CN113642370A - Fingerprint imaging apparatus and fingerprint imaging method - Google Patents
Fingerprint imaging apparatus and fingerprint imaging method Download PDFInfo
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Abstract
A fingerprint imaging apparatus and a fingerprint imaging method, the fingerprint imaging apparatus comprising: a light source adapted to generate light, the light source generating light having a light intensity distribution that conforms to a predetermined distribution code, the distribution code including at least one distribution pattern; the sensing surface is used for forming sensing light carrying fingerprint information on the sensing surface by light rays generated by the light source; an imaging module adapted to image the sensed light. The light source generates light rays according to a preset distribution code; therefore, the light intensity distribution of the light generated by the light source can influence the imaging result of the sensing light, and the clear fingerprint image can be obtained only by obtaining the accurate distribution code, namely, the fingerprint imaging device can encode the fingerprint image through the distribution pattern, so that the security of obtaining the fingerprint image can be effectively improved, and the wide application of the fingerprint imaging device is facilitated.
Description
Technical Field
The present invention relates to the field of fingerprint imaging, and in particular, to a fingerprint imaging apparatus and a fingerprint imaging method.
Background
The fingerprint identification technology collects a fingerprint image of a human body through a fingerprint imaging device, and then compares the fingerprint image with existing fingerprint information in a fingerprint identification system to realize identity identification. Due to the convenience of use and the uniqueness of human fingerprints, fingerprint identification technology has been widely applied to various fields, such as: the security inspection field such as public security bureau, customs, etc., the entrance guard system of buildings, and the consumer goods field such as personal computer and mobile phone, etc.
The fingerprint imaging device used in the fingerprint identification technology is to collect the human fingerprint image by an optical method: after the finger is pressed on the sensing surface, light rays generated by the light source are projected to the sensing surface and reflected and refracted on the sensing surface, so that sensing light carrying fingerprint information is formed; and collecting the reflected light by an optical image sensor to further obtain a fingerprint image.
Fingerprint imaging devices are increasingly used in mobile devices such as notebook computers, tablet computers, mobile phones and the like, so that automatic unlocking and functions of related mobile devices are realized. Especially, the fingerprint identification of the mobile phone is widely applied.
The widespread use of fingerprint imaging devices places ever-increasing demands on their security.
Disclosure of Invention
The invention provides a fingerprint imaging device and a fingerprint imaging method, which aim to improve the safety.
To solve the above problems, the present invention provides a fingerprint imaging device comprising:
the light source is suitable for generating light rays, the light intensity distribution of the light rays generated by the light source accords with a preset distribution code, and the distribution code comprises at least one distribution pattern; the sensing surface is used for forming sensing light carrying fingerprint information on the sensing surface by light rays generated by the light source; an imaging module adapted to image the sensing light.
Optionally, the light source comprises a plurality of display sets, each display set generating light with a light intensity distribution of a distribution pattern.
Optionally, the plurality of display sets generate light in different distribution patterns simultaneously.
Optionally, the distribution patterns of the light rays generated by the adjacent display groups are different.
Optionally, the light source includes one or more display groups, and the display groups sequentially generate light in a plurality of the distribution patterns in a preset imaging time period.
Optionally, the display set sequentially generates light in a plurality of different distribution patterns.
Optionally, the distribution pattern is at least selected from: lambertian distribution, batwing distribution, and side-emitting distribution.
Optionally, the imaging module images the sensing light to obtain a fingerprint photo; the fingerprint imaging device further includes: a processing module that obtains a fingerprint image based on the distribution code and the fingerprint photo.
Optionally, the processing module includes: the function unit obtains a point spread function corresponding to the distribution pattern according to the distribution pattern; an encoding unit that obtains a point spread function corresponding to the distribution code based on a point spread function corresponding to the distribution pattern; and the computing unit is used for obtaining the fingerprint image according to the point spread function corresponding to the distribution code and the fingerprint photo.
Optionally, the encoding unit obtains the distribution-encoded point spread function based on a linear combination of the point spread functions corresponding to the distribution patterns.
Optionally, the light source comprises an OLED display screen.
Optionally, the fingerprint imaging device is a fingerprint imaging device under a screen.
Optionally, of the light generated by the light source, at least the light intensity distribution of the light with the exit angle in the range of 40 degrees to 60 degrees conforms to the distribution code.
Correspondingly, the invention also provides a fingerprint imaging method, which comprises the following steps:
generating light, wherein the light intensity distribution of the generated light accords with a preset distribution code, and the distribution code comprises at least one distribution pattern; the generated light forms sensing light carrying fingerprint information on the sensing surface; imaging the sensed light.
Optionally, in the step of generating light, the light is generated in one or more distribution patterns.
Optionally, in the step of generating light, the light is generated in a plurality of different distribution patterns simultaneously.
Optionally, in the step of generating light, the light is generated in adjacent different distribution patterns.
Optionally, in the step of generating light, the light is sequentially generated in a plurality of distribution patterns within a preset imaging time period.
Optionally, the light is generated in sequence in a plurality of different said distribution patterns.
Optionally, the distribution pattern is at least selected from: lambertian distribution, batwing distribution, and side-emitting distribution.
Optionally, the step of imaging the sensing light includes: imaging the sensed light to obtain a fingerprint photograph; after imaging the sensing light to obtain a fingerprint photo, the fingerprint imaging method further comprises: obtaining a fingerprint image based on the distribution code and the fingerprint photo.
Optionally, the step of obtaining the fingerprint image includes: obtaining a point spread function corresponding to the distribution pattern according to the distribution pattern; obtaining a point spread function corresponding to the distribution code based on the point spread function corresponding to the distribution pattern; and acquiring the fingerprint image according to the point spread function corresponding to the distribution code and the fingerprint photo.
Optionally, in the step of obtaining the point spread function corresponding to the distribution code, the point spread function of the distribution code is obtained based on a linear combination of the point spread functions corresponding to the distribution pattern.
Optionally, in the step of generating light, an OLED display screen is used to generate light.
Optionally, the fingerprint imaging method is applied to an off-screen fingerprint imaging device.
Optionally, in the step of generating light rays, at least the light intensity distribution of the light rays with the exit angle in the range of 40 degrees to 60 degrees conforms to the distribution code.
Compared with the prior art, the technical scheme of the invention has the following advantages:
the light source generates light rays according to a preset distribution code; therefore, the light intensity distribution of the light generated by the light source can influence the imaging result of the sensing light, and the clear fingerprint image can be obtained only by obtaining the accurate distribution code, namely, the fingerprint imaging device can encode the fingerprint image through the distribution pattern, so that the security of obtaining the fingerprint image can be effectively improved, and the wide application of the fingerprint imaging device is facilitated.
In the fingerprint imaging method, light is generated in a distribution coding mode comprising at least one distribution pattern, and then fingerprint imaging is carried out; the light intensity distribution of the generated light can influence the imaging result of the sensing light, and a clear fingerprint image can be obtained only by obtaining an accurate distribution pattern; therefore, the fingerprint imaging method of the invention can encrypt the fingerprint image through at least one distribution code of a distribution pattern, and can decode the fingerprint image on the basis of obtaining the preset distribution code to obtain a clear fingerprint image; therefore, the fingerprint imaging method can effectively improve the security of fingerprint imaging.
In an alternative aspect of the present invention, the light source includes a plurality of display sets, each of which generates light with a light intensity distribution of one distribution pattern, that is, when the distribution pattern is plural, the plurality of display sets generate light with a plurality of the distribution patterns at the same time; alternatively, the display set sequentially generates light in a plurality of distribution patterns within a preset imaging time period. The number of distribution patterns in the distribution codes is increased, the complexity of the distribution codes can be effectively improved, and the security of the fingerprint imaging device for obtaining the fingerprint images is further improved.
In an alternative aspect of the invention, the plurality of display sets produce light simultaneously in different distribution patterns; or the display group sequentially generates light rays in a plurality of different distribution patterns, so that the complexity of distribution coding is effectively improved, the security of obtaining a fingerprint image is improved, and the wide application of the fingerprint imaging device is facilitated.
In the alternative of the invention, the light source comprises an OLED display screen, and the fingerprint imaging device can be set as a fingerprint imaging device under the screen, so that the screen occupation ratio can be ensured without additional setting, and the function of displaying the distribution pattern by the light source can be realized; and the security of fingerprint imaging can be effectively improved on the premise of not increasing the fingerprint image and the fingerprint image details.
In the alternative scheme of the invention, the light intensity distribution of the light with at least the emergence angle in the range of 40-60 degrees in the generated light conforms to the distribution code, so that the smooth collection of the fingerprint image can be ensured, the noise can be inhibited, and the signal-to-noise ratio is higher; and when the light source is the OLED display screen, the advantage of a large viewing angle can be considered, and the use experience of the electronic equipment is improved.
Drawings
FIG. 1 is a schematic diagram of a fingerprint imaging device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an optical path structure of the fingerprint imaging apparatus shown in FIG. 1;
FIG. 3 is a functional block diagram of the processing module 140 in the fingerprint imaging device shown in FIG. 2;
figure 4 is a flow chart of one embodiment of a method of imaging a fingerprint of the present invention.
Detailed Description
As is known from the background art, the security of the fingerprint imaging device in the prior art needs to be improved.
The light source adopted by the existing fingerprint imaging device is often a uniform light source (a surface light source or a linear light source) or a point light source; the point spread function of the optical system in the fingerprint imaging device is generally relatively simple, and after the sensing light is imaged, a fingerprint image can be obtained according to the point spread function of the corresponding uniform light source or point light source, and the point spread function of the uniform light source or point light source is well known, so that the safety of the fingerprint imaging device is affected.
On the other hand, in the prior art, the security of the fingerprint imaging device is often improved by increasing the area of the fingerprint image. However, the area of the fingerprint imaging device is often increased by the method, the application environment of the fingerprint imaging device is affected, and especially when the fingerprint imaging device and the display screen are arranged together, the screen occupation ratio of the electronic equipment is often affected, and the use experience of the electronic equipment is affected.
To solve the technical problem, the present invention provides a fingerprint imaging device comprising: the light source is suitable for generating light rays, the light intensity distribution of the light rays generated by the light source accords with a preset distribution code, and the distribution code comprises at least one distribution pattern; the sensing surface is used for forming sensing light carrying fingerprint information on the sensing surface by light rays generated by the light source; an imaging module adapted to image the sensing light.
In the technical scheme of the invention, the light source generates light rays according to a preset distribution code; therefore, the light intensity distribution of the light generated by the light source can influence the imaging result of the sensing light, and the clear fingerprint image can be obtained only by obtaining the accurate distribution code, namely, the fingerprint imaging device can encode the fingerprint image through the distribution pattern, so that the security of obtaining the fingerprint image can be effectively improved, and the wide application of the fingerprint imaging device is facilitated.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, a schematic structural diagram of a fingerprint imaging apparatus according to an embodiment of the present invention is shown.
As shown in fig. 1, the fingerprint imaging apparatus includes:
a light source 110, the light source 110 being adapted to generate light, the light intensity distribution of the light generated by the light source 110 conforming to a predetermined distribution code L, the distribution code L including at least one distribution pattern Li(θ); the sensing surface 120, on which the sensing light 123 carrying fingerprint information is formed by the light generated by the light source 110; an imaging module 130, the imaging module 130 being adapted to image the sensed light 120.
The light source 110 generates light rays with a preset distribution code L; therefore, the light intensity distribution of the light generated by the light source 110 may affect the imaging result of the sensing light, and a clear fingerprint image may be obtained only by obtaining the accurate distribution code L, that is, the fingerprint imaging apparatus of the present invention can obtain a clear fingerprint image through the distribution pattern LiAnd (theta) the fingerprint imaging is coded, so that the security of obtaining the fingerprint image can be effectively improved, and the wide application of the fingerprint imaging device is facilitated.
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The light source 110 is used to generate light for fingerprint imaging.
In this embodiment, the light source 110 includes: and the OLED display screen. The OLED display has the advantage of a wide viewing angle, that is, the range of the exit angle of the light generated by the light source 110 is wide, so that the display effect can be effectively improved, and the user experience can be improved.
Referring to fig. 2 in combination, a schematic diagram of an optical path structure of the fingerprint imaging apparatus shown in fig. 1 is shown.
The light generated by the light source 110 exits at an exit angle θ. Since the light source 110 includes an OLED display, the range of the exit angle θ of the light generated by the light source 110 is large, and the larger the range of the exit angle θ of the generated light is, the better.
As shown in fig. 2, when the exit angle θ of the light generated by the light source 110 is too small, such as the light 11 or the light 12 in fig. 2, after the light is projected onto the sensing surface 120, most of the light exits from the sensing surface 120 and is rarely reflected, and thus cannot be used for obtaining a fingerprint image. Only when the exit angle theta is greater than the total reflection angle thetac(angle of total reflection θ)cTypical angle of total reflection θ at the interface of glass and air, related to the optical index of the material on both sides of the sensing surfacec42 degrees) of light can be used to obtain a fingerprint image.
On the other hand, when the exit angle θ is too large, as shown in fig. 1, the reflected light formed after the light 13 is projected onto the sensing surface 120 interferes with the imaging of the imaging module 130 (for example, the light 13 may form an optical waveguide), which becomes noise, affects the signal-to-noise ratio, and causes a problem that the obtained fingerprint image is not clear enough.
Therefore, in the embodiment, in the light generated by the light source, the light intensity distribution of the light with at least the emergence angle theta in the range of 40 degrees to 60 degrees conforms to the distribution code, so that the smooth collection of the fingerprint image can be ensured, the noise can be inhibited, and the signal-to-noise ratio is higher; and when the light source is the OLED display screen, the advantage of a large viewing angle can be considered, and the use experience of the electronic equipment is improved.
In addition, the fingerprint imaging device is an off-screen fingerprint imaging device, that is, the imaging module 130 of the fingerprint imaging device is disposed right below the OLED display screen. Will fingerprint image device sets up to fingerprint image device setting under the screen, can make the screen account for further increase to become possible, can effectively improve and use experience.
As shown in fig. 2, in the present embodiment, the light source 110 includes a plurality of display sets 111, each display set 111 generates light with a light intensity distribution of a distribution pattern, that is, each display set 111 generates light with an independent distribution pattern, that is, the light intensity distribution of the light generated by each display set 111 conforms to a distribution pattern li(θ), the light intensity distribution of the light generated by all the display sets 111 constitutes the distribution code L.
In some embodiments, the display module 110 includes a plurality of discrete display groups 111, the plurality of discrete display groups 111 may have the same or different spacing, and the plurality of discrete display groups 111 may be a plurality of display areas in the display module 110.
Specifically, the plurality of display groups 111 are simultaneously distributed in different distribution patterns li(theta) to generate light, thereby effectively increasing the complexity of the distribution code L and effectively increasing the distribution pattern L in the distribution code Li(theta) complexity, thereby effectively improving the security of the fingerprint imaging device for obtaining the fingerprint image.
It should be noted that, in other embodiments of the present invention, the plurality of display sets may also be simultaneously distributed in the same distribution pattern li(θ) generating light; in another embodiment of the present invention, the display groups may be partially simultaneously distributed in the same distribution pattern li(θ) generating light. The invention determines whether the display sets are simultaneously distributed in the same or different distribution patterns liThe (θ) generation light is not limited.
Furthermore, the display groups 111 which are adjacent in position generate a light distribution pattern li(θ) are not the same, thereby increasing the distribution pattern li(theta) complexity, improving the security of the fingerprint imaging device.
In order to be able to further increase the distribution pattern L in the distribution code Li(theta) complexity, and improves the security of the fingerprint imaging apparatus, in this embodiment, the display set 111 sequentially displays a plurality of the distribution patterns l in a preset imaging time periodi(θ) generating light.
Specifically, the display groups 111 adjacent in time sequence are distributed in different distribution patterns li(theta) generating light to increase the distribution pattern liThe complexity of (theta) improves the security of the fingerprint imaging device.
Specifically, the display group 111 sequentially has a plurality of different distribution patterns li(theta) generating light to further increase the distribution pattern li(θ) to increase the security of the fingerprint imaging device.
In another aspect, the distribution pattern liThe complexity of (θ) itself affects the complexity of the corresponding point spread function, and thus the amount of computation in the fingerprint image obtaining process, so in order to achieve both computational efficiency and security, in the embodiment, as shown in fig. 2, the distribution pattern l isi(θ) is selected from at least: lambertian distribution (Lambertian distribution), Batwing distribution (Batwing distribution), and Side-emitting distribution (Side-emitting distribution). In other embodiments of the present invention, the distribution pattern li(θ) is dependent on the design of the light source and may be selected from other light intensity distribution patterns. The invention is not limited in this regard.
With continued reference to fig. 1, the fingerprint imaging device further comprises: a sensing surface 120. The sensing surface 120 is a surface for providing finger contact; the imaging module 130 images the sensing light to obtain a fingerprint photograph. Specifically, the imaging module 130 collects the sensing light 123 for imaging and performing photoelectric conversion, so as to obtain a fingerprint picture.
In some embodiments, the imaging module 130 may be a photosensor, comprising an array of photosensitive pixels, each pixel comprising a photodiode or a phototransistor.
In some embodiments, the imaging module 130 may include a TFT circuit region and a photo-detection thin film transistor region provided with a photosensitive thin film transistor.
In this embodiment, the sensing surface 120 is a glass surface. Specifically, the fingerprint imaging device is an under-screen fingerprint imaging device using an OLED display screen, and the sensing surface 120 is a surface of a cover plate glass of the OLED display screen.
In optical systems, the Point Spread Function (PSF) describes the response of an imaging system to a Point source. Therefore, the result of the convolution of the point spread function with the fingerprint image is the imaging result of the sensing light, i.e. the fingerprint picture, which can be expressed as:
y＝hx+n
wherein y represents a fingerprint picture, h represents a point spread function, x represents a fingerprint image, and n represents noise.
In this embodiment, the distribution code L includes a plurality of distribution patterns Li(theta), the light source 110 includes a plurality of display groups 111, each display group 111 being in a distribution pattern li(θ) the light intensity distribution produces light; each of the distribution patterns li(theta) each of the distribution patterns l can be obtained by obtaining a fingerprint picture corresponding to itiThe result of the convolution of (theta) with the fingerprint image is the distribution pattern li(θ) the corresponding fingerprint photo, which can be expressed as:
yi＝h[li(θ)]*+n
wherein, yiPresentation distribution Pattern li(theta) fingerprint photograph obtained correspondingly, h [ l ]i(θ)]Presentation distribution Pattern li(theta) corresponding point spread function, li(θ) represents a distribution pattern, x represents a fingerprint image, and n represents noise.
The imaging module 130 images the sensing light, so that all distribution patterns li(θ) the superposition of the obtained fingerprint photos, i.e. the fingerprint photos obtained by the imaging module 130, can be expressed as:
where Y denotes a fingerprint photograph obtained by the imaging module 130, and miPresentation distribution Pattern li(theta) weight in the distribution code L, h [ L ]i(θ)]Presentation distribution Pattern li(theta) corresponding point spread function, li(θ) represents a distribution pattern, x represents a fingerprint image, and n represents noise.
In particular, according to the distribution pattern liThe linear combination of the point spread functions corresponding to (θ) obtains the point spread function of the distribution code L, so the fingerprint picture obtained by the imaging module 130 can be represented as:
wherein h (L) represents the point spread function corresponding to the distribution code L, x represents the fingerprint image, Li(θ) represents the distribution pattern li(θ)，miRepresents the weight of the distribution pattern in the distribution code L, Y represents the fingerprint picture obtained by the imaging module 130, and n represents noise.
Therefore, the imaging module 140 images the sensing light to obtain a fingerprint photograph; with continued reference to fig. 2, the fingerprint imaging device further comprises: a processing module 140, said processing module 140 obtaining a fingerprint image based on said distribution code L and said fingerprint picture.
It should be noted that, the processing module 140 further stores the distribution code L in advance for controlling the light source 110, so that the light source 110 includes at least one distribution pattern LiThe distribution code L of (θ) generates light.
Therefore, in this embodiment, the processing module 140 is connected to the imaging module 130, and obtains the fingerprint picture obtained by the imaging module 130 from the imaging module 130; the processing module 140 also stores the distribution code L in advance; the processing module 140 obtains a fingerprint image according to the distribution code L and the fingerprint photo.
Referring collectively to fig. 3, a functional block diagram of the processing module 140 in the fingerprint imaging device of fig. 2 is shown.
In this embodiment, the processing module 140 includes: a function unit 141, the function unit 141 according to the distribution pattern li(theta) obtaining the distribution pattern li(θ) a corresponding point spread function; an encoding unit 142, the encoding unit 142 based on the distribution pattern li(θ) obtaining a point spread function corresponding to the distribution code L by the corresponding point spread function; a calculating unit 143, wherein the calculating unit 143 obtains the fingerprint image according to the point spread function corresponding to the distribution code L and the fingerprint photo.
Specifically, the function unit 141 is pre-stored with a plurality of distribution patterns li(θ) distribution code L, said function unit 141 according to said distribution pattern Li(theta) obtaining the distribution pattern li(θ) a corresponding point spread function.
The encoding unit 142 is connected to the function unit 141, and obtains the distribution pattern i from the function unit 141i(θ) a corresponding point spread function; the encoding unit 142 is based on the distribution pattern ii(θ) obtaining a point spread function corresponding to the distribution code L.
Specifically, the encoding unit 142 is based on the distribution pattern li(θ) obtaining a point spread function of the distribution code L from a linear combination of the corresponding point spread functions.
The calculating unit 143 is connected to the encoding unit 142, and obtains a point spread function corresponding to the distribution code L from the encoding unit 142; the computing unit 143 is connected to the imaging module 130, and obtains a fingerprint picture from the imaging module 130; the computing unit 143 obtains the fingerprint image according to the point spread function of the distribution code L and the fingerprint photo.
Specifically, the calculating unit 143 may obtain the fingerprint image by calculating a reverse deconvolution (blid deconvolution) based on the fingerprint image obtained by the imaging module 130 and the point spread function of the distribution code L. Specifically, the calculating unit 143 performs blind deconvolution calculation by the method of addy's description.
Correspondingly, the invention also provides a fingerprint imaging method, which specifically comprises the following steps: generating light, wherein the light intensity distribution of the generated light accords with a preset distribution code, and the distribution code comprises at least one distribution pattern; the generated light forms sensing light carrying fingerprint information on the sensing surface; imaging the sensed light.
Generating light rays in a distribution coding mode comprising at least one distribution pattern, and further performing fingerprint imaging; the light intensity distribution of the generated light can influence the imaging result of the sensing light, and a clear fingerprint image can be obtained only by obtaining an accurate distribution pattern; therefore, the fingerprint imaging method of the invention can encrypt the fingerprint image through at least one distribution code of a distribution pattern, and can decode the fingerprint image on the basis of obtaining the preset distribution code to obtain a clear fingerprint image; therefore, the fingerprint imaging method can effectively improve the security of fingerprint imaging.
Referring to fig. 4, a flow chart of an embodiment of the fingerprint imaging method of the present invention is shown.
Firstly, step S110 is executed to generate light, the light intensity distribution of the generated light conforms to a preset distribution code L, and the distribution code L includes at least one distribution pattern Li(θ)。
Referring to fig. 1 in combination, there is shown a schematic diagram of a fingerprint imaging apparatus used in the fingerprint imaging method shown in fig. 4.
The fingerprint imaging device comprises a light source 110, the light source 110 is adapted to generate light with a light intensity distribution of a preset distribution code L, the distribution code L comprises at least one distribution pattern Li(theta). In this embodiment, the distribution code L includes a plurality of distribution patterns Li(theta), in the step of generating light, in one or more distribution patterns li(θ) generating light.
Specifically, the light source 110 includes a plurality of display groups111, each display group 111 being in a distribution pattern liThe light intensity distribution of (θ) generates light, i.e., each display set 111 generates light in an independent distribution pattern, i.e., the light intensity distribution of light generated by each display set 111 conforms to a distribution pattern li(θ), the light intensity distribution of the light generated by all the display sets 111 constitutes the distribution code L.
It should be noted that, in this embodiment, the fingerprint imaging method is applied to an off-screen fingerprint imaging apparatus. Specifically, in the step of generating light, the OLED display screen is used to generate light. The fingerprint imaging method is applied to the under-screen fingerprint imaging device adopting the OLED display screen, so that a larger screen occupation ratio can be ensured, the fingerprint imaging function can be realized, and the user experience can be effectively improved.
Referring to fig. 2 in combination, a schematic diagram of an optical path structure of the fingerprint imaging apparatus shown in fig. 1 is shown.
In the step of generating light, the generated light is emitted at a certain emission angle θ. Since the light source 110 includes an OLED display, the range of the exit angle θ of the light generated by the light source 110 is large, and the larger the range of the exit angle θ of the generated light is, the better.
As shown in fig. 2, when the exit angle θ of the light generated by the light source 110 is too small, such as the light 11 or the light 12 in fig. 2, after the light is projected onto the sensing surface 120, most of the light exits from the sensing surface 120 and is rarely reflected, and thus cannot be used for obtaining a fingerprint image. Only when the exit angle theta is greater than the total reflection angle thetac(angle of total reflection θ)cTypical angle of total reflection θ at the interface of glass and air, related to the optical index of the material on both sides of the sensing surfacec42 degrees) of light can be used to obtain a fingerprint image.
On the other hand, when the exit angle θ is too large, as shown in fig. 1, the reflected light formed after the light 13 is projected onto the sensing surface 120 interferes with the imaging of the imaging module 130 (for example, the light 13 may form an optical waveguide), which becomes noise, affects the signal-to-noise ratio, and causes a problem that the obtained fingerprint image is not clear enough.
Therefore, in the step of generating light, the light intensity distribution of the light with at least the emergence angle θ in the range of 40 degrees to 60 degrees conforms to the distribution code, so that smooth collection of fingerprint images can be ensured, noise can be suppressed, and the signal-to-noise ratio is higher; and when the light source is the OLED display screen, the advantage of a large viewing angle can be considered, and the use experience of the electronic equipment is improved.
In addition, the fingerprint imaging device is an off-screen fingerprint imaging device, that is, the imaging module 130 of the fingerprint imaging device is disposed right below the OLED display screen. Will fingerprint image device sets up to fingerprint image device setting under the screen, can make the screen account for further increase to become possible, can effectively improve and use experience.
In some embodiments, the display module 110 includes a plurality of discrete display groups 111, the plurality of discrete display groups 111 may have the same or different spacing, and the plurality of discrete display groups 111 may be a plurality of display areas in the display module 110.
In this embodiment, in the step of generating light, a plurality of different distribution patterns l are simultaneously usedi(theta) to generate light, thereby effectively increasing the complexity of the distribution code L and effectively increasing the distribution pattern L in the distribution code Li(theta) complexity, thereby effectively improving the security of the fingerprint imaging device for obtaining the fingerprint image.
It should be noted that, in other embodiments of the present invention, the light generating step may also be performed in the same distribution pattern l at the same timei(θ) generating light; in another embodiment of the present invention, in the step of generating light, the distribution pattern l of the light may be partiallyi(θ) are the same. The invention determines whether the distribution patterns l are the same or different at the same timeiThe (θ) generation light is not limited.
In addition, in the present embodiment, in the step of generating light, the distribution patterns l are different and adjacent in positioni(theta) to generate light to increase the distribution pattern li(theta) complexity, improving the security of the fingerprint imaging device.
In order to be able to further increase the distribution pattern L in the distribution code Li(theta) complexity to improve the security of the fingerprint imaging device, in this embodiment, the step of generating light rays is performed in a predetermined imaging time period in sequence in a plurality of the distribution patterns li(theta) generating light, that is, as shown in FIG. 1, the same display group 111 is sequentially arranged in a plurality of distribution patterns li(θ) generating light.
In particular, a plurality of different distribution patterns l are applied in successioni(theta) generating light to further increase the distribution pattern li(θ) to increase the security of the fingerprint imaging device. In this embodiment, different distribution patterns l adjacent in time sequencei(theta) generating light to increase the distribution pattern liThe complexity of (theta) improves the security of the fingerprint imaging device.
In another aspect, the distribution pattern liThe complexity of (θ) itself affects the complexity of the corresponding point spread function, and thus the amount of computation in the fingerprint image obtaining process, so in order to achieve both computational efficiency and security, in the embodiment, as shown in fig. 2, the distribution pattern l isi(θ) is selected from at least: lambertian distribution (Lambertian distribution), Batwing distribution (Batwing distribution), and Side-emitting distribution (Side-emitting distribution). In other embodiments of the present invention, the distribution pattern li(θ) depending on the design of the light source, it may also be selected from other light intensity distribution patterns. The invention is not limited in this regard.
Next, step S120 is executed, and the generated light forms sensing light carrying fingerprint information on the sensing surface 120.
In particular, the sensing surface 120 is used to provide a surface for finger contact. In this embodiment, the fingerprint imaging method is applied to an under-screen fingerprint imaging device using an OLED display screen, so the sensing surface 120 is the surface of the cover plate glass of the OLED display screen.
After that, step S130 is performed to image the sensing light.
Specifically, the step of imaging the sensing light includes: the sensed light is imaged to obtain a fingerprint photo. Referring to fig. 1 in combination, in this embodiment, the imaging module 130 collects the sensing light 123 for imaging and performing photoelectric conversion, so as to obtain a fingerprint photo.
It should be noted that in some embodiments, the imaging module 130 may be a photosensor, including an array of photosensitive pixels, each pixel including a photodiode or a phototransistor. In some embodiments, the imaging module 130 may include a TFT circuit region and a photo-detection thin film transistor region provided with a photosensitive thin film transistor.
In optical systems, the Point Spread Function (PSF) describes the response of an imaging system to a Point source. Therefore, the result of the convolution of the point spread function with the fingerprint image is the imaging result of the sensing light, i.e. the fingerprint picture, which can be expressed as:
y＝h*x+n
wherein y represents a fingerprint picture, h represents a point spread function, x represents a fingerprint image, and n represents noise.
In this embodiment, the distribution code L includes a plurality of distribution patterns Li(theta), in the step of generating light, in one or more distribution patterns li(θ) the light intensity distribution produces light; each of the distribution patterns li(theta) each of the distribution patterns l can be obtained by obtaining a fingerprint picture corresponding to itiThe result of the convolution of (theta) with the fingerprint image is the distribution pattern li(θ) the corresponding fingerprint photo, which can be expressed as:
yi＝h[li(θ)]*x+n
wherein, yiPresentation distribution Pattern li(theta) fingerprint photograph obtained correspondingly, h [ l ]i(θ)]Presentation distribution Pattern li(theta) corresponding point spread function, li(θ) represents a distribution pattern, x represents a fingerprint image, and n represents noise.
The step of imaging the sensed light is to image the sensed lightLine imaging, so all distribution patterns li(θ) the superposition of the obtained fingerprint photos, i.e. the obtained fingerprint photos, can be expressed as:
where Y denotes a fingerprint photograph obtained by the imaging module 130, and miPresentation distribution Pattern li(theta) weight in the distribution code L, h [ L ]i(θ)]Presentation distribution Pattern li(theta) corresponding point spread function, li(θ) represents a distribution pattern, x represents a fingerprint image, and n represents noise.
In particular, according to the distribution pattern liThe linear combination of the point spread functions corresponding to (θ) obtains the point spread function of the distribution code L, so the obtained fingerprint picture can be expressed as:
wherein h (L) represents the point spread function corresponding to the distribution code L, x represents the fingerprint image, Li(θ) represents the distribution pattern li(θ)，miRepresents the weight of the distribution pattern in the distribution code L, Y represents the fingerprint picture obtained by the imaging module 130, and n represents noise.
Therefore, after imaging the sensing light to obtain a fingerprint photograph, the fingerprint imaging method further includes: obtaining a fingerprint image based on the distribution code L and the fingerprint picture.
It should be noted that, in this embodiment, before the step of generating light, the fingerprint imaging method further includes: the distribution code L is pre-stored for generating light. In particular, with reference to fig. 1, the distribution code L is pre-stored for controlling the light source 110 to comprise at least one distribution pattern LiThe pattern of distribution codes L of (θ) produces light.
Specifically, the step of obtaining the fingerprint image includes: according to the distributionStyle li(theta) obtaining the distribution pattern li(θ) a corresponding point spread function; based on the distribution pattern li(θ) obtaining a point spread function corresponding to the distribution code by the corresponding point spread function; and acquiring the fingerprint image according to the point spread function corresponding to the distribution code and the fingerprint photo.
In this embodiment, in the step of obtaining the point spread function corresponding to the distribution code L, the point spread function is based on the distribution pattern Li(θ) obtaining a point spread function of the distribution code L from a linear combination of the corresponding point spread functions.
Further, as described above, the finally obtained fingerprint picture is obtained by convolution calculation, and therefore, the fingerprint image can be obtained by blind deconvolution (blind deconvolution) calculation on the basis of the finally obtained fingerprint picture and the point spread function of the distribution code L. Specifically, blind deconvolution calculation can be performed by the method of addy's description.
In summary, in the fingerprint imaging device provided by the present invention, the light source generates light according to a preset distribution code; therefore, the light intensity distribution of the light generated by the light source can influence the imaging result of the sensing light, and the clear fingerprint image can be obtained only by obtaining the accurate distribution code, namely, the fingerprint imaging device can encode the fingerprint image through the distribution pattern, so that the security of obtaining the fingerprint image can be effectively improved, and the wide application of the fingerprint imaging device is facilitated. In the fingerprint imaging method, light is generated in a distribution coding mode comprising at least one distribution pattern, and then fingerprint imaging is carried out; the light intensity distribution of the generated light can influence the imaging result of the sensing light, and a clear fingerprint image can be obtained only by obtaining an accurate distribution pattern; therefore, the fingerprint imaging method of the invention can encrypt the fingerprint image through at least one distribution code of a distribution pattern, and can decode the fingerprint image on the basis of obtaining the preset distribution code to obtain a clear fingerprint image; therefore, the fingerprint imaging method can effectively improve the security of fingerprint imaging.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (26)
1. A fingerprint imaging apparatus, comprising:
the light source is suitable for generating light rays, the light intensity distribution of the light rays generated by the light source accords with a preset distribution code, and the distribution code comprises at least one distribution pattern;
the sensing surface is used for forming sensing light carrying fingerprint information on the sensing surface by light rays generated by the light source;
an imaging module adapted to image the sensing light.
2. The fingerprint imaging apparatus of claim 1, wherein said light source comprises a plurality of display sets, each display set producing light with a light intensity distribution in a distribution pattern.
3. The fingerprint imaging apparatus of claim 2, wherein said plurality of display sets produce light in different distribution patterns simultaneously.
4. The fingerprint imaging apparatus of claim 2, wherein the distribution pattern of light generated by adjacent display sets is different.
5. The fingerprint imaging apparatus of claim 1, wherein said light source comprises one or more display sets that sequentially generate light in a plurality of said distribution patterns during a predetermined imaging time period.
6. The fingerprint imaging apparatus of claim 5, wherein said display set sequentially generates light in a plurality of different distribution patterns.
7. The fingerprint imaging apparatus of claim 1, wherein the distribution pattern is selected from at least: lambertian distribution, batwing distribution, and side-emitting distribution.
8. The fingerprint imaging apparatus of claim 1, wherein the imaging module images the sensing light to obtain a fingerprint photograph;
the fingerprint imaging device further includes: a processing module that obtains a fingerprint image based on the distribution code and the fingerprint photo.
9. The fingerprint imaging apparatus of claim 8, wherein the processing module comprises:
the function unit obtains a point spread function corresponding to the distribution pattern according to the distribution pattern;
an encoding unit that obtains a point spread function corresponding to the distribution code based on a point spread function corresponding to the distribution pattern;
and the computing unit is used for obtaining the fingerprint image according to the point spread function corresponding to the distribution code and the fingerprint photo.
10. The fingerprint imaging apparatus according to claim 9, wherein said encoding unit obtains the distribution-encoded point spread function based on a linear combination of the point spread functions corresponding to the distribution patterns.
11. The fingerprint imaging device of claim 1, wherein the light source comprises an OLED display.
12. The fingerprint imaging device of claim 1, wherein said fingerprint imaging device is an off-screen fingerprint imaging device.
13. The fingerprint imaging apparatus of claim 1, wherein the light source generates light having a light intensity distribution of at least light rays having an exit angle in a range of 40 degrees to 60 degrees, in accordance with the distribution code.
14. A method of fingerprint imaging, comprising:
generating light, wherein the light intensity distribution of the generated light accords with a preset distribution code, and the distribution code comprises at least one distribution pattern;
the generated light forms sensing light carrying fingerprint information on the sensing surface;
imaging the sensed light.
15. The method of imaging a fingerprint of claim 14 wherein the step of generating light generates light in one or more distribution patterns.
16. The method of imaging a fingerprint of claim 15 wherein the step of generating light simultaneously generates light in a plurality of different distribution patterns.
17. The method of imaging a fingerprint of claim 15 wherein the step of generating light generates light in adjacent different distribution patterns.
18. The fingerprint imaging method of claim 14, wherein the generating of light rays step sequentially generates light rays in a plurality of said distribution patterns for a preset imaging period.
19. The method of imaging a fingerprint of claim 18 wherein the light is generated in a plurality of different said distribution patterns in sequence.
20. The fingerprint imaging method of claim 14, wherein said distribution pattern is selected from at least: lambertian distribution, batwing distribution, and side-emitting distribution.
21. The fingerprint imaging method of claim 14, wherein the step of imaging the sensing light comprises: imaging the sensed light to obtain a fingerprint photograph;
after imaging the sensing light to obtain a fingerprint photo, the fingerprint imaging method further comprises: obtaining a fingerprint image based on the distribution code and the fingerprint photo.
22. The fingerprint imaging method of claim 21, wherein the step of obtaining the fingerprint image comprises:
obtaining a point spread function corresponding to the distribution pattern according to the distribution pattern;
obtaining a point spread function corresponding to the distribution code based on the point spread function corresponding to the distribution pattern;
and acquiring the fingerprint image according to the point spread function corresponding to the distribution code and the fingerprint photo.
23. The fingerprint imaging method of claim 22, wherein the step of obtaining point spread functions corresponding to the distribution code obtains the distribution-coded point spread functions based on a linear combination of the distribution-pattern-corresponding point spread functions.
24. The method of claim 14, wherein the step of generating light includes generating light using an OLED display.
25. The fingerprint imaging method of claim 14, wherein the fingerprint imaging method is applied in an off-screen fingerprint imaging device.
26. The fingerprint imaging method of claim 14, wherein in said step of generating light, at least the light intensity distribution of light having an exit angle in the range of 40 degrees to 60 degrees conforms to said distribution code.
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| CN202010396107.8A CN113642370A (en) | 2020-05-11 | 2020-05-11 | Fingerprint imaging apparatus and fingerprint imaging method |
| TW110116819A TWI803870B (en) | 2020-05-11 | 2021-05-10 | Fingerprint imaging device and fingerprint imaging method |
| US17/316,890 US11600098B2 (en) | 2020-05-11 | 2021-05-11 | Apparatus and method for fingerprint imaging |
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