CN111133442B

CN111133442B - Fingerprint detection device and electronic equipment

Info

Publication number: CN111133442B
Application number: CN201980004078.1A
Authority: CN
Inventors: 谢浩; 杜灿鸿; 汪海翔
Original assignee: Shenzhen Goodix Technology Co Ltd
Current assignee: Shenzhen Goodix Technology Co Ltd
Priority date: 2019-08-06
Filing date: 2019-08-06
Publication date: 2023-08-22
Anticipated expiration: 2039-08-06
Also published as: WO2021022680A1; CN111133442A; WO2021022488A1; CN210605741U

Abstract

A fingerprint detection device is capable of improving fingerprint detection performance. The device is suitable for being used below a display screen to realize off-screen optical fingerprint detection, and comprises: a first light guide layer disposed above the image collection unit for transmitting an oblique light signal incident to a finger above the display screen and returned through the finger to the image collection unit, wherein the oblique light signal includes a reflected light signal and a transmitted light signal from the finger, the reflected light signal being attenuated by a linear polarization unit located in an optical path between the finger and the image collection unit such that a proportion of the transmitted light signal reaching the image collection unit relatively increases; the image acquisition unit is used for receiving the inclined light signals by pixels below the first light guide layer in the image acquisition unit, and the inclined light signals are used for acquiring fingerprint images of the finger.

Description

Fingerprint detection device and electronic equipment

Technical Field

The embodiment of the application relates to the field of fingerprint detection, and in particular relates to a fingerprint detection device and electronic equipment.

Background

The fingerprint detection technology under the optical screen is to collect an optical signal formed by the reflection or transmission of light rays on a finger, wherein the optical signal carries fingerprint information of the finger, so that fingerprint detection under the screen is realized. For special fingers, such as drier fingers, an air gap exists between the fingerprint and the display screen, and the air gap can lead to the reflection difference of ridges and valleys of the fingerprint to light rays to be small, so that the contrast of the fingerprint image is reduced, and the fingerprint detection performance is affected.

Disclosure of Invention

The embodiment of the application provides a fingerprint detection device and electronic equipment, which can improve fingerprint detection performance.

In a first aspect, there is provided a fingerprint detection apparatus adapted for use below a display screen to enable off-screen optical fingerprint detection, the apparatus comprising:

a first light guide layer disposed above the image collection unit for transmitting an oblique light signal incident to a finger above the display screen and returned through the finger to the image collection unit, wherein the oblique light signal includes a reflected light signal and a transmitted light signal from the finger, the reflected light signal being attenuated by a linear polarization unit located in an optical path between the finger and the image collection unit such that a proportion of the transmitted light signal reaching the image collection unit relatively increases;

The image acquisition unit is used for receiving the inclined light signals by pixels below the first light guide layer in the image acquisition unit, and the inclined light signals are used for acquiring fingerprint images of the finger.

In one possible implementation, the linear polarization unit is integrated inside the display screen and is located above a mechanical light emitting diode OLED layer of the display screen.

In one possible implementation, the linear polarization unit is located between the display screen and the image acquisition unit.

In one possible implementation, the polarization direction of the linear polarization unit is perpendicular to the incidence plane of the oblique optical signal; alternatively, the polarization direction of the linear polarization unit is parallel to the incidence plane of the oblique optical signal; alternatively, the included angle between the polarization direction of the linear polarization unit and the incident surface of the oblique optical signal is 45 °.

In one possible implementation, the oblique angle of the oblique optical signal is less than or equal to the brewster angle.

In one possible implementation, the first light guiding layer includes: a microlens array formed of a plurality of microlenses for converging the oblique optical signals; and at least one light blocking layer arranged below the micro lens array, wherein each light blocking layer comprises a plurality of openings corresponding to the micro lenses respectively, and the inclined optical signals converged by each micro lens pass through the openings corresponding to each micro lens in different light blocking layers to reach the image acquisition unit.

In one possible implementation, the projection of the collecting surface of each microlens in the microlens array on a plane perpendicular to its optical axis is rectangular or circular.

In one possible implementation, the curvature in each direction of the collection surface of each microlens in the microlens array is the same.

In one possible implementation, a last light blocking layer of the at least one light blocking layer is integrated in the image acquisition unit.

In one possible implementation, the apertures of the openings corresponding to the same microlenses in different light blocking layers decrease sequentially from top to bottom.

In one possible implementation, the apparatus further includes: and the transparent medium layer is used for connecting the micro lens array, the at least one light blocking layer and the image acquisition unit and filling the opening in the at least one light blocking layer.

In one possible implementation, the first light guiding layer includes: and the optical functional film layer is used for selecting the inclined optical signals from the optical signals in all directions returned by the finger and transmitting the inclined optical signals to the image acquisition unit.

In one possible implementation, the optical functional film layer is further configured to: and refracting the selected oblique light signals so that the oblique light signals are vertically incident on the pixels of the image acquisition unit.

In one possible implementation, the optical functional film layer is a grating film or a prism film.

In one possible implementation, the optical functional film layer is integrated in the image acquisition unit or is provided above the image acquisition unit as a device that is relatively independent of the image acquisition unit.

In one possible implementation, the first light guiding layer includes: a light guide channel array formed of a plurality of light guide channels.

In one possible implementation, the plurality of light guide channels are formed of optical fibers, air vias, or light transmissive materials.

In one possible implementation, the first light guiding layer is disposed horizontally, and the plurality of light guiding channels are inclined with respect to a surface of the first light guiding layer to guide the inclined light signals to the image acquisition unit.

In one possible implementation, the plurality of light guide channels are formed by optical fibers, the first light guide layer is disposed horizontally, the plurality of light guide channels are perpendicular to a surface of the first light guide layer, and the oblique light signal reaches the image acquisition unit after at least one total reflection in each of the plurality of light guide channels.

In one possible implementation, the plurality of light guiding channels are perpendicular to a surface of the first light guiding layer, and the first light guiding layer is obliquely arranged to guide the oblique light signals to the image acquisition unit.

In one possible implementation, the apparatus further includes: the second light guide layer is arranged above the image acquisition unit and is used for transmitting the light signals in the second direction returned by the finger to the image acquisition unit; the pixels below the second light guide layer in the image acquisition unit are used for receiving the light signals in the second direction, the light signals in the second direction are used for acquiring fingerprint images of the finger, the inclined light signals transmitted by the first light guide layer are light signals in the first direction, and the second direction is different from the first direction.

In one possible implementation, the second direction is a vertical direction or an oblique direction.

In one possible implementation, the apparatus further includes: the filtering layer is arranged in the light path between the display screen and the image acquisition unit and is used for filtering out optical signals of non-target wave bands and transmitting the optical signals of the target wave bands.

In one possible implementation, the filter layer is a plating film formed on a surface of any layer in the optical path.

In a possible implementation, the image acquisition unit comprises one optical fingerprint sensor or a plurality of optical fingerprint sensors spliced together.

In a second aspect, there is provided a fingerprint detection device adapted for use under a display screen to enable off-screen optical fingerprint detection, the device comprising:

the first light guide layer is arranged above the image acquisition unit and is used for transmitting the light signals which are incident to the finger above the display screen and return through the finger in the first direction to the image acquisition unit;

the second light guide layer is arranged above the image acquisition unit and is used for transmitting the light signals in the second direction returned by the finger to the image acquisition unit;

the image acquisition unit is characterized in that pixels below the first light guide layer in the image acquisition unit are used for receiving light signals in the first direction, pixels below the second light guide layer in the image acquisition unit are used for receiving light signals in the second direction, the light signals in the first direction and the light signals in the second direction are used for acquiring fingerprint images of the finger, and the first direction is different from the second direction.

In one possible implementation, the oblique light signal comprises a reflected light signal and a transmitted light signal from the finger, wherein the reflected light signal is attenuated by a linear polarization unit located in the optical path between the finger to the image acquisition unit such that the proportion of the transmitted light signal reaching the image acquisition unit is relatively increased.

In one possible implementation, the first direction is an oblique direction, and the second direction is a vertical direction or an oblique direction.

In one possible implementation, the incident surface of the optical signal in the first direction is perpendicular to the polarization direction of the linear polarization unit; alternatively, the incident surface of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit; alternatively, the angle between the incident surface of the optical signal in the first direction and the polarization direction of the linear polarization unit is 45 °.

In one possible implementation, the linear polarization unit is integrated inside the display screen and located above the OLED layer of the display screen.

In a third aspect, an electronic device is provided, comprising:

a display screen; the method comprises the steps of,

the apparatus of fingerprint detection in the first aspect or any possible implementation manner of the first aspect, or the apparatus of fingerprint detection in the second aspect or any possible implementation manner of the second aspect.

Based on the technical scheme, the inclined light is adopted for fingerprint detection, and the linear polarization unit is adopted, so that the reflected light energy in the light passing through the linear polarization unit is attenuated, the proportion of the transmitted light signals of the finger reaching the image acquisition unit is relatively increased, and the fingerprint detection performance, particularly the detection performance of special fingers such as dry fingers, is improved.

Drawings

Fig. 1A and 2A are schematic structural views of an electronic device to which the present application can be applied.

Fig. 1B and 2B are schematic cross-sectional views of the electronic device shown in fig. 1A and 2A, respectively, along A-A'.

Fig. 3 is a schematic block diagram of an apparatus for fingerprint detection according to an embodiment of the present application.

Fig. 4 is a schematic diagram of fingerprint detection based on reflected and transmitted light signals of a finger.

Fig. 5A and 5B are schematic diagrams of a relationship between a distance between a finger and a display screen and a contrast of a fingerprint image.

Fig. 6 is a schematic diagram of one possible linear polarization unit of an embodiment of the present application.

Fig. 7 is a schematic diagram of a possible first light guiding layer according to an embodiment of the present application.

Fig. 8 is a schematic diagram of a possible first light guiding layer according to an embodiment of the present application.

Fig. 9 is a schematic diagram of a possible first light guiding layer according to an embodiment of the present application.

Fig. 10A and 10B are schematic diagrams of a possible first light guiding layer according to an embodiment of the present application.

Fig. 11A, 11B and 11C are schematic diagrams of a possible first light guiding layer according to an embodiment of the present application.

Fig. 12 is a schematic block diagram of an apparatus for fingerprint detection according to another embodiment of the present application.

Fig. 13A, 13B and 13C are schematic diagrams of fingerprint detection based on light rays in different directions.

Fig. 14 is a schematic view of a possible second light guiding layer according to an embodiment of the present application.

Fig. 15 is a schematic view of a possible second light guiding layer according to an embodiment of the present application.

Detailed Description

The technical scheme of the application will be described below with reference to the accompanying drawings.

It should be understood that embodiments of the present application may be applied to fingerprint systems, including but not limited to optical, ultrasound or other fingerprint detection systems and medical diagnostic products based on optical, ultrasound or other fingerprint imaging, and are described by way of example only with respect to optical fingerprint systems, but should not be construed as limiting the embodiments of the present application in any way, as well as other systems employing optical, ultrasound or other imaging techniques, etc.

As a common application scenario, the optical fingerprint system provided by the embodiment of the application can be applied to smart phones, tablet computers and other mobile terminals or other electronic devices with display screens; more specifically, in the above electronic device, the optical fingerprint module may be disposed in a partial area or a whole area Under the display screen, thereby forming an Under-screen (or Under-screen) optical fingerprint system. Alternatively, the optical fingerprint module may be partially or fully integrated into the display screen of the electronic device, so as to form an In-screen (In-display or In-screen) optical fingerprint system.

The optical underscreen fingerprint detection technology uses light returned from the top surface of the device display assembly for fingerprint sensing and other sensing operations. The returned light carries information about an object (e.g., a finger) in contact with the top surface, and by collecting and detecting the returned light, a specific optical sensor module located below the display screen is realized. The design of the optical sensor module may be such that the desired optical imaging is achieved by properly configuring the optical elements for collecting and detecting the returning light.

Fig. 1A and 2A show schematic diagrams of electronic devices to which embodiments of the present application may be applied. Fig. 1A and 2A are schematic directional diagrams of the electronic device 10, and fig. 1B and 2B are schematic partial cross-sectional diagrams of the electronic device 10 shown in fig. 1A and 2A along A-A', respectively.

The electronic device 10 includes a display 120 and an optical fingerprint module 130. The optical fingerprint module 130 is disposed in a local area below the display screen 120. The optical fingerprint module 130 includes an optical fingerprint sensor including a sensing array 133 having a plurality of optical sensing units 131 (which may also be referred to as pixels, photosensitive pixels, pixel units, etc.). The sensing area of the sensing array 133 or the sensing area thereof is the fingerprint detection area 103 (also referred to as a fingerprint collection area, a fingerprint identification area, etc.) of the optical fingerprint module 130. As shown in fig. 1, the fingerprint detection area 103 is located in the display area of the display screen 120. In an alternative embodiment, the optical fingerprint module 130 may be disposed at other locations, such as a side of the display screen 120 or an edge non-transparent area of the electronic device 10, and the optical signal from at least a portion of the display area of the display screen 120 is guided to the optical fingerprint module 130 through an optical path design, so that the fingerprint detection area 103 is actually located in the display area of the display screen 120.

It should be appreciated that the area of the fingerprint detection area 103 may be different from the area of the sensing array 133 of the optical fingerprint module 130, for example, by a light path design such as lens imaging, a reflective folded light path design, or other light converging or reflecting light path design, the area of the fingerprint detection area 103 of the optical fingerprint module 130 may be made larger than the area of the sensing array 133 of the optical fingerprint module 130. In other alternative implementations, if the light path is guided, for example, by light collimation, the fingerprint detection area 103 of the optical fingerprint module 130 may be designed to substantially coincide with the area of the sensing array of the optical fingerprint module 130.

Thus, when the user needs to unlock the electronic device 10 or perform other fingerprint verification, the user only needs to press the finger against the fingerprint detection area 103 on the display screen 120, so as to implement fingerprint input. Since fingerprint detection can be implemented in the screen, the electronic device 10 adopting the above structure does not need to have a special reserved space on the front surface to set fingerprint keys (such as Home keys), so that a comprehensive screen scheme can be adopted, that is, the display area of the display screen 120 can be basically expanded to the front surface of the whole electronic device 10.

As an alternative implementation, as shown in fig. 1B, the optical fingerprint module 130 includes a light detecting portion 134 and an optical component 132. The light detecting part 134 includes the sensing array 133 and a reading circuit and other auxiliary circuits electrically connected to the sensing array 133, which may be fabricated on a chip (Die) such as an optical imaging chip or an optical fingerprint sensor by a semiconductor process. The sensing array 133 is specifically a photo detector (photo detector) array, which includes a plurality of photo detectors distributed in an array, and the photo detectors may be used as the optical sensing units as described above. The optical component 132 may be disposed above the sensing array 133 of the light detecting portion 134, and may specifically include a Filter layer (Filter), a light guiding layer (also called a light path guiding structure), and other optical elements, where the Filter layer may be used to Filter out ambient light penetrating the finger, and the light guiding layer is mainly used to guide reflected light reflected from the finger surface to the sensing array 133 for optical detection.

In particular implementations, the optical assembly 132 may be packaged in the same optical fingerprint component as the light detection section 134. For example, the optical component 132 may be packaged in the same optical fingerprint chip as the optical detecting portion 134, or the optical component 132 may be disposed outside the chip in which the optical detecting portion 134 is located, for example, the optical component 132 is attached to the chip, or some of the components of the optical component 132 are integrated in the chip.

The light guiding layer of the optical component 132 may be, for example, a Collimator (Collimator) layer fabricated on a semiconductor silicon wafer, and has a plurality of collimating units or a micropore array, where the collimating units may be small holes, the light vertically incident to the collimating units from the reflected light reflected by the finger may pass through and be received by the optical sensing units below the collimating units, and the light with an excessive incident angle is attenuated by multiple reflections inside the collimating units, so each optical sensing unit basically only receives the reflected light reflected by the fingerprint lines above the optical sensing units, and the sensing array 133 may detect the fingerprint image of the finger.

In another implementation, the light guiding layer may also be an optical Lens (Lens) layer having one or more Lens units, such as a Lens group of one or more aspheric lenses, for converging the reflected light reflected from the finger to the sensing array 133 of the light detecting part 134 thereunder, so that the sensing array 133 may image based on the reflected light, thereby obtaining a fingerprint image of the finger. Optionally, the optical lens layer may further form a pinhole in the optical 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 module 130, so as to improve the fingerprint imaging effect of the optical fingerprint module 130.

In other implementations, the light guiding layer may also specifically employ a Micro-Lens layer having a Micro Lens array formed of a plurality of Micro lenses, which may be formed over the sensing array 133 of the light sensing portion 134 by a semiconductor growth process or other processes, and each Micro Lens may correspond to one of sensing cells of the sensing array 133, respectively. And, other optical film layers, such as a dielectric layer or a passivation layer, can be formed between the microlens layer and the sensing unit. More specifically, a light blocking layer (or referred to as a light blocking layer, etc.) having micro holes (or referred to as openings) formed between its corresponding micro lens and sensing unit may be further included between the micro lens layer and the sensing unit, and the light blocking layer may block optical interference between adjacent micro lenses and sensing unit, and allow light corresponding to the sensing unit to be condensed into the micro holes by the micro lenses and transmitted to the sensing unit via the micro holes for optical fingerprint imaging.

It should be appreciated that several implementations of the light guiding layer described above may be used alone or in combination. For example, a microlens layer may be further provided above or below the collimator layer or the optical lens layer. Of course, when the collimator layer or the optical lens layer is used in combination with the microlens layer, the specific laminated structure or the optical path thereof may need to be adjusted according to actual needs.

As an alternative implementation manner, the display screen 120 may be a display screen with a self-luminous display unit, such as an Organic Light-Emitting Diode (OLED) display screen or a Micro-LED (Micro-LED) display screen. Taking an OLED display as an example, the optical fingerprint module 130 may use a display unit (i.e., an OLED light source) of the OLED display 120 located in the fingerprint detection area 103 as an excitation light source for optical fingerprint detection. When the finger 140 is pressed against the fingerprint detection area 103, the display 120 emits a beam of light 111 towards the target finger 140 above the fingerprint detection area 103, which light 111 is reflected at the surface of the finger 140 to form reflected light or scattered inside the finger 140 to form scattered light. In the related patent application, the above reflected light and scattered light are collectively referred to as reflected light for convenience of description. Since the ridge (ridge) 141 and the valley (valley) 142 of the fingerprint have different light reflection capacities, the reflected light 151 from the ridge and the reflected light 152 from the valley have different light intensities, and the reflected light is received by the sensing array 133 in the optical fingerprint module 130 and converted into corresponding electrical signals, i.e. fingerprint detection signals after passing through the optical component 132; fingerprint image data may be obtained based on the fingerprint detection signal and further fingerprint matching verification may be performed to implement an optical fingerprint detection function at the electronic device 10.

In other implementations, the optical fingerprint module 130 may also use an internal light source or an external light source to provide an optical signal for fingerprint detection. In this case, the optical fingerprint module 130 may be adapted to a non-self-luminous display screen, such as a liquid crystal display screen or other passive light emitting display screen. Taking the application to a liquid crystal display having a backlight module and a liquid crystal panel as an example, to support the under-screen fingerprint detection of the liquid crystal display, the optical fingerprint system of the electronic device 10 may further include an excitation light source for optical fingerprint detection, where the excitation light source may be specifically an infrared light source or a light source of non-visible light with a specific wavelength, and may be disposed below the backlight module of the liquid crystal display or disposed in an edge area below a protective cover plate of the electronic device 10, and the optical fingerprint module 130 may be disposed below the edge area of the liquid crystal panel or the protective cover plate and guided by an optical path so that fingerprint detection light may reach the optical fingerprint module 130; alternatively, the optical fingerprint module 130 may be disposed below the backlight module, and the backlight module may be configured to allow the fingerprint detection light to pass through the liquid crystal panel and the backlight module and reach the optical fingerprint module 130 by making holes or other optical designs on the film layers such as the diffusion sheet, the brightness enhancement sheet, and the reflection sheet. When the optical fingerprint module 130 is used to provide an optical signal for fingerprint detection using an internal light source or an external light source, the detection principle is consistent with the above description.

In a specific implementation, the electronic device 10 may further include a transparent protective cover plate, which may be a glass cover plate or a sapphire cover plate, located above the display screen 120 and covering the front surface of the electronic device 10. Thus, in the embodiment of the present application, the pressing of the finger against the display screen 120 actually means pressing the cover plate above the display screen 120 or the surface of the protective layer covering the cover plate.

The electronic device 10 may further include a circuit board 150, where the circuit board 150 is disposed below the optical fingerprint module 130. The optical fingerprint module 130 may be adhered to the circuit board 150 by a back adhesive, and electrically connected to the circuit board 150 by soldering with a pad and a metal wire. The optical fingerprint module 130 may enable 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 module 130 may receive a control signal of the processing unit of the electronic device 10 through the circuit board 150, and may also output a fingerprint detection signal from the optical fingerprint module 130 to the processing unit or the control unit of the electronic device 10 through the circuit board 150.

In some implementations, the optical fingerprint module 130 may include only one optical fingerprint sensor, where the area of the fingerprint detection area 103 of the optical fingerprint module 130 is smaller and the position is fixed, so that the user needs to press the finger to a specific position of the fingerprint detection area 103 when inputting the fingerprint, otherwise, the optical fingerprint module 130 may not be able to collect the fingerprint image, resulting in poor user experience. In other alternative embodiments, the optical fingerprint module 130 may specifically include a plurality of optical fingerprint sensors. The optical fingerprint sensors may be disposed side by side below the display screen 120 in a spliced manner, and the sensing areas of the optical fingerprint sensors together form the fingerprint detection area 103 of the optical fingerprint module 130. Thus, the fingerprint detection area 103 of the optical fingerprint module 130 can be extended to the main area of the lower half of the display screen, that is, to the finger usual pressing area, thereby realizing the blind press type fingerprint input operation. Further, when the number of the optical fingerprint sensors is sufficient, the fingerprint detection area 103 may be further extended to a half display area or even the whole display area, so as to implement half-screen or full-screen fingerprint detection.

For example, in the electronic device 10 shown in fig. 2A and 2B, when the optical fingerprint device 130 in the electronic device 10 includes a plurality of optical fingerprint sensors, the plurality of optical fingerprint sensors may be disposed side by side under the display screen 120 by, for example, splicing, and sensing areas of the plurality of optical fingerprint sensors together form the fingerprint detection area 103 of the optical fingerprint device 130.

Optionally, corresponding to the plurality of optical fingerprint sensors of the optical fingerprint device 130, the optical component 132 may have a plurality of light guiding layers therein, where each light guiding layer corresponds to one optical fingerprint sensor and is respectively attached to and disposed above the corresponding optical fingerprint sensor. Alternatively, the plurality of optical fingerprint sensors may share a unitary light guiding layer, i.e. the light guiding layer has an area large enough to cover the sensing array of the plurality of optical fingerprint sensors. In addition, the optical component 132 may further include other optical elements, such as a Filter (Filter) or other optical film, which may be disposed between the light guide layer and the optical fingerprint sensor or between the display screen 120 and the light guide layer, and is mainly used to isolate the influence of the external interference light on the optical fingerprint detection. The optical filter may be used to filter out ambient light that penetrates through the finger and enters the optical fingerprint sensor through the display screen 120, similar to the light guiding layer, and the optical filter may be set for each optical fingerprint sensor to filter out interference light, or may also use a large-area optical filter to cover the plurality of optical fingerprint sensors simultaneously.

The light guide layer can also adopt an optical Lens (Lens), and a small hole formed above the optical Lens can be matched with the optical Lens through a shading material to converge fingerprint detection light to an optical fingerprint sensor below so as to realize fingerprint imaging. Similarly, each optical fingerprint sensor may be configured with one optical lens for fingerprint imaging, or the plurality of optical fingerprint sensors may use the same optical lens for light convergence and fingerprint imaging. In other alternative embodiments, each optical fingerprint sensor may even have two sensing arrays (Dual Array) or multiple sensing arrays (Multi-Array), and two or more optical lenses are simultaneously configured to optically image the two or more sensing arrays, thereby reducing imaging distance and enhancing imaging effect.

The number, size and arrangement of the fingerprint sensors shown above are only examples, and may be adjusted according to actual requirements. For example, the number of the fingerprint sensors may be 2, 3, 4 or 5, and the fingerprint sensors may be distributed in a square or circular shape.

The embodiment of the application can be applied to detection of various fingers, and particularly can be applied to detection of dry fingers. By dry finger, it is meant a drier finger or a cleaner finger. The existing scheme for detecting fingerprints by adopting vertical light rays has poor fingerprint detection effect on dry fingers, and the scheme for detecting fingerprints provided by the embodiment of the application can improve the fingerprint detection performance on dry fingers.

The fingerprint detection device provided by the embodiment of the application is suitable for being used below a display screen to realize the optical fingerprint detection under the screen. Fig. 3 shows a schematic diagram of an apparatus 300 for fingerprint detection according to an embodiment of the present application. The apparatus 300 comprises a first light guiding layer 310 and an image acquisition unit 320. The image acquisition unit 320 may refer to the above description of the light detection portion 134, and this embodiment will not be described in detail.

The first light guiding layer 310 is disposed above the image capturing unit 320. The first light guiding layer 310 is configured to transmit an oblique light signal incident on a finger above the display screen and returned by the finger to the image acquisition unit 320.

The optical signals returned by the finger comprise reflected optical signals and transmitted optical signals from the finger. Wherein the reflected light signal is attenuated after passing through the linear polarization unit 330 such that the proportion of the transmitted light signal reaching the image acquisition unit 320 is relatively increased.

The linear polarization unit 330 is disposed in the optical path between the finger and the image acquisition unit 320. The linear polarization unit 330 serves to attenuate the reflected light signal, thereby relatively increasing the proportion of the transmitted light signal reaching the image acquisition unit 320.

The linear polarization unit 330 may be integrated inside the display screen so as to be part of the display screen, e.g. above an OLED layer of the display screen; alternatively, the linear polarization unit 330 is located between the first light guiding layer 310 and the image acquisition unit 320; alternatively, the linear polarization unit 330 is integrated in the image acquisition unit 320 so as to be part of the image acquisition unit 320, for example, above the pixel array of the image acquisition unit 320.

The image acquisition unit 320 includes one optical fingerprint sensor or a plurality of optical fingerprint sensors spliced together, such as shown in fig. 2A and 2B. Wherein each optical fingerprint sensor comprises a pixel array formed of a plurality of pixels. The pixels of the image acquisition unit 320 located below the first light guide layer 310 are used to receive the oblique light signals, which are used to acquire the fingerprint image of the finger.

The detection principle of the embodiment of the present application is described in detail below with reference to fig. 4, 5A, and 5B.

In fingerprint detection, the optical signal incident on the finger above the display screen 340 and returned by the finger includes two parts, one is the reflected optical signal from the finger and the other is the transmitted optical signal from the finger. For example, as shown in fig. 4, a fingerprint image obtained using the reflected light signal shown on the left side appears as a valley, a ridge, and a dark (positive color fingerprint). And as the contact between the finger and the display screen is better, the darker the ridge, the better the contrast between the ridge and the valley. The fingerprint image obtained by using the transmitted light signal shown on the right side is represented as a valley ridge (a reverse color fingerprint) because blood and tissue exist in the ridge of the fingerprint, light is scattered in the ridge and exits from the ridge, and light incident to the valley of the fingerprint is rapidly weakened after multiple reflections at the valley, so that the light exiting from the valley is very weak, and thus the fingerprint image is represented as a valley ridge. Since the fingerprint images obtained by the reflected light imaging and the transmitted light imaging are in opposite states, when the reflected light and the transmitted light exist at the same time, the normal-color fingerprint and the reverse-color fingerprint cancel each other out, and the fingerprint images are easily blurred.

Fig. 5A and 5B show the relationship between the distance between the finger and the display screen and the contrast of the fingerprint image, wherein fig. 5A shows fingerprint detection using a vertical light signal and fig. 5B shows fingerprint detection using oblique light. The abscissa is the distance between the finger and the display screen, and the ordinate is the contrast of the fingerprint image. When the fingerprint is in good contact with the display screen, the reflected light imaging is dominant, the fingerprint image shows the characteristic of bright valley and dark valley, and the fingerprint detection performance of the normal finger is good. When the contact between the fingerprint and the display screen becomes worse gradually, the imaging effect of the reflected light becomes weaker gradually as the distance between the ridge and the display screen becomes larger, the imaging of the transmitted light becomes dominant gradually, and the fingerprint image presents the characteristic of valley, ridge and brightness. When the reflected light imaging and the transmitted light imaging are in a state of potential enemy, the contrast of the fingerprint image is the lowest, and this stage is referred to as a transition zone. In this transition zone, the fingerprint images of the resulting finger have poor contrast due to the mutual cancellation of the reflected light imaged and the transmitted light imaged fingerprint images.

Reflected light imaging is more sensitive to changes in distance between the finger and the display screen, while transmitted light imaging is less sensitive to changes in distance. Thus, in detecting a dry finger, it is desirable that the transmitted light imaging dominates, increasing the specific gravity of the transmitted light to reduce the transition zone, thereby improving fingerprint detection performance.

In the embodiment of the application, the inclined light is adopted for fingerprint detection, and the linear polarization unit is used for attenuating the reflected light signals of the fingers so as to relatively increase the proportion of the transmitted light signals reaching the image acquisition unit, thereby improving the fingerprint detection performance, and particularly the identification performance of special fingers such as dry fingers.

As can be seen from fig. 5A and 5B, the transition zone is significantly reduced when fingerprint detection is performed using an oblique optical signal, relative to fingerprint detection using a vertical optical signal, thus improving the detection performance of a dry finger.

The angle between the polarization direction of the linear polarization unit 330 and the incident surface of the oblique optical signal is between 0 ° and 90 °. For example, the polarization direction of the linear polarization unit 330 is perpendicular to the incident surface of the oblique optical signal, parallel to the incident surface of the oblique optical signal, or at an angle of 45 ° to the incident surface of the oblique optical signal.

Fig. 6 shows one possible linear polarization unit 330 of an embodiment of the present application. It is assumed that the linear polarization unit 330 is located above the OLED layer 341 in the display screen 340. The light emitted from the OLED layer 341 passes through the linear polarization unit 330 and becomes linearly polarized light, and irradiates the finger 350 above the cover plate 342. After being transmitted by the finger 350, the polarization direction of the transmitted light is unchanged, so that the transmitted light can return through the linear polarization unit 330 and be transmitted to the image acquisition unit 320 after being guided by the light guide layer 310.

For the light reflected by the finger 350, the reflected light from the finger 350 includes p-waves and s-waves, wherein the p-waves have a polarization direction parallel to the incident plane of the light, and the s-waves have a polarization direction perpendicular to the incident plane, which is perpendicular to the display screen 340, because the light is obliquely incident to the finger 350.

If the polarization of the linear polarization unit 330 is parallel to the incidence plane of the oblique light (or referred to as the receiving plane of the oblique light signal), s-waves in the reflected light of the finger are attenuated, and only p-waves can return through the linear polarization unit 330 and be transmitted to the image acquisition unit 320 after being guided by the light guide layer 310. If the polarization of the linear polarization unit 330 is perpendicular to the incident plane, the p-wave in the reflected light of the finger is attenuated, and only the s-wave can return through the linear polarization unit 330 and be transmitted to the image acquisition unit 320 after being guided by the light guiding layer 310, as shown in fig. 6. The reflected light signal of the finger is weakened no matter the p wave or the s wave is weakened, and the transmitted light signal of the finger is unchanged, so that the proportion of the transmitted light signal in the light signal returned by the finger is relatively increased, the transition zone is reduced, and the detection performance of the dry finger is improved.

Typically, the reflected light has fewer p-waves than s-waves, and if the angle of incidence reaches the brewster angle, there is no p-wave in the reflected light, and only s-waves remain, so the reflected light is perfectly polarized with its polarization direction perpendicular to the plane of incidence. When the incident angle exceeds the Brewster angle, both the s wave and the p wave increase until the total reflection angle is reached and then the s wave and the p wave are totally reflected. Therefore, it is preferable that if the tilt angle of the tilted light signal returned by the finger is less than or equal to the brewster angle, the reflected light signal returned by the finger can be made as small as possible.

Embodiments of the present application provide three possible implementations of the first light guiding layer 310. The following is a detailed description with reference to fig. 7 to 12.

Mode 1

The first light guide layer 310 includes a microlens array formed of a plurality of microlenses 311, and at least one light blocking layer 312 disposed under the microlens array.

Wherein each microlens 311 is used to converge the oblique light signal returned by the finger. Each of the at least one light blocking layer 312 includes a plurality of openings 313 corresponding to the plurality of microlenses 311, respectively, and the oblique optical signal converged by each microlens 311 passes through the openings 313 corresponding to the microlens 311 in the different light blocking layer 312 to reach the image pickup unit 320.

The projection of the condensing surface of the microlens 311 on a plane perpendicular to the optical axis thereof may be rectangular or circular. The condensing surface of the microlens 311 is a surface for condensing light. The collecting surface may be spherical or aspherical. Preferably, the curvature of the collecting surface in each direction is the same, so that the imaging focal points of the microlenses 311 in each direction are located at the same position, thereby ensuring the imaging quality.

Each microlens 311 corresponds to one pixel 321 in the image pickup unit 320, wherein the oblique optical signals converged by the microlens 311 pass through the aperture corresponding to the microlens 311 in the different light blocking layers to reach the pixel 321 corresponding to the microlens 311.

Since the apertures in the light-blocking layers are used for guiding the light, the lines of the apertures in the different light-blocking layers corresponding to each of the microlenses should be inclined at an angle equal or approximately equal to the angle of inclination of the oblique light signal in order for the oblique light signal to reach the image acquisition unit.

It should be appreciated that embodiments of the present application do not consider the effect of refraction between the various layers on light transmission.

The light blocking layer 312 may be provided in one or more layers.

For example, as shown in fig. 7, when one light blocking layer 312 is used, the light blocking layer 312 may be integrated in the image pickup unit 320, for example, by using a metal mask (mask) to form a light blocking layer over the pixel array.

For example, as shown in fig. 8 and 9, when a plurality of light blocking layers 312 are used, the inclination angle of the line connecting the openings corresponding to each microlens in the different light blocking layers is equal to the inclination angle of the inclined optical signal returned by the finger. For each pixel, the openings corresponding to the pixel in the plurality of light blocking layers are sequentially offset from top to bottom, so that the pixel 321 can receive the inclined light signals returned by the finger, and the light signals in other directions are blocked.

Alternatively, the last light blocking layer among the plurality of light blocking layers may be integrated in the image pickup unit 320, for example, as shown in fig. 8 and 9, when one light blocking layer is integrated in the image pickup unit 320, the light blocking layer has higher reliability.

Alternatively, the apertures of the openings corresponding to the same microlenses in different light blocking layers are sequentially reduced from top to bottom. For example, as shown in fig. 8 and 9, the aperture of the opening in the upper light blocking layer is set to be larger than that in the lower light blocking layer, so that more (a certain angular range) optical signals can be directed to the corresponding pixels.

Optionally, a transparent dielectric layer is further disposed between the microlens array, the at least one light blocking layer, and the image acquisition unit.

The transparent medium layer is used for connecting the micro lens array, the at least one light blocking layer and pixels in the image acquisition unit and filling the openings in the at least one light blocking layer.

The transparent medium layer can transmit the optical signal of the target wave band (namely, the optical signal of the wave band required by fingerprint detection). For example, the transparent dielectric layer may be oxide or nitride.

Optionally, the transparent dielectric layer may include multiple layers to perform protection, transition, and buffering functions, respectively.

For example, a transition layer may be provided between the inorganic layer and the organic layer to achieve a tight connection; a protective layer may be provided over the layer susceptible to oxidation to achieve protection.

Mode 2

The first light guiding layer 310 includes an optical functional film 314 for selecting the oblique light signal among the light signals of the various directions returned by the finger and transmitting the oblique light signal to the image capturing unit 320.

The optical functional film layer 314 may be, for example, a grating film or a prism film.

For example, as shown in fig. 10A, the optical functional film 314 can transmit the oblique light 316 with a specific angle, and transmit the light 316 to the image capturing unit 320, while blocking the light with other angles.

Further, optionally, the optical functional film 314 may be further configured to refract the oblique optical signal, so that the oblique optical signal can be perpendicularly incident on the pixel of the image capturing unit 320.

For example, as shown in fig. 10B, the optical functional film 314 can transmit the oblique light 316 with a specific angle, and refract the light 316 to make it vertically incident to the image capturing unit 320. Since the pixel of the image capturing unit 320 has the highest quantum efficiency for the vertically received light, the optimal photoelectric conversion efficiency can be obtained, and the fingerprint detection performance can be further improved.

Alternatively, the optical functional film 314 may be integrated in the image pickup unit 320 or provided over the image pickup unit 320 as a device relatively independent from the image pickup unit 320.

Mode 3

The first light guide layer 310 includes a light guide channel array formed of a plurality of light guide channels 315.

The light guide channel 315 may be formed of, for example, an optical fiber, an air through hole, or a light transmitting material.

In one implementation, the first light guiding layer 310 is disposed horizontally, and the plurality of light guiding channels 315 are inclined with respect to the surface of the first light guiding layer 310 to guide the inclined light signals to the image capturing unit 320.

For example, as shown in fig. 11A, the first light guiding layer 310 is disposed parallel to the display screen 340, and the light guiding channel 315 is an inclined channel with the same inclination angle as that of the inclined light signal returned by the finger, so that the inclined light signal can reach the image acquisition unit 320 through the light guiding channel 315, and the light signals in other directions are blocked.

In another implementation, the plurality of light guide channels 315 are perpendicular to the surface of the first light guide layer 310, and the first light guide layer 310 is disposed obliquely to guide the oblique light signal to the image acquisition unit 320.

For example, as shown in fig. 11B, the light guide channel 315 is a vertical channel, which is perpendicular to the surface of the first light guide layer 310, at this time, the first light guide layer 310 may be obliquely disposed such that the oblique angle is the same as that of the oblique optical signal returned by the finger, so that the oblique optical signal can reach the image acquisition unit 320 through the light guide channel 315, and the optical signals in other directions are blocked.

In another implementation, the first light guiding layer 310 is disposed horizontally, the plurality of light guiding channels 315 are perpendicular to the surface of the first light guiding layer 310, and the oblique light signal reaches the image capturing unit 320 after at least one total reflection in each light guiding channel 315 of the plurality of light guiding channels 315.

For example, as shown in fig. 11C, the first light guiding layer 310 is disposed parallel to the display screen 340, and the light guiding channels 315 are vertical channels, and the light guiding channels 315 are optical fibers. Since the optical fiber can transmit incident light rays with a specific angle, the optical fiber can guide oblique light signals with a specific angle reflected by a finger. After entering from one end of the optical fiber 315, the oblique optical signal undergoes multiple total reflections in the optical fiber 315 and finally exits from the other end of the optical fiber 315, so as to reach the image acquisition unit 320.

Embodiments of the present application also provide another implementation of the fingerprint detection apparatus 300. As shown in fig. 12, the fingerprint detection device 300 includes a first light guiding layer 320, a second light guiding layer 360, and an image acquisition unit 320.

The second light guiding layer 360 is disposed above the image capturing unit 320, and is configured to transmit the light signal in the second direction returned by the finger to the image capturing unit 320.

The pixels of the image acquisition unit 320 located below the second light guiding layer 360 are configured to receive the light signals in the second direction, where the light signals in the second direction are used to acquire the fingerprint image of the finger. The oblique optical signal transmitted by the first light guide layer is an optical signal in a first direction, and the second direction is different from the first direction.

In this embodiment, the fingerprint detection device 300 may further comprise a second light guiding layer 360 in addition to the first light guiding layer 320 described above. The first light guiding layer 320 is configured to transmit a light signal in a first direction, which is incident to a finger above the display screen and returned by the finger, to the image acquisition unit 320; and the second light guiding layer 360 is configured to transmit the optical signal in the second direction returned by the finger to the image capturing unit 320. The fingerprint detection performance is improved because the optical signals in different directions can be detected simultaneously to perform fingerprint detection.

The first direction is different from the second direction, and if the first direction is an oblique direction, the second direction may be an oblique direction or a vertical direction. When the first direction and the second direction are both oblique directions, the oblique angle of the light ray in the second direction may be the same or different from the oblique angle of the light ray in the first direction.

In this embodiment, the incident surface of the optical signal in the first direction may be perpendicular to the polarization direction of the linear polarization unit 330; alternatively, the incident plane of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit 330; alternatively, the incident plane of the optical signal in the first direction may be at an angle, for example, 45 ° with respect to the polarization direction of the linear polarization unit 330, which is not limited in the present application.

For example, as shown in fig. 13A, the first direction is an oblique direction, which forms an angle with the display screen, wherein fig. 13A is a top view, and the arrow shown can be considered as a projection of the incident plane of the light ray in the first direction into the display screen, wherein the dotted line indicates the polarization direction of the linear polarization unit 330. The second direction is a vertical direction, which is perpendicular to the display screen. In the fingerprint detection area 103, the oblique light signal of the first direction returned by the finger is transmitted to the image acquisition unit 320 through the first light guiding layer 310, and the vertical light signal returned by the finger is transmitted to the image acquisition unit 320 through the second light guiding layer 360.

As another example, as shown in fig. 13B, both the first direction and the second direction are oblique directions, but the incidence plane of the optical signal in the first direction is perpendicular to the polarization direction of the linear polarization unit 330, and the incidence plane of the optical signal in the second direction is parallel to the polarization direction of the linear polarization unit 330. Where fig. 13B is a top view, the arrows shown may be considered as projections of the planes of incidence of the light rays in the first direction and the second direction within the display screen, where the dashed lines represent the polarization directions of the linear polarization units 330.

For another example, the incident plane of the optical signal in the first direction is perpendicular to the polarization direction of the linear polarization unit 330, and the angle between the optical signal in the second direction and the polarization direction of the linear polarization unit 330 is 45 °.

Optionally, the apparatus 300 may further include further light guiding layers for transmitting light signals in different directions to the image acquisition unit 320, respectively. For example, as shown in fig. 13C, by providing four light guiding layers, light rays from four different directions of A, B, C, D may be respectively guided to the image capturing unit 320.

In this embodiment, by adopting different light guiding layers, light signals in different directions are transmitted to the image acquisition unit for fingerprint detection, and fingerprint detection performance is improved.

For example, when fingerprint detection is performed on a dry finger using oblique light, the size of ridge-Gu Chazhi is mainly focused, and the larger the difference, the higher the contrast, the easier the feature points are found, and further fingerprint detection is performed. For a dry finger, the contrast of the fingerprint image obtained when the fingerprint is detected with oblique light is better than when the fingerprint is detected with perpendicular light. But for a normal finger the contrast of the fingerprint image obtained when the fingerprint is detected with perpendicular light is better than when the fingerprint is detected with oblique light.

In this embodiment, when fingerprint detection is performed, if the first light guide layer 310 and the second light guide layer 360 are respectively used for transmitting an oblique light signal and a vertical light signal, a part of fingerprint information of a finger can be transmitted to the image acquisition unit 320 through the first light guide layer 320, and the first light guide layer 320 transmits the oblique light signal carrying the part of fingerprint information to a corresponding pixel, so that a better fingerprint image can be obtained when the finger is a dry finger; the other part of fingerprint information of the finger can be transmitted to the image acquisition unit 320 through the second light guide layer 360, and the second light guide layer 360 transmits the vertical light signal carrying the part of fingerprint information to the corresponding pixel, so that a better fingerprint image can be acquired when the finger is a normal finger. Therefore, whether the finger is a dry finger or a normal finger, a better fingerprint image can be obtained, the fingerprint detection performance of the normal finger and the dry finger is considered, the success rate of fingerprint detection is improved, and the user experience is improved.

In the embodiment of the present application, the second light guiding layer 360 may be implemented in the above-described mode 1, mode 2 or mode 3.

For example, in case of mode 1, the second light guide layer 360 includes a microlens array and at least one light blocking layer to achieve guiding of vertical light. The guiding of light in a certain direction can be achieved by providing an offset of the position of the aperture in at least one light-blocking layer. For example, as shown in fig. 14, when the second light guiding layer 360 is used to guide a vertical light signal, each light blocking layer 362 includes a plurality of openings 363 corresponding to a plurality of microlenses, respectively, and the openings corresponding to the same microlens in different light blocking layers 362 are vertically arranged from top to bottom, so that the inclined light signal converged by each microlens 361 passes through the openings corresponding to the microlens 361 in the different light blocking layers to vertically reach the image capturing unit 320. That is, the lines of the openings corresponding to the micro lenses 361 in the different light blocking layers are perpendicular to the display screen, so that the vertical light signal returned from the finger can reach the pixels 321 of the image capturing unit 320, while the oblique light is blocked.

For another example, in the case of mode 2, the second light guiding layer 360 includes an optical functional film 317 to screen the vertical light. For example, as shown in fig. 15, the optical functional film 317 can transmit the vertical light 318, and transmit the light 318 to the image capturing unit 320, while blocking the oblique light.

For another example, in the case of embodiment 3, the vertical light is guided by the light guide channel array. The second light guide layer 360 is disposed parallel to the display screen, and each light guide channel is perpendicular to the surface of the second light guide layer 360, thereby allowing the vertical light signal returned from the finger to pass therethrough while the oblique light is blocked.

Additional features of the second light guiding layer 360 may be referred to the previous description of the first light guiding layer 310, and are not repeated here for brevity.

The relative positions of the first light guiding layer 310 and the second light guiding layer 360 are not limited in the embodiment of the present application. For example, as shown in fig. 13A to 13C, the first light guiding layer 310 and the second light guiding layer 360 may be placed side by side. Wherein the first light guiding layer 310 is used to guide the light signal of the first direction returned by the finger to the pixel below it, and the second light guiding layer 360 is used to guide the light signal of the second direction returned by the finger to the pixel below it.

Optionally, the apparatus 300 further comprises a filtering layer. The filtering layer is disposed in the optical path between the display screen and the image acquisition unit 320, and is configured to filter out the optical signal of the non-target band and transmit the optical signal of the target band.

Optionally, the transmittance of the filter layer to light of the target wave band is more than or equal to 80%, and the cut-off rate to light of the non-target wave band is more than or equal to 80%.

Alternatively, the filter layer may be a separately formed filter layer. For example, the filter layer may be a filter layer formed using blue crystal or blue glass as a carrier.

Alternatively, the filter layer may be a plating film formed on the surface of any one of the optical paths. For example, the filter layer may be formed by plating a film on the surface of the pixel, the surface of any one of the transparent dielectric layers, the lower surface of the microlens, or the like.

Optionally, the apparatus 300 for fingerprint detection may further include: dielectric and metal layers, which may include pixel connection circuitry.

For example, a dielectric and metal layer may be disposed over the photosensitive pixels in a front-lit manner (Front Side Illumination, FSI); the dielectric and metal layers may also be disposed under the photosensitive pixels in a backside illuminated (Back Side Illumination, BSI) manner.

The embodiment of the application also provides electronic equipment, which comprises the fingerprint detection device in the various embodiments of the application.

Optionally, the electronic device further comprises a display screen, which may be a common non-folding display screen, which may also be a foldable display screen, or a so-called flexible display screen.

As an example and not by way of limitation, the electronic device in the embodiments of the present application may be a portable or mobile computing device such as a terminal device, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a game device, an in-vehicle electronic device, or a wearable intelligent device, and other electronic devices such as an electronic database, an automobile, and a bank automated teller machine (Automated Teller Machine, ATM). The wearable intelligent device comprises full functions, large size and complete or partial functions which can be realized independent of the intelligent mobile phone, for example: smart watches or smart glasses, etc., and are only focused on certain application functions, and need to be used in combination with other devices, such as smart phones, as well as devices for monitoring physical signs, such as smart bracelets, smart jewelry, etc.

It should be noted that, on the premise of no conflict, the embodiments and/or technical features in the embodiments described in the present application may be combined with each other arbitrarily, and the technical solutions obtained after combination should also fall into the protection scope of the present application.

It should be understood that the specific examples in the embodiments of the present application are intended to help those skilled in the art to better understand the embodiments of the present application, and not to limit the scope of the embodiments of the present application, and that those skilled in the art may make various modifications and variations on the basis of the above embodiments, and that these modifications or variations fall within the scope of the present application.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A device for fingerprint detection, adapted for use below a display screen for off-screen optical fingerprint detection, the display screen including a fingerprint detection area, the device comprising:

a first light guide layer disposed above the image acquisition unit, for transmitting an oblique light signal incident to a finger above the fingerprint detection area and returned through the finger to the image acquisition unit, wherein the oblique light signal includes a reflected light signal and a transmitted light signal from the finger, the reflected light signal is attenuated after passing through a linear polarization unit located in an optical path between the finger and the image acquisition unit, so that a proportion of the transmitted light signal reaching the image acquisition unit relatively increases, an inclination angle of the oblique light signal is less than or equal to brewster's angle, and an area of the fingerprint detection area is greater than or equal to an area of the image acquisition unit;

2. The device of claim 1, wherein the linear polarization unit is integrated inside the display screen and is located above an organic light emitting diode OLED layer of the display screen.

3. The apparatus of claim 1, wherein the linear polarization unit is located between the display screen and the image acquisition unit.

4. A device according to any one of claims 1 to 3,

the polarization direction of the linear polarization unit is perpendicular to the incidence plane of the inclined optical signal; or alternatively, the process may be performed,

the polarization direction of the linear polarization unit is parallel to the incidence plane of the inclined optical signal; or alternatively, the process may be performed,

the included angle between the polarization direction of the linear polarization unit and the incident surface of the inclined optical signal is 45 degrees.

5. A device according to any one of claims 1 to 3, wherein the first light guiding layer comprises:

a microlens array formed of a plurality of microlenses for converging the oblique optical signals;

And at least one light blocking layer arranged below the micro lens array, wherein each light blocking layer comprises a plurality of openings corresponding to the micro lenses respectively, and the inclined optical signals converged by each micro lens pass through the openings corresponding to each micro lens in different light blocking layers to reach the image acquisition unit.

6. The apparatus of claim 5, wherein the collection surface of each microlens in the array of microlenses has a rectangular or circular shape projected on a plane perpendicular to its optical axis.

7. The apparatus of claim 5, wherein the curvature in each direction of the collection surface of each microlens in the array of microlenses is the same.

8. The apparatus according to claim 5, wherein a last light blocking layer of the at least one light blocking layer is integrated in the image capturing unit.

9. The device of claim 5, wherein the apertures of openings in different light blocking layers corresponding to the same microlens decrease sequentially from top to bottom.

10. The apparatus of claim 5, wherein the apparatus further comprises:

and the transparent medium layer is used for connecting the micro lens array, the at least one light blocking layer and the image acquisition unit and filling the opening in the at least one light blocking layer.

11. A device according to any one of claims 1 to 3, wherein the first light guiding layer comprises:

and the optical functional film layer is used for selecting the inclined optical signals from the optical signals in all directions returned by the finger and transmitting the inclined optical signals to the image acquisition unit.

12. The device of claim 11, wherein the optically functional film layer is further configured to:

and refracting the selected oblique light signals so that the oblique light signals are vertically incident on the pixels of the image acquisition unit.

13. The device of claim 11, wherein the optically functional film layer is a grating film or a prism film.

14. The apparatus of claim 11, wherein the optical functional film is integrated in the image acquisition unit or is disposed over the image acquisition unit as a relatively independent device from the image acquisition unit.

15. A device according to any one of claims 1 to 3, wherein the first light guiding layer comprises:

a light guide channel array formed of a plurality of light guide channels.

16. The device of claim 15, wherein the plurality of light guide channels are formed from optical fibers, air vias, or light transmissive materials.

17. The apparatus of claim 15, wherein the first light guide layer is disposed horizontally and the plurality of light guide channels are inclined with respect to a surface of the first light guide layer to guide the inclined light signals to the image acquisition unit.

18. The apparatus of claim 15, wherein the plurality of light guide channels are formed of optical fibers, the first light guide layer is disposed horizontally, the plurality of light guide channels are perpendicular to a surface of the first light guide layer, and the oblique light signal reaches the image acquisition unit after at least one total reflection within each of the plurality of light guide channels.

19. The apparatus of claim 15, wherein the plurality of light guide channels are perpendicular to a surface of the first light guide layer, the first light guide layer being disposed obliquely to direct the oblique light signals to the image acquisition unit.

20. A device according to any one of claims 1 to 3, further comprising:

the second light guide layer is arranged above the image acquisition unit and is used for transmitting the optical signals in the second direction returned by the finger to the image acquisition unit, wherein the inclined optical signals transmitted by the first light guide layer are optical signals in the first direction, and the second direction is different from the first direction;

The pixels below the second light guide layer in the image acquisition unit are used for receiving the light signals in the second direction, and the light signals in the second direction are used for acquiring fingerprint images of the finger.

21. The device of claim 20, wherein the second direction is a vertical direction or an oblique direction.

22. A device according to any one of claims 1 to 3, further comprising:

the filtering layer is arranged in the light path between the display screen and the image acquisition unit and is used for filtering out optical signals of non-target wave bands and transmitting the optical signals of the target wave bands.

23. The device of claim 22, wherein the filter layer is a plating film formed on a surface of any one of the optical paths.

24. A device according to any one of claims 1 to 3, wherein the image acquisition unit comprises one optical fingerprint sensor or a plurality of optical fingerprint sensors spliced together.

25. A device for fingerprint detection, adapted for use below a display screen for off-screen optical fingerprint detection, the display screen including a fingerprint detection area, the device comprising:

The first light guide layer is arranged above the image acquisition unit and is used for transmitting the light signals which are incident to the finger above the fingerprint detection area and return to the image acquisition unit through the finger in the first direction, and the area of the fingerprint detection area is larger than or equal to that of the image acquisition unit;

26. The apparatus of claim 25, wherein the light signals comprise reflected light signals and transmitted light signals from the finger, wherein the reflected light signals are attenuated by a linear polarization unit located in the light path between the finger to the image acquisition unit such that the proportion of the transmitted light signals reaching the image acquisition unit is relatively increased.

27. The device of claim 26, wherein the first direction is an oblique direction and the second direction is a vertical direction or an oblique direction.

28. The device of claim 27, wherein the linear polarization unit is integrated inside the display screen and is located above an organic light emitting diode OLED layer of the display screen.

29. The apparatus of claim 27, wherein the linear polarization unit is located between the display screen and the image acquisition unit.

30. The apparatus of claim 26, wherein the device comprises a plurality of sensors,

the incidence surface of the optical signal in the first direction is perpendicular to the polarization direction of the linear polarization unit; or alternatively, the process may be performed,

the incident surface of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit; or alternatively, the process may be performed,

an included angle between an incident surface of the optical signal in the first direction and a polarization direction of the linear polarization unit is 45 degrees.

31. The apparatus of claim 26, wherein the angle of inclination of the optical signal in the first direction is less than or equal to the brewster angle.

32. An electronic device, comprising:

a display screen; the method comprises the steps of,

The apparatus of any one of claims 1 to 31, disposed below the display screen to enable off-screen optical fingerprint detection.