59; 2.21 < CT2 / CT3 < 3.1; where CT1 is the thickness of the first lens on the optical axis, CT2 is the thickness of the second lens on the optical axis, and CT3 is the thickness of the third lens on the optical axis.

[0019] In this embodiment, the thickness CT2 of the second lens on the optical axis is greater than the thickness CT1 of the first lens on the optical axis, and also greater than the thickness CT3 of the third lens on the optical axis. Using this thicker biconvex lens as the second lens not only gives it higher strength but also provides better aberration correction, thus improving the imaging quality of the lens system. Furthermore, the thicknesses of adjacent lenses in the lens system can mutually constrain each other, ensuring that the thickness of each lens in the lens system meets the manufacturing process requirements and that their imaging performance is mutually compatible. While maintaining the required imaging quality, this also makes the lens system more robust, effectively preventing damage from external forces and extending its service life.

[0020] In some possible implementations, the optical parameters of each lens in the lens system satisfy at least one of the following relationships: 1.5 < n1 < 1.6; 1.5 < n2 < 1.6; 1.5 < n3 < 1.6; where n1 is the refractive index of the first lens, n2 is the refractive index of the second lens, and n3 is the refractive index of the third lens.

[0021] In some possible implementations, at least one of the two surfaces of the first lens is aspherical, at least one of the two surfaces of the second lens is aspherical, and at least one of the two surfaces of the third lens is aspherical.

[0022] In some possible implementations, the lens system further includes an aperture stop disposed between the first lens and the second lens.

[0023] In some possible implementations, the system parameters of the lens system satisfy at least one of the following: field of view greater than 120°; F-number less than 2; distortion less than 6.5%.

[0024] In a second aspect, an optical fingerprint device is provided for being disposed below a display screen. The optical fingerprint device includes: a fingerprint image sensor, and a lens system as described in the first aspect or any possible embodiment of the first aspect; wherein the fingerprint image sensor is disposed below the lens system and is used to receive fingerprint light signals transmitted through the display screen and the lens system, and to process the fingerprint light signals to obtain a fingerprint image.

[0025] In some possible implementations, the thickness of the display screen is less than or equal to 1.2 mm, and / or the display screen is a flexible screen.

[0026] Thirdly, an electronic device is provided, comprising: a display screen, and an optical fingerprint device according to the second aspect or any possible embodiment of the second aspect; wherein the optical fingerprint device is disposed below the display screen to achieve under-display fingerprint detection. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of an electronic device to which the embodiments of this application may be applied.

[0028] Figure 2 A schematic structural diagram of a lens system is provided for an embodiment of this application.

[0029] Figure 3 Another schematic structural diagram of the lens system is provided for embodiments of this application.

[0030] Figure 4 yes Figure 3 The diagram shows the astigmatism and distortion curves of the lens system with the layout shown.

[0031] Figure 5 yes Figure 3 The MTF diagram of the lens system with the layout shown.

[0032] Figure 6 Another schematic structural diagram of the lens system is provided for embodiments of this application.

[0033] Figure 7 yes Figure 6 The diagram shows the astigmatism and distortion curves of the lens system with the layout shown.

[0034] Figure 8 yes Figure 6 The MTF diagram of the lens system with the layout shown.

[0035] Figure 9 Another schematic structural diagram of the lens system is provided for embodiments of this application.

[0036] Figure 10 yes Figure 9 The diagram shows the astigmatism and distortion curves of the lens system with the layout shown.

[0037] Figure 11 yes Figure 9 The MTF diagram of the lens system with the layout shown.

[0038] Figure 12 This is a schematic block diagram of an optical fingerprint device provided in an embodiment of this application.

[0039] Figure 13 This is a schematic structural diagram of an optical fingerprint device provided in an embodiment of this application.

[0040] Figure 14 This is a schematic block diagram of an electronic device provided in an embodiment of this application. Detailed Implementation

[0041] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0042] The embodiments of this application can be applied to optical fingerprint systems. As a common application scenario, the optical fingerprint system provided in the embodiments of this application can be applied to smartphones, tablets, and other mobile terminals or other electronic devices with displays; more specifically, in the above-mentioned electronic devices, the optical fingerprint system can be set in a partial area or the entire area under the display screen, thereby forming an under-display optical fingerprint system.

[0043] like Figure 1 The diagram shows a structural schematic of an electronic device to which this application embodiment can be applied. The electronic device 10 includes a display screen 120 and an optical fingerprint device 130, wherein the optical fingerprint device 130 is disposed in a partial area below the display screen 120. The optical fingerprint device 130 includes a fingerprint image sensor, which includes a sensor array 133 having multiple optical sensing units 131. The sensing area of ​​the sensor array 133 in the display screen 120 is the fingerprint detection area of ​​the optical fingerprint device 130. In some embodiments, the fingerprint detection area may be located within the display area of ​​the display screen 120.

[0044] It is understood that the area of ​​the fingerprint detection area may be different from the area of ​​the sensing array 133 of the optical fingerprint device 130. For example, through optical path design such as lens imaging, reflective folding optical path design, or other optical path design such as light convergence or reflection, the area of ​​the fingerprint detection area of ​​the optical fingerprint device 130 may be larger than the area of ​​the sensing array of the optical fingerprint device 130.

[0045] As an optional implementation method, such as Figure 1 As shown, the optical fingerprint device 130 includes a light detection section 134 and an optical component 132. The light detection section 134 includes a sensor array 133 and a reading circuit and other auxiliary circuits electrically connected to the sensor array 133. It can be fabricated on a single chip (die) using semiconductor technology, such as an optical imaging chip or a fingerprint image sensor. The optical component 132 can be disposed above the sensor array of the light detection section 134. It can specifically include a light guide layer or a light path guiding structure and other optical elements. The light guide layer or light path guiding structure is mainly used to guide reflected light from the finger surface to the sensor array for optical detection.

[0046] The light guide layer or optical path guiding structure of the optical component 132 can be implemented in various ways. For example, in some embodiments, the light guide layer or optical path guiding structure can be an optical lens layer, which has one or more lenses for converging the reflected light from the finger onto the sensing array of the light detection portion 134 below it, so that the sensing array can form an image based on the reflected light to obtain a fingerprint image of the finger. Optionally, the optical lens layer can also form a pinhole in the optical path of the lens unit. The pinhole can cooperate with the optical lens layer to expand the field of view of the optical fingerprint device, thereby improving the fingerprint imaging effect of the optical fingerprint device 130.

[0047] As an optional embodiment, the display screen 120 can be a display screen with self-emissive display units, such as an Organic Light-Emitting Diode (OLED) display screen or a Micro-LED display screen. Taking an OLED display screen as an example, the optical fingerprint device 130 can use the display unit (i.e., OLED light source) of the OLED display screen 120 located in the fingerprint detection area as the excitation light source for optical fingerprint detection. When the finger 140 is pressed on the fingerprint detection area, the display screen 120 emits a beam of light 111 towards the target finger 140 above the fingerprint detection area. This light 111 is reflected on the surface of the finger 140 to form reflected light or scattered through the inside of the finger 140 to form scattered light. In the relevant patent applications, for ease of description, the above-mentioned reflected light and scattered light are collectively referred to as reflected light. Because the ridges and valleys of a fingerprint have different light-reflecting abilities, the reflected light 151 from the fingerprint ridge and the reflected light 152 from the fingerprint valley have different light intensities. After passing through the optical component 132, the reflected light is received by the optical detection part 134 in the optical fingerprint device 130 and converted into a corresponding electrical signal, namely a fingerprint detection signal. Based on the fingerprint detection signal, fingerprint image data can be obtained, and fingerprint matching verification can be further performed, thereby realizing the optical fingerprint recognition function in the electronic device 10.

[0048] In other embodiments, the optical fingerprint device 130 may also employ a built-in light source or an external light source to provide the light signal for fingerprint detection. In this case, the optical fingerprint device 130 can be applied to a non-self-emissive display, such as a liquid crystal display or other passively illuminated display.

[0049] It should be understood that, in a specific implementation, the electronic device 10 also includes a transparent protective cover, which can be a glass cover or a sapphire cover, located above the display screen 120 and covering the front of the electronic device 10. This is because, in this embodiment, the so-called finger pressing on the display screen 120 actually refers to pressing on the cover above the display screen 120 or the surface of the protective layer covering the cover.

[0050] In the above-described embodiments, the optical component 132 may include a lens system formed by one or more lenses to transmit the fingerprint light signal formed after reflection or scattering by the finger. The design of this lens system affects the final fingerprint imaging quality and thus the fingerprint recognition effect; therefore, the design of this lens system is particularly important in the entire optical fingerprint system.

[0051] In some related technologies, the lens system has a relatively large thickness, for example, more than 1.9 mm. This thickness can also be characterized by the optical length of the lens system, which is the distance between the first lens facing the object side and the imaging plane of the lens system. This large thickness of the lens system results in a relatively large thickness for the optical fingerprint device it houses, which is detrimental to its installation in electronic devices.

[0052] Especially when the lens system and its optical fingerprint device are used under the display screen of electronic devices, it will affect the installation space of both under the display screen, and thus affect the application and promotion of the lens system and its optical fingerprint device in thin mid-to-high-end mobile phones.

[0053] In view of this, this application provides a novel lens system that can reduce the thickness of the lens system itself while maintaining superior imaging performance, which is conducive to the promotion and application of the lens system in more scenarios.

[0054] Figure 2 A schematic structural diagram of a lens system 200 provided in an embodiment of this application is shown.

[0055] like Figure 2 As shown, the lens system 200 includes a first lens 210, a second lens 220, and a third lens 230 arranged sequentially from the object side to the image side.

[0056] Specifically, the first lens 210 is a negative power lens, having a concave surface facing the object and a concave surface facing the image. The second lens 220 is a positive power lens, having a convex surface facing the object and a convex surface facing the image. The third lens 230 is a positive power lens, having a convex surface facing the object.

[0057] The maximum image height Y', focal length f, and optical length CTL of the lens system 200 on the imaging plane satisfy 1.25 < |Y' / (f*CTL)| < 1.45, where the optical length CTL is the distance from the object-oriented surface of the first lens 210 to the imaging plane of the lens system 200.

[0058] In this embodiment, the first lens 210 of the lens system 200, facing the object side, has a negative optical power, which enables the lens system 200 to obtain a larger object-side field of view. The second lens 220 of the lens system 200 has a positive optical power, which can converge light and shorten the overall optical length of the lens system 200. Furthermore, the third lens 230 of the lens system 200, facing the image side, also has a positive optical power, which can further converge light, shortening the overall optical length of the lens system 200 while ensuring the imaging quality of the imaging plane.

[0059] The first lens 210 has a concave surface facing the object side and a concave surface facing the image side, that is, the first lens 210 is a double concave lens. Both concave surfaces of the first lens 210 are located in the paraxial region of the first lens 210. During the imaging process of the lens system 200, the imaging quality of the paraxial region of the first lens 210 has a significant impact on the final imaging effect of the lens system 200. Therefore, in this embodiment, the surface design of the paraxial region of the first lens 210 can ensure the imaging performance of the first lens 210 throughout the entire lens system 200.

[0060] The second lens 220 has a convex surface facing the object side and a convex surface facing the image side, that is, the second lens 220 is a biconvex lens. The convex surfaces on both sides of the second lens 220 may also be located in the paraxial region of the second lens 220. Alternatively, in some other embodiments, for ease of manufacturing, all surfaces on both sides of the second lens 220 may be designed as convex surfaces.

[0061] The third lens 230 has a convex surface facing the object. Optionally, the surface of the third lens 230 facing the object and located in the paraxial region is convex. During the imaging process of the second lens 220, the design of the object-facing surface of the third lens 230 has a significant impact on the imaging of the entire lens system 200. Therefore, in this embodiment, the object-facing surface of the third lens 230 is designed to ensure the imaging performance of the third lens 230 in the entire lens system 200.

[0062] It should be noted that the surface shape of the third lens 230 facing the image side has little impact on the imaging performance of the lens system 200. Therefore, the surface of the third lens 230 facing the image side can be convex, concave, or flat. This application embodiment does not specifically limit it.

[0063] Furthermore, in addition to the surface design of the first lens 210, the second lens 220 and the third lens 230 described above, in the embodiments of this application, the maximum image height Y', focal length f and optical length CTL of the lens system 200 on the imaging plane satisfy 1.25 < |Y' / (f*CTL)| < 1.45.

[0064] Specifically, the maximum image height Y' of the lens system 200 on the imaging plane is the radius of the maximum imaging circle of the lens system 200 on the imaging plane. When the lens system 200 is applied to an optical fingerprint device, a fingerprint image sensor can be disposed on the imaging plane of the lens system 200, and the fingerprint image sensor may include the features described above. Figure 1 The light detection section 134 in the illustrated embodiment is used to detect the fingerprint light signal transmitted through the lens system 200.

[0065] The optical length CTL of the lens system 200 is the distance from the object-side surface of the first lens 210 to the imaging plane of the lens system 200. More specifically, the optical length CTL of the lens system 200 is the shortest distance between the vertex of the first lens 210 closest to the object side and the imaging plane of the lens system 200.

[0066] The maximum image height Y', focal length f, and optical length CTL of the lens system 200 exhibit a high correlation, affecting not only the overall size of the lens system 200 but also its optical imaging performance. In this embodiment, Y' / f can be used to characterize the maximum field of view (FOV) of the lens system 200; a larger Y' / f results in a larger FOV. In the design of the |Y' / (f*CTL)| ratio, a larger Y' / f and a smaller CTL allow |Y' / (f*CTL)| to have a larger ratio value greater than 1.25. In other words, when |Y' / (f*CTL)| > 1.25, a lens system 200 with a smaller optical length and a larger FOV can be designed, thus balancing the overall thickness of the lens system 200 and its imaging quality. Furthermore, in this embodiment, when |Y' / (f*CTL)|<1.45, the optical length CTL of the lens system 200 can be limited from being too small, thereby affecting the imaging performance of the lens system 200. Therefore, through the technical solution of this embodiment, the maximum image height Y', focal length f, and optical length CTL of the lens system 200 on the imaging plane are designed to satisfy 1.25<|Y' / (f*CTL)|<1.45, which can ensure that the lens system 200 has better imaging quality while reducing the overall thickness of the lens system 200.

[0067] In some applications, when the lens system is positioned below the display screen, the thickness of the display screen can be used to transmit optical signals. However, when the display screen thickness decreases—for example, from 1.5mm for a rigid screen to 1mm for a flexible screen—the total optical path length (TTL) between the lower surface of the display screen and the imaging surface of the lens system increases to ensure the total imaging optical path length from the object side (i.e., the upper surface of the display screen) to the imaging surface. This means that when the lens system is applied to a thinner flexible screen, it requires more under-screen space.

[0068] Through the technical solutions of the embodiments of this application, a lens system 200 with a smaller thickness can be designed, which is less than the thickness of a traditional lens system. By reducing the overall thickness of the lens system 200, it can be well applied to thinner flexible screens, supporting its application in mid-to-high-end mobile phones with flexible screens currently in mainstream products. Alternatively, the lens system 200 with a smaller thickness provided in the embodiments of this application can also be applied to traditionally thicker rigid screens, reducing the thickness space occupied by the lens system 200 below the rigid screen, which is beneficial for reducing the thickness of rigid screen mobile phones or providing more space for other components in rigid screen mobile phones.

[0069] In addition to the above-mentioned design of lens system 200 to satisfy 1.25<|Y' / (f*CTL)|<1.45 to ensure that lens system 200 has better imaging performance and smaller thickness, this application also provides another technical solution, namely, designing lens system 200 to satisfy -1.1<f1*f3 / CTL<-0.65, which can also ensure that lens system 200 has better imaging performance and smaller thickness, where f1 is the focal length of the first lens 210 and f3 is the focal length of the third lens 230.

[0070] In this technical solution, f1 represents the refractive power of the first lens 210, and f3 represents the refractive power of the third lens 230. With a larger f1 for the first lens 210, the lens system 200 can have a larger field of view (FOV), increasing its detection area. Furthermore, with a larger f3 for the third lens 230, the distance between the third lens 230 and the imaging plane of the lens system 200 can be shortened, thereby reducing the optical length (CTL) of the lens system 200. In the design of the f1*f3 / CTL ratio, a larger f1*f3 and a smaller CTL result in a larger ratio value greater than -1.1. In other words, when f1*f3 / CTL > -1.1, a lens system 200 with a smaller optical length and a larger FOV can be designed, thus balancing the overall thickness of the lens system 200 and its image quality. Furthermore, in this embodiment, when f1*f3 / CTL < -0.65, the optical length CTL of the lens system 200 can be limited from being too small, thereby affecting the imaging performance of the lens system 200. Therefore, through the technical solution of this embodiment, the focal length f1 of the first lens, the focal length f3 of the third lens, and the optical length CTL of the lens system 200 are designed to satisfy -1.1 < f1*f3 / CTL < -0.65, which can ensure that the lens system 200 has better imaging quality while reducing the overall thickness of the lens system 200.

[0071] It should be noted that, in one embodiment of this application, the lens system 200 may be designed to satisfy only 1.25 < |Y' / (f*CTL)| < 1.45; or, in another embodiment of this application, the lens system 200 may be designed to satisfy only -1.1 < f1*f3 / CTL < -0.65; or, in a third embodiment of this application, the lens system 200 may be designed to satisfy both 1.25 < |Y' / (f*CTL)| < 1.45 and -1.1 < f1*f3 / CTL < -0.65. This allows for a comprehensive reduction in the overall thickness of the lens system 200 through multi-dimensional parameter design, while ensuring that the lens system 200 has superior imaging quality.

[0072] Optionally, in any of the above embodiments, the optical length CTL can satisfy 1.5mm < CTL < 1.7mm.

[0073] In this embodiment, the optical length CTL of the lens system 200 is between 1.5mm and 1.7mm. Compared with the large optical length of the traditional lens system 200 (over 1.9mm), the thickness space required by the lens system 200 can be compressed by 0.2mm to 0.4mm, which is beneficial for the installation and promotion of the lens system 200 in thin electronic devices.

[0074] Optionally, in some embodiments, the optical power distribution of each lens in the lens system 200 may satisfy at least one of the following relationships:

[0075] -1.5 < f1 / f2 < -1.2;

[0076] 0.26 < f2 / f3 < 0.39;

[0077] -1.61 < f1 / f 12 <-1.45;

[0078] 0.85 < f2 / f 12 <1.19;

[0079] 1.3 < f2 / f 23 <1.45;

[0080] 3.71 < f3 / f 23 <4.95;

[0081] 1 < f 12 / f 23 <1.29;

[0082] 1.51 < f 12 / f<1.65;

[0083] 1.2 < f 23 / f<1.45;

[0084] Where f1 is the focal length of the first lens 210, f2 is the focal length of the second lens 220, f3 is the focal length of the third lens 230, and f 12 f is the combined focal length of the first lens 210 and the second lens 220. 23 f is the combined focal length of the second lens 220 and the third lens 230, and f is the overall focal length of the lens system 200.

[0085] By means of the technical solution of this embodiment, while taking into account the reduction of the overall thickness of the lens system 200, the optical power distribution of the lens system 200 can be further optimized, so that the lens system 200 can obtain a more reasonable optical group structure, and control the aberration to be reasonably distributed among the first lens 210, the second lens 220 and the third lens 230, thereby further improving the optical imaging quality of the lens system 200.

[0086] Optionally, in some embodiments, the surface profile of each lens in the lens system 200 may satisfy at least one of the following relationships:

[0087] 1.1 < f1 / r1 < 1.39;

[0088] -0.55 < f1 / r2 < -0.31;

[0089] 0.51 < f2 / r3 < 0.69;

[0090] -1.59 < f2 / r4 < -1.41;

[0091] 3.1 < f3 / r5 < 5.2;

[0092] 1.4 < f3 / r6 < 3.7;

[0093] Wherein, r1 is the radius of curvature of the surface of the first lens 210 facing the object side, r2 is the radius of curvature of the surface of the first lens 210 facing the image side, r3 is the radius of curvature of the surface of the second lens 220 facing the object side, r4 is the radius of curvature of the surface of the second lens 220 facing the image side, r5 is the radius of curvature of the surface of the third lens 230 facing the object side, and r6 is the radius of curvature of the surface of the third lens 230 facing the image side.

[0094] Specifically, for the three lenses in the lens system 200, the surface shape of each lens can be designed by designing the ratio of the focal length to the radius of curvature of each lens.

[0095] For the first lens 210, the relationship between its focal length f1 and the radii of curvature r1 and r2 of the two surfaces can satisfy 1.1 < f1 / r1 < 1.39 and / or -0.55 < f1 / r2 < -0.31. Through reasonable curvature distribution and surface design of the first lens 210, it is beneficial for the lens system 200 to obtain a larger FOV, and effectively correct the aberrations caused by large-angle incident light due to the large FOV, reduce the imaging pressure of subsequent optical elements, and effectively improve the imaging quality.

[0096] For the second lens 220, the relationship between its focal length f2 and the radii of curvature r3 and r4 of the two surfaces can satisfy 0.51 < f2 / r3 < 0.69 and / or -1.59 < f2 / r4 < -1.41. Through reasonable curvature distribution and surface design of the second lens 220, the second lens 220 can effectively converge light and further correct aberrations, control the distortion generated by the lens system 200, and thus further improve the imaging quality of the lens system 200.

[0097] For the third lens 230, the relationship between its focal length f3 and the radii of curvature r5 and r6 of the two surfaces can satisfy 3.1 < f3 / r5 < 5.2 and / or 1.4 < f3 / r6 < 3.7. Through reasonable curvature distribution and surface design of the third lens 230, the third lens 230 can further converge light and further correct aberrations, ensuring the imaging height on the imaging surface and comprehensively improving the imaging quality of the lens system 200.

[0098] In summary, by designing the ratio of focal length to radius of curvature of each lens in the lens system 200, the surface shape of each lens is designed, so that the lenses cooperate with each other to form a lens system 200 with a small thickness, large FOV, small aberration and small distortion, thus ensuring the overall performance of the lens system 200.

[0099] Optionally, in some embodiments, the surface profile of each lens in the lens system 200 may satisfy at least one of the following relationships:

[0100] -0.45 < r1 / r2 < -0.21;

[0101] -3.9 < r3 / r4 < -1.95;

[0102] 0.6 < r5 / r6 < 0.8.

[0103] By designing the proportional relationship between the radii of curvature of the two surfaces of the first lens 210, the second lens 220, and the third lens 230 through the technical solution of this embodiment, the radii of curvature of the two surfaces of each lens can be mutually constrained, preventing large differences in the radii of curvature and surface shape of the two surfaces of each lens, which would lead to a decrease in the manufacturing precision of the lens surface. The reasonable design of the radii of curvature of the first lens 210, the second lens 220, and the third lens 230 can reduce the sensitivity of each lens; that is, even if the first lens 210, the second lens 220, and the third lens 230 have certain production and assembly tolerances during production and assembly, the optical imaging performance of the first lens 210, the second lens 220, and the third lens 230 can still be guaranteed. Through the technical solution of this embodiment, the manufacturing yield of the lens system 200 can be improved.

[0104] Optionally, in some embodiments, the thickness of each lens in the lens system 200 along the optical axis satisfies at least one of the following relationships:

[0105] 0.45 < CT1 / CT2 < 0.59;

[0106] 2.21 < CT2 / CT3 < 3.1;

[0107] Wherein, CT1 is the thickness of the first lens 210 on the optical axis, CT2 is the thickness of the second lens 220 on the optical axis, and CT3 is the thickness of the third lens 230 on the optical axis.

[0108] Specifically, the thickness of each lens in the lens system 200 along the optical axis characterizes the strength of each lens; a thicker lens generally indicates greater strength. In the technical solution of this application embodiment, the thickness CT2 of the second lens 220 along the optical axis is greater than the thickness CT1 of the first lens 210 and greater than the thickness CT3 of the third lens 230. Using this thicker biconvex lens as the second lens 220 not only gives it higher strength but also better aberration correction, thus improving the imaging quality of the lens system 200. Furthermore, the thicknesses of adjacent lenses in the lens system 200 can mutually constrain each other, ensuring that the thickness of each lens in the lens system 200 meets the manufacturing process requirements and that their imaging performance is compatible. While maintaining the imaging quality of the lens system 200, this also makes the lens system 200 more robust, effectively preventing damage from external forces and extending its service life.

[0109] Optionally, in some embodiments, the optical parameters of each lens in the lens system 200 satisfy at least one of the following relationships:

[0110] 1.5 < n1 < 1.6;

[0111] 1.5 < n² < 1.6;

[0112] 1.5 < n3 < 1.6.

[0113] Wherein, n1 is the refractive index of the first lens 210, n2 is the refractive index of the second lens 220, and n3 is the refractive index of the third lens 230.

[0114] Through the technical solution of this embodiment, the first lens 210, the second lens 220, and the third lens 230 in the lens system 200 can be lenses with low refractive index. Refractive index is also important for the image quality of the lens. Using lenses with lower refractive index to design the lens system 200 can effectively reduce the chromatic aberration of the lens system 200 and provide a proper balance of aberrations.

[0115] Optionally, in order to effectively reduce the manufacturing cost of the lens system 200, the material of each lens in the lens system 200 can be resin or plastic. This embodiment provides a low-cost, low-refractive-index, and low-dispersion-coefficient resin or plastic for manufacturing the lenses in the lens system 200, thereby reducing the manufacturing cost of the lens system 200 while ensuring its optical imaging performance.

[0116] Optionally, in some embodiments, at least one of the two surfaces of the first lens 210 is aspherical, at least one of the two surfaces of the second lens 220 is aspherical, and at least one of the two surfaces of the third lens 230 is aspherical.

[0117] Through the technical solution of this embodiment, at least one surface of each lens in the lens system 200 can be aspherical. Compared with a spherical design, designing at least one surface of a lens as aspherical allows for more flexible surface design of the lens, thereby increasing the design freedom of the lens system 200. Furthermore, aspherical lenses can correct aberrations generated at the lens edges and eliminate spherical aberration in the lens system 200. Further, if the surface of the third lens 230 in the lens system 200 is designed aspherical, it can correct the residual aberrations of the first lens 210 and the second lens 220, improving the overall imaging quality of the lens system 200.

[0118] Optionally, in some embodiments, the lens system 200 further includes an aperture stop disposed between the first lens 210 and the second lens 220.

[0119] Through the technical solution of this embodiment, the aperture can be used to adjust the size of the light signal or the imaging range. By setting the aperture in the lens system 200, the light signal or imaging range received by the lens system 200 can be adjusted. When the lens system 200 is applied to an optical fingerprint device, the light signal carrying fingerprint information can be imaged onto the surface of the fingerprint image sensor to the greatest extent, enabling the fingerprint image sensor to obtain more fingerprint information and further improving the resolution of fingerprint recognition.

[0120] By designing the structure and / or parameters of the lens system 200 in any of the above embodiments, the lens system 200 can achieve better imaging performance. Specifically, the system parameters of the lens system 200 can satisfy at least one of the following: field of view (FOV) greater than 120°, F-number less than 2, or distortion less than 6.5%.

[0121] When the field of view (FOV) of the lens system 200 is greater than 120°, this large FOV ensures that the lens system 200 can have a sufficiently large object-side field of view while maintaining a small optical length, allowing the imaging surface to acquire enough object-side information. For example, when the lens system 200 is applied to an optical fingerprint device, the optical fingerprint device can have a large fingerprint detection area, thereby facilitating the acquisition of sufficient fingerprint information for recognition and ensuring the accuracy of fingerprint recognition.

[0122] The F-number, also written as Fno, is a parameter representing the light-gathering capability of a lens. A smaller F-number means more light enters the lens per unit time, allowing for a shorter exposure time. In lens system 200, with an F-number less than 2, this smaller F-number enables a shorter exposure time, improving the detection capability of weak light signals. When lens system 200 is used in an under-display optical fingerprint device, it can adapt to the low transmittance environment of the screen, further enhancing the detection capability of weak fingerprint signals.

[0123] Lens distortion is used to measure the degree of visual distortion in an image. When the distortion of the lens system 200 is controlled within 6.5%, the imaging effect of the lens system 200 is superior. When the lens system 200 is applied to an under-display optical fingerprint device, controlling the distortion of the lens system 200 can reduce fingerprint ridge deformation caused by distortion, and also reduce the impact of moiré patterns caused by the screen structure on fingerprint imaging.

[0124] In summary, through the technical solutions of the embodiments of this application, the lens system 200 can be designed to have a large FOV, a small F number, and small distortion, thereby effectively improving the overall imaging performance of the lens system 200.

[0125] Figure 3 Another schematic structural diagram of the lens system 200 provided in this application embodiment is shown. Optionally, the lens system 200 may be disposed below the display screen 20 of an electronic device. The display screen 20 may be... Figure 1 The display screen 120 shown, for example, the display screen 20 can be an OLED display or other type of display screen. For ease of light path illustration, the left side of the display screen 20 is the side facing the outside of the electronic device, and the right side of the display screen 20 is the side facing the inside of the electronic device.

[0126] like Figure 3 As shown, in this lens system 200, from the object side to the image side, the following are arranged in sequence: a first lens 210, an aperture stop (not shown in the figure), a second lens 220, and a third lens 230. The object side is the side of the lens system 200 facing the display screen 20, and the image side is the side of the lens system 200 facing away from the display screen 20. A fingerprint image sensor may be disposed on one side of the image side.

[0127] To illustrate the lens system 200 provided in this application in more detail, the design parameters of the lens system 200 in several specific embodiments are given below.

[0128] In the following embodiments, the upper and lower surfaces of the display screen 20 are designated as S1 and S2 respectively, the two surfaces of the first lens 210 are designated as S3 and S4 respectively, the surface of the aperture is designated as S5, the two surfaces of the second lens 220 are designated as S6 and S7 respectively, the two surfaces of the third lens 230 are designated as S8 and S9 respectively, and the imaging surface of the lens system 200 is designated as S10.

[0129] Optionally, the optical length, focal length, and maximum image height of the lens system 200 can be designed according to the embodiments described above. Furthermore, the focal length, radius of curvature, thickness, and refractive index of the first lens 210, the second lens 220, and the third lens 230 in the lens system 200 can be designed to give the lens system 200 a smaller optical length and better optical imaging performance. For example, the lens system 200 can meet at least one of the following requirements: optical length CTL is between 1.5 mm and 1.7 mm, field of view (FOV) is greater than 120°, F-number is less than 2, or distortion is less than 6.5%.

[0130] Optionally, the lens system 200 can also be designed to have good optical imaging performance by taking at least one of the radius of curvature, thickness, material, effective diameter and conic coefficient of each surface (i.e. S1 to S10 above) in the lens system 200, and / or the aspherical higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A20, etc. of the aspherical lens in the lens system 200.

[0131] Example 1

[0132] The shapes of the components in the lens system 200 of this embodiment 1 can be seen in [reference]. Figure 3 As shown. In this embodiment 1, the focal length, radius of curvature, and thickness of the first lens 210, the second lens 220, and the third lens 230 in the lens system 200 can be designed using the proportions shown in Table 1 below. The radius of curvature, thickness, material, effective diameter, and conic coefficient of each surface S1 to S10 in the lens system 200 can be the parameters shown in Table 2 below, and the aspherical higher-order coefficients of the aspherical surfaces in S1 to S10 can be the parameters shown in Table 3 below.

[0133] Table 1

[0134]

[0135]

[0136] Table 2

[0137]

[0138] Table 3

[0139]

[0140]

[0141] It should be understood that blank positions corresponding to parameters in Tables 1 to 3 of this application embodiment indicate that the parameter is not present. In Table 1, "BK7" represents the model of optical glass, and "APL5014CL" represents the material of transparent resin. In Table 3, "E+02" represents "10 to the power of 2", and similarly, other values ​​can be deduced accordingly.

[0142] Based on the parameters shown in Tables 1 to 3, the parameters of the lens system 200 provided in this embodiment 1 are as follows: TTL = 2.995mm (distance between S2 and S10), CTL = 1.633mm (distance between S3 and S10), f = 0.328mm, Fno = 1.5, FOV = 134.9°.

[0143] Figures 4 to 5 The images shown are, in order, the astigmatism and distortion aberration curves and the magnitude (MTF) graph of the optical transfer function of the lens system 200 provided in Embodiment 1. Figure 4 Figure (a) in the figure is an astigmatism curve. Figure 4 Figure (b) in the figure is a curve showing the distortion difference.

[0144] from Figures 4 to 5 The simulation diagram shows that the maximum object height Y of the lens system 200 is approximately 5.0 mm. Therefore, the object-side field of view is relatively large, and the maximum distortion is approximately -5.8%. The lens system 200 exhibits good performance with a large object-side FOV, low distortion, and low dispersion and chromatic aberration.

[0145] Example 2

[0146] The shape of each component in the lens system 200 of this embodiment 2 can be seen in [reference]. Figure 6 As shown. In this embodiment 2, the focal length, radius of curvature, and thickness of the first lens 210, the second lens 220, and the third lens 230 in the lens system 200 can be designed using the corresponding proportions in Table 4 below. The radius of curvature, thickness, material, effective diameter, and conic coefficient of each surface S1 to S10 in the lens system 200 can be the parameters shown in Table 5 below, and the aspherical higher-order coefficients of the aspherical surfaces in S1 to S10 can be the parameters shown in Table 6 below.

[0147] Table 4

[0148]

[0149]

[0150] Table 5

[0151]

[0152]

[0153] Table 6

[0154]

[0155] Based on the parameters shown in Tables 4 to 6, the parameters of the lens system 200 provided in this embodiment 2 are as follows: TTL = 2.69mm (distance from S2 to S10), CTL = 1.595mm (distance between S3 and S10), f = 0.293mm, Fno = 1.45, FOV = 136°.

[0156] Figures 7 to 8 The images shown are, in order, the astigmatism and distortion aberration curves and the magnitude (MTF) of the optical transfer function of the lens system 200 provided in Embodiment 2. Figure 7 Figure (a) in the figure is an astigmatism curve. Figure 7 Figure (b) in the figure is a curve showing the distortion difference.

[0157] from Figures 7 to 8 The simulation diagram shows that the maximum object height Y of the lens system 200 is 4.74 mm, and the maximum distortion is approximately -6.2%. Furthermore, the lens system 200 has a relatively small F-number (Fno), i.e., 1.45, therefore, it can have a shorter exposure time.

[0158] Example 3

[0159] The shapes of the components in the lens system 200 of this embodiment 3 can be seen in [reference]. Figure 9 As shown. In this embodiment 3, the focal length, radius of curvature, and thickness of the first lens 210 and the second lens 220 in the lens system 200 can be designed using the proportions shown in Table 7 below. The radius of curvature, thickness, material, effective diameter, and conic coefficient of each surface S1 to S10 in the lens system 200 can be the parameters shown in Table 8 below, and the aspherical higher-order coefficients of the aspherical surfaces in S1 to S10 can be the parameters shown in Table 9 below.

[0160] Table 7

[0161]

[0162]

[0163] Table 8

[0164]

[0165] Table 9

[0166]

[0167]

[0168] Based on the parameters shown in Tables 7 to 9, the parameters of the lens system 200 provided in this embodiment 3 are as follows: TTL = 2.991mm (distance from S2 to S10), CTL = 1.629mm (distance between S3 and S10), f = 0.341mm, Fno = 1.45, FOV = 134.8°.

[0169] Figures 10 to 11 The images shown are, in order, the astigmatism and distortion aberration curves and the magnitude (MTF) of the optical transfer function of the lens system 200 provided in Embodiment 3. Figure 10 Figure (a) in the figure is an astigmatism curve. Figure 10 Figure (b) in the figure is a curve showing the distortion difference.

[0170] from Figures 10 to 11 The simulation diagram shows that the maximum object height Y of the lens system 200 is approximately 5.0 mm, and the maximum distortion is approximately -6%. Furthermore, the lens system 200 can also have a relatively small F-number (Fno), i.e., 1.45, and therefore can have a shorter exposure time.

[0171] In summary, in the several illustrative embodiments provided in this application, by designing the parameters of each lens in the lens system 200, the lens system 200 can have better imaging performance. Specifically, the lens system 200 can have a smaller optical length CTL, a larger FOV, a smaller F number, and smaller distortion.

[0172] In addition to the lens system 200 described above, this application also provides an optical fingerprint device.

[0173] Figure 12 A schematic block diagram of an optical fingerprint device 300 provided in an embodiment of this application is shown, such as... Figure 12 As shown, the optical fingerprint device 300 may include a lens system 200 and a fingerprint image sensor 310.

[0174] In some related embodiments, the optical fingerprint device 300 may also be referred to as a fingerprint recognition device or a fingerprint detection device. The optical fingerprint device 300 can generate a fingerprint image based on the optical imaging principle of the lens system 200, thereby performing fingerprint recognition or fingerprint detection.

[0175] Optionally, the optical fingerprint device 300 can be disposed below the display screen of an electronic device to achieve under-display fingerprint recognition or fingerprint detection.

[0176] Specifically, in this embodiment, the lens system 200 in the optical fingerprint device 300 can be any of the lens systems described in the above embodiments. The fingerprint image sensor 310 is disposed below the lens system 200 and is used to receive the fingerprint light signal transmitted by the lens system 200 and process the fingerprint light signal to obtain a fingerprint image.

[0177] Specifically, the fingerprint image sensor 310 can be disposed on the imaging surface of the lens system 200. In other words, the surface of the fingerprint image sensor 310 can be the imaging surface of the lens system 200.

[0178] The fingerprint light signal transmitted through the lens system 200 is a light signal that has been reflected or scattered by the finger, and therefore carries fingerprint information. The fingerprint image sensor 310 can convert the fingerprint light signal into an electrical signal, thereby forming a fingerprint image with fingerprint information.

[0179] It is understandable that, with the optical fingerprint device 300 positioned below the display screen, the fingerprint image sensor 310 can receive the fingerprint light signal transmitted through the display screen and the lens system 200. The specific fingerprint imaging process of the fingerprint image sensor 310 can be found above. Figure 1 The relevant descriptions of the embodiments shown will not be repeated here.

[0180] Figure 13 A schematic structural diagram of an optical fingerprint device 300 provided in an embodiment of this application is shown.

[0181] like Figure 13 As shown, the optical fingerprint device 300 is disposed below the display screen 20. The display screen 20 can provide a light source for the optical fingerprint device 300. Specifically, when a user presses their finger on the display screen 20, the display screen 20 can emit a light source signal to the user's finger. After being reflected or scattered by the finger, the light source signal forms a fingerprint light signal carrying fingerprint information.

[0182] The optical fingerprint device 300 may include a lens system 200 and a bracket 340 for mounting the lens system 200. Optionally, the first lens 210 and the second lens 220 in the lens system 200 may be interference-fitted into the bracket 340 to improve the overall reliability of the lens system 200.

[0183] Specifically, the bracket 340 can be used to control the defocus and eccentricity accuracy of the first lens 210 and the second lens 220 in the lens system 200, thereby improving the imaging performance of the lens system 200. The bracket 340 can be formed by metal stamping or by other methods, and this application does not specifically limit the method.

[0184] In addition to the lens system 200 and the bracket 340, the optical fingerprint device 300 also includes a circuit board 320, which is disposed below the fingerprint image sensor 310 and electrically connected to the fingerprint image sensor 310. The circuit board 320 is used to realize the transmission of electrical signals between the optical fingerprint device 300 and the outside.

[0185] Optionally, the circuit board 320 can be a flexible printed circuit (FPC), and a reinforcing plate 330 can be provided below the FPC to support and reinforce it, thereby improving the mechanical strength and reliability of the entire optical fingerprint device 300. As an example, the reinforcing plate 330 can be a steel plate or a printed circuit board (PCB), etc.

[0186] The lower surface of the fingerprint image sensor 310 can be bonded to the circuit board 320 using chip bonding adhesive to achieve a structural connection between the fingerprint image sensor 310 and the circuit board 320. Alternatively, the fingerprint image sensor 310 can be electrically connected to the circuit board 320 via wire bonding or other electrical connection methods, facilitating the transmission of relevant electrical signals from the fingerprint image sensor 310 to external electronic devices via the circuit board 320.

[0187] See also Figure 13 As shown, an infrared (IR) filter 240 may be provided on the upper surface of the fingerprint image sensor 310. The IR filter 240 can be attached to the upper surface of the fingerprint image sensor 310 by means of filter adhesive.

[0188] In this embodiment, the IR filter 240, the fingerprint image sensor 310, the circuit board 320, and the reinforcing plate 330 are connected together by an adhesive layer to form a fingerprint image sensor module. This module can be bonded to the bracket 340 on which the lens system 200 is mounted by the adhesive layer to form an integrated optical fingerprint device 300, thereby facilitating the installation of the integrated optical fingerprint device 300 below the display screen 20.

[0189] This application also provides an electronic device, such as... Figure 14As shown, the electronic device 400 may include the optical fingerprint device 300 and the display screen 20 in the above embodiment. The optical fingerprint device 300 is disposed below the display screen 20 to realize under-display fingerprint recognition.

[0190] Optionally, in some embodiments, the display screen 20 can be a display screen with a small thickness, for example, the display screen 20 can be less than or equal to 1.2 mm. In Tables 2, 5 and 8 shown in Embodiments 1 to 3 above, the thickness of the S1 surface can be the thickness of the display screen 20.

[0191] Optionally, the display screen 20 can be a thinner display screen or a flexible screen, the substrate material of which can be a flexible material. This flexible screen can be applied to mainstream mid-to-high-end mobile phones and other electronic devices.

[0192] In some specific implementations, the optical fingerprint device 300 can be disposed in the middle frame of the electronic device 400, thereby realizing the placement of the optical fingerprint device 300 below the display screen 20 of the electronic device 400.

[0193] Optionally, in order to protect the display screen 20, the lower surface of the display screen 20 may be provided with a protective layer or heat dissipation layer such as foam and copper foil. The area of ​​the foam and copper foil above the lens system 200 in the optical fingerprint device 300 is opened so that the light signal including fingerprint information can enter the lens system 200, thereby enabling the optical fingerprint device 300 to perform fingerprint recognition function.

[0194] As an example and not a limitation, electronic device 400 can be a mobile phone, tablet computer, laptop computer, desktop computer, in-vehicle electronic device, or wearable smart device, etc. Wearable smart devices include those that are fully functional, large in size, and can achieve complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as those that focus on a specific type of application function and need to be used in conjunction with other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0195] It should be noted that, without conflict, the various embodiments and / or technical features described in this application can be arbitrarily combined with each other, and the resulting technical solutions should also fall within the protection scope of this application.

[0196] For ease of explanation, in the various embodiments of this application, the same reference numerals denote the same components, and for brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0197] Unless otherwise stated, all technical and scientific terms used in the embodiments of this application have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0198] It should be understood that the specific examples in the embodiments of this application are only for the purpose of helping those skilled in the art to better understand the embodiments of this application, and are not intended to limit the scope of the embodiments of this application. Those skilled in the art can make various improvements and modifications based on the above embodiments, and all such improvements or modifications fall within the protection scope of this application.

[0199] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A lens system, characterized in that, The lens group with optical power in the lens system consists of a first lens, a second lens, and a third lens arranged sequentially from the object side to the image side; The first lens is a negative optical power lens, and the first lens has a concave surface facing the object side and a concave surface facing the image side; The second lens is a positive power lens, and the second lens has a convex surface facing the object side and a convex surface facing the image side; The third lens is a positive power lens, and the third lens has a convex surface facing the object. The maximum image height of the lens system on the imaging plane ,focal length And optical length CTL satisfies Wherein, the optical length CTL is the distance from the object-facing surface of the first lens to the imaging surface; The focal length of the first lens The focal length of the third lens And the optical length CTL satisfies .

2. The lens system according to claim 1, characterized in that, The optical length CTL satisfies .

3. The lens system according to claim 1 or 2, characterized in that, The optical power distribution of each lens in the lens system satisfies at least one of the following relationships: ； ； ； ； ； ； ； ； ； in, Let be the focal length of the first lens. Let be the focal length of the second lens. The focal length of the third lens is... The combined focal length of the first lens and the second lens. The combined focal length of the second lens and the third lens. The focal length of the lens system is given.

4. The lens system according to claim 1 or 2, characterized in that, The surface shape of each lens in the lens system satisfies at least one of the following relationships: ； ； ； ； ； ； in, Let be the focal length of the first lens. Let be the radius of curvature of the surface of the first lens facing the object. Let be the radius of curvature of the surface of the first lens facing the image side. Let be the focal length of the second lens. Let be the radius of curvature of the surface of the second lens facing the object side. Let be the radius of curvature of the surface of the second lens facing the image side. The focal length of the third lens is... The radius of curvature of the surface of the third lens facing the object side. Let be the radius of curvature of the surface of the third lens facing the image side.

5. The lens system according to claim 4, characterized in that, The surface shape of each lens in the lens system also satisfies at least one of the following relationships: ； ； 。 6. The lens system according to claim 1 or 2, characterized in that, The thickness of each lens in the lens system along the optical axis satisfies at least one of the following relationships: ； ； in, Let be the thickness of the first lens along the optical axis. Let be the thickness of the second lens along the optical axis. The thickness of the third lens on the optical axis.

7. The lens system according to claim 1 or 2, characterized in that, The optical parameters of each lens in the lens system satisfy at least one of the following relationships: ； ； ； in, Let be the refractive index of the first lens. Let be the refractive index of the second lens. is the refractive index of the third lens.

8. The lens system according to claim 1 or 2, characterized in that, At least one of the two surfaces of the first lens is aspherical, at least one of the two surfaces of the second lens is aspherical, and at least one of the two surfaces of the third lens is aspherical.

9. The lens system according to claim 1 or 2, characterized in that, The lens system also includes: An aperture stop is positioned between the first lens and the second lens.

10. The lens system according to claim 1 or 2, characterized in that, The system parameters of the lens system satisfy at least one of the following: Field of view greater than 120°; The F-number is less than 2; The distortion is less than 6.5%.

11. An optical fingerprint device, characterized in that, For placement beneath a display screen, the optical fingerprint device comprises: a fingerprint image sensor, and a lens system as described in any one of claims 1 to 10; The fingerprint image sensor is located below the lens system and is used to receive fingerprint light signals transmitted through the display screen and the lens system, and to process the fingerprint light signals to obtain a fingerprint image.

12. The optical fingerprint device according to claim 11, characterized in that, The thickness of the display screen is less than or equal to 1.2 mm, and / or the display screen is a flexible screen.

13. An electronic device, characterized in that, include: The display screen, and the optical fingerprint device as described in claim 11 or 12; The optical fingerprint device is located below the display screen to enable under-display fingerprint detection.

Images