TW202111605A - In-display fingerprint recognition system for purifying fingerprint images capable of effectively removing noise and overlap of an fingerprint image - Google Patents

Abstract

An in-display fingerprint recognition system for purifying fingerprint images uses total internal reflection transmission of light in a light guide panel to detect fingerprints, which is characterized in that a filter element is provided on at least one of a light entrance end and a light exit end of the light guide panel. After the light is filtered by the filter element, a first part of the light within a specified angle or wavelength range can be guided out from the light exit end, and a second part of the light outside the specified angle or wavelength range will not be guided out. Thereby, through the mechanism of filtering the angle and wavelength of the incident light, the noise and overlap of the fingerprint image can be effectively removed.

Description

Under-screen fingerprint recognition system for purifying fingerprint images

The present invention relates to an under-screen fingerprint identification technology, in particular to an under-screen fingerprint identification system for purifying fingerprint images.

Fingerprint recognition is a type of biometric identification technology. It uses the unique fingerprint information on the human finger to recognize it. It is widely used due to its advantages in security and convenience. For example, almost all of today's smart phones The fingerprint recognition function is added, which can provide fingerprint encryption and fingerprint unlocking.

Based on the trend of the panel market, combining the fingerprint recognition function with the display function of the display panel is a hot topic that the industry is actively researching. The fingerprint recognition system is integrated or integrated into the display panel. If the fingerprint recognition components are placed above the display panel, since the silicon wafer-based photosensitive element is opaque, it will be exposed outside the display panel , And placing it under the display panel has the problem of penetration, which may not be able to receive the reflected light of the fingerprint well, which affects the accuracy of fingerprint recognition. Therefore, there are certain limitations in integrating the fingerprint recognition system into the display panel, and it is difficult not to interfere with the product design.

Currently, an under-screen fingerprint recognition technology that applies the optical "Frustrated Total Internal Reflection" (FTIR) principle has been actively developed, which can break through the appearance limitations of traditional fingerprint recognition products. However, in order to achieve a high screen-to-body ratio and a small-volume optical module in the under-screen fingerprint recognition system, the angle of the incident light cannot be well collimated, which often allows a lot of noise to enter the light guide panel, resulting in a lot of images. The overlapping images at different angles affect the accuracy of fingerprint recognition.

In view of the above problems, the main purpose of the present invention is to provide an under-screen fingerprint recognition system for purifying fingerprint images. A filter element is provided at the light entrance or exit end of the light guide panel, so that the light source angle or the light source inside the light guide panel can exist. The wavelength range is reduced to achieve the effect of removing the overlap of the fingerprint image.

Therefore, in order to achieve the above objective, the present invention provides an under-screen fingerprint recognition system for purifying fingerprint images, which mainly includes a light guide panel, a light source, a filter element, a signal amplifier and a photosensitive element. Wherein, the surface of the light guide panel has a fingerprint sensing area for finger pressing, and the light guide panel has a light entrance end and a light exit end. The light source is used to emit light, and the light is guided into the light guide panel from the light entrance end and transmitted in the light guide panel through the total internal reflection effect. The filter element is arranged at at least one of the light entrance end and the light exit end to filter light so that the first part of the light within a specified angle or wavelength range is derived from the light exit end, and the light is within the specified angle or wavelength range The second part outside is not exported. The signal amplifier receives the first part of the light, and amplifies the first part before exporting it. The photosensitive element faces the fingerprint sensing area, and receives the first part of the light amplified by the signal amplifier, and processes the first part into a fingerprint image, so as to achieve the purpose of fingerprint recognition.

According to an embodiment of the present invention, the filter element has at least one hole or slit, so that the first part of the light can pass through the hole or the slit, and the second part of the light cannot pass.

According to an embodiment of the present invention, the filter element is a multilayer filter film, so that the first part of the light can penetrate the multilayer filter film, and the second part of the light cannot penetrate.

According to an embodiment of the present invention, the light guide panel is respectively provided with a first light guide portion and a second light guide portion adjacent to the light entrance end and the light exit end, so that the light introduced by the light entrance end passes through the first light guide The light part is transmitted to the fingerprint sensing area, and is transmitted to the light emitting end through the second light guide part.

According to an embodiment of the present invention, the filter element is a reflective coating on a partial surface of the first light guide part or the second light guide part, so that the first part of the light is reflected by the reflective coating, and the second part of the light is reflected by the reflective coating. Part of it does not pass through the reflective coating and is not reflected.

According to an embodiment of the present invention, the filter element is a reflective coating on the surface of at least one of the first light guide portion and the second light guide portion, and the reflective coating has a flat reflective area and a chamfer to make light The first part of the light is reflected by the reflective area of the reflective coating, and the second part of the light is not guided into the signal amplifier and the sensing element through the chamfer of the reflective coating.

According to an embodiment of the present invention, the specified wavelength range is between 380 and 1400 nanometers (nm).

According to an embodiment of the present invention, the specified angle range is the angle between the traveling direction of the light and the normal direction of the surface or bottom surface of the light guide panel, and the specified angle range is 0-10 degrees.

The under-screen fingerprint recognition system for purifying fingerprint images provided by the present invention uses filter elements to filter the angle and wavelength of incident light, so that a part of the light within the specified angle or wavelength range can be exported and detected without being exported The rest is to avoid generating unnecessary noise to interfere with the quality of the sensing, thereby improving the recognition rate of the fingerprint image.

Detailed descriptions are given below by specific embodiments, so that it will be easier to understand the purpose, technical content, features, and effects of the present invention. The following detailed descriptions are combined with specific embodiments and accompanying drawings to make it easier to understand the purpose, technical content, characteristics and effects of the present invention.

Please refer to FIG. 1 and FIG. 2, which illustrate a cross-sectional view and a bottom view of the under-screen fingerprint recognition system 20 for purifying fingerprint images according to the first embodiment of the present invention. The fingerprint recognition system 20 under the screen is mainly composed of a light guide panel 21, a light source 22, a filter element 25, a signal amplifier 23 and a photosensitive element 24.

In this embodiment, the surface of the light guide panel 21 has a fingerprint sensing area 211 that can be pressed by the finger A; in practical applications, the fingerprint sensing area 211 can be provided on the entire surface or a partial area of the light guide panel 21. In this embodiment, the light guide panel 21 has a light entrance end 212 and a light exit end 213 on both sides, respectively, and a first light guide portion 214 and a second light guide portion 215 are respectively provided at the light entrance end 212 and the light exit end 213. Specifically, the first light guide portion 214 and the second light guide portion 215 can be reflective plates for adjusting the transmission angle of light; in practical applications, the positions of the light entrance end 212 and the light exit end 213 can also be designed to be the light guide The middle cut end of the panel 21. The material of the light guide panel 21 can be glass, the first light guide 214 and the second light guide 215 can be in the form of a mirror or an optical fiber, and the first light guide 214 and the second light guide 215 are opposite to the light guide. The panel 21 can be provided separately. Of course, the first light guide portion 214 and the second light guide portion 215 can also be designed as an integrated structure with the light guide panel 21.

In this embodiment, the light source 22 is adjacent to the first light guide portion 214 and emits light toward the first light guide portion 214. After the light passes through the light entrance end 212, it is reflected by the first light guide portion 214 or transmitted to the light guide panel. In 21, the total internal reflection (TIR) effect transmission is performed through the reflection of the fingerprint sensing area 211, and then transmitted to the light output end 213, and then reflected or transmitted through the second light guide 215.

To further explain, in order to allow the light to be totally internally reflected in the light guide panel 21, the angle between the light and the normal direction of the surface or bottom surface of the light guide panel 21 (here for the convenience of the following description, referred to as the incident angle θ) , The minimum angle is arcsin (n ₀ /n ₂ ) and arcsin (n ₁ /n ₂ ) to achieve total internal reflection. Therefore, when the light travels in the light guide panel 21, its incident angle θ must be greater than the minimum angle required for the above two items of total internal reflection at the same time, that is, the incident angle θ must be greater than arcsin (n ₀ /n ₂ ) and arcsin (N ₁ /n ₂ ); where n ₀ is the refractive index of the surface of the light guide panel 21; n ₁ is the refractive index of the bottom surface of the light guide panel 21; and n ₂ is the refractive index of the light guide panel 21.

In this embodiment, the refractive index of the light guide panel 21 is 1.5. When the surface and the bottom surface of the light guide panel 21 are both adjacent to the air, the light traveling direction in the light guide panel 21 is different from the normal direction of the surface or bottom surface. The included angle, that is, the incident angle θ is greater than 43 degrees; when only one of the surface and bottom of the light guide panel 21 is adjacent to the air, and the other side is adjacent to the material with a refractive index of 1.4, the light in the light guide panel 21 The angle between the traveling direction and the normal direction of the surface or bottom surface, that is, the incident angle θ is greater than 70 degrees.

Furthermore, the wavelength of light can be between 380 and 1400 nanometers (nm); in practical applications, it can be divided into the visible light range (380 to 780 nm) and the near infrared range (780 to 1400 nm). To further explain, when the wavelength of the visible light range is used, it is visible to the naked eye, and different wavelengths can be used to mark the effective or ineffective area to help users understand the available area; when the wavelength of the near-infrared range is used, it is invisible to the naked eye and is suitable for use Under the display panel (under display) or in an environment where the demand is not noticed by the user.

In the above-mentioned embodiment, the light source 22 is used to provide collimated light. Specifically, it can be a collimated light source of a laser (Laser), a vertical cavity surface shot laser (VCSEL), or a non-collimated light source and secondary optics. Furthermore, the secondary optical element can be selected from the group consisting of a parabolic surface condenser, a compound parabolic condenser (CPC), a lens, a lens, a Fresnel lens, and a combination thereof. Alternatively, the light source 22 can provide uncollimated light, and then a high-order angle filter is arranged on the photosensitive element 24 side, which can also achieve fingerprint imaging. For the detailed features of the various implementation aspects of the light source 22, please refer to the optical fingerprint recognition system described in the Republic of China Invention Patent Application No. 106145847, which is incorporated herein by reference, and will not be repeated.

In the present invention, in order to limit the light transmitted in the light guide panel 21 to a specified angle or wavelength range to avoid the generation of noise and remove the overlap of the fingerprint image, the filter element 25 is used to emit the light source 22 The light is filtered so that the exported light can be reduced to a specified angle or wavelength range; the better specified wavelength range is about 380～1400 nanometers (nm), and the specified angle range refers to the direction of light travel and the guide The included angle of the normal direction of the surface or bottom surface of the light panel 21, and the preferable specified angle range is 0-10 degrees.

In this embodiment, the filter element 25 is disposed at the light entrance end 212 and the light exit end 213 on both sides of the light guide panel 21 to filter the light emitted by the light source 22 to make the first part of the light within a specified angle or wavelength range It is derived from the light emitting end 213, and the second part of the light outside the specified angle or wavelength range is not derived. In this embodiment, a filter element 25 is provided at each of the light entrance end 212 and the light exit end 213 to minimize the angle or wavelength range of the light entering and exiting the light guide panel 21; in practical applications, the filter element 25 can also be used. It is only provided at the light input end 212 or the light output end 213.

Furthermore, the filter element 25 of this embodiment has a hollow slit 251. The slit 251 on the light guide panel 21 needs to be located in the vertical projection direction of the light source 22 and the signal amplifier 23. The material of the slit 251 penetrates the light source 22 The ratio is preferably less than 1%. As shown in Figure 2, the width d _{1 of the} slit 251 is less than 0.5 millimeters (mm), preferably less than 0.3 mm, and the thickness is less than 2 mm. In addition, the slit length L ₁ at the light entrance end 212 is less than the length of the light source 22, and the slit length L ₁ at the light exit end 213 is less than the length of the signal amplifier 23 and greater than the length of the photosensitive element 24. The length of each element is It is the same direction as the length L _{1 of the slit 251.} In addition, the filter element 25 can be designed to have strip-shaped slits, but can also have a single hole or a plurality of holes arranged in an array, or the holes can be circular holes or other geometric shapes, such as rectangles; in practice As long as the structural design of the slit or hole can achieve the effect that the first part of the light can pass, but the second part of the light cannot pass.

In this embodiment, the signal amplifier 23 is adjacent to the second light guide portion 215, and is used to receive the first part of the light derived from the second light guide portion 215, and amplify the first part before exporting; the signal amplifier 23 can be a mirror surface form.

In this embodiment, the photosensitive element 24 is adjacent to the signal amplifier 23 for receiving the first part of the light amplified by the signal amplifier 23, and processing the first part into a fingerprint image, so as to achieve the purpose of fingerprint recognition.

In the above embodiment, a lens, a Prism film, an angular filter, or a combination thereof may be further included between the photosensitive element 24 and the signal amplifier 23. For the detailed features of the various implementations of the photosensitive element 24 and the signal amplifier 23, please also refer to the optical fingerprint recognition system described in the Republic of China Invention Patent Application No. 106145847, which is incorporated herein by reference. Go into details.

In use of the under-screen fingerprint recognition system 20 of the present invention, when the user presses the fingerprint sensing area 211 on the surface of the light guide panel 21 with a finger A, the total internal reflection of the light in the light guide panel 21 will be destroyed. The light element 25 filters the light so that the light guide panel 21 only exports the first part of the light within the specified angle or wavelength range, and does not lead out the remaining part (ie the second part of the light), so it will not cause unnecessary noise , The photosensitive element 24 can more accurately detect the first part of the light, and process it into a clear fingerprint image, so as to achieve the purpose of improving the fingerprint recognition effect.

In addition, please refer to FIG. 3, which shows a cross-sectional view of the under-screen fingerprint recognition system 20 for purifying fingerprint images provided by the second embodiment of the present invention.

In this embodiment, the filter element 25 includes a multi-layer filter film 252 respectively disposed at the light entrance end 212 and the light exit end 213 of the light guide panel 21, and the multi-layer filter film 252 can also select the light entrance end 212 and the light exit end 213. One end of the light is set so that the first part of the light can pass through the multilayer filter film 252, while the second part of the light cannot pass, so as to reduce the angle or wavelength range of the light entering or exiting the light guide panel 21. Specifically, the multilayer filter film 252 of this embodiment is made of a combination of high refractive index and low refractive index materials, such as the combination of titanium dioxide (TiO ₂ ) and silicon _{dioxide (SiO 2} ), and the two are stacked layers The number is greater than 20, the overall thickness is less than 5 microns (μm), the transmittance of light emitted by the light source 22 is greater than 80%, and it is preferable to have a filtering mechanism for angles, such as the direction of light travel and the surface of the light guide panel 21 or The normal direction of the bottom surface is parallel within 0-10 degrees, and it can pass through the multilayer filter film 252. The angle between the traveling direction of the light and the normal direction of the light guide panel 21 or the bottom surface is greater than 10 degrees, and it cannot penetrate the multilayer filter. The light film 252, of course, the smaller the angle of the filtered light, the better.

Please refer to FIG. 4 and FIG. 5, which respectively show a cross-sectional view and a top view of the under-screen fingerprint recognition system 20 for purifying fingerprint images provided by the third embodiment of the present invention.

In this embodiment, the filter element 25 includes a reflective coating 253 respectively disposed on the partial surfaces of the first light guide portion 214 and the second light guide portion 215 of the light guide panel 21, and the reflective coating 253 can also be selected as the first guide The light portion 214 and one of the two ends of the second light guide portion 215 are arranged so that the first part of the light is reflected by the reflective coating 253, and the second part of the light is not reflected by the reflective coating 253. In this embodiment, the reflective coating 253 has a reflectivity of more than 80% for the light emitted by the light source 22, which can be penetrated by the visible light source, and the light of the other wavelength bands is reflected in the light guide panel 21. Furthermore, the smaller the area of the reflective coating 253, the smaller the angle range of light that can enter or exit the light guide panel 21. In this embodiment, the width d _{2 of the} reflective coating 253 is reduced from z/cotα to less than 0.5z/cotα, and the length L _{2 of the} reflective coating 253 is greater than the length of the photosensitive element 24; where z is the thickness of the light guide panel 21, α It is the angle between the first light guide portion 214 or the second light guide portion 215 and the bottom surface of the light guide panel 21, and the length direction of the photosensitive element 24 is the same as _{the length L 2 direction of the reflective coating.}

Please refer to FIG. 6, which is a cross-sectional view of the under-screen fingerprint recognition system 20 for purifying fingerprint images provided by the fourth embodiment of the present invention.

In this embodiment, the filter element 25 is a reflective coating 254 formed on the surface of the first light guide portion 214 and the second light guide portion 215 of the light guide panel 21, and one of the two ends can also be selected. The center of the coating 254 has a flat reflection area 256, and the design of chamfers 255 on both sides, so that the first part of the light entering the reflection area 256 of the reflection coating 254 can be reflected and guided into the signal amplifier 23 and the sensing element 24. The second part of the light entering the chamfer 255 area of the reflective coating 254 does not pass through the reflective area 256 and will not be guided to the signal amplifier 23 and the sensing element 24. To further illustrate, since the reflective coating 254 of this embodiment is provided with a chamfer 255, the reflective area 256 that can effectively reflect light is reduced, and the light angle range that can meet the aforementioned total internal reflection condition is also reduced. In this embodiment, the angle of the light needs to meet the conditions of total internal reflection of the reflective area 256 of the reflective coating 254 of the first light guide portion 214 and the second light guide portion 215 at the same time, in order to be smoothly transmitted through the light guide panel 21. In this embodiment, the size of the reflective area 256 of the reflective coating 254 with a chamfer 255 is equivalent to the size of the reflective coating 253 provided only in a partial area in the third embodiment, and its width is reduced from z/cotα to less than 0.5z/ cotα; where z is the thickness of the light guide panel 21, and α is the angle between the first light guide portion 214 or the second light guide portion 215 and the bottom surface of the light guide panel 21.

In the present invention, the above embodiments are directed to the various specific aspects provided by the filter element 25, which can be combined in practical applications. For example, the filter element 25 may include a slit 251 and a reflective coating 254 with a chamfer 255, or, The filter element 25 may include a slit 251 and a reflective coating 253 and other structures.

On the other hand, the present invention can be applied to products in which an under-screen fingerprint recognition system is integrated with a display panel. As shown in FIG. 7, in this embodiment, the light guide panel 21 is disposed above a display panel 30, and the photosensitive element 24 is concealed on the back of the display panel 30; in practical applications, the light guide panel 21 can be attached to the display panel 30 by coating optical glue 216 or dispensing glue according to the design requirements. In order to easily achieve fingerprint recognition on the entire surface, guide The light panel 21 preferably adopts a method of coating the entire bottom surface with optical glue. Since the photosensitive element 24 of the present invention does not use the reflected light of receiving fingerprints for detection, it does not cause the problem of insufficient penetration, which makes it more widely used.

In addition, the present invention can also combine the under-screen fingerprint recognition system with the camera lens of the mobile phone. That is to say, the present invention can be shared with the camera lens of the mobile phone to reach the photosensitive element 24, so that the under-screen fingerprint recognition system 20 for purifying fingerprint images is not used. Occupies too much structural space, so that the volume of the final product can be simplified. For the detailed content of this part, please refer to the optical fingerprint recognition system described in the Republic of China Invention Patent Application No. 106145847, which is incorporated herein by reference, and will not be repeated.

In the embodiment of the present invention, the type, shape, number, and relative position of the light guide panel 21 and its first light guide portion 214 and second light guide portion 215, light source 22, filter element 25, signal amplifier 23 and photosensitive element 24 The equivalence relationship is only taken as an example, and is not limited thereto, and anything equal to the spirit of the case does not depart from the scope of the present invention.

In summary, the under-screen fingerprint recognition system for purifying fingerprint images disclosed in the present invention uses the principle that light can be transmitted in the light guide panel through the total internal reflection effect to detect fingerprints, and in order to avoid the interference of noise, In the present invention, the light transmitted in the light guide panel is filtered by the filter element, the angle or wavelength of the incident light is filtered, and only the part of the light within the specified angle or wavelength range is exported, and the rest is not exported. It can effectively solve the problem that the conventional fingerprint image under the screen is prone to overlap, which is beneficial to improve the recognition rate of fingerprint sensing.

Only the above are only preferred embodiments of the present invention, and are not used to limit the scope of implementation of the present invention. Therefore, all equivalent changes or modifications made in accordance with the characteristics and spirit of the application scope of the present invention shall be included in the patent application scope of the present invention.

20: Under-screen fingerprint recognition system 21: Light guide panel 211: Fingerprint sensing area 212: Light entrance 213: Light exit 214: First light guide 215: Second light guide 216: Optical glue 22: Light source 23: Signal amplifier 24: photosensitive element 25: filter element 251: slit 252: multilayer filter film 253: reflective coating 254: reflective coating 255: chamfer 256: reflective area 30: display panel A: fingers d ₁ , d ₂ : Width L ₁ , L ₂ : length z: thickness θ: incident angle α: included angle

Figure 1 is a cross-sectional view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the first embodiment of the present invention. Figure 2 is a bottom view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the first embodiment of the present invention. Figure 3 is a cross-sectional view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the second embodiment of the present invention. Figure 4 is a cross-sectional view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the third embodiment of the present invention. FIG. 5 is a top view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the third embodiment of the present invention. Figure 6 is a cross-sectional view of the under-screen fingerprint recognition system for purifying fingerprint images provided by the fourth embodiment of the present invention. FIG. 7 is a schematic diagram of the combination of an under-screen fingerprint recognition system for purifying fingerprint images and a display panel provided by the fifth embodiment of the present invention.

20: Fingerprint recognition system under the screen

21: Light guide panel

211: Fingerprint sensing area

212: light end

213: light end

214: The first light guide

215: second light guide

22: light source

23: signal amplifier

24: photosensitive element

25: filter element

251: Slit

A: Finger

θ: incident angle

Claims (12)

An under-screen fingerprint identification system for purifying fingerprint images, including: A light guide panel with a light entrance end and a light exit end, and the surface has a fingerprint sensing area that can be pressed by a finger; A light source for emitting a light, the light is guided into the light guide panel from the light entrance end and reflected by the fingerprint sensing area for total internal reflection transmission; A filter element is arranged on at least one of the light entrance end and the light exit end to filter the light so that the first part of the light within a specified angle or wavelength range is derived from the light exit end. The second part outside the specified angle or wavelength range is not exported; A signal amplifier that receives the first part of the light and amplifies the first part; and A photosensitive element, facing away from the fingerprint sensing area, receives the first part of the light amplified by the signal amplifier, and processes the first part into a fingerprint image. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the filter element has at least one hole or slit, so that the first part of the light can pass through the hole or slit, and the light The second part of it could not be passed. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the filter element is a multilayer filter film, so that the first part of the light can penetrate the multilayer filter film, and The second part of the light cannot penetrate. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the light guide panel is provided with a first light guide portion and a second light guide at the vicinity of the light entrance end and the light exit end, respectively The light part enables the light introduced by the light entrance end to be transmitted to the fingerprint sensing area through the first light guide part, and to the light exit end through the second light guide part. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 4, wherein the filter element is a partial surface of at least one of the first light guide portion and the second light guide portion The reflective coating makes the first part of the light reflect through the reflective coating, and the second part of the light does not pass through the reflective coating and is not reflected. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 4, wherein the filter element is a reflection on the surface of at least one of the first light guide portion and the second light guide portion The reflective coating has a flat reflective area and a chamfer, so that the first part of the light is reflected by the reflective region of the reflective coating, and the second part of the light passes through the inverted portion of the reflective coating The angle is not introduced into the signal amplifier and the sensing element. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the fingerprint sensing area is all or a partial area of the surface of the light guide panel. The under-screen fingerprint recognition system for purifying fingerprint images as described in claim 1, wherein the light guide panel is arranged above a display panel. The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the light source is a collimated light source or a combination of a non-collimated light source and a secondary optical element. The under-screen fingerprint recognition system for purifying fingerprint images as described in claim 9, wherein the collimated light source is a laser (Laser) or a vertical cavity surface laser (VCSEL). The under-screen fingerprint recognition system for purifying fingerprint images as described in claim 1, wherein the specified wavelength range is between 380 and 1400 nanometers (nm). The under-screen fingerprint recognition system for purifying fingerprint images according to claim 1, wherein the specified angle range is the angle between the traveling direction of the light and the normal direction of the surface or a bottom surface of the light guide panel, and The specified angle range is 0 to 10 degrees.

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