CN210295124U

CN210295124U - Fingerprint detection device and electronic equipment

Info

Publication number: CN210295124U
Application number: CN201921285172.2U
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: 2020-04-10
Anticipated expiration: 2029-08-06

Abstract

A fingerprint detection device can improve fingerprint detection performance. The device is applicable to display screen below in order to realize optical fingerprint detection under the screen, the device includes: the first light guide layer is arranged above the image acquisition unit and used for transmitting an inclined light signal which is incident to a finger above the display screen and returns through the finger to the image acquisition unit, wherein the inclined light signal comprises a reflected light signal and a transmitted light signal from the finger, and the reflected light signal is attenuated after passing through a linear polarization unit in a light path between the finger and the image acquisition unit, so that the proportion of the transmitted light signal reaching the image acquisition unit is relatively increased; the image acquisition unit is arranged in the image acquisition unit, pixels below the first light guide layer are used for receiving the inclined light signals, and the inclined light signals are used for acquiring the fingerprint image 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 more particularly relates to a fingerprint detection device and an electronic device.

Background

The technology for detecting the fingerprints under the optical screen is to collect optical signals formed by reflecting or transmitting light rays on a finger, wherein the optical signals carry fingerprint information of the finger, so that the fingerprint detection under the screen is realized. For a special finger, for example, a dry finger, an air gap exists between the fingerprint and the display screen, and the air gap can cause the reflection difference of the ridges and valleys of the fingerprint to light to be small, so that the contrast of the fingerprint image is reduced, and the fingerprint detection performance is influenced.

SUMMERY OF THE UTILITY MODEL

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

In a first aspect, a fingerprint detection apparatus is provided, which is suitable for use under a display screen to realize optical fingerprint detection under the display screen, and includes:

the first light guide layer is arranged above the image acquisition unit and used for transmitting an inclined light signal which is incident to a finger above the display screen and returns through the finger to the image acquisition unit, wherein the inclined light signal comprises a reflected light signal and a transmitted light signal from the finger, and the reflected light signal is attenuated after passing through a linear polarization unit in a light path between the finger and the image acquisition unit, so that the proportion of the transmitted light signal reaching the image acquisition unit is relatively increased;

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

In one possible implementation, the linear polarization unit is integrated inside the display screen and located above the organic 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 manner, the polarization direction of the linear polarization unit is perpendicular to the incident plane of the oblique optical signal; or the polarization direction of the linear polarization unit is parallel to the incidence plane of the inclined optical signal; or, an included angle between the polarization direction of the linear polarization unit and the incidence plane of the oblique optical signal is 45 °.

In one possible implementation, the tilt angle of the tilted optical signal is less than or equal to brewster's angle.

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

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

In one possible implementation, the curvatures in the respective directions of the light-condensing surfaces of each of the microlenses in the microlens array are 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 microlens in different light blocking layers are sequentially reduced 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 guide layer includes: and the optical function film layer is used for selecting the inclined optical signal from the optical signals in all directions returned by the finger and transmitting the inclined optical signal to the image acquisition unit.

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

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

In a possible implementation, the optically functional film layer is integrated in the image acquisition unit or is arranged above the image acquisition unit as a relatively separate device from the image acquisition unit.

In one possible implementation, the first light guide layer includes: an array of light-conducting channels formed from a plurality of light-conducting channels.

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

In a possible implementation manner, the first light guide layer is horizontally disposed, 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 signal to the image acquisition unit.

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

In a possible implementation manner, the plurality of light guide channels are perpendicular to the surface of the first light guide layer, and the first light guide layer is obliquely arranged to guide the oblique light signal 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 used for transmitting the optical signal in the second direction returned by the finger to the image acquisition unit; the pixels of the image acquisition unit, which are located below the second light guide layer, are used for receiving the light signals in the second direction, and the light signals in the second direction are used for acquiring the fingerprint image of the finger, wherein the oblique 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: and the filtering layer is arranged in a light path between the display screen and the image acquisition unit and used for filtering optical signals of non-target wave bands and transmitting the optical signals of the target wave bands.

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

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

In a second aspect, a fingerprint detection apparatus is provided, which is suitable for use under a display screen to realize optical fingerprint detection under the display screen, and includes:

the first light guide layer is arranged above the image acquisition unit and used for transmitting an optical signal which is incident to a finger above the display screen and returns by the finger in a first direction to the image acquisition unit;

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

the image acquisition unit is arranged below the first light guide layer and used for receiving the light signals in the first direction, the image acquisition unit is arranged below the second light guide layer and used for receiving the 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 the fingerprint images of the fingers, and the first direction is different from the second direction.

In one possible implementation, the oblique light signal includes a reflected light signal and a transmitted light signal from the finger, wherein the reflected light signal is attenuated after passing through a linear polarization unit located in a light path between the finger and the image acquisition unit, so that a proportion of the transmitted light signal reaching the image acquisition unit is relatively increased.

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

In one possible implementation manner, the incident surface of the optical signal in the first direction is perpendicular to the polarization direction of the linear polarization unit; or, the incidence surface of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit; or, an included 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 an OLED layer of the display screen.

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

a display screen; and the number of the first and second groups,

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

Based on the technical scheme, oblique 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 transmission light signals of the finger reaching the image acquisition unit is relatively increased, the fingerprint detection performance is improved, and particularly the fingerprint identification performance on 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 is applicable.

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

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 disclosure.

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

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

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

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

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 views of fingerprint detection according to different directions of light rays.

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

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

Detailed Description

The technical solution in the present application will be described below with reference to the accompanying drawings.

It should be understood that the embodiments of the present application can be applied to fingerprint systems, including but not limited to optical, ultrasonic or other fingerprint detection systems and medical diagnostic products based on optical, ultrasonic or other fingerprint imaging, and the embodiments of the present application are only illustrated by way of example of an optical fingerprint system, but should not constitute any limitation to the embodiments of the present application, and the embodiments of the present application are also applicable to other systems using optical, ultrasonic or other imaging technologies, and the like.

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 electronic device, the optical fingerprint module may be disposed in a partial area or an entire area below the display screen, so as to form an Under-screen (or Under-screen) optical fingerprint system. Or, the optical fingerprint module can also be partially or completely integrated inside the display screen of the electronic device, so as to form an In-display or In-screen optical fingerprint system.

Optical underscreen fingerprint detection techniques use light returning from the top surface of a device display assembly for fingerprint sensing and other sensing operations. The returning light carries information about an object (e.g., a finger) in contact with the top surface, and by collecting and detecting the returning 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 appropriately configuring the optical elements for collecting and detecting the returned light.

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

The electronic device 10 includes a display screen 120 and an optical fingerprint module 130. Wherein, 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, light sensing pixels, pixel units, etc.). The sensing array 133 is located in an area or a sensing area thereof, which is the fingerprint detection area 103 (also called 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 a display area of the display screen 120. In an alternative embodiment, the optical fingerprint module 130 may be disposed at other positions, such as the side of the display screen 120 or the edge opaque region of the electronic device 10, and the optical path is designed to guide the optical signal from at least a part of the display region of the display screen 120 to the optical fingerprint module 130, so that the fingerprint detection region 103 is actually located in the display region of the display screen 120.

It should be understood 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 designing an optical path such as lens imaging, a reflective folded optical path, or other optical path designs such as light convergence or reflection, the area of the fingerprint detection area 103 of the optical fingerprint module 130 may be 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 by, for example, 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.

Therefore, when the user needs to unlock or otherwise verify the fingerprint of the electronic device 10, the user only needs to press a finger on the fingerprint detection area 103 of the display screen 120, so as to input the fingerprint. Since fingerprint detection can be implemented in the screen, the electronic device 10 with the above structure does not need to reserve a special space on the front surface thereof to set a fingerprint key (such as a Home key), so that a full-screen scheme can be adopted, that is, the display area of the display screen 120 can be substantially extended 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 detection portion 134 and an optical assembly 132. The light detecting portion 134 includes the sensing array 133 and a reading circuit and other auxiliary circuits electrically connected to the sensing array 133, which can be fabricated on a chip (Die) by a semiconductor process, such as an optical imaging chip or an optical fingerprint sensor. 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 can be used as the optical sensing units as described above. The optical assembly 132 may be disposed above the sensing array 133 of the light detecting portion 134, and may specifically include a Filter layer (Filter) for filtering ambient light penetrating through the finger, a light guiding layer (also called a light path guiding structure) for guiding reflected light reflected from the surface of the finger to the sensing array 133 for optical detection, and other optical elements.

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

For example, the light guide layer may specifically be a Collimator (collimater) layer manufactured on a semiconductor silicon wafer, and the collimater layer has a plurality of collimation units or a micro-pore array, the collimation units may specifically be small holes, in reflected light reflected back from a finger, light perpendicularly incident to the collimation units may pass through and be received by an optical sensing unit below the collimation units, and light with an excessively large angle of incidence is attenuated by multiple reflections inside the collimation units, so that each optical sensing unit can basically only receive reflected light reflected back from fingerprint grains directly above the optical sensing unit, and the sensing array 133 may detect a fingerprint image of the finger.

In another implementation, the light guide layer may also be an optical Lens (Lens) layer, which has one or more Lens units, such as a Lens group composed of one or more aspheric lenses, and is used to converge the reflected light reflected from the finger to the sensing array 133 of the light detection portion 134 therebelow, so that the sensing array 133 can image based on the reflected light, thereby obtaining the fingerprint image of the finger. Optionally, the optical lens layer may further form a pinhole in an optical path of the lens unit, and the pinhole may cooperate with the optical lens layer to enlarge a field of view of the optical fingerprint module 130, so as to improve a fingerprint imaging effect of the optical fingerprint module 130.

In other implementations, the light guide layer may also specifically adopt a Micro-Lens (Micro-Lens) layer, the Micro-Lens layer has a Micro-Lens array formed by a plurality of Micro-lenses, which may be formed above the sensing array 133 of the light detection portion 134 through a semiconductor growth process or other processes, and each Micro-Lens may respectively correspond to one of the sensing units of the sensing array 133. 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 shielding layer, a light blocking layer, or the like) having micro holes (or referred to as open holes) may be further included between the microlens layer and the sensing unit, wherein the micro holes are formed between the corresponding microlenses and the sensing unit, and the light blocking layer may block optical interference between adjacent microlenses and the sensing unit, and enable light corresponding to the sensing unit to be converged into the micro holes through the microlenses and transmitted to the sensing unit through the micro holes for optical fingerprint imaging.

It should be understood that several implementations of the light guide layer described above may be used alone or in combination. For example, a microlens layer may be further disposed 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 lamination structure or optical path thereof may need to be adjusted according to actual needs.

As an alternative implementation manner, the display screen 120 may adopt a display screen having a self-Light Emitting display unit, such as an Organic Light-Emitting Diode (OLED) display screen or a Micro-LED (Micro-LED) display screen. Taking an OLED display screen as an example, the optical fingerprint module 130 may use a display unit (i.e., an OLED light source) of the OLED display screen 120 located in the fingerprint detection area 103 as an excitation light source for optical fingerprint detection. When the finger 140 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, and the light 111 is reflected at the surface of the finger 140 to form reflected light or scattered light by scattering inside the finger 140. In the related patent application, the above-mentioned reflected light and scattered light are collectively referred to as reflected light for convenience of description. Because the ridges (ridges) 141 and the valleys (valley)142 of the fingerprint have different light reflection capabilities, the reflected light 151 from the ridges and the reflected light 152 from the valleys of the fingerprint have different light intensities, and after passing through the optical assembly 132, 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; fingerprint image data can be obtained based on the fingerprint detection signal, and fingerprint matching verification can be further performed, so that an optical fingerprint detection function is realized in 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 suitable for a non-self-luminous display screen, such as a liquid crystal display screen or other passive luminous display screen. Taking an application to a liquid crystal display screen having a backlight module and a liquid crystal panel as an example, to support the underscreen fingerprint detection of the liquid crystal display screen, 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 specifically be 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 screen or 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 through a light path so that the 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 open holes or perform other optical designs on film layers such as a diffusion sheet, a brightness enhancement sheet, and a reflection sheet to allow the fingerprint detection light to pass through the liquid crystal panel and the backlight module and reach the optical fingerprint module 130. When the optical fingerprint module 130 is used to provide an optical signal for fingerprint detection by 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, which may be a glass cover or a sapphire cover, located above the display screen 120 and covering the front surface of the electronic device 10. Therefore, in the embodiment of the present application, the pressing of the finger on the display screen 120 actually means pressing on 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, and the circuit board 150 is disposed below the optical fingerprint module 130. The optical fingerprint module 130 can be adhered to the circuit board 150 by a back adhesive and electrically connected to the circuit board 150 by soldering a pad and a metal wire. Optical fingerprint module 130 may be electrically interconnected and signal-routed to other peripheral circuits or other components of electronic device 10 via circuit board 150. For example, the optical fingerprint module 130 may receive a control signal of a processing unit of the electronic device 10 through the circuit board 150, and may further 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, and the area of the fingerprint detection area 103 of the optical fingerprint module 130 is small 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 collect the fingerprint image and cause poor user experience. In other alternative embodiments, the optical fingerprint module 130 may specifically include a plurality of optical fingerprint sensors. A plurality of optics fingerprint sensor can set up side by side through the concatenation mode the below of display screen 120, just a plurality of optics fingerprint sensor's response area constitutes jointly optics fingerprint module 130's fingerprint detection area 103. Thereby the fingerprint detection area 103 of optical fingerprint module 130 can extend to the main area of the lower half of display screen, extend to the finger and press the region conventionally promptly to realize blind formula fingerprint input operation of pressing. Further, when the number of the optical fingerprint sensors is sufficient, the fingerprint detection area 103 may also be extended to a half display area or even the entire display area, thereby realizing half-screen or full-screen fingerprint detection.

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

Optionally, corresponding to the plurality of optical fingerprint sensors of the optical fingerprint device 130, there may be a plurality of light guide layers in the optical component 132, where each light guide layer corresponds to one optical fingerprint sensor respectively, and is attached to and disposed above the corresponding optical fingerprint sensor respectively. Alternatively, the plurality of optical fingerprint sensors may share a single light guiding layer, i.e. the light guiding layer has a large enough area to cover the sensing array of the plurality of optical fingerprint sensors. In addition, the optical assembly 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 mainly used for isolating the influence of external interference light on the detection of the optical fingerprint. The optical filter may be configured to filter ambient light that penetrates a finger and enters the optical fingerprint sensors through the display screen 120, and similar to the light guide layer, the optical filter may be respectively disposed to filter interference light for each optical fingerprint sensor, or may also cover the plurality of optical fingerprint sensors simultaneously with one large-area optical filter.

The light guide layer can also adopt an optical Lens (Lens), and a small hole can be formed above the optical Lens through a shading material and matched with the optical Lens to enable the fingerprint detection light to be converged to the optical fingerprint sensor below so as to realize fingerprint imaging. Similarly, each optical fingerprint sensor may be configured with an optical lens for fingerprint imaging, or the 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 configured to cooperate with the two or more sensing arrays to perform optical imaging, so as to reduce the imaging distance and enhance the imaging effect.

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

The embodiment of the application can be applied to detection of various fingers, and is particularly suitable for detection of dry fingers. By dry finger is meant a relatively dry finger or a relatively clean finger. The scheme that adopts perpendicular light to carry out fingerprint detection at present is not good enough to the fingerprint detection effect of dry finger, and the fingerprint detection's that this application embodiment provided scheme can promote the fingerprint detection performance to dry finger.

The fingerprint detection device of the embodiment of the application is suitable for optical fingerprint detection under the display screen below in order to realize the screen. Fig. 3 shows a schematic diagram of an apparatus 300 for fingerprint detection according to an embodiment of the present application. The device 300 includes a first light guide layer 310 and an image capture unit 320. The image capturing unit 320 can refer to the above description of the light detecting portion 134, and the description of this embodiment is omitted.

The first light guide layer 310 is disposed above the image capturing unit 320. The first light guide layer 310 is used for transmitting an oblique light signal, which is incident to a finger above the display screen and returns through the finger, to the image acquisition unit 320.

The optical signal returned by the finger comprises a reflected optical signal and a transmitted optical signal from the finger. Wherein the reflected light signal is attenuated after passing through the linear polarization unit 330, so 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 an optical path from the finger to the image capturing unit 320. The linear polarization unit 330 is used 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 as a part of the display screen, for example, above an OLED layer of the display screen; alternatively, the linear polarization unit 330 is located between the first light guide layer 310 and the image acquisition unit 320; alternatively, the linear polarization unit 330 is integrated in the image capturing unit 320, so as to be a part of the image capturing unit 320, for example, above the pixel array of the image capturing unit 320.

The image capture unit 320 may comprise 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 by a plurality of pixels. The pixels of the image capturing unit 320 located below the first light guide layer 310 are configured to receive the oblique light signals, and the oblique light signals are configured to obtain a fingerprint image of the finger.

The detection principle of the embodiment of the present invention will be described in detail with reference to fig. 4, 5A, and 5B.

In fingerprint detection, the light signal incident on and returning through the finger above the display screen 340 includes two portions, one is a reflected light signal from the finger, and the other is a transmitted light signal from the finger. For example, as shown in fig. 4, a fingerprint image acquired using the reflected light signal shown on the left side appears as bright valleys and dark ridges (a positive color fingerprint). And the darker the ridge, the better the contrast between the ridge and the valley, as the contact between the finger and the display screen is better. The fingerprint image acquired by the transmitted light signal shown on the right side is represented as dark valley and bright ridge (reverse color fingerprint), because blood and tissue exist in the ridge of the fingerprint, light can be scattered in the ridge and emitted from the ridge, and the light incident to the valley of the fingerprint is rapidly attenuated after being reflected for multiple times at the valley, so that the light emitted from the valley is very weak, and the dark valley and bright ridge are represented. Since the fingerprint images obtained by reflected light imaging and transmitted light imaging are in opposite states, when reflected light and transmitted light exist simultaneously, the positive color fingerprint and the negative color fingerprint cancel each other out, and the fingerprint image is easily blurred.

Fig. 5A and 5B illustrate a relationship between a distance between a finger and a display screen and a contrast of a fingerprint image, in which fig. 5A illustrates fingerprint detection using a vertical light signal and fig. 5B illustrates fingerprint detection using an 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 contact between the fingerprint and the display screen is good, the reflected light imaging is mainly dominant, the fingerprint image presents the characteristic of bright valley and dark ridge, and the fingerprint detection performance of a normal finger is good. When the contact between the fingerprint and the display screen gradually becomes worse, the imaging effect of the reflected light gradually weakens along with the increase of the distance between the ridge and the display screen, the imaging of the transmitted light gradually dominates, and the fingerprint image presents the characteristic of dark valley and bright ridge. When the reflected light imaging and the transmitted light imaging are in a state of equal potential, the contrast of the fingerprint image is the lowest, and the stage is called a transition zone. In the transition zone, the contrast of the fingerprint image of the finger finally obtained is poor because the fingerprint images of the reflected light imaging and the transmitted light imaging are mutually offset.

The reflected light imaging is more sensitive to changes in the distance between the finger and the display screen, while the transmitted light imaging is less sensitive to changes in the distance. Therefore, in the detection of dry fingers, it is desirable that the transmitted light imaging is dominant, and the proportion of the transmitted light is increased to reduce the transition zone, thereby improving the fingerprint detection performance.

In the embodiment of the application, the fingerprint detection is performed by adopting the oblique light, and the reflected light signal of the finger is attenuated by the linear polarization unit, so that the proportion of the transmitted light signal reaching the image acquisition unit is relatively increased, the fingerprint detection performance is improved, and particularly, the identification performance of the special finger such as a dry finger is improved.

As can be seen from fig. 5A and 5B, compared with the fingerprint detection using the vertical optical signal, the transition zone is significantly reduced when the fingerprint detection is performed using the oblique optical signal, so that the detection performance for dry fingers is improved.

The angle between the polarization direction of the linear polarization unit 330 and the incident plane 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 forms an angle of 45 ° with 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 then becomes linearly polarized light to irradiate 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 light can return through the linear polarization unit 330, and is guided by the light guide layer 310 and transmitted to the image acquisition unit 320.

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

If the polarization polarity of the linear polarization unit 330 is parallel to the incident plane of the oblique light (or referred to as the receiving plane of the oblique light signal), the s-wave in the reflected light of the finger is attenuated, and only the p-wave can pass through the linear polarization unit 330, return, and be guided by the light guide layer 310 and transmitted to the image acquisition unit 320. If the polarization polarity 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 remaining s-wave can return through the linear polarization unit 330 and be guided by the light guide layer 310 to be transmitted to the image acquisition unit 320, for example, as shown in fig. 6. No matter p wave or s wave is attenuated, the reflected light signal of the finger is weakened, but 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 increased relatively, the transition zone is reduced, and the detection performance of the dry finger is improved.

In general, the p-waves in the reflected light are generally less than the s-waves, and if the angle of incidence reaches Brewster's angle, there are no p-waves in the reflected light, only the s-waves remain, and the reflected light is fully 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 angle of total reflection is reached and then are totally reflected. Therefore, it is preferable to make the reflected light signal returned by the finger as small as possible if the tilt angle of the tilted light signal returned by the finger is smaller than or equal to the brewster angle.

The embodiment of the present application provides three possible implementations of the first light guiding layer 310. The following is described in detail 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 optical signal returned by the finger. Each light-blocking layer 312 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 light signals converged by each microlens 311 pass through the openings 313 corresponding to the microlenses 311 in different light-blocking layers 312 to reach the image capturing unit 320.

The projection of the light-condensing surface of the microlens 311 on a plane perpendicular to its optical axis may be rectangular or circular. The light condensing surface of the microlens 311 is a surface for condensing light. The light-condensing surface may be a spherical surface or an aspherical surface. Preferably, the curvatures of the light-condensing surfaces in all directions are the same, so that the imaging focuses of the microlenses 311 in all directions are at the same position, thereby ensuring the imaging quality.

Each microlens 311 corresponds to a pixel 321 in the image capturing unit 320, wherein the oblique light signal converged by the microlens 311 passes through an opening corresponding to the microlens 311 in a different light blocking layer to reach the pixel 321 corresponding to the microlens 311.

Since the light is guided by the openings in the light-blocking layers, in order to allow the oblique light signals to reach the image capturing unit, the connecting lines of the openings corresponding to the microlenses in different light-blocking layers should be oblique, and the oblique angle of the connecting lines is equal to or approximately equal to the oblique angle of the oblique light signals.

It should be understood that the 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 with one or more layers.

For example, as shown in fig. 7, when a light-blocking layer 312 is used, the light-blocking layer 312 may be integrated into the image capturing 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 connecting line of the openings corresponding to each microlens in 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 light blocking layers are sequentially arranged in an offset manner from top to bottom, so that the pixel 321 can receive the oblique optical signal returned by the finger and block optical signals in other directions.

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

Optionally, the apertures of the openings corresponding to the same microlens 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 upper light-blocking layer is larger than the aperture of the lower light-blocking layer, so that more (a certain range of angles) of the light signal can be guided to the corresponding pixel.

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

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

The transparent medium layer can be transparent to the optical signal of the target waveband (namely, the optical signal of the waveband required by fingerprint detection). For example, the transparent dielectric layer may be an oxide or a nitride.

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

For example, a transition layer may be disposed between the inorganic layer and the organic layer to achieve a tight connection; a protective layer may be provided over the easily oxidizable layer to provide protection.

Mode 2

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

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

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

Further, optionally, the optical function film layer 314 may also be used to refract the oblique light signal, so that the oblique light signal can be vertically incident on the pixel of the image capturing unit 320.

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

Alternatively, the optical function film layer 314 may be integrated in the image capturing unit 320 or disposed over the image capturing unit 320 as a separate device with respect to the image capturing unit 320.

Mode 3

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

The light guide channel 315 may be formed of, for example, an optical fiber, an air via, or a light-transmissive material.

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

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

In another implementation, the 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 signals to the image capturing unit 320.

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

In another implementation manner, the first light guide layer 310 is horizontally disposed, the light guide channels 315 are perpendicular to the surface of the first light guide layer 310, and the oblique light signal reaches the image acquisition unit 320 after being totally reflected at least once in each light guide channel 315 of the light guide channels 315.

For example, as shown in fig. 11C, the first light guide layer 310 is disposed parallel to the display screen 340, and the light guide channel 315 is a vertical channel, and the light guide channel 315 is an optical fiber. Since the optical fiber can transmit incident light at a specific angle, the optical fiber can guide an oblique optical signal reflected by a finger at a specific angle. 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, thereby reaching the image acquisition unit 320.

The embodiment of the present application also provides another implementation manner of the apparatus 300 for fingerprint detection. As shown in fig. 12, the fingerprint detection apparatus 300 includes a first light guide layer 320, a second light guide layer 360, and an image capturing unit 320.

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

The pixels of the image capturing unit 320 located below the second light guide layer 360 are configured to receive the light signal in the second direction, and the light signal in the second direction is configured to obtain a fingerprint image of the finger. The oblique light signal transmitted by the first light guide layer is a light signal in a first direction, and the second direction is different from the first direction.

In this embodiment, the fingerprint detection apparatus 300 may further include a second light guide layer 360 in addition to the first light guide layer 320. The first light guide layer 320 is configured to transmit an optical 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 guide layer 360 is used for transmitting the optical signal of the second direction returned by the finger to the image acquisition unit 320. Because the optical signals in different directions can be detected simultaneously, the fingerprint detection is carried out, and therefore the fingerprint detection performance is improved.

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 inclined directions, the inclination angle of the light in the second direction may be the same as or different from the inclination angle of the light 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 surface of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit 330; alternatively, the incident surface of the optical signal in the first direction and the polarization direction of the linear polarization unit 330 form a certain angle, for example, 45 °, which is not limited in this application.

For example, as shown in fig. 13A, the first direction is an oblique direction, which has an angle with the display screen, where fig. 13A is a top view, the arrow shown can be regarded as a projection of the incident plane of the light ray of the first direction in the display screen, and the dotted line represents 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 in the first direction returned by the finger is transmitted to the image capturing unit 320 through the first light guiding layer 310, and the vertical light signal returned by the finger is transmitted to the image capturing unit 320 through the second light guiding layer 360.

For another example, as shown in fig. 13B, the first direction and the second direction are both oblique directions, but 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 incident 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 can be regarded as the projection of the incident plane of the light rays in the first direction and the second direction in the display screen, and the dotted lines indicate the polarization direction of the linear polarization unit 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 more light guide layers respectively for transmitting light signals in different directions to the image capturing unit 320. For example, as shown in fig. 13C, four light guide layers may be arranged to guide light rays from A, B, C, D in four different directions to the image capturing unit 320.

In this embodiment, through adopting different leaded light layers, transmit not equidirectional light signal to image acquisition unit to be used for fingerprint detection, improved fingerprint detection performance.

For example, when fingerprint detection is performed on dry fingers by using oblique light, the main concern is the magnitude of the ridge-valley difference, and the larger the difference is, the higher the contrast is, the easier feature points are found, and the fingerprint detection is further performed. For a dry finger, the contrast of the fingerprint image obtained when the fingerprint is optically detected with oblique light is better than when the fingerprint is optically detected with vertical light. However, for a normal finger, the contrast of the fingerprint image obtained when the fingerprint is detected using vertical light is superior to that when the fingerprint is detected using oblique light.

In this embodiment, during fingerprint detection, if the first light guide layer 310 and the second light guide layer 360 are respectively used for transmitting oblique light signals and vertical light signals, 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 signals carrying the part of fingerprint information to corresponding pixels, so that a better fingerprint image can be obtained when the finger is a dry finger; and another part of fingerprint information of finger can transmit to image acquisition unit 320 through second leaded light layer 360, and second leaded light layer 360 will carry this part of fingerprint information's perpendicular light signal transmission to corresponding pixel to can acquire better fingerprint image when the finger is normal finger. Therefore, no matter 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 guide layer 360 can also be implemented by the above-mentioned mode 1, mode 2, or mode 3.

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

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

For another example, in the case of the method 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, so that a vertical light signal returned by a finger can pass through, and oblique light is blocked.

For reference, the aforementioned description of the first light guide layer 310 can be referred to for other features of the second light guide layer 360, and for brevity, the description is omitted here.

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

Optionally, the apparatus 300 further comprises a filter layer. The filtering layer is disposed in a light path from the display screen to the image capturing unit 320, and is configured to filter out optical signals in a non-target waveband and transmit the optical signals in a target waveband.

Optionally, the transmittance of the filter layer to light in a target wavelength band is greater than or equal to 80%, and the cut-off rate to light in a non-target wavelength band is greater 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 by using blue crystal or blue glass as a carrier.

Optionally, the filter layer may be a plated film formed on a 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, or the lower surface of the microlens.

Optionally, the apparatus 300 for fingerprint detection may further include: a dielectric and a metal layer, which may include connection circuitry for the pixels.

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

The embodiment of the present application further provides an electronic device, which includes the fingerprint detection apparatus in the various embodiments of the present application.

Optionally, the electronic device further includes a display screen, which may be a common non-foldable display screen, or a flexible display screen.

By way of example and not 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 smart device, and other electronic devices such as an electronic database, an automobile, and an Automated Teller Machine (ATM). This wearable smart machine includes that the function is complete, the size is big, can not rely on the smart mobile phone to realize complete or partial function, for example: smart watches or smart glasses and the like, and only focus on a certain type of application function, and need to be used in cooperation with other devices such as smart phones, such as various smart bracelets for physical sign monitoring, smart jewelry and other devices.

It should be noted that, without conflict, the embodiments and/or technical features in the embodiments described in the present application may be arbitrarily combined with each other, and the technical solutions obtained after the combination also fall within the protection scope of the present application.

It should be understood that the specific examples in the embodiments of the present application are for the purpose of promoting a better understanding of the embodiments of the present application, and are not intended to limit the scope of the embodiments of the present application, and that various modifications and variations can be made by those skilled in the art based on the above embodiments and fall within the scope of the present application.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by 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 fingerprint detection device is suitable for being used below a display screen to realize optical fingerprint detection under the screen, and comprises:

2. The device of claim 1, wherein the linear polarization unit is integrated inside the display screen and 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. The device according to any one of claims 1 to 3,

the polarization direction of the linear polarization unit is vertical to the incidence plane of the inclined optical signal; alternatively, the first and second electrodes may be,

the polarization direction of the linear polarization unit is parallel to the incidence plane of the inclined optical signal; alternatively, the first and second electrodes may be,

and an included angle between the polarization direction of the linear polarization unit and the incidence plane of the inclined optical signal is 45 degrees.

5. The apparatus of any of claims 1-3, wherein the tilt angle of the tilted optical signal is less than or equal to Brewster's angle.

6. The apparatus of 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 the light blocking layers are arranged below the micro lens array, each light blocking layer comprises a plurality of openings corresponding to the micro lenses, and inclined light signals converged by the micro lenses pass through the openings corresponding to the micro lenses in different light blocking layers and reach the image acquisition unit.

7. The apparatus of claim 6, wherein the projection of the light collection surface of each microlens in the microlens array on a plane perpendicular to its optical axis is rectangular or circular.

8. The apparatus of claim 6, wherein the curvature in each direction of the light-gathering surface of each microlens in the microlens array is the same.

9. The apparatus according to claim 6, wherein a last light-blocking layer of the at least one light-blocking layer is integrated in the image acquisition unit.

10. The apparatus of claim 6, wherein the apertures of the openings corresponding to the same microlens in different light-blocking layers decrease sequentially from top to bottom.

11. The apparatus of claim 6, further comprising:

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.

12. The apparatus of any one of claims 1 to 3, wherein the first light guiding layer comprises:

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

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

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

14. The apparatus of claim 12, wherein the optical function film layer is a grating film or a prism film.

15. The device of claim 12, wherein the optically functional film layer is integrated in the image capture unit or disposed over the image capture unit as a relatively separate device from the image capture unit.

16. The apparatus of any one of claims 1 to 3, wherein the first light guiding layer comprises:

an array of light-conducting channels formed from a plurality of light-conducting channels.

17. The apparatus of claim 16, wherein the plurality of light-conducting channels are formed from optical fibers, air vias, or light-transmissive materials.

18. The apparatus of claim 16, wherein the first light guide layer is horizontally disposed, and the plurality of light guide channels are tilted with respect to a surface of the first light guide layer to guide the tilted light signal to the image acquisition unit.

19. The apparatus according to claim 16, wherein the plurality of light guide channels are formed by optical fibers, the first light guide layer is horizontally disposed, 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 capturing unit after at least one total reflection in each of the plurality of light guide channels.

20. The apparatus of claim 16, wherein the plurality of light guide channels are perpendicular to a surface of the first light guide layer, the first light guide layer being obliquely disposed to guide the oblique light signals to the image acquisition unit.

21. The apparatus of any one of claims 1 to 3, further comprising:

the second light guide layer is arranged above the image acquisition unit and used for transmitting an optical signal in a second direction returned by the finger to the image acquisition unit, wherein the inclined 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;

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

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

23. The apparatus of any one of claims 1 to 3, further comprising:

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

24. The apparatus of claim 23, wherein the filter layer is a coating formed on a surface of any one of the layers in the optical path.

25. The apparatus 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.

26. A fingerprint detection device is suitable for being used below a display screen to realize optical fingerprint detection under the screen, and comprises:

27. The apparatus of claim 26, wherein the optical signal comprises a reflected optical signal and a transmitted optical signal from the finger, wherein the reflected optical signal is attenuated after passing through a linear polarization unit located in an optical path between the finger and the image capture unit such that a proportion of the transmitted optical signal reaching the image capture unit is relatively increased.

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

29. The device of claim 28, wherein the linear polarization unit is integrated inside the display screen and located above an Organic Light Emitting Diode (OLED) layer of the display screen.

30. The apparatus of claim 28, wherein the linear polarization unit is located between the display screen and the image acquisition unit.

31. The apparatus of any one of claims 28 to 30,

the incident surface of the optical signal in the first direction is vertical to the polarization direction of the linear polarization unit; alternatively, the first and second electrodes may be,

the incident surface of the optical signal in the first direction is parallel to the polarization direction of the linear polarization unit; alternatively, the first and second electrodes may be,

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

32. The apparatus of any one of claims 28 to 30, wherein the angle of inclination of the first direction is less than or equal to brewster's angle.

33. An electronic device, comprising:

a display screen; and the number of the first and second groups,

the device of any one of claims 1 to 32, disposed below the display screen to enable off-screen optical fingerprint detection.