Lens system, fingerprint identification device and terminal equipment

Abstract

The embodiment of the invention provides a lens system, a fingerprint identification device and terminal equipment. The lens system comprises a first lens and a second lens which are sequentially arranged from an object side to an image side; the first lens is a lens with negative focal power, and the surface, facing the object side, of the first lens is the surface with the largest size in the lens system; the second lens is a lens with positive focal power; the maximum effective size D11 of the surface, facing the object side, of the first lens and the maximum effective size D21 of the surface, facing the object side, of the second lens meet the following conditions: 0.2 lt; (D11-D21) / THlt; tH is the distance from the surface, facing the object side, of the first lens to the surface, facing the object side, of the second lens in the optical axis direction; the maximum image height Y ', the focal length f and the optical length CTL of the lens system on an imaging surface meet the following conditions: 0.5 lt; y ' / (f * CTL) lt; 1.24, the optical length CTL represents the distance from the surface, facing the object side, of the first lens to the imaging surface. According to the technical scheme, the lens system has a small horizontal direction size and good imaging performance.

Description

Technical Field

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

[0002] Optical under-screen fingerprint recognition is one of the most important solutions for unlocking mobile phones and has been widely used in smartphones.

[0003] Miniaturization is the development trend of mobile phone modules, and fingerprint recognition modules are no exception. Smaller fingerprint recognition module size can leave more space for other modules. The small module size solution in the related technology only reduces the thickness of the module, that is, the size in the vertical direction of the screen. The reduction of the horizontal module size (that is, the size parallel to the screen direction) is also very important, which can directly leave more space for other components such as batteries and sound chambers.

[0004] In view of this, how to provide an optical imaging system and a fingerprint recognition device with a small horizontal module size and high performance is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the above problems, the embodiments of the present application provide a lens system, a fingerprint recognition device and a terminal device, wherein the module size in the horizontal direction is small and has high imaging performance.

[0006] In a first aspect, an embodiment of the present application provides a lens system, comprising: a first lens and a second lens arranged in sequence from the object side to the image side; the first lens is a lens with negative optical focal length, and the second lens is a lens with positive optical focal length; the surface of the first lens facing the object side is the largest surface in the lens system; the maximum effective size D11 of the surface of the first lens facing the object side and the maximum effective size D21 of the surface of the second lens facing the object side satisfy: 0.2<(D11-D21) / TH<1.8, wherein TH is the distance from the surface of the first lens facing the object side to the surface of the second lens facing the object side in the optical axis direction; the maximum image height Y', focal length f and optical length CTL of the lens system on the imaging plane satisfy: 0.5<|Y' / (f*CTL)|<1.24, wherein the optical length CTL represents the distance from the surface of the first lens facing the object side to the imaging plane.

[0007] Through the technical solution of the embodiment of the present application, a lens system is provided. By designing the maximum effective size of the surfaces of the first lens and the second lens facing the object side, and the distance from the surface of the first lens facing the object side to the surface of the second lens facing the object side, the lens system can have a smaller horizontal dimension and a larger field of view. In addition, by designing the relationship among the maximum image height Y', focal length f, and optical length CTL of the lenses in the lens system, the lens system can have better imaging quality and take into account the overall thickness of the lens system. In summary, the lens system provided by the embodiment of the present application has a smaller horizontal dimension, a larger field of view while having better imaging quality, which is beneficial to the popularization and use of the lens system in fingerprint imaging devices or other imaging devices.

[0008] In some possible implementation manners, the focal length f1 of the first lens and the combined focal length f12 of the first lens and the second lens satisfy: -7 < f1 / f12 < -0.5; and / or, the focal length f2 of the second lens and the combined focal length f12 of the first lens and the second lens satisfy: 0.45 < f2 / f12 < 1.4.

[0009] Through the technical solution of this implementation manner, when the focal length f1 of the first lens and the combined focal length f12 of the first lens and the second lens satisfy -7 < f1 / f12 < -0.5, the size of the first lens can be reduced and the lens system can have a larger field of view. When the focal length f2 of the second lens and the combined focal length f12 of the first lens and the second lens satisfy 0.45 < f2 / f12 < 1.4, the light can be quickly focused, shortening the overall thickness of the lens system. Through the power distribution of the first lens and the second lens, the lens system obtains a more reasonable optical group structure, controls the reasonable distribution of aberrations between the first lens and the second lens, and can take into account the overall thickness, horizontal dimension, field of view, and optical imaging quality of the lens system.

[0010] In some possible implementation manners, the focal length f1 of the first lens and the radius of curvature r1 of the surface of the first lens facing the object side satisfy: -0.4 < r1 / f1 < 0.9; and / or, the focal length f1 of the first lens and the radius of curvature r2 of the surface of the first lens facing the image side satisfy: -5 < f1 / r2 < 8.

[0011] Through the technical solution of this implementation manner, by designing the ratio relationship between the radii of curvature of the two surfaces of the first lens and the focal length of the first lens, the surface shape and optical performance of the first lens can be further optimized. Through the reasonable curvature distribution and surface shape design of the first lens, the aberrations generated by the large-angle incident light brought by the large field of view can be effectively corrected, the imaging pressure of the subsequent optical elements can be reduced, and the imaging quality can be effectively improved. In summary, this technical solution enables the lens system to take into account a smaller horizontal dimension, a larger field of view, and higher imaging quality.

[0012] In some possible embodiments, the thickness CT1 of the first lens on the optical axis and the focal length f of the lens system satisfy: 0.35 < CT1 / f < 0.65.

[0013] Through the technical solution of this embodiment, when the thickness CT1 of the first lens on the optical axis and the focal length f of the lens system satisfy 0.35 < CT1 / f < 0.65, the first lens can have a smaller horizontal dimension and better strength, which can improve the yield of the production and manufacturing of the lens system. In addition, the reasonable thickness of the first lens can further optimize the imaging quality. In summary, this technical solution can take into account the horizontal dimension, strength and imaging quality, and has a high production and manufacturing yield.

[0014] In some possible embodiments, the focal length f2 of the second lens and the radius of curvature r3 of the surface of the second lens facing the object side satisfy: 0.2 < f2 / r3 < 1.0; and / or, the radius of curvature r3 of the surface of the second lens facing the object side and the radius of curvature r4 of the surface of the second lens facing the image side satisfy: -0.65 < r4 / r3 < -0.2.

[0015] Through the technical solution of this embodiment, by designing the proportional relationship of the radii of curvature of the two surfaces of the second lens, the aberration caused by reducing the maximum effective size of the first lens can be further optimized, and the imaging ability of the lens system can be improved. By designing the proportional relationship between the radius of curvature of the surface of the second lens facing the object side and the focal length of the second lens, the surface shape and optical performance of the second lens can be further optimized.

[0016] In some possible embodiments, the thickness CT1 of the first lens on the optical axis and the thickness CT2 of the second lens on the optical axis satisfy: 0.2 < CT1 / CT2 < 0.6.

[0017] Through the technical solution of this embodiment, by designing the proportional relationship of the thicknesses of the first lens and the second lens on the optical axis, the strength of the first lens and the second lens can be improved, the overall thickness of the lens system can be shortened, and it is helpful to correct aberration.

[0018] In some possible embodiments, the refractive index n1 and Abbe number v1 of the first lens satisfy: 1.5 < n1 < 1.7, 20 < v1 < 60; and / or, the refractive index n2 and Abbe number v2 of the second lens satisfy: 1.5 < n2 < 1.7, 20 < v2 < 60.

[0019] Through the technical solution of this embodiment, the first lens and the second lens can be lenses with a low refractive index and a low dispersion coefficient. The refractive index and the dispersion coefficient are also important for the imaging quality of the lens. By designing the lens system with the first lens and the second lens having a lower refractive index and a smaller dispersion, the dispersion of the lens system can be effectively reduced, and an appropriate aberration balance can be provided. In addition, the lens with a low refractive index can reduce the production cost. In summary, this embodiment can reduce the production cost and have a high imaging quality.

[0020] In some possible embodiments, the lens system further includes a third lens disposed on the image side of the second lens; the third lens is a lens with a positive optical power; the focal length f3 of the third lens and the focal length f of the lens system satisfy: 3 < f3 / f < 5.5.

[0021] Through the technical solution of this embodiment, by designing the focal length distribution of the third lens, the focal length of the third lens can be distributed within a reasonable range, which can reduce the overall thickness of the lens system, reduce the imaging pressure of the second lens, and enable the lens system to obtain better imaging capabilities.

[0022] In some possible embodiments, the focal length f3 of the third lens and the radius of curvature r5 of the surface of the third lens facing the object side satisfy: 3.2 < f3 / r5 < 5.0; and / or, the focal length f3 of the third lens and the radius of curvature r6 of the surface of the third lens facing the image side satisfy: 2.1 < f3 / r6 < 3.8.

[0023] Through the technical solution of this embodiment, by designing the ratio relationship between the radii of curvature of the two surfaces of the third lens and the focal length of the third lens, the surface shape and optical performance of the third lens can be further optimized. Through the reasonable curvature distribution and surface shape design of the third lens, the aberration can be further corrected, and the imaging capabilities of the lens system can be improved.

[0024] In some possible embodiments, the refractive index n3 and the Abbe number v3 of the third lens satisfy: 1.5 < n3 < 1.7, 20 < v3 < 60.

[0025] Through the technical solution of this embodiment, the third lens can be a lens with a low refractive index and a low dispersion coefficient. The refractive index and the dispersion coefficient are also important for the imaging quality of the lens. By designing the lens system with the third lens having a lower refractive index and a smaller dispersion, the dispersion of the lens system can be effectively reduced, and an appropriate aberration balance can be provided. In addition, the lens with a low refractive index can reduce the production cost. In summary, this embodiment can reduce the production cost and have a high imaging quality.

[0026] In some possible embodiments, the system parameter of the lens system satisfies that the F number is less than or equal to 2.0.

[0027] Through the technical solution of this implementation, when the F number of the lens system is less than or equal to 2.0, the small F number can obtain a shorter exposure time. When the lens system is applied to an under-screen fingerprint recognition device, the lens system can adapt to the low transmittance environment of the screen and improve the detection capability of weak fingerprint signals.

[0028] In some possible implementations, system parameters of the lens system satisfy that the field of view FOV is greater than 110°.

[0029] Through the technical solution of this embodiment, when the FOV of the lens system is greater than 110°, the large FOV can ensure that the lens system can have a sufficiently large object field of view while maintaining a small optical length, so that the imaging surface can obtain enough object information. For example, when the lens system is applied to a fingerprint recognition device, the fingerprint recognition device can obtain enough fingerprint information for recognition, ensuring the accuracy of fingerprint recognition.

[0030] In some possible implementations, the lens system further includes: an aperture stop, which is arranged on a side of the lens facing the image side.

[0031] 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 to adjust the light signal or the imaging range, the light signal carrying the fingerprint information can be imaged on the surface of the fingerprint image sensor to the greatest extent, so that the fingerprint image sensor can obtain more fingerprint information, and the resolution of fingerprint recognition can be further improved.

[0032] In a second aspect, an embodiment of the present application provides a fingerprint recognition device, comprising: a fingerprint image sensor, and the lens system in the first aspect or any possible implementation of the first aspect; wherein the fingerprint image sensor is arranged below the lens system, for receiving a fingerprint light signal transmitted by the lens system, and processing the fingerprint light signal to obtain a fingerprint image.

[0033] In some possible implementations, the fingerprint recognition device further includes: a bracket; wherein the lens system is interference-fitted in the bracket.

[0034] In some possible implementations, the fingerprint recognition device further includes: a circuit board; wherein the circuit board is disposed below the fingerprint image sensor and electrically connected to the fingerprint image sensor, and the circuit board is used to realize electrical signal transmission between the fingerprint recognition device and the outside.

[0035] In a third aspect, a terminal device is provided, comprising: a display screen, and a fingerprint recognition device according to the second aspect or any possible implementation manner of the second aspect; wherein the fingerprint recognition device is arranged under the display screen to realize under-screen fingerprint recognition.

[0036] These and other aspects of the present application will become more clearly understood in the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 It is a schematic diagram of the structure of an electronic device to which the embodiments of the present application can be applied.

[0039] Figure 2A A schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0040] Figure 2B Another schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0041] Figure 3 Another schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0042] Figure 4 yes Figure 3 Astigmatism and distortion graphs for the lens system with the illustrated layout.

[0043] Figure 5 yes Figure 3 MTF diagram of the lens system with the layout shown.

[0044] Figure 6 Another schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0045] Figure 7 yes Figure 6 Astigmatism and distortion graphs for the lens system with the illustrated layout.

[0046] Figure 8 yes Figure 6 MTF diagram of the lens system with the layout shown.

[0047] Fig. 9 Another schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0048] Fig.10 yes Fig. 9 Astigmatism and distortion graphs for the lens system with the illustrated layout.

[0049] Fig.11 yes Fig. 9 MTF diagram of the lens system with the layout shown.

[0050] Fig.12 Another schematic structural diagram of a lens system is provided for an embodiment of the present application.

[0051] Fig.13 yes Fig.12 Astigmatism and distortion graphs for the lens system with the illustrated layout.

[0052] Fig.14 yes Fig.12 MTF diagram of the lens system with the layout shown.

[0053] Fig.15 It is a schematic block diagram of a fingerprint recognition device provided in an embodiment of the present application.

[0054] Fig.16 It is a schematic structural diagram of a fingerprint recognition device provided in an embodiment of the present application.

[0055] Fig.17 It is a schematic block diagram of a terminal device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0056] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0057] In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0058] In the embodiments of the present application, it should be noted that, in this article, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0059] Moreover, the terms "comprises," "comprising," or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0060] In the description of the embodiments of the present application, words such as "example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "example" or "for example" in the embodiments of the present application is not to be interpreted as being more preferred or having more advantages than another embodiment or design. The use of words such as "example" or "for example" is intended to present relative concepts in a clear manner.

[0061] In addition, the "plurality" in the embodiments of the present application refers to two or more than two. In view of this, in the embodiments of the present application, "plurality" can also be understood as "at least two". "At least one" can be understood as one or more, for example, one, two or more. For example, including at least one means including one, two or more, and there is no limit on which ones are included. For example, including at least one of A, B and C, then A, B, C, A and B, A and C, B and C, or A, B and C can be included.

[0062] It should be noted that, in the embodiments of the present application, "and / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after are in an "or" relationship.

[0063] It should be noted that in the embodiments of the present application, "connection" can be understood as electrical connection, and the connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be either a direct connection between A and B or an indirect connection between A and B through one or more other electrical components.

[0064] It should be understood that the embodiments of the present application can be applied to optical fingerprint systems, including but not limited to optical fingerprint recognition systems and products based on optical fingerprint imaging. The embodiments of the present application are only described using the optical fingerprint system as an example, but should not constitute any limitation to the embodiments of the present application. The embodiments of the present application are also applicable to other systems that use optical imaging technology, etc.

[0065] As a common application scenario, the optical fingerprint system provided in the embodiment of the present application can be applied to smartphones, tablet computers and other mobile terminals or other electronic devices with display screens; more specifically, in the above-mentioned electronic devices, the fingerprint recognition device can be specifically an optical fingerprint device, which can be set in a local area or the entire area below the display screen, thereby forming an under-display optical fingerprint system.

[0066] like Figure 1 The structure diagram of an electronic device to which the embodiment of the present application can be applied is shown, and the electronic device 10 includes a display screen 120 and an optical fingerprint device 130, wherein the optical fingerprint device 130 is arranged in a local area below the display screen 120. The optical fingerprint device 130 includes a fingerprint image sensor, and the fingerprint image sensor includes a sensing array 133 having a plurality of optical sensing units 131. The area where the sensing array 133 is located or its sensing area is the fingerprint detection area 103 of the optical fingerprint device 130. Figure 1 As shown, the fingerprint detection area 103 is located in the display area of ​​the display screen 120. In an alternative embodiment, the optical fingerprint device 130 can also be set in other positions, such as the side of the display screen 120 or the non-light-transmitting area at the edge of the electronic device 10, and the optical signal of at least part of the display area of ​​the display screen 120 is guided to the optical fingerprint device 130 through the optical path design, so that the fingerprint detection area 103 is actually located in the display area of ​​the display screen 120.

[0067] It should be understood that the area of ​​the fingerprint detection area 103 may be different from the area of ​​the sensing array of the optical fingerprint device 130. For example, the area of ​​the fingerprint detection area 103 of the optical fingerprint device 130 may be larger than the area of ​​the sensing array of the optical fingerprint device 130 through optical path designs such as lens imaging, reflective folded optical path design, or other light convergence or reflection.

[0068] As an optional implementation, Figure 1 As shown, the optical fingerprint device 130 includes a light detection part 134 and an optical component 132. The light detection part 134 includes a sensing array 133 and a reading circuit and other auxiliary circuits electrically connected to the sensing array 133, which can be made on a chip (Die) through semiconductor technology, such as an optical imaging chip or a fingerprint image sensor. The optical component 132 can be arranged above the sensing array of the light detection part 134, and can specifically include a light guide layer or a light path guiding structure and other optical elements. The light guide layer or the light path guiding structure is mainly used to guide the reflected light reflected from the finger surface to the sensing array for optical detection.

[0069] There are multiple implementation schemes for the light-guiding layer or light-path guiding structure of the optical component 132. For example, in some embodiments, the light-guiding layer or light-path guiding structure may be an optical lens (Lens) layer, which has one or more lenses, and is used to converge the reflected light reflected from the finger to the sensing array of the light detection part 134 below it, so that the sensing array can be imaged based on the reflected light, thereby obtaining the fingerprint image of the finger. Optionally, the optical lens layer may also form a pinhole in the light path of the lens unit, and the pinhole may cooperate with the optical lens layer to expand the field of view of the optical fingerprint device to improve the fingerprint imaging effect of the optical fingerprint device 130.

[0070] As an optional embodiment, the display screen 120 may be a display screen having a self-luminous display unit, such as an organic light-emitting diode (OLED) display screen or a micro-light-emitting diode (Micro-LED) display screen. Taking the OLED display screen as an example, the optical fingerprint device 130 may use the display unit (i.e., OLED light source) of the OLED display screen 120 located in the fingerprint detection area 103 as an excitation light source for optical fingerprint detection. When the finger 140 presses on the fingerprint detection area 103, the display screen 120 emits a beam of light 111 to the target finger 140 above the fingerprint detection area 103. The light 111 is reflected on the surface of the finger 140 to form reflected light or is scattered inside the finger 140 to form scattered light. In the relevant patent application, for the convenience of description, the above-mentioned reflected light and scattered light are collectively referred to as reflected light. Since the ridges and valleys of a fingerprint have different reflective capabilities for light, 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, i.e., 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.

[0071] In other embodiments, the optical fingerprint device 130 may also use a built-in light source or an external light source to provide an optical signal for fingerprint detection. In this case, the optical fingerprint device 130 may be applicable to a non-self-luminous display screen, such as a liquid crystal display screen or other passive light-emitting display screens.

[0072] It should be understood that, in a specific implementation, the electronic device 10 further includes a transparent protective cover plate, which may be a glass cover plate or a sapphire cover plate, which is located above the display screen 120 and covers the front of the electronic device 10. Because, in the embodiment of the present application, the so-called finger pressing on the display screen 120 actually refers to pressing on the cover plate above the display screen 120 or the surface of the protective layer covering the cover plate.

[0073] It should also be understood that Figure 1 As shown, the electronic device 10 may further include a circuit board 150, which is disposed below the optical fingerprint device 130. The optical fingerprint device 130 may realize electrical interconnection and signal transmission with other peripheral circuits or other elements of the electronic device 10 through the circuit board 150. For example, the optical fingerprint device 130 may receive a control signal of a processing unit of the electronic device 10 through the circuit board 150, and may also output a fingerprint detection signal from the optical fingerprint device 130 to a processing unit or a control unit of the electronic device 10 through the circuit board 150.

[0074] In the above application embodiment, the optical component 132 may include a lens system formed by one or more lenses, so as to achieve the transmission of the fingerprint light signal formed after being reflected or scattered by the finger. The relevant design of the lens system will affect the final fingerprint imaging quality and thus affect the fingerprint recognition effect. Therefore, the design of the lens system is particularly important in the entire optical fingerprint system.

[0075] In some related technologies, in order to reduce the volume of the optical fingerprint device 130, the thickness of the optical component 132 is usually reduced, that is, the size in the vertical screen direction (called the Z direction). The reduction of the module size in the horizontal direction (that is, the size parallel to the screen direction, called the XY direction) is also very important, which can directly leave more space for other components such as batteries and sound chambers.

[0076] In view of this, the present application provides a lens system with a smaller horizontal size. The lens system may include two or more lenses. By performing relevant designs on the two or more lenses, the lens system can have a smaller horizontal size characteristic and better imaging performance.

[0077] Figure 2A FIG. 2 shows a schematic structural diagram of a lens system 200 provided in an embodiment of the present application. Figure 2A As shown, the lens system 200 includes a first lens 210 and a second lens 220 which are arranged in sequence from the object side to the image side.

[0078] Specifically, the first lens 210 is a lens with negative optical power, and the second lens 220 is a lens with positive optical power. The surface of the first lens 210 facing the object is the largest surface in the lens system 200. The maximum effective size D11 of the surface of the first lens 210 facing the object and the maximum effective size D21 of the surface of the second lens 220 facing the object satisfy: 0.2<(D11-D21) / TH<1.8, where TH is the distance from the surface of the first lens facing the object to the surface of the second lens facing the object in the optical axis direction.

[0079] The maximum effective size of the surface of the first lens 210 and the second lens 220 facing the object, and the distance from the surface of the first lens 210 facing the object to the surface of the second lens 220 facing the object, have a high correlation with the horizontal size and field of view of the lens system 200. In the embodiment of the present application, (D11-D21) / TH reflects the change trend of the maximum effective size of the first lens 210 relative to the maximum effective size of the second lens 220, and can characterize the angle of light when it propagates between the first lens 210 and the second lens 220. When (D11-D21) / TH satisfies 0.2<(D11-D21) / TH<1.8, the lens system 200 can have a smaller horizontal size and a larger field of view. For example, when the lens system 200 is applied to a fingerprint recognition device of an electronic device such as a mobile phone, the fingerprint recognition device can have a larger fingerprint detection area, and the size of the fingerprint recognition device in the direction parallel to the display screen is smaller, which can save the internal space of the electronic device for setting other modules.

[0080] Specifically, if the first lens 210 is a circular lens, the maximum effective size D11 of the surface of the first lens 210 facing the object may be the effective diameter (or effective radius) of the surface of the first lens 210 facing the object; if the first lens 210 is a rectangular or polygonal lens, the maximum effective size D11 of the surface of the first lens 210 facing the object may be the diagonal length of the surface of the first lens 210 facing the object, etc. Similarly, the maximum effective size D21 of the surface of the second lens 220 facing the object may be the effective diameter (or effective radius) or the diagonal length, etc.

[0081] In a typical implementation, the first lens 210 and the second lens 220 are circular lenses. The surface of the first lens 210 facing the object is the largest surface of the lens system 200, the effective diameter of the surface of the first lens facing the object is the largest effective diameter in the lens system 200, and the first lens 210 is the lens with the largest horizontal size in the lens system 200. At this time, D11-D21 is the difference between the effective diameter of the surface with the largest diameter in the lens system 200 and the surface of the second lens 220 facing the object, and the ratio of the distance between the two on the optical axis represents the relationship between the diameter of the surface where D11 is located and the distance from the second lens 220, which can represent the angle of light when it propagates between the first lens 210 and the second lens 220. When (D11-D21) / TH satisfies 0.2<(D11-D21) / TH<1.8, the lens system 200 can have a larger field of view while having a smaller lens diameter.

[0082] In addition to the above-mentioned design of the changing trend of the first lens 210 and the second lens 220, in the embodiment of the present application, the maximum image height Y', the focal length f and the optical length CTL of the lens system 200 on the imaging plane satisfy: 0.5<|Y' / (f*CTL)|<1.24, wherein the optical length CTL represents the distance from the surface of the first lens 210 facing the object side to the imaging plane.

[0083] Specifically, the maximum image height Y' of the lens system 200 on the imaging surface may be the radius of the maximum imaging circle of the lens system 200 on the imaging surface. In the case where the lens system 200 is applied to an optical fingerprint device, a fingerprint image sensor may be provided on the imaging surface of the lens system 200, and the fingerprint image sensor may include the above Figure 1 The light detection part 134 in the illustrated embodiment is used to detect the fingerprint light signal transmitted through the lens system 200 .

[0084] The optical length CTL of the lens system 200 is the distance from the surface of the first lens 210 facing the object to the imaging surface of the lens system 200. The distance may be the distance along the optical axis from the surface of the first lens 210 facing the object to the imaging surface of the lens system 200. More specifically, the optical length CTL of the lens system 200 may be the shortest distance between the vertex of the first lens 210 closest to the object and the imaging surface of the lens system 200.

[0085] The maximum image height Y', focal length f and optical length CTL of the lens system 200 on the imaging plane have a high correlation, which can not only affect the overall size of the lens system 200, but also affect the optical imaging performance of the lens system 200. In the embodiment of the present application, Y' / f can be used to characterize the maximum field of view (FOV) of the lens system 200. Specifically, the maximum field of view (FOV) is used to characterize the field of view of the lens. When the lens sizes are equal, the larger the FOV, the larger the information of the lens can be obtained, that is, the larger the amount of information that can be obtained by using the lens with a large FOV. The larger the Y' / f, the larger the FOV of the lens system 200. In the ratio design of |Y' / (f*CTL)|, the larger the Y' / f and the smaller the CTL, the larger the ratio value of |Y' / (f*CTL)| can be greater than 0.5. In other words, when |Y' / (f*CTL)|>0.5, a lens system 200 with a smaller optical length and a larger FOV can be designed, thereby taking into account both the overall thickness and imaging quality of the lens system 200. In addition, in the embodiment of the present application, when |Y' / (f*CTL)|<1.24, the optical length CTL of the lens system 200 can be limited to be too small, thereby affecting the imaging performance of the lens system 200. Therefore, through the technical solution of the embodiment of the present application, the maximum image height Y', focal length f and optical length CTL of the lens system 200 on the imaging plane are designed to meet 0.5<|Y' / (f*CTL)|<1.24, while taking into account the reduction of the overall thickness of the lens system 200, the lens system 200 can be guaranteed to have a better imaging quality.

[0086] Through the technical solution of the embodiment of the present application, the larger FOV ensures that the lens system 200 can obtain a larger object field of view under a small object distance, thereby obtaining more fingerprint information to improve the accuracy of fingerprint recognition.

[0087] In summary, through the technical solution of the embodiment of the present application, by designing the relationship between the maximum effective size of the surface of the first lens 210 and the second lens 220 facing the object in the lens system 200, and the distance from the surface of the first lens 210 facing the object to the surface of the second lens 220 facing the object, the lens system 200 can have a smaller horizontal dimension and a larger field of view. In addition, by designing the relationship between the maximum image height Y', the focal length f and the optical length CTL of the lens system 200, the lens system 200 can have a better field of view, imaging quality and take into account the overall thickness of the lens system. In summary, the lens system provided by the embodiment of the present application has a smaller horizontal dimension and a larger field of view while having better imaging quality, which is conducive to the promotion and use of the lens system in fingerprint imaging devices or other imaging devices.

[0088] Optionally, through the above-mentioned related designs of the lens system 200, the system parameters of the lens system 200 can satisfy that the F number is less than or equal to 2.0.

[0089] The F number, also written as Fno., is a parameter that indicates the light transmission capacity of a lens. The smaller the F number, the larger the aperture, which means that more light enters the lens per unit time and the shorter the exposure time can be.

[0090] When the F number is less than or equal to 2.0, the small F number can obtain a shorter exposure time. When the lens system 200 is applied to an under-screen fingerprint recognition device, the lens system 200 can adapt to the low transmittance environment of the screen and improve the detection capability of weak fingerprint signals.

[0091] Optionally, through the related design of the above-mentioned lens system 200, the system parameters of the lens system 200 can satisfy the field of view FOV greater than 110°.

[0092] Specifically, as mentioned above, when the lens sizes are equal, the larger the FOV, the larger the area of ​​information that can be obtained by the lens, that is, the amount of information that can be obtained by using the lens with a large FOV is greater.

[0093] When the FOV of the lens system is greater than 110°, the large FOV can ensure that the lens system 200 can have a sufficiently large object field of view while maintaining a small optical length, so that the imaging surface can obtain enough object information. For example, when the lens system 200 is applied to a fingerprint recognition device, the fingerprint recognition device can obtain enough fingerprint information for recognition, ensuring the accuracy of fingerprint recognition.

[0094] In summary, through the technical solution of the embodiment of the present application, the lens system 200 can have a larger FOV and a smaller F number by designing the first lens 210 and the second lens 220 in the lens system 200, thereby effectively improving the overall imaging performance of the lens system 200.

[0095] Optionally, in some embodiments, the refractive index n1 of the first lens 210 satisfies 1.7>n1>1.5, and the Abbe number v1 satisfies 20 <v1<60。

[0096] Optionally, in some embodiments, the refractive index n1 of the second lens 220 satisfies 1.7>n1>1.5, and the Abbe number v1 satisfies 20 <v1<60。

[0097] Through the technical solution of this embodiment, the lens system 200 is designed using the first lens 210 and the second lens 220 with lower refractive index and smaller dispersion, which can effectively reduce the dispersion of the lens system 200 and provide just the right aberration balance. In addition, the lens with a low refractive index can reduce the production cost. In summary, this embodiment can reduce the production cost and has high imaging quality.

[0098] Optionally, in some embodiments, the focal length f1 of the first lens 210 and the combined focal length f12 of the first lens 210 and the second lens 220 satisfy: -7 < f1 / f12 < -0.5.

[0099] Through the technical solution of this embodiment, when the focal length f1 of the first lens 210 and the combined focal length f12 of the first lens 210 and the second lens 220 satisfy -7 < f1 / f12 < -0.5, while reducing the size of the first lens 210, the lens system 200 can have a large field of view angle.

[0100] Optionally, in some embodiments, the focal length f2 of the second lens 220 and the combined focal length f12 of the first lens 210 and the second lens 220 satisfy: 0.45 < f2 / f12 < 1.4.

[0101] Through the technical solution of this embodiment, when the focal length f2 of the second lens 220 and the combined focal length f12 of the first lens 210 and the second lens 220 satisfy 0.45 < f2 / f12 < 1.4, the light can be quickly focused and the thickness of the lens system 200 can be shortened.

[0102] In summary, the distribution of the optical power of the first lens 210 can increase the field of view angle of the lens system 200, and the distribution of the optical power of the second lens 220 can enable the second lens 220 to provide a large optical power for focusing light. Through the distribution of the optical power of the first lens 210 and the second lens 220, the lens system 200 obtains a more reasonable optical structure, controls the reasonable distribution of aberrations between the first lens and the second lens, and can take into account the thickness, horizontal dimension, field of view angle and optical imaging quality of the lens system.

[0103] Optionally, in some embodiments, the focal length f1 of the first lens 210 and the radius of curvature r1 of the surface of the first lens 210 facing the object side satisfy: -0.4 < r1 / f1 < 0.9; and / or, the focal length f1 of the first lens 210 and the radius of curvature r2 of the surface of the first lens 210 facing the image side satisfy: -5 < f1 / r2 < 8.

[0104] Through the technical solution of this embodiment, by designing the ratio relationship between the radii of curvature of the two surfaces of the first lens 210 and the focal length of the first lens 210, the surface shape and optical performance of the first lens 210 can be further optimized. Through the reasonable curvature distribution and surface shape design of the first lens 210, it is possible to effectively correct the aberration generated by the large-angle incident light brought by the large FOV, reduce the imaging pressure on the subsequent optical elements, and effectively improve the imaging quality. In summary, this technical solution enables the lens system 200 to take into account a smaller horizontal dimension, a larger field of view angle, and a higher imaging quality.

[0105] Optionally, in some embodiments, the thickness CT1 of the first lens 210 on the optical axis and the focal length f of the lens system 200 satisfy: 0.35 < CT1 / f < 0.65.

[0106] Through the technical solution of this embodiment, when the thickness CT1 of the first lens 210 on the optical axis and the focal length f of the lens system 200 satisfy 0.35 < CT1 / f < 0.65, the first lens 210 can have a smaller horizontal dimension and better strength, which can improve the production yield of the lens system 200. In addition, the reasonable thickness of the first lens 210 can further optimize the imaging quality. In summary, this technical solution can take into account the horizontal dimension, strength, and imaging quality, and has a high production yield.

[0107] Optionally, in some embodiments, the focal length f2 of the second lens 220 and the radius of curvature r3 of the surface of the second lens 220 facing the object side satisfy: 0.2 < f2 / r3 < 1.0; and / or, the radius of curvature r3 of the surface of the second lens 220 facing the object side and the radius of curvature r4 of the surface of the second lens 220 facing the image side satisfy: -0.65 < r4 / r3 < -0.2.

[0108] Through the technical solution of this embodiment, by designing the ratio relationship between the radii of curvature of the two surfaces of the second lens 220, the aberration caused by the maximum effective size of the smaller first lens 210 can be further optimized, and the imaging ability of the lens system 200 can be improved. By designing the ratio relationship between the radii of curvature of the two surfaces of the second lens 220 and the focal length of the second lens 220, the surface shape and optical performance of the second lens 220 can be further optimized.

[0109] Optionally, in some embodiments, the thickness CT1 of the first lens 210 on the optical axis and the thickness CT2 of the second lens 220 on the optical axis satisfy: 0.2 < CT1 / CT2 < 0.6.

[0110] Through the technical solution of this embodiment, by designing the proportional relationship of the thicknesses of the first lens 210 and the second lens 220 on the optical axis, the strength of the first lens 210 and the second lens 220 can be improved, the overall thickness of the lens system 200 can be shortened, and it is helpful to correct aberration.

[0111] Optionally, in some embodiments, as Figure 2B shown, the lens system 200 may further include a third lens 230, which is disposed on the image side of the second lens 220. Specifically, the third lens 230 is a lens with positive optical power, and the focal length f3 of the third lens 230 and the focal length f of the lens system satisfy: 3 < f3 / f < 5.5.

[0112] Through the technical solution of this embodiment, by designing the focal length distribution of the third lens 230, the focal length of the third lens 230 can be distributed within a reasonable range, the total thickness of the lens system 200 can be reduced, the imaging pressure on the second lens 220 can be reduced, and the lens system 200 can obtain better imaging capabilities.

[0113] Optionally, in some embodiments, the focal length f3 of the third lens 230 and the radius of curvature r5 of the surface of the third lens 230 facing the object side satisfy: 3.2 < f3 / r5 < 5.0; and / or, the focal length f3 of the third lens 230 and the radius of curvature r6 of the surface of the third lens 230 facing the image side satisfy: 2.1 < f3 / r6 < 3.8.

[0114] Through the technical solution of this embodiment, by designing the proportional relationship between the radii of curvature of the two surfaces of the third lens 230 and the focal length of the third lens 230, the surface shape and optical performance of the third lens 230 can be further optimized. Through the reasonable curvature distribution and surface shape design of the third lens 230, the aberration can be further corrected and the imaging capabilities of the lens system 200 can be improved.

[0115] Optionally, in some embodiments, the refractive index n3 and Abbe number v3 of the third lens 230 satisfy: 1.5 < n3 < 1.7, 20 < v3 < 60.

[0116] Through the technical solution of this embodiment, the third lens 230 can be a lens with a low refractive index and a low dispersion coefficient. The refractive index and dispersion coefficient are also important for the imaging quality of the lens. Using the third lens 230 with a lower refractive index and smaller dispersion to design the lens system 200 can effectively reduce the dispersion of the lens system 200 and provide an appropriate aberration balance. In addition, the lens with a low refractive index can reduce the production cost. In summary, this embodiment can reduce the production cost and have high imaging quality.

[0117] Optionally, in order to effectively reduce the production and manufacturing costs of the first lens 210, the second lens 220 and the third lens 230, the materials of the first lens 210, the second lens 220 and the third lens 230 may be resin, and the first lens 210, the second lens 220 and the third lens 230 may be formed by injection molding of the resin material. Therefore, through the technical solution of this embodiment, a low-cost, low-refractive-index, low-abbematic-coefficient resin material may be provided to manufacture the first lens 210, the second lens 220 and the third lens 230, thereby reducing the manufacturing cost of the lens system 200 and ensuring the optical imaging performance of the lens system 200.

[0118] Figure 3 200 is another schematic structural diagram of the lens system 200 provided in an embodiment of the present application. Optionally, the lens system 200 may be disposed below a display screen 20 of an electronic device. The display screen 20 may be Figure 1 The display screen 120 shown in the figure, for example, can be an OLED display screen or other types of display screens. For the convenience of optical 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.

[0119] like Figure 3 As shown, in the lens system 200, from the object side to the image side, there are arranged in sequence: a first lens 210, an aperture (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. An imaging surface 240 may be arranged on one side of the image side, for example, the imaging surface 240 may be a sensing surface of a fingerprint image sensor.

[0120] Specifically, in the embodiment of the present application, the aperture can be used to adjust the size of the light signal or the imaging range. By setting the aperture to adjust the light signal or the imaging range, the light signal carrying the fingerprint information can be imaged on the surface of the fingerprint image sensor to the greatest extent, so that the fingerprint image sensor can obtain more fingerprint information, and the resolution of fingerprint recognition can be further improved.

[0121] Continue to see Figure 3 As shown, in some embodiments, the lens system 200 may further include an infrared (IR) filter layer (not shown in the figure), and the IR filter layer is disposed on the side of the third lens 230 facing the image side. Optionally, in some embodiments, the lens system 200 further includes: an infrared filter layer, which is disposed on the side of the third lens 230 facing the image side.

[0122] Specifically, the infrared light filter layer is used to prevent infrared light in the external ambient light from interfering with imaging. For example, when the lens system 200 is used in a fingerprint recognition device, the infrared light filter layer can prevent the problem of fingerprints being unable to be recognized due to strong ambient light when the user is outdoors.

[0123] In some embodiments, the infrared filter layer can be directly formed on the imaging surface 240 of the lens system 200. Specifically, the imaging surface 240 of the lens system 200 is provided with an image sensor, such as a fingerprint image sensor, which can be deposited on the sensing surface of the fingerprint image sensor by coating (such as sputtering, evaporation or coating, etc.) (or process), and the infrared filter layer can be made of inorganic coating layer materials.

[0124] Through the technical solution of this embodiment, the infrared light filter layer is directly formed on the imaging surface 240, and there is no need to add an additional contact layer on the imaging surface 240 to ensure the adhesion or flatness between the film layers, thereby reducing the number of optical path film layer structures and simplifying the process, further reducing the thickness of the lens system 200, and taking into account the structural stability of the lens system 200.

[0125] Alternatively, in some other embodiments, the lens system 200 may further include: a filter layer carrier (not shown in the figure), which is used to fix the infrared light filter layer on the side of the third lens 230 facing the image side. The infrared light filter layer is arranged on the filter layer carrier to form an infrared light filter layer carrier.

[0126] Furthermore, the lens system 200 may also include a filter layer bonding adhesive (not shown in the figure) for bonding the infrared light filter layer carrier to the imaging surface.

[0127] Specifically, the imaging surface 240 of the lens system 200 may be provided with an image sensor, such as a fingerprint image sensor, the filter layer carrier may be a glass carrier having a certain thickness, etc., the infrared light filter layer may be plated on the glass carrier, and the filter layer bonding adhesive may be used to bond the infrared light filter layer carrier to the surface of the fingerprint image sensor, for example, it may be bonded to the sensing surface of the fingerprint image sensor.

[0128] Through the technical solution of this embodiment, the infrared light filter layer can be formed by being arranged on a filter layer carrier independent of the fingerprint image sensor to form an infrared light filter layer carrier, which can reduce the process difficulty of arranging the infrared light filter layer carrier on the surface of the fingerprint sensor, and the installation method in the lens system is easy to achieve, thereby reducing the installation cost of the infrared light filter layer in the lens system and improving the production efficiency and manufacturing yield of the lens system.

[0129] Alternatively, in some other embodiments, the lens system 200 may further include a lens barrel (not shown in the figure), and the first lens 210, the second lens 220, the third lens 230 and the infrared light filter layer carrier are fixed in the lens barrel.

[0130] Through the technical solution of this embodiment, the infrared light filter layer is formed by being arranged on a filter layer carrier independent of the fingerprint image sensor. The infrared light filter layer carrier is arranged in the lens barrel, which can avoid direct contact between the infrared light filter layer carrier and the fingerprint image sensor, reduce the difficulty of setting the infrared light filter layer carrier, and easily achieve the installation method in the lens system 200, thereby reducing the installation cost of the infrared light filter layer in the lens system 200 and improving the production efficiency and manufacturing yield of the lens system 200.

[0131] In order to more specifically illustrate the lens system 200 provided by the present application, design parameters of the lens system 200 of several specific embodiments are given below.

[0132] In the following embodiments, in order from the object side to the image side, the upper and lower surfaces of the display screen 20 are respectively recorded as S1 and S2, the two surfaces of the first lens 210 are respectively recorded as S3 and S4, the surface of the aperture is recorded as S5, the two surfaces of the second lens 220 are respectively recorded as S6 and S7, the two surfaces of the third lens 230 are respectively recorded as S8 and S9, and the imaging surface 240 of the lens system 200 is recorded as S10.

[0133] Optionally, the optical length, focal length, radius of curvature, thickness, refractive index, dispersion coefficient, etc. of the first lens 210, the second lens 220, and the third lens 230 in the lens system 200 may be designed according to the above embodiments, so that the lens system 200 has good optical imaging performance. For example, the lens system 200 may satisfy at least one of the following: the field of view FOV is greater than 110°, and the F number is less than or equal to 2.0.

[0134] Optionally, the lens system 200 can also have good optical imaging performance by designing at least one of the curvature radius, thickness, material, and cone coefficient of each surface (i.e., S1 to S10 mentioned above) in the lens system 200, and / or the aspheric high-order coefficients A4, A6, A8, A10, A12, A14, A16, A20, etc. of the aspheric lens in the lens system 200.

[0135] Example 1

[0136] The configuration of each component in the lens system 200 of the first embodiment can be seen in Figure 3As shown. In this embodiment 1, the lens system 200 includes three lenses: a first lens 210, a second lens 220 and a third lens 230. The optical length, focal length, radius of curvature, thickness, refractive index and dispersion coefficient 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 1 below. The radius of curvature, thickness, material and conic coefficient of each surface of S1 to S10 in the lens system 200 can use the corresponding parameters in Table 2 below, and the aspheric high-order coefficients of the aspheric surfaces in S1 to S10 use the parameters shown in Table 3 below.

[0137] Table 1

[0138] project parameter f3 / f 4.310 f1 / f12 -1.303 f2 / f12 0.840 r1 / f1 0.059 f1 / r2 -1.757 f2 / r3 0.774 f3 / r5 4.282 f3 / r6 3.060 CT1 / CT2 0.424 CT1 / f 0.515 r4 / r3 -0.554 r5 / r6 0.715 |Y' / f*CTL| 0.908 (D11-D21) / TH 0.915

[0139] Table 2

[0140]

[0141] Table 3

[0142] surface A4 A6 A8 A10 A12 S3 4.42E+00 -3.59E+00 -2.71E+00 -1.61E+01 9.39E+01 S4 1.62E+01 4.36E+01 4.55E+03 -6.37E+04 -6.21E+04 S6 6.92E-01 -2.32E+02 4.46E+03 -8.68E+04 5.26E+05 S7 -1.06E+01 1.48E+02 -1.94E+03 1.66E+04 -5.71E+04 S8 -3.70E+00 5.66E+00 -1.26E+02 3.80E+02 -1.36E+03 S9 -3.75E+00 1.04E+00 2.36E+01 -2.25E+01 -2.41E+02 surface A14 A16 A18 A20 S3 2.47E+02 7.81E+02 8.49E+02 -1.64E+04 S4 -3.62E+06 2.97E+08 1.80E+09 -5.66E+10 S6 3.17E+06 1.89E+08 4.48E+09 -1.41E+11 S7 2.63E+05 -1.24E+06 -1.29E+07 8.71E+07 S8 3.41E+03 2.86E+04 5.85E+04 -4.54E+06 S9 -4.77E+02 1.58E+03 8.13E+03 -1.73E+04

[0143] It should be understood that the blank corresponding to the parameter in Tables 1 to 3 of the embodiments of the present application indicates that there is no such parameter. In Table 2, "n = 1.52" represents that the refractive index of the material is 1.52, and similarly, other values ​​can be deduced accordingly. In Tables 2 and 3, "E+02" represents "10 to the power of 2", and similarly, other values ​​can be deduced accordingly.

[0144] 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: f=0.450 mm, Fno=1.45, FOV=116°, CTL=1.647 mm. f is the overall focal length of the lens system 200. CTL can be the distance from the surface S3 of the first lens 210 facing the display screen 20 to the imaging surface S10 (i.e., the imaging surface 240) along the optical axis. The imaging surface 240 here can be the sensing surface of the fingerprint image sensor, which will not be described in detail below for the sake of brevity.

[0145] Figures 4 to 5 The astigmatism and distortion curves and the modulus value (MTF) of the optical transfer function (Optical Transfer Function) of the lens system 200 provided in the first embodiment are shown in sequence. Figure 4 Figure (a) is the astigmatism curve. Figure 4 Figure (b) is the distortion curve.

[0146] from Figures 4 to 5The simulation diagram shown shows that the object-side field of view of the lens system 200 is relatively large, i.e., FOV=116°. The lens system 200 has good performances of relatively large object-side FOV, small distortion, small dispersion and small chromatic aberration. In addition, the lens system 200 has a relatively small F number (Fno), i.e., 1.45, and therefore can have a relatively small exposure time, which can further adapt to a screen with low transmittance.

[0147] Example 2

[0148] The configuration of each component in the lens system 200 of the second embodiment can be seen in Figure 6 As shown. In this embodiment 2, the lens system 200 includes three lenses: a first lens 210, a second lens 220, and a third lens 230. The optical length, focal length, radius of curvature, thickness, refractive index, and dispersion coefficient 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. The radius of curvature, thickness, material, and conic coefficient of each surface of S1 to S10 in the lens system 200 can use the corresponding parameters in Table 5, and the aspheric high-order coefficients of the aspheric surfaces of S1 to S10 use the parameters shown in Table 6.

[0149] Table 4

[0150]

[0151]

[0152] Table 5

[0153]

[0154] Table 6

[0155]

[0156]

[0157] 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: f=0.450 mm, Fno=1.45, FOV=105°, CTL=1.515 mm. f is the overall focal length of the lens system 200. CTL can be the distance from the surface S3 of the first lens 210 facing the display screen 20 to the imaging surface S10 (i.e., the imaging surface 240) along the optical axis. The imaging surface 240 here can be the sensing surface of the fingerprint image sensor, which will not be described in detail below for the sake of brevity.

[0158] Figures 7 and 8The astigmatism and distortion curves and the modulus value (MTF) of the optical transfer function (Optical Transfer Function) of the lens system 200 provided in the second embodiment are shown in sequence. Figure 7 Figure (a) is the astigmatism curve. Figure 7 Figure (b) is the distortion curve.

[0159] from Figures 7 and 8 The simulation diagram shows that the lens system 200 has good performances of large object FOV, small distortion, small dispersion and chromatic aberration. In addition, the lens system 200 has a small F number (Fno), i.e., 1.45, and therefore can have a short exposure time, which can further adapt to a screen with low transmittance.

[0160] Example 3

[0161] The configuration of each component in the lens system 200 of the third embodiment can be seen in Fig. 9 As shown. In this embodiment 3, the lens system 200 includes only two lenses, the first lens 210 and the second lens 220. The optical length, focal length, radius of curvature, thickness, refractive index and dispersion coefficient of the first lens 210 and the second lens 220 in the lens system 200 can be designed using the corresponding proportions in Table 7. The radius of curvature, thickness, material and conic coefficient of each surface of S1 to S10 in the lens system 200 can use the corresponding parameters in Table 8, and the aspheric high-order coefficients of the aspheric surfaces of S1 to S10 use the parameters shown in Table 9.

[0162] Table 7

[0163]

[0164]

[0165] Table 8

[0166]

[0167] Table 9

[0168]

[0169]

[0170] 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: f=0.462mm, Fno=1.46, FOV=116°, CTL=1.599mm. f is the overall focal length of the lens system 200. CTL can be the distance from the surface S3 of the first lens 210 facing the display screen 20 to the imaging surface S10 (i.e., the imaging surface 240) along the optical axis. The imaging surface 240 here can be the sensing surface of the fingerprint image sensor, which will not be described in detail below for the sake of brevity.

[0171] Figure 10 to Figure 11 The astigmatism and distortion curves and the modulus value (MTF) of the optical transfer function (Optical Transfer Function) of the lens system 200 provided in the third embodiment are shown in sequence. Fig.10 Figure (a) is the astigmatism curve. Fig.10 Figure (b) is the distortion curve.

[0172] from Figure 10 to Figure 11 The simulation diagram shows that the lens system 200 has good performances of large object FOV, small distortion, small dispersion and chromatic aberration. In addition, the lens system 200 has a small F number (Fno), i.e., 2.04, and therefore can have a short exposure time, which can further adapt to a screen with low transmittance.

[0173] In summary, in several exemplary embodiments provided in the present 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 larger FOV and a smaller F number.

[0174] Example 4

[0175] The configuration of each component in the lens system 200 of the fourth embodiment can be seen in Fig.12 As shown. In this embodiment 4, the lens system 200 includes only two lenses, the first lens 210 and the second lens 220. The optical length, focal length, radius of curvature, thickness, refractive index and dispersion coefficient of the first lens 210 and the second lens 220 in the lens system 200 can be designed using the corresponding proportions in Table 10. The radius of curvature, thickness, material and cone coefficient of each surface of S1 to S10 in the lens system 200 can use the corresponding parameters in Table 11, and the aspheric high-order coefficients of the aspheric surfaces of S1 to S10 use the parameters shown in Table 12.

[0176] Table 10

[0177] project parameter f3 / f f1 / f12 -6.398 f2 / f12 1.193 r1 / f1 0.142 f1 / r2 4.397 f2 / r3 0.497 f3 / r5 f3 / r6 CT1 / CT2 0.369 CT1 / f 0.471 r4 / r3 -0.304 r5 / r6 |Y' / f*CTL| 0.947 (D11-D21) / TH 1.221

[0178] Table 11

[0179]

[0180] Table 12

[0181]

[0182]

[0183] Based on the parameters shown in Tables 10 to 12, the parameters of the lens system 200 provided in this embodiment 4 are as follows: f=0.446mm, Fno=1.45, FOV=116°, CTL=1.592mm. f is the overall focal length of the lens system 200. CTL can be the distance from the surface S3 of the first lens 210 facing the display screen 20 to the imaging surface S10 (i.e., the imaging surface 240) along the optical axis. The imaging surface 240 here can be the sensing surface of the fingerprint image sensor, which will not be described in detail below for the sake of brevity.

[0184] Figure 13 to Figure 14 The astigmatism and distortion curves and the modulus value (MTF) of the optical transfer function (Optical Transfer Function) of the lens system 200 provided in the third embodiment are shown in sequence. Fig.13 Figure (a) is the astigmatism curve. Fig.13 Figure (b) is the distortion curve.

[0185] from Figure 13 to Figure 14 The simulation diagram shows that the lens system 200 has good performances of large object FOV, small distortion, small dispersion and chromatic aberration. In addition, the lens system 200 has a small F number (Fno), i.e., 2.04, and therefore can have a short exposure time, which can further adapt to a screen with low transmittance.

[0186] In summary, in several exemplary embodiments provided in the present 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 larger FOV and a smaller F number.

[0187] In addition to the above-mentioned lens system 200, the embodiment of the present application also provides a fingerprint recognition device.

[0188] Fig.15 A schematic block diagram of a fingerprint recognition device 300 provided in an embodiment of the present application is shown. Fig.15 As shown, the fingerprint recognition device 300 may include a lens system 200 and a fingerprint image sensor 310 .

[0189] The lens system 200 may be any of the lens systems in the above embodiments. The fingerprint image sensor 310 is disposed below the lens system 200 and is used to receive the fingerprint optical signal transmitted by the lens system 200 and process the fingerprint optical signal to obtain a fingerprint image.

[0190] Specifically, the fingerprint image sensor 310 may be disposed on the imaging surface 240 of the lens system 200 . In other words, the surface of the fingerprint image sensor 310 may be the imaging surface 240 of the lens system 200 .

[0191] The fingerprint optical signal transmitted by the lens system 200 is a light signal reflected or scattered by the finger, and thus carries the fingerprint information of the finger. The fingerprint image sensor 310 can convert the fingerprint optical signal into an electrical signal, thereby forming a fingerprint image with fingerprint information.

[0192] Fig.16 A schematic structural diagram of a fingerprint recognition device 300 provided in an embodiment of the present application is shown.

[0193] like Fig.16 As shown, the fingerprint recognition device 300 is disposed below the display screen 20. The display screen 20 can provide a light source for the fingerprint recognition device 300. Specifically, when the user's finger presses on the display screen 20, the display screen 20 can emit a light source signal to the user's finger, and the light source signal is reflected or scattered by the finger to form a fingerprint light signal carrying fingerprint information.

[0194] The fingerprint recognition device 300 may include: a lens system 200 and a bracket 340 for assembling the lens system 200. Optionally, the first lens 210 in the lens system 200 may be interference fitted in the bracket 340 to improve the overall reliability of the lens system 200.

[0195] Specifically, the bracket 340 can be used to control the accuracy of the defocus and decentering of the first lens 210 in the lens system 200, thereby facilitating the control of the imaging performance of the lens system 200. The bracket 340 can be formed by metal stamping, or can also be prepared by other methods, which is not specifically limited in the present application.

[0196] In addition to the lens system 200 and the bracket 340, the fingerprint recognition device 300 also includes: a circuit board 320, which is arranged 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 fingerprint recognition device 300 and the outside.

[0197] Optionally, the circuit board 320 may be a flexible printed circuit (FPC), and a reinforcing plate 330 may be provided under the FPC to support and reinforce the FPC, thereby improving the mechanical strength and reliability of the entire fingerprint recognition device 300. As an example, the reinforcing plate 330 may be a steel plate or a printed circuit board (PCB).

[0198] The lower surface of the fingerprint image sensor 310 can be attached to the circuit board 320 by chip attaching adhesive to achieve structural connection between the fingerprint image sensor 310 and the circuit board 320. In addition, the fingerprint image sensor 310 can be electrically connected to the circuit board 320 by wire bonding or other electrical connection methods, so that the relevant electrical signals of the fingerprint image sensor 310 can be transmitted to external electronic devices through the circuit board 320.

[0199] Continue to see Fig.16 As shown, the upper surface of the fingerprint image sensor 310 may be provided with an extra-optical light filter layer 350 , and the extra-optical light filter layer 350 may be attached to the upper surface of the fingerprint image sensor 310 by means of a light filter layer bonding adhesive.

[0200] In the embodiment of the present application, the extra-optical filter layer 350, the fingerprint image sensor 310, the circuit board 320 and the reinforcement plate 330 are connected to each other through an adhesive layer to form a fingerprint image sensor module. The module can be bonded to the bracket 340 equipped with the lens system 200 through the adhesive layer to form an integrated fingerprint recognition device 300, thereby facilitating the installation of the integrated fingerprint recognition device 300 under the display screen 20.

[0201] The present application also provides a terminal device, such as Fig.17 As shown, the terminal device 400 may include the fingerprint recognition device 300 and the display screen 20 in the above embodiment. The fingerprint recognition device 300 is arranged below the display screen 20 to realize the fingerprint recognition under the screen.

[0202] Optionally, in some implementations, the fingerprint recognition device 300 may be disposed in a middle frame of the terminal device 400 , thereby enabling the fingerprint recognition device 300 to be disposed below the display screen 20 of the terminal device 400 .

[0203] Optionally, in order to protect the display screen 20, a protective layer or a heat dissipation layer such as foam and copper foil may be provided on the lower surface of the display screen 20, wherein the foam and copper foil areas corresponding to the lens system 200 in the fingerprint recognition device 300 are opened so that the optical signal including the fingerprint information can enter the lens system 200, thereby enabling the fingerprint recognition device 300 to perform the fingerprint recognition function.

[0204] As an example but not limitation, the terminal device 400 can be a mobile phone, a tablet computer, a laptop computer, a desktop computer, an in-vehicle electronic device or a wearable smart device, etc. The wearable smart device includes a full-featured, large-sized, and non-reliant smart phone to achieve complete or partial functions, such as: smart watches or smart glasses, etc., as well as devices that only focus on a certain type of application function and need to be used in conjunction with other devices such as smart phones, such as various types of smart bracelets and smart jewelry for vital sign monitoring.

[0205] It should be noted that, under the premise of no conflict, the various embodiments described in this application and / or the technical features in each embodiment can be arbitrarily combined with each other, and the technical solution obtained after the combination should also fall within the protection scope of this application.

[0206] For ease of description, in each embodiment of the present application, the same reference numerals represent the same components, and for the sake of 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 the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0207] Unless otherwise stated, all technical and scientific terms used in the embodiments of the present application have the same meaning as those generally understood by those skilled in the art of the present application. The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit the scope of this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items.

[0208] It should be understood that the specific examples in the embodiments of the present application are only to help those skilled in the art to better understand the embodiments of the present application, rather than to limit the scope of the embodiments of the present application. Those skilled in the art can make various improvements and modifications based on the above embodiments, and these improvements or modifications all fall within the scope of protection of the present application.

[0209] The above are only preferred embodiments of the present application, and are not intended to limit the present application in any form. Although the present application has been disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technical personnel in the field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present application. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A lens system, characterized in that: Including: A first lens and a second lens arranged in sequence from the object side to the image side; The first lens is a lens with negative optical power, and the second lens is a lens with positive optical power; The surface of the first lens facing the object side is the largest surface in size in the lens system; The maximum effective size D11 of the surface of the first lens facing the object side and the maximum effective size D21 of the surface of the second lens facing the object side satisfy: 0.2 < (D11 - D21) / TH < 1.8, where TH is the distance from the surface of the first lens facing the object side to the surface of the second lens facing the object side in the optical axis direction; The maximum image height Y', focal length f, and optical length CTL of the lens system on the imaging surface satisfy: 0.5 < |Y' / (f * CTL)| < 1.24, where the optical length CTL represents the distance from the surface of the first lens facing the object side to the imaging surface; 2. The lens system according to claim 1, wherein: The focal length f1 of the first lens and the combined focal length f12 of the first lens and the second lens satisfy: -7 < f1 / f12 < -0.5; and / or, The focal length f2 of the second lens and the combined focal length f12 of the first lens and the second lens satisfy: 0.45 < f2 / f12 < 1.4; 3. The lens system according to claim 2, characterized in that: The focal length f1 of the first lens and the radius of curvature r1 of the surface of the first lens facing the object side satisfy: -0.4 < r1 / f1 < 0.9; and / or, The focal length f1 of the first lens and the radius of curvature r2 of the surface of the first lens facing the image side satisfy: -5 < f1 / r2 < 8; 4. The lens system according to claim 2, wherein: The thickness CT1 of the first lens on the optical axis and the focal length f of the lens system satisfy: 0.35 < CT1 / f < 0.65; 5. The lens system according to claim 2, wherein: The focal length f2 of the second lens and the radius of curvature r3 of the surface of the second lens facing the object side satisfy: 0.2 < f2 / r3 < 1.0; and / or, The radius of curvature r3 of the surface of the second lens facing the object side and the radius of curvature r4 of the surface of the second lens facing the image side satisfy: -0.65 < r4 / r3 < -0.2; 6. The lens system according to claim 1, wherein: The thickness CT1 of the first lens on the optical axis and the thickness CT2 of the second lens on the optical axis satisfy: 0.2 < CT1 / CT2 < 0.6; 7. The lens system according to claim 1, wherein: The refractive index n1 and Abbe number v1 of the first lens satisfy: 1.5 < n1 < 1.7, 20 < v1 < 60; and / or, The refractive index n2 and Abbe number v2 of the second lens satisfy: 1.5 < n2 < 1.7, 20 < v2 < 60; 8. The lens system according to any one of claims 1 to 7, characterized in that: The lens system further includes a third lens, which is arranged on the image-side of the second lens; The third lens is a lens with positive optical power; The focal length f3 of the third lens and the focal length f of the lens system satisfy: 3 < f3 / f < 5.5; 9. The lens system according to claim 8, wherein: The focal length f3 of the third lens and the radius of curvature r5 of the surface of the third lens facing the object side satisfy: 3.2 < f3 / r5 < 5.0; and / or, The focal length f3 of the third lens and the radius of curvature r6 of the surface of the third lens facing the image side satisfy: 2.1 < f3 / r6 < 3.8; 10. The lens system according to claim 8, wherein: The refractive index n3 and Abbe number v3 of the third lens satisfy: 1.5 <n3<1.7,20<v3<60。 11. The lens system according to any one of claims 1 to 7, characterized in that: The system parameters of the lens system satisfy that the F number is less than or equal to 2.

0.

12. The lens system according to any one of claims 1 to 7, wherein: The system parameters of the lens system satisfy that the field of view FOV is greater than 110°.

13. The lens system according to any one of claims 1 to 7, characterized in that: The lens system further comprises: The aperture is disposed between the first lens and the second lens.

14. A fingerprint recognition device, characterized in that: include: A fingerprint image sensor, and a lens system as claimed in any one of claims 1 to 13; The fingerprint image sensor is arranged below the lens system, and is used to receive the fingerprint light signal transmitted by the lens system, and process the fingerprint light signal to obtain a fingerprint image.

15. The fingerprint recognition device according to claim 14, characterized in that: The fingerprint recognition device further comprises: a bracket; wherein the lens system is interference fitted in the bracket.

16. The fingerprint recognition device according to claim 14, characterized in that: The fingerprint recognition device further includes: a circuit board; The circuit board is arranged below the fingerprint image sensor and is electrically connected to the fingerprint image sensor. The circuit board is used to realize the transmission of electrical signals between the fingerprint recognition device and the outside.

17. The fingerprint recognition device according to claim 16, characterized in that: The fingerprint recognition device further includes: a reinforcement plate; Wherein, the reinforcement plate is arranged below the circuit board, and the reinforcement plate is used to increase the mechanical strength and reliability of the fingerprint recognition device.

18. A terminal device, characterized in that: include: A display screen, and a fingerprint recognition device as claimed in any one of claims 14 to 17; Among them, the fingerprint recognition device is arranged under the display screen to realize under-screen fingerprint recognition.

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