A living body recognition device and electronic equipment

Abstract

The application discloses a living body recognition device, which comprises a light source for projecting infrared light at a first power; a parallel polarizer located on the light path of the infrared light to irradiate the target object with the polarized state; a multifunctional polarizer located on the reflection signal path of the target object and comprising at least two states of parallel polarization and vertical polarization; an infrared sensor for receiving the reflection signal passing through the multifunctional polarizer; and a processor for calculating a first AOP according to the reflection signals of the parallel polarization and the vertical polarization, and determining whether the target object is a living body. The application has the characteristics of multi-dimensional information, good noise suppression, high accuracy and good recognition effect.

Description

Technical Field

[0001] This invention relates to the field of liveness detection technology, and more specifically, to a liveness detection device and electronic device. Background Technology

[0002] In some 2D and 3D payment and recognition fields, there is an increasing demand for high-quality images and accurate results. Polarization technology, due to its unique light field processing capabilities, is being increasingly applied in this field. Differential imaging can effectively suppress some noise and obtain images of superior quality.

[0003] An invention provides a method and apparatus for liveness detection, which performs liveness detection by determining whether the incident light is linearly polarized. The liveness detection method includes: incidenting the incident light onto a set of polarizers, where each polarizer does not overlap with the others in the direction of light propagation; detecting the intensity of light transmitted through each polarizer to obtain a set of light intensities corresponding to each polarizer; and determining that the liveness detection has failed if the set of light intensities meets predetermined conditions. When the incident light is emitted from a liquid crystal display screen, the incident light is linearly polarized, and the liveness detection fails. This invention uses passive light source detection, which is susceptible to interference from external light sources, unstable, and can only identify planar prostheses; its recognition effect is poor for three-dimensional prostheses, such as silicone prostheses, face molds, and hand molds.

[0004] An invention discloses a face liveness detection method based on polarization imaging, comprising the steps of: real-time acquisition of polarization images of the target from multiple angles; and polarization analysis of the polarization images using a polarization-based face feature learning and classification network model based on a Siamese neural network structure to identify the authenticity of the target. This invention employs a non-contact, real-time detection method, requiring no active user cooperation and achieving accurate detection even without user cooperation, resulting in a better user experience. However, this invention utilizes a Siamese neural network structure for learning and training, which is time-consuming and ineffective in recognizing and distinguishing different materials.

[0005] However, the current polarization scheme is still lacking in distinguishing between living organisms and silicone, and breakthroughs are needed in this technology to make up for this disadvantage.

[0006] The above background information is provided only to aid in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0007] To address this, the present invention incorporates a parallel polarizer at the transmitting end to ensure that the emitted light is linearly polarized, and a multifunctional polarizer at the receiving end to obtain reflected signals with different polarization directions. The first AOP is then calculated to determine whether the target object is a living entity. This invention features multidimensional information, good noise suppression, high accuracy, and good recognition performance.

[0008] In a first aspect, the present invention provides a liveness detection device, characterized in that it comprises:

[0009] A light source used to project infrared light at a first power;

[0010] A parallel polarizer is located in the optical path of the infrared light so that the infrared light illuminates the target object in a polarized state.

[0011] A multifunctional polarizer is located on the reflected signal optical path of the target object and includes at least two states: parallel polarization and vertical polarization.

[0012] An infrared sensor is used to receive the reflected signal after passing through the multifunctional polarizer;

[0013] The processor is configured to calculate a first AOP based on the reflected signals of the parallel polarization and the vertical polarization, thereby determining whether the target object is a living body.

[0014] Optionally, the liveness detection device is characterized in that the multifunctional polarizer includes at least a first polarization region, a second polarization region, a third polarization region, and a fourth polarization region.

[0015] The polarization direction of the first polarization region is the same as the polarization direction of the parallel polarizer;

[0016] The second polarization region has a first polarization direction;

[0017] The third polarization region has a second polarization direction;

[0018] The polarization direction of the fourth polarization region is perpendicular to the polarization direction of the parallel polarizer;

[0019] The first polarization direction and the second polarization direction are neither the same as nor perpendicular to the polarization direction of the parallel polarizer.

[0020] Optionally, in the liveness detection device, the angle between the first polarization direction and the polarization direction of the parallel polarizer is no more than 45 degrees; and the angle between the second polarization direction and the polarization direction of the parallel polarizer is not less than 45 degrees.

[0021] Optionally, the liveness detection device is characterized in that there are multiple first polarization regions, second polarization regions, third polarization regions and fourth polarization regions, and they are arrayed on the multifunctional polarizer.

[0022] Optionally, the liveness detection device is characterized in that any four adjacent regions each include the first polarization region, the second polarization region, the third polarization region, and the fourth polarization region, so as to obtain the polarization characteristics of each region.

[0023] Optionally, the liveness detection device is characterized in that: S2 of the Stokes parameter is formed based on the polarization information of the second polarization region and the third polarization region; S1 of the Stokes parameter is formed based on the polarization information of the first polarization region and the fourth polarization region; a first AOP can be calculated based on S1 and S2 to obtain the polarization characteristics of the target object; when the polarization characteristics are within a preset range, it is determined to be a live object, otherwise it is a spurious object.

[0024] Optionally, the liveness detection device is characterized in that the intensity of the light source is adjusted to a second power to obtain a second AOP for liveness detection.

[0025] Optionally, the liveness detection device is characterized in that, when the liveness detection results of the first AOP and the second AOP are different, the intensity of the light source is adjusted to a third power, and the third AOP is calculated to obtain the liveness detection result; the third power is the average of the first power and the second power.

[0026] Optionally, the liveness detection device is characterized in that the light source can project both structured light and floodlight, and has different powers; when adjusting the intensity of the light source, the projection type of the light source is changed.

[0027] In a second aspect, the present invention provides an electronic device, characterized in that it includes the liveness detection device described in any of the preceding claims.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention projects polarized light and receives at least two different polarization signals during reception, enabling simultaneous acquisition of human body surface and vein features. This provides more information dimensions than existing technologies and allows for more comprehensive liveness detection.

[0030] This invention effectively suppresses noise and obtains clearer signals and more accurate data by simultaneously equipping polarizers at both the transmitting and receiving ends.

[0031] This invention utilizes the first AOP to determine whether the target object is a living body, making full use of the information difference between the human body surface and veins. It has a good recognition effect on various types of prostheses such as planar prostheses and silicone prostheses, thus making the liveness recognition effect more accurate. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0033] Figure 1 This is a schematic diagram of the structure of a liveness detection device according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of a multifunctional polarizer in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of another multifunctional polarizer in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of a switchable light source in an embodiment of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0038] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] The present invention provides a liveness detection device, which aims to solve the problems existing in the prior art.

[0040] The technical solutions of the present invention and how they solve the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0041] This invention sets a parallel polarizer at the transmitting end to make the emitted light linearly polarized, and sets a multi-functional polarizer at the receiving end to obtain reflected signals in different polarization directions. Then, the first AOP is calculated to determine whether the target object is a living object. It has the characteristics of multi-dimensional information, good noise suppression, high accuracy and good recognition effect.

[0042] Figure 1 This is a schematic diagram of the structure of a liveness detection device according to an embodiment of the present invention. Figure 1 As shown, a liveness detection device in an embodiment of the present invention includes:

[0043] Light source 1 is used to project infrared light at a first power.

[0044] Specifically, the light source can project both structured light spots and floodlight. The intensity of the light source must meet safety standards for the human body and eyes. The first power is a power that allows the infrared sensor to obtain a clear reflected signal. In some embodiments, the light source is an infrared floodlight, and correspondingly, the infrared sensor is a floodlight sensor to obtain more comprehensive target object data. In this embodiment, the light source is the transmitter. In some embodiments, components such as collimators and projection lenses are also included to achieve better projection effects.

[0045] Parallel polarizer 2 is located in the optical path of the infrared light so that the infrared light illuminates the target object in a polarized state.

[0046] Specifically, the parallel polarizer converts the light emitted by the light source 1 into linearly polarized light. Due to the characteristics of polarized light, the light intensity is strongest in the polarization direction. The light source 1 and the parallel polarizer 2 constitute the emitting end of this embodiment.

[0047] The multifunctional polarizer 3 is located on the reflected signal optical path of the target object and includes at least two states: parallel polarization and vertical polarization.

[0048] Specifically, the multifunctional polarizer and the infrared sensor constitute the receiving end of this embodiment. The multifunctional polarizer is located at the front end of the infrared sensor and is used to receive reflected light. Figure 2As shown, the multifunctional polarizer includes at least two polarization states, ensuring that the reflected light has at least two polarization information. For parallel polarization, since its polarization direction is the same as that of the parallel polarizer, its signal is the strongest. For perpendicular polarization, since its polarization direction is perpendicular to that of the parallel polarizer, its signal is the weakest. In the human body, when linearly polarized light is incident on the skin, the skin surface reflects the polarized light while maintaining its polarization state. Internal skin tissues scatter and reflect the light, changing its polarization direction as it exits. Parallel polarization can acquire surface information and can be used to extract skin surface textures for matching, satisfying the surface information extraction function of conventional cameras. Perpendicular polarization can acquire penetrating internal information and can be used to extract subcutaneous tissue information, including vein information, for some in vivo and medical imaging applications. The multifunctional polarizer can be of any shape, such as circular, square, or elliptical. Preferably, the shape of the multifunctional polarizer is the same as that of the infrared sensor.

[0049] Infrared sensor 4 is used to receive the reflected signal after passing through the multifunctional polarizer.

[0050] Specifically, the distance between the multifunctional polarizer and the infrared sensor should not exceed 6 mm. The closer the distance between the multifunctional polarizer and the infrared sensor, the better; it can be any value among 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, and 6 mm, or other values. The closer the distance between the multifunctional polarizer and the infrared sensor, the more singular the light detected by the infrared sensor, resulting in better image quality. When the distance between the infrared sensor and the multifunctional polarizer is greater, the possibility of interference between reflected light from different areas increases. In this embodiment, less signal interference results in higher accuracy of the obtained polarization information and more accurate identification of live objects.

[0051] Processor 5 is used to calculate a first AOP based on the reflected signals of the parallel polarization and the vertical polarization, and then determine whether the target object is a living body.

[0052] Specifically, the polarization direction AOP (Angle of Polarization) is used to calculate the proportions of parallel polarization and perpendicular polarization, thereby obtaining the angle θ of the polarized light. In the case of only parallel polarization and perpendicular polarization, in the calculation of the first AOP, S2 is the intensity of perpendicularly polarized light and S1 is the intensity of parallelly polarized light.

[0053] Figure 3 This is a schematic diagram of another multifunctional polarizer in an embodiment of the present invention. Figure 3 As shown, another multifunctional polarizer in this embodiment of the invention includes at least a first polarization region 31, a second polarization region 32, a third polarization region 33, and a fourth polarization region 34.

[0054] The polarization direction of the first polarization region is the same as the polarization direction of the parallel polarizer;

[0055] The second polarization region has a first polarization direction;

[0056] The third polarization region has a second polarization direction;

[0057] The polarization direction of the fourth polarization region is perpendicular to the polarization direction of the parallel polarizer;

[0058] The first polarization direction and the second polarization direction are neither the same as nor perpendicular to the polarization direction of the parallel polarizer.

[0059] Specifically, the first, second, third, and fourth polarization regions are fabricated on a multifunctional polarizer using an etching process. The first polarization region is parallel polarized, and the fourth polarization region is perpendicular polarized. The polarization directions of the second and third polarization regions are neither parallel nor perpendicular. Furthermore, the polarization directions of the second and third polarization regions are different. The angle between the first polarization direction and the polarization direction of the parallel polarizer does not exceed 45 degrees; the angle between the second polarization direction and the polarization direction of the parallel polarizer is not less than 45 degrees. There are multiple first, second, third, and fourth polarization regions, and they are arrayed on the multifunctional polarizer. Any four adjacent regions contain the first, second, third, and fourth polarization regions to obtain the polarization characteristics of each region.

[0060] This embodiment adopts the Stokes-proposed method using four parameters to describe the intensity and polarization state of light waves. These are: S0, S1, S2, and S3. S0 represents the total incident light intensity, S1 represents the intensity difference between the x and y components, S2 represents the intensity difference between the +45° and -45° polarization components, and S3 represents the intensity difference between the left-hand and right-hand circularly polarized components. In calculations, S0, S1, S2, and S3 are generally normalized, with S0 values ​​between 0 and 1, and S1, S2, and S3 values ​​between -1 and +1. For naturally unpolarized light, I... x =I y I +45 =I -45 I l =I r If S1, S2, or S3 is not 0, it indicates that polarized light exists.

[0061] S1=I x -I y ;

[0062] S2=I +45 -I-45 ;

[0063] The polarization direction AOP (Angle of Polarization) is the angle θ between the principal axis of the ellipse in elliptically polarized light and the x-axis of the conventional coordinate system.

[0064]

[0065] Based on the polarization information of the second polarization region and the third polarization region, Stokes parameter S2 is formed; the polarization information of the first polarization region and the fourth polarization region is formed into Stokes parameter S1; based on S1 and S2, the first AOP can be calculated to obtain the polarization characteristics of the target object; when the polarization characteristics are within a preset range, it is determined to be a living object, otherwise it is a spur.

[0066] When the first polarization direction is 45 degrees and the second polarization direction is -45 degrees, θ can be directly calculated using the above formula. When the first and second polarization directions do not conform to the above formula, it is necessary to calculate the light intensity at 45 degrees and -45 degrees for both polarization directions, and then use the above formula for calculation.

[0067] When the first, second, third, and fourth polarization regions are arrayed on a multifunctional polarizer, and any four adjacent regions contain all four different polarization regions, four different polarization characteristics of each region can be obtained. These characteristics are then calculated using the aforementioned formula to obtain the AOP (Average Opposite Polarization) of each polarization region. By calculating sequentially across the entire image, the AOP of all regions in the image can be obtained, resulting in a precise AOP image, i.e., the polarization characteristics of the entire image.

[0068] In some embodiments, the first, second, third, and fourth polarization regions are all spaced by the same distance *d*, and this distance *d* is proportional to the distance *t* between the multifunctional polarizer and the infrared sensor. However, due to manufacturing processes, the edges of the first, second, third, and fourth polarization regions exhibit irregularities and complex diffraction and scattering phenomena. This reduces the effectiveness of the signals received by the infrared sensor at the edges of these regions, thus discarding signals within a distance *s* from the edges of these regions on the infrared sensor. Distance *s* is proportional to distance *t*.

[0069] In some embodiments, the intensity of the light source is adjusted to a second power to obtain a second AOP for liveness detection. Due to individual differences and variations in surface and vein characteristics of different parts of the human body, the signals collected by infrared light emitted at a certain power will not be the same for the human body. Therefore, it is necessary to adjust the intensity of the light source and perform the functions or steps of the aforementioned embodiments to obtain a second AOP, thereby performing liveness detection and obtaining a liveness detection result.

[0070] In some embodiments, the light source can project both structured light and floodlight, and has different powers; adjusting the intensity of the light source changes the projection type. For example... Figure 4 As shown, the light source includes a light-emitting unit 11 and an electrically controlled glass 12. When the light-emitting unit 11 is working, it projects a structured light beam. The electrically controlled glass can be switched between a first state and a second state by controlling the voltage. In the first state, the electrically controlled glass is transparent, and the beam is emitted in the form of structured light. In the second state, the electrically controlled glass is opaque, and the beam is emitted in the form of floodlight after diffusion. Due to the significant light loss during diffusion, the light power in the second state is less than that in the first state. Therefore, the light intensity can also be changed by altering the projection type of the light source.

[0071] In some embodiments, when the liveness detection results of the first AOP and the second AOP differ, the intensity of the light source is adjusted to a third power, and a third AOP is calculated to obtain the liveness detection result; the third power is the average of the first power and the second power. When the results of the first AOP and the second AOP are consistent, this liveness detection result is taken as the final result. When the liveness detection results of the first AOP and the second AOP differ, there may be some data anomalies, such as surface roughness or multi-layered materials. An additional third power is used for data acquisition and calculation to obtain the final liveness detection result.

[0072] This invention also provides an electronic device that includes the liveness detection device provided in any of the above embodiments. This electronic device can be a mobile phone, tablet computer, payment terminal, or digital camera, etc. The liveness detection electronic device provided by this invention utilizes polarization characteristics for liveness detection, providing a highly accurate liveness detection capability that effectively resists various types of spoofing attacks.

[0073] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0074] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A living body identification device characterized by comprising: include: A light source used to project infrared light at a first power; A parallel polarizer is located in the optical path of the infrared light so that the infrared light illuminates the target object in a polarized state. A multifunctional polarizer is located on the reflected signal optical path of the target object and includes at least two states: parallel polarization and vertical polarization. An infrared sensor is used to receive the reflected signal after passing through the multifunctional polarizer; The processor is configured to calculate a first AOP based on the reflected signals of the parallel polarization and the vertical polarization, and then determine whether the target object is a living body; The multifunctional polarizer includes at least a first polarization region, a second polarization region, a third polarization region, and a fourth polarization region; The polarization direction of the first polarization region is the same as the polarization direction of the parallel polarizer; The second polarization region has a first polarization direction; The third polarization region has a second polarization direction; The polarization direction of the fourth polarization region is perpendicular to the polarization direction of the parallel polarizer; The first polarization direction and the second polarization direction are neither the same as nor perpendicular to the polarization direction of the parallel polarizer; According to the polarization information of the second polarization region and the third polarization region, the Stokes parameters are composed of ; the polarization information of the first polarization region and the fourth polarization region, the Stokes parameters are composed of ; according to and The first AOP can be calculated to obtain the polarization characteristics of the target object; when the polarization characteristics are within a preset range, it is determined as a living body, otherwise as a false body.

2. The living body identification apparatus according to claim 1, wherein The angle between the first polarization direction and the polarization direction of the parallel polarizer does not exceed 45 degrees; the angle between the second polarization direction and the polarization direction of the parallel polarizer is not less than 45 degrees.

3. The living body identification apparatus according to claim 1, wherein There are multiple first polarization regions, second polarization regions, third polarization regions and fourth polarization regions, and they are arrayed on the multifunctional polarizer.

4. The living body identification apparatus according to claim 3, wherein Each of the four adjacent regions contains the first polarization region, the second polarization region, the third polarization region, and the fourth polarization region to obtain the polarization characteristics of each region.

5. A living body identification device characterized by comprising: include: A light source used to project infrared light at a first power; A parallel polarizer is located in the optical path of the infrared light so that the infrared light illuminates the target object in a polarized state. A multifunctional polarizer is located on the reflected signal optical path of the target object and includes at least two states: parallel polarization and vertical polarization. An infrared sensor is used to receive the reflected signal after passing through the multifunctional polarizer; The processor is configured to calculate a first AOP based on the reflected signals of the parallel polarization and the vertical polarization, thereby determining whether the target object is a living body, and adjust the intensity of the light source to a second power to obtain a second AOP, thereby determining whether the target object is a living body. When the liveness detection results of the first AOP and the second AOP are different, the intensity of the light source is adjusted to the third power, and the third AOP is calculated to obtain the liveness detection result; the third power is the average of the first power and the second power.

6. The living body identification apparatus according to claim 5, wherein The light source can project both structured light and floodlight, and has different powers; adjusting the intensity of the light source changes the projection type.

7. An electronic device, comprising: The liveness detection device includes any one of claims 1-6.

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