CN213211051U

CN213211051U - Fingerprint detection device and electronic equipment

Info

Publication number: CN213211051U
Application number: CN202022720985.9U
Authority: CN
Inventors: 王滨
Original assignee: Chengdu Microlcl Technology Co ltd
Current assignee: Chengdu Microlcl Technology Co ltd
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2021-05-14
Anticipated expiration: 2030-11-23

Abstract

The utility model relates to a fingerprint identification technical field especially relates to a fingerprint detection device, fingerprint detection device control method and electronic equipment. The fingerprint detection device comprises a display layer and a lower layer, wherein the lower layer comprises: the liquid crystal micro-lens array layer is used for separating reflected light at different angles and comprises a plurality of liquid crystal micro-lens units distributed in an array; the collimator layer is positioned on one side, far away from the display layer, of the liquid crystal lens array layer and used for collimating the reflected light, the collimator layer comprises a micropore array layer, and the micropore array layer is provided with small holes which correspond to the liquid crystal microlens units one by one; an image sensor for sensing the collimated reflected light; the utility model discloses can make the total characteristic SNR of demonstration layer and lower floor maintain higher level all the time.

Description

Fingerprint detection device and electronic equipment

Technical Field

The utility model relates to a fingerprint identification technical field especially relates to a fingerprint detection device and electronic equipment.

Background

The under-screen (under display) fingerprint identification technology integrates a fingerprint sensor below a display screen, and because certain intervals are formed among pixels of the display screen, light leakage areas are formed at the intervals, so that light can be ensured to penetrate through the display screen. When a user touches and presses the screen by a finger, the screen can emit light to illuminate the finger area, and the reflected light illuminating the fingerprint returns to the image sensor clung to the display screen through the gaps of the pixels of the screen. The finger fingerprint includes ridge areas and valley areas. Because the fingerprint tissue in the ridge area absorbs light, the light reflected from the ridge becomes dark; the light reflected from the valleys is relatively bright. Therefore, the brightness difference generated by the ridges and the valleys can form a fingerprint pattern on the image sensor, and the fingerprint sensor arranged under the display screen realizes the identification of the fingerprint under the screen by detecting the reflected light carrying the fingerprint information of the user.

At present, a collimator layer is adopted in fingerprint identification to collimate reflected light carrying fingerprint information, so that the reflected light collimated by the collimator layer and reaching an image sensor has a reflected fingerprint area and an imaging area which are basically the same. And meanwhile, the micro-lens layer is adopted to separate the reflected light rays with different angles. Although the foregoing schemes all contribute to improving the overall characteristic signal-to-noise ratio of the display layer and the underlying layers, the overall characteristic signal-to-noise ratio of the display layer and the underlying layers is degraded due to the environmental susceptibility of the microlens array.

SUMMERY OF THE UTILITY MODEL

In view of this, the embodiment of the utility model provides a fingerprint detection device and electronic equipment for solve present fingerprint identification technique and can't guarantee that the total characteristic SNR of external environment change back display layer and following each layer maintains the technical problem at higher level all the time.

The utility model adopts the technical proposal that:

in a first aspect, the utility model provides a fingerprint detection device, include:

a display layer and a lower layer, the lower layer comprising:

the liquid crystal micro-lens array layer is used for separating reflected light at different angles and comprises a plurality of liquid crystal micro-lens units distributed in an array;

the collimator layer is positioned on one side, far away from the display layer, of the liquid crystal lens array layer and used for collimating the reflected light, the collimator layer comprises a micropore array layer, and the micropore array layer is provided with small holes which correspond to the liquid crystal microlens units one by one;

an image sensor for sensing the collimated reflected light.

Preferably, the focal length of the liquid crystal microlens unit is configured such that the total characteristic signal-to-noise ratio of the display layer and the lower layer satisfies a first condition.

Preferably, the liquid crystal microlens array layer includes a first substrate, a first electrode layer, an insulating layer, a second electrode layer, a liquid crystal layer, a third electrode layer and a second substrate layer, which are sequentially arranged from the display layer to the image sensor direction, the first electrode layer and the third electrode layer are transparent electrode layers, and the second electrode layer includes light through holes arranged in an array.

Preferably, the geometric centers of the liquid crystal microlens cells are arranged in such a manner as to be located at vertices of a rectangle or a regular hexagon.

Preferably, the liquid crystal display further comprises a polarizing element, wherein the polarizing element is positioned in the light path from the display screen to the liquid crystal micro-lens array layer.

Preferably, the image sensor is a pixilated image sensor.

Preferably, the liquid crystal micro-lens array further comprises a transparent protective layer which covers the side of the display layer far away from the liquid crystal micro-lens array layer.

Preferably, the first condition is that the total characteristic signal-to-noise ratio of the display layer and the lower layer is maximum.

Preferably, the first condition is that the total characteristic signal-to-noise ratio of the display layer and the lower layer is greater than a first threshold.

In a second aspect, the present invention provides an electronic device, comprising a processor and the fingerprint detection apparatus of the first aspect.

Has the advantages that: the utility model discloses a fingerprint detection device, fingerprint detection device's control method and electronic equipment utilize the liquid crystal microlens array to separate the reverberation of different angles, make the reverberation that adjacent region jetted into to one side unable collimator layer of passing through. Meanwhile, the reflected light carrying the fingerprint information of the user is collimated by the collimator layer, so that the imaging area of the reflected light on the image sensor corresponds to the area of the display screen contacted by the finger one by one, the interference of light rays of other areas is reduced, and the imaging effect is obviously improved. The utility model discloses the characteristics that still utilize liquid crystal microlens array's focus can be adjusted through driving voltage carry out dynamic configuration according to the focus of liquid crystal microlens unit to the total characteristic SNR that makes the demonstration layer and following each layer satisfy all the time and can accurately carry out fingerprint identification's requirement, effectively avoided because environmental change causes the demonstration layer and following each layer total characteristic SNR changes the harmful effects to the fingerprint identification effect.

Drawings

In order to more clearly illustrate the technical solution of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and for those skilled in the art, without creative efforts, other drawings can be obtained according to these drawings, and these drawings are all within the protection scope of the present invention.

Fig. 1 is a schematic structural view of a fingerprint detection device in embodiment 1 of the present invention;

fig. 2 is a schematic structural diagram of a liquid crystal microlens array according to embodiment 1 of the present invention;

FIG. 3 is a schematic diagram of reflected light being focused on an image sensor after being adjusted by a liquid crystal micro-lens array;

FIG. 4 is a diagram illustrating a change in the focal position of reflected light rays after a conventional microlens array is subjected to environmental influences;

FIG. 5 is a schematic diagram of another variation of the focal position of reflected light after environmental influences have caused a conventional microlens array;

FIG. 6 is a schematic diagram showing that light obliquely incident in different directions passes through the same aperture position of the liquid crystal microlens and then generates a phase difference;

fig. 7 is a schematic structural view of a regular hexagonal arrangement of microlens arrays according to embodiment 1 of the present invention;

fig. 8 is a schematic structural view of a microlens array of example 1 of the present invention arranged in a rectangular shape;

fig. 9 is a flowchart of a control method of a fingerprint detection device according to the present invention;

fig. 10 is a flowchart illustrating another method for controlling a fingerprint detection device according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the drawings in the embodiments of the present invention are combined below to clearly and completely describe the technical solutions in the embodiments of the present invention. It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element. In case of conflict, various features of the embodiments and examples of the present invention may be combined with each other and are within the scope of the present invention.

Example 1:

as shown in fig. 1, embodiment 1 of the present invention discloses a fingerprint detection device, which includes a display layer 10 and a lower layer, wherein the display layer 10 can be a self-luminous display screen, which adopts a display unit with self-luminous properties as a display pixel. For example, the display screen may be an Organic Light-Emitting Diode (OLED) display screen or a Micro-LED (Micro-LED) display screen. When an OLED display screen is used in this embodiment, the fingerprint detection device may use a display unit (i.e., an OLED light source) of the OLED display screen located in the fingerprint detection area as an excitation light source for detecting a fingerprint. When a finger presses the fingerprint detection area, the display screen emits a beam of light to the finger to be detected above the fingerprint detection area, and the light is reflected on the surface of the finger to form reflected light 50 or scattered through the inside of the finger to form scattered light. In other alternative embodiments, the Display 120 may also be a Liquid Crystal Display (LCD) or other passive light emitting Display, which is not limited in this embodiment of the present application.

In addition, the display screen can also be a display screen with a touch function, namely a touch display screen. The display screen with the touch function is adopted, the image of the electronic equipment can be displayed, touch operation such as touch or pressing of a user can be detected, the electronic equipment is controlled according to the detected touch operation, and the touch display screen can provide a man-machine interaction interface for the user.

In addition, a transparent layer may be disposed above the display layer 10, and the transparent layer covers the surface of the display layer 10 to protect the display layer 10. The transparent layer may be a glass cover layer, a sapphire cover layer, or the like.

The lower layer includes:

the liquid crystal micro-lens array layer 20 is used for separating the reflected light 50 at different angles, and the liquid crystal micro-lens array layer 20 comprises a plurality of liquid crystal micro-lens units 82 distributed in an array; the liquid crystal microlens elements 82 in the liquid crystal microlens array layer 20 can be driven to zoom by a voltage.

The collimator layer 30 is located on one side, far away from the display layer 10, of the liquid crystal lens array layer, the collimator layer 30 is used for collimating the reflected light 50, the collimator layer 30 comprises a micropore array layer, and the micropore array layer is provided with small holes 31 which correspond to the liquid crystal microlens units 82 in a one-to-one mode;

the aforementioned collimator layer 30 may include a plurality of collimating units. In the reflected light 50 reflected from the ridge area 61 and the valley area 62 of the finger, the light perpendicularly incident to the collimating unit can pass through and be received by the image sensor 40 below the collimating unit, and the light with an excessively large incident angle is attenuated by multiple reflections inside the collimating unit, so that each optical sensing unit on the image sensor 40 can basically only receive the reflected light 50 reflected from the fingerprint directly above the optical sensing unit, thereby effectively improving the image resolution, further improving the fingerprint identification effect, and enabling the fingerprint detection device to more accurately detect the fingerprint image of the finger. The collimator layer 30 of the present embodiment may adopt a micropore array layer, and a plurality of small holes 31 arranged in an array are disposed on the micropore array layer, and the small holes 31 serve as the collimation units. Since the small holes 31 of the micro hole array layer correspond to the liquid crystal micro lens units 82 one to one, the collimating units of the collimator layer 30 also correspond to the liquid crystal micro lens units 82 one to one. The area between adjacent apertures 31 is an opaque light-blocking area that blocks light obliquely incident through adjacent areas to avoid interference of light rays from adjacent areas.

As shown in fig. 3, in the present embodiment, the liquid crystal microlens units 82 are disposed above the small holes 31 of the micro-hole array layer in a one-to-one correspondence manner, so that the reflected light 50 entering the liquid crystal microlens units 82 at certain specific angles (for example, perpendicular to the liquid crystal microlens units 82) can pass through the small holes 31 of the micro-hole array layer by converging through the liquid crystal microlenses, while the reflected light 50 entering the liquid crystal microlenses at other angles, for example, from adjacent regions obliquely relative to the liquid crystal microlens units 82 falls on the light-shielding region of the micro-hole array layer, and thus cannot reach the corresponding region of the image sensor 40. In this way, the liquid crystal microlens unit 82 can separate the reflected light 50 at different angles, so that only the reflected light 50 of the region corresponding to the small hole 31 of the micropore array layer can reach the corresponding region of the image sensor 40 after being collimated by the micropore array, thereby realizing the effect of narrow field of view. Thus, the area of the image formed by the reflected light 50 on the image sensor 40 corresponds to the area of the display screen contacted by the finger, so that the interference of light rays in other areas is reduced, and the imaging effect is obviously improved.

In addition, the fingerprint identification device of this embodiment further includes a first microlens array layer, where the first microlens array layer is located on a side of the liquid crystal microlens array layer away from the display layer or a side close to the display layer. The first microlens array layer can adopt other common microlens arrays which do not need to be driven by voltage, namely, a liquid crystal microlens array is added on the basis of the original common microlens array to form a combination of the common microlens array and the liquid crystal microlens array, and each liquid crystal microlens unit 82 corresponds to one common microlens unit 81. The liquid crystal micro lens array is arranged above or below the common micro lens array. When the total characteristic signal-to-noise ratio mode is changed, the driving voltage of the liquid crystal lens is changed, so that the focal length of the combination of the whole common micro lens array and the liquid crystal micro lens array is finely adjusted, and the total characteristic signal-to-noise ratio is improved. The liquid crystal micro lens array only needs to finely adjust the focal length, so that the focal length change range of the liquid crystal micro lens can be reduced, and the response time is prolonged.

An image sensor 40 for sensing the collimated reflected light 50; the image sensor 40 is a TFT-based organic imaging device. TFT-based organic imaging devices are organic imaging devices fabricated on TFT-based electronic readout backplanes. The organic imaging device may be an organic semiconductor photodiode array. Organic semiconductor photodiodes can be made, for example, from a stack of evaporated ultrathin (e.g., <100nm) films of organic substances such as chloroboron (e.g., SubPc/C-60).

The focal length of the liquid crystal microlens element 82 is configured such that the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer satisfies a first condition.

According to the gaussian equation 1/s + 1/l-1/f, when the light field is a narrow field of view and the image distance l is constant, changing the object distance s does not affect the total characteristic signal-to-noise ratio of the touch display layer 10 and the layers below, while changing the focal distance f decreases the signal-to-noise ratio. Since the microlens array is susceptible to environmental influences such as temperature, the focal length of the microlenses changes, the focal position of the light changes from the position in fig. 3 to the position in fig. 4 or 5, and the overall characteristic signal-to-noise ratio of the touch display layer 10 and the underlying layers decreases. In the case where the total characteristic signal-to-noise ratio of the touch display layer 10 and the layers below is low, the image sensor 40 may collect an image with poor effect, which may affect the accuracy of fingerprint recognition. In this embodiment, the focal length of the liquid crystal microlens array can be dynamically configured according to the current total characteristic signal-to-noise ratio by using the characteristic that the focal length of the liquid crystal microlens array can be adjusted by the driving voltage, so that the total characteristic signal-to-noise ratio of the display layer 10 and the following layers can meet the requirement of fingerprint identification.

The aforementioned first condition may be that the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is maximized. That is, the liquid crystal microlens element 82 is configured to have a focal length value corresponding to the maximum total characteristic signal-to-noise ratio of the display layer 10 and the lower layer. The maximum total characteristic signal-to-noise ratio of the display layer 10 and the lower layer herein means that the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is scanned by using the variable-focus characteristic of the liquid crystal microlens within the variable-focus range of the liquid crystal lens, all the total characteristic signal-to-noise ratios obtained by scanning are compared, the maximum value among the total characteristic signal-to-noise ratios is selected, and the first condition is satisfied when the total characteristic signal-to-noise ratio of the display layer 10 and the lower layers is equal to the maximum value of the focal length of the liquid crystal microlens unit 82. By adopting the above conditions, the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer can be always maintained at an optimal level by dynamically adjusting the focal length of the liquid crystal microlens unit 82, so that the fingerprint detection device has the best identification effect no matter how the external environment changes.

Further, the aforementioned first condition may be that the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is greater than a first threshold value. With the foregoing conditions, the minimum total characteristic signal-to-noise ratio of the display layer 10 and the lower layer that satisfies the requirement can be obtained as the first threshold according to the accuracy requirement of fingerprint identification. The system detects the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer, and when the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is lower than a set first threshold, the focal length of the liquid crystal micro lens is adjusted until the current total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is higher than the set first threshold. In the foregoing manner, the focal length of the liquid crystal microlens element 82 can be configured according to the specific requirements of fingerprint identification without repeatedly adjusting the total characteristic signal-to-noise ratio of the focal length scanning display layer 10 and the lower layer. Therefore, the accuracy of the fingerprint detection device in long-term use is ensured, and the system overhead is saved. The first threshold may be different in different application scenarios, and may also be flexibly adjusted according to different accuracy requirements of fingerprint identification.

In the present embodiment, for convenience of focal length adjustment, the focal lengths of the liquid crystal microlens units 82 in the liquid crystal microlens array can be adjusted in the same manner, for example, all the liquid crystal microlens units 82 are driven by the same set of driving voltages.

The total characteristic snr of different regions is different due to different properties of the liquid crystal microlens elements 82 of the respective regions during the manufacturing process, or different properties of the respective liquid crystal microlens elements 82, or different total characteristic snr of different apertures 31. For this embodiment, the focal length of the liquid crystal microlens can be adjusted in different regions, or the focal length of each liquid crystal microlens unit 82 can be adjusted individually. For example, different driving voltages are used to adjust the focal length of the liquid crystal micro lens in different areas. For example, each liquid crystal microlens element 82 is configured with an independent driving voltage, so that the focal length of each liquid crystal microlens element 82 can be independently adjusted. By adopting the method, the property difference of different liquid crystal micro-lens units 82 can be overcome, so that the focal length of each liquid crystal micro-lens unit 82 can meet the condition of the total characteristic signal-to-noise ratio corresponding to the focal length.

The fingerprint detection device of the present embodiment may further include a transparent separation layer 70 between the micro-pore array layer and the image sensor 40, the transparent separation layer 70 being used to separate the micro-pore array layer from the image sensor 40 by a certain distance.

In addition, since the refractive index of the liquid crystal molecules is related to the incident angle, and the pretilt angle of the liquid crystal molecules in the liquid crystal microlens unit is fixed to rotate in the same fixed direction with the voltage, the light obliquely incident from different directions passes through the same aperture position of the liquid crystal microlens, and then a phase difference is generated, as shown in fig. 6, the liquid crystal microlens has different focal powers for the light incident from different directions. In this embodiment, the transverse surface of the small hole 31 is formed in an elliptical shape to avoid the above-mentioned problem. In other embodiments, the aforementioned aperture 31 may be circular or have other shapes, and is not limited herein. The following describes a specific structure of the liquid crystal microlens array used in the fingerprint detection device. As shown in fig. 2, the liquid crystal microlens array layer 20 includes a first substrate 21, a first electrode layer 22, an insulating layer 23, a second electrode layer 24, a liquid crystal layer 25, a third electrode layer 26, and a second substrate 27, which are sequentially disposed from the display layer 10 toward the image sensor 40, the first electrode layer 22 and the third electrode layer 26 are transparent electrode layers, and the second electrode layer 24 is provided with light passing holes 241 arranged in an array.

The first electrode layer 22 and the third electrode layer 26 are made of transparent electrodes, such as ITO electrodes, AZO electrodes, and the like. The light passing hole 241 may be a circular light passing hole 241, and in other embodiments, may also be other light passing holes 241 with symmetrical shapes, such as a rectangular light passing hole 241, a regular polygonal light passing hole 241, and the like, which is not limited herein. Wherein the third electrode layer 26 is used as a common electrode of the liquid crystal microlens to provide a reference voltage for the first electrode layer 22 and the second electrode layer. The third electrode layer 26 and the second electrode layer 24 are separated by the liquid crystal layer 25, and the porous electrode and the second electrode unit are separated by a thin insulating layer 23, so that the first electrode layer 22 and the second electrode layer 24 are insulated, and the liquid crystal micro-lens array can keep a small thickness. The first substrate 21 and the second substrate 27 are used as a support structure of the liquid crystal microlens element, and may be made of a transparent material having certain strength and rigidity, such as a glass substrate, a plastic substrate, or the like. To maintain the shape of the liquid crystal layer 25, the present embodiment may further provide a spacer for supporting the liquid crystal layer 25 in the liquid crystal layer 25.

When the liquid crystal micro-lens array works, working voltage is applied to each electrode layer, non-uniform electric field distribution is generated in a liquid crystal area, liquid crystal molecules are non-uniformly deflected under the action of the non-uniform electric field, and the spatial distribution of the refractive index of the liquid crystal molecules is also non-uniformly changed, so that light beams are focused at a specific position. When the regulating voltage is changed, the focal position of the micro lens is changed, so that the regulating process of the focal position of the liquid crystal micro lens is completed. In order to form the electric field for driving the liquid crystal microlens array, in the present embodiment, a first driving voltage V1 may be applied between the first electrode layer 22 and the third electrode layer 26, and a second driving voltage V2 may be applied between the second electrode layer 24 and the third electrode layer 26. And the first driving voltage V1 and the second driving voltage V2 are independent driving voltages, so the values of the first driving voltage V1 and the second driving voltage V2 can be adjusted independently. The present embodiment can adjust the focal length value of the liquid crystal microlens array by adjusting the values of the first driving voltage V1 and the second driving voltage V2.

The liquid crystal micro-lens array of the embodiment adopts the structure and the driving mode, so that the focal length is increased along with the driving voltage in a monotonous way, the focal length is very convenient to adjust, and the focal length can be adjusted in a positive and negative range. Therefore, the liquid crystal microlens array of the present embodiment can be used to conveniently scan the above-mentioned total characteristic signal-to-noise ratio, so that the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer in the fingerprint detection device can be always kept at a high level.

The second electrode layer 24 may also be a structure including a plurality of electrode units, and each electrode unit is provided with a corresponding light-passing hole. Each electrode unit forms the aforementioned liquid crystal microlens element 82 together with the other functional layers of the liquid crystal microlens array. An independent driving voltage may be applied to each electrode unit, i.e., the second driving voltage V2 of each electrode unit may be independently adjusted, so that the focal length of each liquid crystal microlens element 82 may be adjusted according to the aforementioned overall characteristic signal-to-noise ratio.

The liquid crystal microlens elements 82 may be arranged in a rectangular array or in a regular hexagonal array. As shown in fig. 7, when the liquid crystal microlens elements 82 are arranged in a rectangular array, the geometric center of the liquid crystal microlens elements 82 (i.e., the geometric center of the light passing hole 241) is located at the position of four vertices of the rectangle. As shown in fig. 6, when the liquid crystal microlens elements 82 are arranged in a regular hexagonal array, the geometric centers of the liquid crystal microlens elements 82 (i.e., the geometric centers of the light passing holes 241) are located at six vertex positions of a regular hexagon.

The aperture of the light-passing hole 241 of the liquid crystal microlens unit 82

Is 50um to 5um, and different pore diameters can be selected according to different requirements. The focal length of the lens according to the fresnel approximation is:

wherein

d_LCδ n is determined by the potential difference between the center and the edge of the lens, which is the thickness of the liquid crystal layer 25. For example

d_LC15um, 0.2 ≤ f ≤ and ≤ infinity, and distance between lenses is P, wherein the distance between lenses satisfies

In the present embodiment, the image sensor 40 is a pixilated image sensor 40. The reflected light 50 can be collimated by the collimator layer 30, and the collimation process can make the area of the finger surface contacting the transparent cover layer correspond to the image formed on the pixelated image sensor 40 one-to-one, so that the problem that the incident light and the reflected light 50 cannot correspond can be solved, and even if the reflected light 50 collimated by the collimator layer 30 and reaching the pixelated image sensor 40 has the same reflected fingerprint area and imaging area.

The fingerprint sensing device of this embodiment further comprises a polarizing element, such as a polarizer, located in the light path from the display to the liquid crystal lens array layer. Reflected light 50 atThe liquid crystal micro lens array is filtered by the polarization element before passing through the liquid crystal micro lens array, and only the light beam in the specified direction can reach the liquid crystal micro lens array through the polarization element. If the polarizing element is not arranged, the luminous flux of the sensor can be obtained when the liquid crystal micro lens is not in operation

Then taking the luminous flux of the sensor when the liquid crystal micro lens works

Wherein

Involving part of the luminous flux of the liquid-crystal microlens when it is not in operation, i.e.

By using

The whole luminous flux modulated by the liquid crystal micro lens can be obtained.

In addition, the fingerprint detection device of the present embodiment further includes a processor that processes fingerprint information detected by the image sensor 40. The Processor may be a Central Processing Unit (CPU), or other general-purpose Processor, a single chip, an ARM, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA), or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like.

Example 2

As shown in fig. 9, the present embodiment provides a method for controlling a fingerprint detection apparatus, for controlling the fingerprint detection apparatus, the method comprising the following steps:

s1: adjusting the focal length of the liquid crystal microlens unit 82 to obtain the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer at different focal lengths;

specifically, the focal length of the liquid crystal microlens unit 82 can be adjusted by adjusting the aforementioned first driving voltage and second driving voltage. The focal length of the liquid crystal microlens element 82 can be varied from near to far. And detecting the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer under the corresponding focal length in the process of changing the focal length of the liquid crystal micro-lens unit 82, namely scanning the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer of the liquid crystal micro-lens unit 82.

S2: selecting the maximum total characteristic signal-to-noise ratio as a target total characteristic signal-to-noise ratio;

in this step, a series of target total characteristic signal-to-noise ratios detected in the process of adjusting the focal length of the liquid crystal microlens unit 82 are compared to obtain the maximum total characteristic signal-to-noise ratio, which is used as the optimal total characteristic signal-to-noise ratio of the liquid crystal microlens unit 82, and the value of the total characteristic signal-to-noise ratio is used as the adjustment target for the subsequent focal length adjustment.

S3: and acquiring a focal length corresponding to the target total characteristic signal-to-noise ratio as the focal length of the liquid crystal micro-lens unit 82.

And finding a focal length corresponding to the target total characteristic signal-to-noise ratio according to the corresponding relation between the total characteristic signal-to-noise ratio detected in the previous focal length adjusting process and the focal length, and then adjusting the driving voltage to enable the focal length of the liquid crystal micro-lens unit 82 to be the focal length value.

By adopting the method, the control method of the embodiment can keep the total characteristic signal-to-noise ratio of the display layer 10 and the lower layer at an optimal value no matter how the influence of the external environment on the current total characteristic signal-to-noise ratio is generated. The total characteristic signal-to-noise ratio can be carried out at certain preset time intervals, and can also be carried out when the external environment changes.

Example 3

As shown in fig. 10, the present embodiment provides another control method of a fingerprint detection device, including the steps of:

s01: acquiring a first threshold value;

in this step, the minimum total characteristic signal-to-noise ratio of the display layer 10 and the lower layer, which can be the minimum for the fingerprint detection device to accurately identify the fingerprint, is obtained as the first threshold according to the accuracy requirement of fingerprint identification. The first threshold is used as a criterion for the later dynamic adjustment.

S02: acquiring the total characteristic signal-to-noise ratio of the current display layer 10 and the lower layer of the liquid crystal micro-lens unit 82;

s03: comparing the current total characteristic signal-to-noise ratio of the display layer 10 and the lower layer with a first threshold value;

s04: the focal length of the liquid crystal microlens element 82 is adjusted if the current total characteristic signal-to-noise ratio of the display layer 10 and the underlying layer is less than a first threshold.

The current total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is smaller than the first threshold, which means that the current total characteristic signal-to-noise ratio is too small to meet the requirement of fingerprint detection accuracy, and at this time, the focal length of the liquid crystal microlens unit 82 needs to be adjusted so as to increase the total characteristic signal-to-noise ratio to a level greater than or equal to the first threshold.

If the current total characteristic signal-to-noise ratio of the display layer 10 and the lower layer is greater than or equal to the first threshold, it indicates that the current characteristic signal-to-noise ratio can satisfy the requirement of fingerprint detection accuracy, and at this time, the focal length of the liquid crystal microlens unit 82 does not need to be adjusted.

By adopting the method, the total characteristic signal-to-noise ratio is not required to be scanned from beginning to end, and only the adjustment is required when the total characteristic signal-to-noise ratio does not reach the standard, so that the total characteristic signal-to-noise ratios of the display layer 10 and the lower layer can meet the requirement of fingerprint identification, and the system overhead is reduced.

Example 4

The present embodiment provides an electronic device including a processor and the fingerprint detection apparatus of embodiment 1. The electronic device may be a portable or mobile computing device such as a smart phone, a notebook computer, a tablet computer, a game device, and other electronic devices such as an electronic database, an automobile, an Automated Teller Machine (ATM), and the like.

It is right above that the embodiment of the present invention provides a fingerprint detection device, a fingerprint detection device control method, and an electronic apparatus.

It is to be understood that the invention is not limited to the particular arrangements and instrumentalities described above and shown in the drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present invention are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications, and additions or change the order between the steps after comprehending the spirit of the present invention.

The functional blocks shown in the above-described block diagrams may be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, plug-in, function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments can be stored in a machine-readable medium or transmitted by a data signal carried by a carrier wave over a transmission medium or a communication link. A "machine-readable medium" may include any medium that can store or transfer information. Examples of a machine-readable medium include electronic circuits, semiconductor memory devices, ROM, flash memory, Erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, Radio Frequency (RF) links, and so forth. The code segments may be downloaded via computer networks such as the internet, intranet, etc.

It should also be noted that the exemplary embodiments of the present invention may describe some methods or systems based on a series of steps or devices. However, the present invention is not limited to the order of the above-described steps, that is, the steps may be performed in the order mentioned in the embodiment, may be performed in an order different from the embodiment, or may be performed simultaneously.

As described above, only the specific embodiments of the present invention are provided, and those skilled in the art can clearly understand that, for the convenience and simplicity of description, the specific working processes of the system, the module and the unit described above can refer to the corresponding processes of the foregoing method embodiments, and are not repeated herein. It should be understood that the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered by the scope of the present invention.

Claims

1. Fingerprint detection device, its characterized in that includes:

a display layer and a lower layer, the lower layer comprising:

an image sensor for sensing the collimated reflected light.

2. The fingerprint detection apparatus according to claim 1, wherein the focal length of the liquid crystal microlens unit is configured such that a total characteristic signal-to-noise ratio of the display layer and the lower layer satisfies the first condition.

3. The fingerprint detection device according to claim 1, wherein the liquid crystal micro-lens array layer comprises a first substrate, a first electrode layer, an insulating layer, a second electrode layer, a liquid crystal layer, a third electrode layer and a second substrate layer, the first substrate, the first electrode layer, the insulating layer, the second electrode layer, the liquid crystal layer, the third electrode layer and the second substrate layer are sequentially arranged from the display layer to the image sensor, the first electrode layer and the third electrode layer are transparent electrode layers, and the second electrode layer comprises light through holes arranged in an array.

4. The fingerprint sensing apparatus of claim 1, wherein the geometric centers of the liquid crystal microlens units are arranged in a manner of being located at vertices of a rectangle or a regular hexagon.

5. The fingerprint sensing device of claim 1, further comprising a polarizing element positioned in the light path from the display screen to the liquid crystal microlens array layer.

6. The fingerprint detection device of any one of claims 1 to 5, wherein the image sensor is a pixilated image sensor.

7. The fingerprint detection apparatus according to any one of claims 1 to 5, further comprising a transparent protection layer covering a side of the display layer remote from the liquid crystal microlens array layer.

8. The fingerprint detection apparatus of claim 2, wherein the first condition is that a total characteristic signal-to-noise ratio of the display layer and the lower layer is maximum.

9. The fingerprint detection apparatus of claim 2, wherein the first condition is that a total characteristic signal-to-noise ratio of the display layer and the lower layer is greater than a first threshold.

10. An electronic device, characterized in that it comprises a processor and a fingerprint detection apparatus according to any one of claims 1 to 9.