CN109919075B - Fingerprint measuring device, fingerprint identification method and system, and medium - Google Patents
Fingerprint measuring device, fingerprint identification method and system, and medium Download PDFInfo
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Abstract
The application discloses a fingerprint measuring device, a fingerprint identification method, a fingerprint identification system and a fingerprint identification medium. This fingerprint measuring device includes: the device comprises a light generation unit, a light splitting unit, a reflection unit, a measurement unit and a photoelectric sensing unit, wherein the light generation unit generates a first light signal and parallelly irradiates the light splitting unit; the optical splitting unit splits the first optical signal into a second optical signal and a third optical signal which are perpendicular to each other, the second optical signal is incident to the measuring unit, the third optical signal is incident to the reflecting unit, a fourth optical signal obtained by scattering of the measuring unit is received, a fifth optical signal reflected by the reflecting unit is received and incident to the photoelectric sensing unit, and the photoelectric sensing unit carries out photoelectric conversion to generate fingerprint measurement and outputs the fingerprint measurement. The scheme provided by the embodiment reduces the requirement on the surface of the fingerprint identification finger and improves the success rate of the fingerprint identification.
Description
Technical Field
The present invention relates to fingerprint identification technologies, and in particular, to a fingerprint measuring device, a fingerprint identification method, a fingerprint identification system, and a fingerprint identification medium.
Background
The fingerprint identification technology is one of the most widely used biometric identification technologies with the lowest price, and in recent years, the fingerprint identification technology is rapidly developed and keeps a strong development trend, and is widely used in many fields such as enterprise attendance machines, intelligent districts, fingerprint locks, fingerprint IC (Integrated Circuit) cards, jurisdictions, finance and the like. With the gradual maturity of the fingerprint identification technology and the gradual reduction of the cost in the future, the application of the fingerprint identification technology in the fields of military, civil use and the like is more and more extensive, so that the method has important practical significance and market value for the research of the fingerprint identification technology.
The fingerprint identification in the market at present mainly comprises three types of optical fingerprint identification, capacitance fingerprint identification and ultrasonic fingerprint identification, wherein the optical fingerprint identification technology appears at the earliest and is the most widely applied fingerprint identification technology at present by virtue of the advantages of mature technology, low cost and the like. The conventional optical fingerprint identification method is based on the principle of total reflection of light, and after light irradiates a fingerprint valley position pressed on the surface of glass through the glass, the light is totally reflected at an interface between air and the glass so as to be reflected to a Charge-Coupled Device (CCD) detector and form a clear fingerprint image. The light rays irradiated on the fingerprint ridge position pressed on the surface of the glass through the glass do not meet the total reflection condition so as not to generate total reflection, therefore, the light rays cannot form a clear fingerprint image on the CCD detector, and are absorbed by the contact interface of the glass and the fingerprint ridge or are reflected to other places in a diffused mode.
However, such an optical fingerprint recognition method based on total reflection as described above has an inherent disadvantage in the accuracy of fingerprint recognition, and is prone to a problem of erroneous recognition in cases such as fingerprint peeling, too shallow a fingerprint, and too dry a fingerprint.
Disclosure of Invention
At least one embodiment of the present invention provides a fingerprint measuring device, a fingerprint identification method, a fingerprint identification system, and a medium, which reduce false fingerprint identification.
To achieve the above object, at least one embodiment of the present invention provides a fingerprint measuring device, including: the device comprises a light generation unit, a light splitting unit, a reflection unit, a measurement unit and a photoelectric sensing unit, wherein the measurement unit comprises a measurement surface for a user to touch, the reflection unit comprises a reflection surface, and the measurement unit comprises a light-emitting diode (LED) and a light-emitting diode (LED) which are arranged in parallel, wherein:
the light generating unit is used for generating a first light signal which is incident to the light splitting unit in parallel;
the optical splitting unit is configured to split the first optical signal into a second optical signal and a third optical signal that are perpendicular to each other, inject the second optical signal to a measurement surface of the measurement unit, and inject the third optical signal to the reflection unit, where the second optical signal is perpendicular to the measurement surface, and the third optical signal is perpendicular to a reflection surface of the reflection unit, receive a fourth optical signal obtained by scattering the second optical signal by the measurement unit, receive a fifth optical signal obtained by reflecting the third optical signal by the reflection unit, and inject the fourth optical signal and the fifth optical signal to the photoelectric sensing unit;
the measuring unit is used for receiving the second optical signal from the light splitting unit, scattering the second optical signal on the measuring surface, and returning a fourth optical signal to the light splitting unit;
the reflection unit is used for receiving the third optical signal from the light splitting unit, reflecting the third optical signal and returning a fifth optical signal to the light splitting unit;
and the photoelectric sensing unit is used for receiving the fourth optical signal and the fifth optical signal incident from the light splitting unit, performing photoelectric conversion to generate fingerprint measurement information and outputting the fingerprint measurement information.
In an embodiment, the light generating unit includes a laser, a filter, and a first lens, wherein:
the laser is used for generating an optical signal and enabling the optical signal to be incident to the filter;
the filter is used for filtering an optical signal input by the laser and outputting the filtered optical signal to the first lens;
the first lens is used for converting the optical signal input by the filter into a parallel optical signal to obtain a first optical signal, and the first optical signal is incident to the optical splitting unit.
In an embodiment, the light splitting unit includes a light splitting prism.
In an embodiment, the photo-sensing unit includes a second lens and a photo-detector, wherein:
the second lens is used for receiving the fourth optical signal and the fifth optical signal incident from the light splitting unit, and the fourth optical signal and the fifth optical signal are incident to the photoelectric detector after being converged;
and the photoelectric detector is used for receiving the optical signal incident from the second lens, performing photoelectric conversion to generate and output the fingerprint measurement information.
An embodiment of the present invention provides a fingerprint identification method applied to a fingerprint measurement apparatus according to any embodiment, including:
acquiring fingerprint measurement information;
processing the fingerprint measurement information to acquire phase information;
determining fingerprint depth information according to the phase information;
and determining fingerprint information according to the fingerprint depth information.
In an embodiment, the processing the fingerprint measurement information to obtain phase information includes:
performing wavelet transformation on the fingerprint measurement information to acquire truncation phase information; acquiring continuous phase information according to the truncated phase information;
the determining fingerprint depth information from the phase information comprises:
and restoring the fingerprint according to the continuous phase information.
In an embodiment, the performing wavelet transform on the fingerprint measurement information to obtain truncated phase information includes:
performing continuous wavelet transform on the fingerprint measurement information f (t):
coefficient W transformed from continuous waveletfExtracting a wavelet ridge from the maximum value of (m, n), and determining truncated phase information according to the amplitude thereof, wherein，Ψm，n(t) is a function of the wavelet basis
And (3) carrying out translation and expansion processing to obtain a set of wavelet basis functions, wherein m is an expansion factor, and n is a translation factor.
In an embodiment, said determining fingerprint depth information from said continuous phase information comprises:
where λ is wavelength information of the first optical signal and Φ (t) is the continuous phase information.
An embodiment of the invention provides a medium on which a computer program is stored, the computer program being executable on a processor, the computer program, when executed by the processor, implementing the steps of the fingerprint identification method according to any of the embodiments.
An embodiment of the present invention provides a fingerprint identification system, including the fingerprint measurement device according to any embodiment, further including: a processor and a memory, the memory storing a program that, when read and executed by the processor, implements the fingerprint identification method of any of the embodiments.
In the embodiment provided by the invention, because the fingerprint information is acquired by scattered light, compared with the fingerprint information acquired by a total reflection mode in the related art, the requirement on the surface of the finger in the scattering mode is lower than that in the total reflection mode, the fingerprint can still be accurately identified under the conditions of fingerprint peeling, too shallow fingerprint and too dry fingerprint, and the problem that the false identification is easy to occur under the conditions of fingerprint peeling, too shallow fingerprint and too dry fingerprint in the conventional fingerprint identification based on the total reflection measurement principle is solved. In addition, the identification precision reaches the nanometer level, and the high precision is achieved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a schematic diagram of a fingerprint recognition device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a fingerprint recognition device according to another embodiment of the present invention;
FIG. 3 is a schematic diagram of a fingerprint recognition device according to another embodiment of the present invention;
FIG. 4 is a schematic diagram of a fingerprint recognition device according to another embodiment of the present invention;
FIG. 5 is a schematic diagram of a fingerprint recognition device according to another embodiment of the present invention;
FIG. 6 is a flowchart of a fingerprint recognition method according to another embodiment of the present invention;
FIG. 7 is a flowchart of a fingerprint recognition method according to an embodiment of the present invention;
FIG. 8 is a diagram illustrating a fingerprint recognition system according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a medium according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.
The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
In the related art, the optical fingerprint identification method is mainly based on the total reflection measurement principle and realizes the identification of the fingerprint according to the reflection effect of the valleys and ridges of the fingerprint on the finger on light. However, such optical fingerprint recognition methods based on total radiation have inherent disadvantages in the accuracy of fingerprint recognition, and are prone to erroneous recognition problems such as fingerprint peeling, too shallow a fingerprint, and too dry a fingerprint.
The embodiment of the invention discloses a fingerprint measuring device and method based on fingerprint depth measurement, which comprises a set of measuring system capable of realizing fingerprint depth measurement and a set of calculating method capable of realizing fingerprint information identification. In the embodiment of the invention, a set of optical measurement system is used for measuring the fingerprint depth between the fingerprint valleys and the fingerprint ridges of the finger, and the fingerprint is restored by combining a corresponding calculation method, so that a novel optical fingerprint measurement device and a novel optical fingerprint measurement method with higher precision are provided.
As shown in fig. 1, an embodiment of the present invention provides a fingerprint measuring device, which can realize fingerprint depth measurement, and includes a light generating unit 1, a light splitting unit 2, a reflecting unit 3, a measuring unit 4, and a photoelectric sensing unit 5, where the reflecting unit 3 includes a reflecting surface 31, the measuring unit 4 includes a measuring surface 41 for a user to touch, and where:
the light generating unit 1 is used for generating a first light signal A1 to be incident to the light splitting unit 2;
the optical splitting unit 2 is configured to split the first optical signal a1 into a second optical signal and a third optical signal that are perpendicular to each other, and inject the second optical signal into the measurement surface of the measurement unit 4, and inject the third optical signal into the reflection unit 3, where the second optical signal is perpendicular to the measurement surface 41, and the third optical signal is perpendicular to the reflection surface 31 of the reflection unit 3, and receive a fourth optical signal obtained by scattering the second optical signal by the measurement unit 4, receive a fifth optical signal obtained by reflecting the third optical signal by the reflection unit 3, and inject the fourth optical signal and the fifth optical signal into the photoelectric sensing unit 5 in parallel;
the measurement unit 4 is configured to receive the second optical signal from the optical splitting unit 2, scatter the second optical signal on the measurement surface, and return a fourth optical signal to the optical splitting unit 2; when the finger 6 touches the measuring surface 41, the fourth optical signal carries fingerprint information; the measuring unit 4 is implemented, for example, using glass or the like.
The reflection unit 3 is configured to receive the third optical signal from the optical splitting unit 2, reflect the third optical signal, and return a fifth optical signal to the optical splitting unit 2; the reflecting unit 3 is, for example, a mirror.
The photoelectric sensing unit 5 is configured to receive the fourth optical signal and the fifth optical signal incident from the light splitting unit 2, perform photoelectric conversion to generate fingerprint measurement information, and output the fingerprint measurement information.
In the embodiment provided by the invention, because the fingerprint information is acquired by scattered light, compared with the fingerprint information acquired by a total reflection mode in the related art, the requirement on the surface of the finger in the scattering mode is lower than that in the total reflection mode, the fingerprint can still be accurately identified under the conditions of fingerprint peeling, too shallow fingerprint and too dry fingerprint, the problem that the false identification is easy to occur under the conditions of fingerprint peeling, too shallow fingerprint and too dry fingerprint in the traditional fingerprint identification based on the total reflection measurement principle is solved, the requirement on the surface of the fingerprint identification finger is reduced, and the success rate of the fingerprint identification is improved. In addition, the scheme provided by the embodiment has the recognition accuracy reaching the nanometer level and has very high accuracy.
In an embodiment, as shown in fig. 2, the light generating unit 1 comprises a laser 11, a filter 12 and a first lens 13, wherein:
the laser 11 is used for generating an optical signal, and the optical signal is incident to the filter 12;
the filter 12 is configured to filter an optical signal input by the laser 11, and output the filtered optical signal to the first lens 13; the optical signal generated by the laser 11 contains part of stray light, which is filtered out and, in addition, beam-expanded. I.e. the filter 12 may be an expanded beam filter.
The first lens 13 is configured to convert the optical signal input by the filter 12 into a parallel optical signal to obtain a first optical signal, and to input the first optical signal to the optical splitting unit 2.
It should be noted that in another embodiment, the light generating unit 1 may comprise only the laser 11.
In an embodiment, the light splitting unit 2 comprises a light splitting prism. The beam splitter prism divides an incident first signal into two parts, one of the upward refracted beam and the directly transmitted beam is incident on the reflection unit, the other is incident on the measurement unit, and receives a reference optical signal (fifth optical signal) reflected back by the reflection unit 3, receives a measurement optical signal (fourth optical signal) scattered back by the measurement unit 4, and transmits one of the fourth optical signal and the fifth optical signal and transmits the other to the photoelectric sensing unit 5 in a refraction mode. When there is no finger on the surface or above the measuring surface, the fourth optical signal and the fifth optical signal are incident on the photoelectric sensing unit 5 in parallel.
In another embodiment, as shown in fig. 3, the photo-sensing unit 5 includes a second lens 51 and a photo-detector 52, wherein:
the second lens 51 is configured to receive the fourth optical signal and the fifth optical signal incident from the light splitting unit 4, and enter the photoelectric sensor 52 after converging the fourth optical signal and the fifth optical signal;
the photodetector 52 is configured to receive the optical signal incident from the second lens 51, perform photoelectric conversion to generate and output the fingerprint measurement information.
The photodetector 52 is a device that performs photoelectric conversion. In this embodiment, the speckle intensity information is converted into fingerprint measurement information and output. The photodetector 52 may be a CCD, or may be other photoelectric conversion devices, such as a cmos (complementary Metal Oxide semiconductor), a point detector, and the like.
As shown in fig. 4, a fingerprint measuring device according to an embodiment of the present invention includes: the fingerprint measuring device comprises a laser 11, a filter 12, a first lens 13, a light splitting unit 2 (a light splitting prism in the embodiment), a reflecting unit 3, a measuring unit 4, a photoelectric sensing unit 5, a second lens 51 and a photoelectric detector 52, and has the following principle:
light emitted from a light source (laser 11) is filtered by a filter 12, then is irradiated onto a first lens 13 and is expanded, the expanded light is irradiated onto a beam splitter prism 2 and is divided into two parts, wherein the light refracted upwards by the beam splitter prism 2 is called a refracted light beam, and the light transmitted through the beam splitter prism 2 is called a transmitted light beam. The transmitted light beam is incident on the reflection unit 3 and then reflected back to the beam splitter prism 2 to form reference light, the refracted light beam is incident on the measuring surface 41 pressed by a finger above and scattered, and scattered light carrying fingerprint information is scattered back to the beam splitter prism 2 to form measuring light. The reference beam is refracted downwards by the beam splitter prism 2, the measuring beam is transmitted downwards through the beam splitter prism 2, both beams are incident on the second lens 51 via the beam splitter prism 2, and then reach the photodetector 52 and form a speckle, and the intensity information of the speckle is recorded and output by the photodetector 52.
It should be noted that the positions of the reflection unit and the measurement unit in fig. 1 to 4 can be interchanged. In another embodiment, as shown in fig. 5, the positions of the reflection unit 3 and the measurement unit 4 are interchanged, at this time, the transmitted beam enters the measurement unit 4, the refracted beam enters the reflection unit 3 and is reflected back to the light splitting unit 2 to form the reference beam, the transmitted beam enters the measurement surface 41 pressed by the finger and is scattered, and the scattered light carrying the fingerprint information is scattered back to the light splitting unit 2 to form the measurement beam. The measuring beam is refracted downward by the beam splitting unit 2, and the reference beam is transmitted downward through the beam splitting unit 2.
Based on the fingerprint measurement device provided in the embodiment of the present invention, an embodiment of the present invention further provides a fingerprint identification method applied to the fingerprint measurement device described in any embodiment, as shown in fig. 6, including:
that is, fingerprint measurement information output by the photoelectric sensing unit is acquired.
and step 604, restoring the fingerprint according to the fingerprint depth information.
The scheme that this embodiment provided, fingerprint identification is carried out through the fingerprint information that receives the scattered light, for obtaining fingerprint information through the total reflection mode among the correlation technique, requirement to finger surface under the scattering mode is less than the requirement to finger surface under the total reflection mode, consequently, still can accurately discern the fingerprint under the too shallow and too dry condition of fingerprint desquamation, the problem of the easy wrong recognition that appears under the too shallow and too dry condition of fingerprint desquamation in overcoming the fingerprint identification based on total reflection measurement principle of tradition, the requirement to fingerprint identification finger surface has been reduced, fingerprint identification success rate has been improved. In addition, the scheme provided by the embodiment has the recognition accuracy reaching the nanometer level and has very high accuracy.
In an embodiment, in step 602, processing the fingerprint measurement information to obtain phase information includes:
performing wavelet transformation on the fingerprint measurement information to acquire truncation phase information; acquiring continuous phase information according to the truncated phase information;
the determining fingerprint depth information from the phase information comprises:
and determining fingerprint depth information according to the continuous phase information.
It should be noted that there are various methods for acquiring the truncated phase information, such as fourier transform method, phase shift algorithm, etc.
There are various methods for acquiring continuous phase information according to the truncated phase information, such as a tracking path phase unwrapping algorithm, a path-independent phase unwrapping algorithm, and the like.
In an embodiment, the performing wavelet transform on the fingerprint measurement information to obtain truncated phase information includes:
performing continuous wavelet transform on the fingerprint measurement information f (t):
coefficient W transformed from continuous waveletfExtracting a wavelet ridge from the maximum value of (m, n), and determining truncated phase information according to the amplitude thereof, wherein Ψm，n(t) is a function of the wavelet basis
And (3) carrying out translation and expansion processing to obtain a set of wavelet basis functions, wherein m is an expansion factor, and n is a translation factor.
In an embodiment, said determining fingerprint depth information from said continuous phase information comprises:
wherein λ is wavelength information of the first optical signal; Φ (t) is continuous phase information based on time variation.
The fingerprint recognition method is described below with an embodiment. As shown in fig. 7, includes:
703, performing wavelet transformation on the speckle information by a processor to obtain truncation phase information;
step 705, the processor calculates the depth of the fingerprint between the fingerprint valleys of the finger according to the continuous phase information, and recovers the fingerprint information according to the fingerprint depth.
In step 703, the processor performs wavelet transform on the speckle information to obtain truncated phase information;
the speckle intensity function I (x, y, t) collected by the photodetector 52 without finger pressure is:
I(x，y，t)＝I0(x，y){1+Vcos[Φ0(x，y)]} (1)
wherein, I0(x, y) is the average intensity of the interference field, V is the modulation visibility, phi0(x, y) is the initial phase.
The speckle intensity function collected by photodetector 52 with finger pressure is:
I(x，y，t)＝I0(x，y){1+Vcos[Φ0(x，y)±4πΔz(x，y，t)/λ]} (2)
where Δ z (x, y, t) is a deformation function on the measuring surface, ± is a moving direction of the fingerprint on the finger with respect to the measuring surface, and takes a positive sign when the fingerprint on the finger is close to the measuring surface, and takes a negative sign otherwise, and λ is a wavelength of the optical signal emitted by the laser (i.e., a wavelength of the first optical signal).
The speckle intensity function I (x, y, t) is the collected fingerprint measurement information, and in this application, Δ z (x, y, t) is determined according to I (x, y, t). Specifically, truncated phase information may be obtained by performing wavelet transform on I (x, y, t), and then the truncated phase information is converted into continuous phase information, and Δ z (x, y, t) is determined from the continuous phase information.
The acquired speckle information is subjected to wavelet transform processing to obtain truncation phase information. The wavelet transform is to perform inner product on the wavelet basis function shifted by tau with the signal f (t) to be analyzed (in this embodiment, f (t)) in different scales a, I (x, y, t)). Let Ψ (x) be M2(R) is square integrable function, and after Fourier transformation, the wavelet basis function meeting the tolerance condition can be obtained
And has the following components:
the wavelet basis function is subjected to translation and expansion processing to obtain a set Ψ (m, n (t)) of wavelet basis functions, that is:
wherein m is a scaling factor and n is a translation factor. The continuous wavelet transform of an arbitrary function f (t) in M2(R) space can be expressed as:
coefficient W transformed from continuous waveletfThe wavelet ridge is extracted from the maximum of (m, n), and its amplitude a (m, n)) can be expressed as:
wherein, Im[Wf(m，n)]Is WfImaginary part of (m, n), Re[Wf(m，n)]Is WfReal part of (m, n). Determining I from the amplitude A (m, n)))m[Wf(m，n)]，Re[Wf(m，n)]Then, by the following formulaObtaining truncated phase information
Comprises the following steps:
the truncated phase information obtained by wavelet transform is a discontinuous phase limited in the range of [ -pi, pi ] due to the characteristics of the arctan function, and therefore needs to be expanded into a continuous phase by a phase unwrapping algorithm. There are various phase unwrapping algorithms, and one of them is described below.
In step 704, the phase unwrapping (or phase unwrapping) performed on the truncated phase information by the processor to obtain continuous phase information includes:
step 801, first determine the compensation phase φSupplement device(x，y)。
At phiCutting blockWhere the (x, y) discontinuity must be a function of Δ φ due to the nature of the arctan functionCutting block(xiY) 2 pi phase step, it is necessary to add a phi to the truncated phase informationSupplement deviceAnd (x, y) ± 2 pi phase compensation, thereby expanding the truncated phase information into continuous phase information.
Let the phase information obtained by equation (7)
Is phiCutting block(x, y), acquiring a truncation phase difference of two adjacent points:
Δφcutting block(xi，y)＝φCutting block(xi，y)-φCutting block(xi-1Y), i 1 … N, N being the total number of points (8)
Then when the sampling frequency is faster than the phase change and the phase is not stepped, the absolute value of the truncated phase difference has the following relationship:
|Δφcutting block(xi，y)|≤2π (9)
Thus, can pass|ΔφCutting block(xiY) l to determine whether the phase is stepped.
The predetermined threshold P is slightly less than 2 π.
Preset x0Is equal to 0, and phiSupplement device(x0Y) is 0, and for any point i, i is 1.. N:
when | Δ φ is satisfiedCutting block(xiY) | > P, the phase is considered to be stepped, otherwise, the phase is considered to be not stepped.
If the phase of the point i is not stepped, then:
φsupplement device(xi，y)＝φSupplement device(x0，y)＝0 (10)
If the phase of the point i is stepped, then:
if delta phiCutting block(xiY) > 0, then:
φsupplement device(xi，y)＝φSupplement device(xi-1，y)-2π (11)
If delta phiCutting block(xiAnd y) < 0, then:
φsupplement device(xi，y)＝φSupplement device(xi-1，y)+2π (12)
And determining the compensation phase of each point according to the steps.
At step 802, the truncated phase and the compensated phase for each point are added to obtain a continuous phase.
I.e. continuous phase phiIs connected with(x, y) is:
φis connected with(x,y)＝φCutting block(x,y)+φSupplement device(x,y) (13)
In step 705, the processor calculates the depth of the fingerprint between fingerprint valleys according to the continuous phase information, including:
according to the time-domain speckle measurement principle, the drop height between the fingerprint valleys and ridges, namely the depth Δ z (t) of the fingerprint, can be obtained from the continuous phase information through the following formula:
where λ is the wavelength of the optical signal emitted by the laser (i.e., the wavelength of the first optical signal), and Φ (t) is the continuous phase information. After the drop height between the fingerprint valleys and the ridges of the finger, namely the depth of the fingerprint, is calculated through the formula (14), fingerprint information can be restored according to the depth of the fingerprint, and the purpose of fingerprint identification is achieved.
In one embodiment, a maximum working distance (i.e., the maximum distance between the finger and the measuring surface) may be set, and when the maximum working distance is within the maximum working distance (the distance between the finger and the measuring surface is less than or equal to the maximum working distance), fingerprint collection is performed, and when the maximum working distance is out, fingerprint collection is not performed. And collecting the speckle light intensity value at the maximum working distance in advance. And determining whether to carry out fingerprint acquisition according to the speckle light intensity value. Of course, the maximum working distance may not be set, and the fingerprint collection may be performed only when the finger is pressed against the measuring surface.
An embodiment of the present invention provides a fingerprint identification apparatus, including a processor and a memory, where the memory stores a program, and the program, when read and executed by the processor, implements the fingerprint identification method according to any embodiment.
Based on the inventive concept of the foregoing embodiment, an embodiment of the present invention provides a fingerprint identification system, as shown in fig. 8, including the fingerprint measuring device according to any one of the foregoing embodiments, further including: a processor 81 and a memory 82, wherein the memory 82 stores a program, and when the program is read and executed by the processor 81, the program realizes the fingerprint identification method according to any one of the embodiments. The fingerprint identification system that this embodiment provided has high accuracy, high sensitivity, can realize the advantage of whole field measurement, not only can overcome the problem that the easy erroneous recognition that appears under the too shallow and too dry condition of fingerprint desquamation, fingerprint among the fingerprint identification based on total reflection measurement principle of tradition, can also further improve fingerprint identification's precision, but wide application in many fields such as enterprise's attendance machine, intelligent residential district, fingerprint lock, fingerprint IC-card, judicial law and finance.
As shown in fig. 9, an embodiment of the present invention provides a medium 90, on which a computer program 91 that can run on a processor is stored, and when executed by the processor, the computer program 91 implements the steps of the fingerprint identification method according to any of the above embodiments.
The following points need to be explained:
(1) the drawings of the embodiments of the invention only relate to the structures related to the embodiments of the invention, and other structures can refer to common designs.
(3) Without conflict, embodiments of the present invention and features of the embodiments may be combined with each other to arrive at new embodiments.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A fingerprint measuring apparatus, comprising: the device comprises a light generation unit, a light splitting unit, a reflection unit, a measurement unit and a photoelectric sensing unit, wherein the measurement unit comprises a measurement surface for a user to touch, the reflection unit comprises a reflection surface, and the measurement unit comprises a light-emitting diode (LED) and a light-emitting diode (LED) which are arranged in parallel, wherein:
the light generating unit is used for generating a first light signal which is incident to the light splitting unit in parallel;
the optical splitting unit is configured to split the first optical signal into a second optical signal and a third optical signal that are perpendicular to each other, inject the second optical signal to a measurement surface of the measurement unit, and inject the third optical signal to the reflection unit, where the second optical signal is perpendicular to the measurement surface, and the third optical signal is perpendicular to a reflection surface of the reflection unit, receive a fourth optical signal obtained by scattering the second optical signal by the measurement unit, receive a fifth optical signal obtained by reflecting the third optical signal by the reflection unit, and inject the fourth optical signal and the fifth optical signal to the photoelectric sensing unit;
the measuring unit is used for receiving the second optical signal from the light splitting unit, scattering the second optical signal on the measuring surface, and returning a fourth optical signal to the light splitting unit;
the reflection unit is used for receiving the third optical signal from the light splitting unit, reflecting the third optical signal and returning a fifth optical signal to the light splitting unit;
and the photoelectric sensing unit is used for receiving the fourth optical signal and the fifth optical signal incident from the light splitting unit, performing photoelectric conversion to generate fingerprint measurement information and outputting the fingerprint measurement information.
2. The fingerprint measurement device of claim 1, wherein the light generation unit comprises a laser, a filter, and a first lens, wherein:
the laser is used for generating an optical signal and enabling the optical signal to be incident to the filter;
the filter is used for filtering an optical signal input by the laser and outputting the filtered optical signal to the first lens;
the first lens is used for converting the optical signal input by the filter into a parallel optical signal to obtain a first optical signal, and the first optical signal is incident to the optical splitting unit.
3. The fingerprint measuring apparatus of claim 1, wherein the light splitting unit comprises a light splitting prism.
4. The fingerprint measurement device of any one of claims 1 to 3, wherein the photo sensing unit comprises a second lens and a photo detector, wherein:
the second lens is used for receiving the fourth optical signal and the fifth optical signal incident from the light splitting unit, and the fourth optical signal and the fifth optical signal are incident to the photoelectric detector after being converged;
and the photoelectric detector is used for receiving the optical signal incident from the second lens, performing photoelectric conversion to generate and output the fingerprint measurement information.
5. A fingerprint recognition method applied to the fingerprint measuring apparatus according to any one of claims 1 to 4, comprising:
acquiring fingerprint measurement information;
processing the fingerprint measurement information to acquire phase information;
determining fingerprint depth information according to the phase information;
and determining fingerprint information according to the fingerprint depth information.
6. The fingerprint recognition method according to claim 5,
the processing the fingerprint measurement information to obtain the phase information comprises:
performing wavelet transformation on the fingerprint measurement information to acquire truncation phase information; acquiring continuous phase information according to the truncated phase information;
the determining fingerprint depth information from the phase information comprises:
and restoring the fingerprint according to the continuous phase information.
7. The fingerprint identification method of claim 6, wherein the performing wavelet transform on the fingerprint measurement information to obtain truncated phase information comprises:
performing continuous wavelet transform on the fingerprint measurement information f (t):
coefficient W transformed from continuous waveletfExtracting a wavelet ridge from the maximum value of (m, n), and determining truncated phase information according to the amplitude thereof, wherein Ψm，n(t) is a function of the wavelet basis
Carry out translational expansionAnd (4) obtaining a set of wavelet basis functions, wherein m is a scaling factor and n is a translation factor.
8. The fingerprint recognition method of claim 6 or 7, wherein the determining fingerprint depth information from the continuous phase information comprises:
where λ is wavelength information of the first optical signal and Φ (t) is the continuous phase information.
9. A computer-readable storage medium, on which a computer program is stored which is executable on a processor, the computer program, when being executed by the processor, implementing the steps of the fingerprint recognition method according to any one of claims 5 to 8.
10. A fingerprint recognition system comprising the fingerprint measuring apparatus according to any one of claims 1 to 4, further comprising: a processor and a memory, the memory storing a program that, when read and executed by the processor, implements the fingerprint identification method according to any one of claims 5 to 8.
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