Material authentication system

Abstract

The disclosure is in the field of material authentication systems. The disclosure relates to a material authentication system comprising: a. an input configured to receive image data comprising a pattern image of an object under patterned illumination, b. a processor configured to generate a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, comparing the feature vector with a reference obtained from an enrollment process and authenticating the object using the comparison result.

Description

[0001] Material Authentication System

[0002] The disclosure is in the field of material authentication systems. The disclosure relates to a material authentication system, a use of the material authentication system for controlling access to a mobile computing device, a method for authentication an object, and a non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform a method for authentication an object.

[0003] Background

[0004] Object authentication, for example face authentication, is a powerful security feature for access control, for example to a device such as a smartphone or building, or for authentication of a person, for example for online payments. To make object authentication even more secure, the material from the characteristic reflection of patterned light can be determined. Such patterned light images are classified with a trained material model, for example as described in WO 2023 / 156315 A1 or WO 2023 / 156319 A1. In this way, it is possible to distinguish between an authentic object and a spoofing object. The identity of a person can be identified from a floodlight image with a 2D image recognition algorithm. Subsequently, a material model can verify if the presented face is a real face or a spoofing mask.

[0005] Different people can have quite different skin types which can be difficult to reliably distinguish from a broad variety of non-skin materials. The same problem arises with other materials, for example leather. A model which is capable of correctly classifying all conceivable types of one material against all conceivable other materials is unfeasible to train due to the enormous need of training data comprising all different conceivable materials, for example skin types and non-skin materials.

[0006] Summary

[0007] The objective of the present disclosure was to provide a material authentication system with material detection functionality which is more robust against spoofing attacks with unconventional materials.

[0008] In one aspect the disclosure relates to a material authentication system comprising: a. an input configured to receive image data comprising a pattern image of an object under patterned illumination, b. a processor configured to generate a feature vector from the image data, wherein the feature vector represents an interaction of patterned light with the object, comparing the feature vector with a reference obtained from an enrollment process and authenticating the object using the comparison result.

[0009] In another aspect the disclosure relates to a material authentication system comprising: a. an input configured to receive image data comprising a pattern image of an object under patterned illumination, b. a processor configured to generate a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, comparing the feature vector with a reference obtained from an enrollment process and authenticating the object using the comparison result.

[0010] In another aspect the disclosure relates to a use of the material authentication system according to the disclosure for controlling access to a mobile computing device.

[0011] In another aspect the disclosure relates to a method for authentication an object comprising: a. receiving image data comprising a pattern image of the object under patterned illumination, b. generating a feature vector from the image data, wherein the feature vector represents an interaction of patterned light with the object, c. comparing the feature vector with a reference obtained from an enrollment process, and d. authenticating the object using the comparison result.

[0012] In another aspect the disclosure relates to a method for authentication an object comprising: a. receiving image data comprising a pattern image of the object under patterned illumination, b. generating a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, c. comparing the feature vector with a reference obtained from an enrollment process, and d. authenticating the object using the comparison result.

[0013] In another aspect the disclosure relates to a non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform a method comprising: a. receiving image data comprising a pattern image of an object under patterned illumination, b. generating a feature vector from the image data, wherein the feature vector represents an interaction of patterned light with the object, c. comparing the feature vector with a reference obtained from an enrollment process and d. authenticating the object using the comparison result.

[0014] In another aspect the disclosure relates to a non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform a method comprising: a. receiving image data comprising a pattern image of an object under patterned illumination, b. generating a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, c. comparing the feature vector with a reference obtained from an enrollment process and d. authenticating the object using the comparison result.

[0015] The comparison with reference feature vectors from an enrollment process makes the model more robust against spoofing attacks with unconventional materials, i.e. with materials for which a material model has not been trained. This is because the model does not have to classify which material it recognizes, but it only needs to make sure that the material upon authentication is the same as that during enrollment. Furthermore, the enrollment makes it possible to distinguish between different species of the same material, e.g. two humans of quite different skin types, and thus further increasing the security. The solution of the present disclosure is easy to implement and requires little training data. The approach is flexible, i.e. can be used for a broad variety of objects, even objects of materials for which the system has not been trained.

[0016] The term "material authentication system” may refer to a device, part of a device or device assembly which can be used to authenticate a material of an object, i.e. determine if the object is made of an expected material. Examples for material authentication may be in the context of apparel, such as authenticating if a suit is of silk or if a jacket is of real leather. Material authentication may be in the context of quality control such as ensuring the correct material composition of a good, such as chocolate or medical implants. Material authentication may be used for biometric authentication, i.e. the material authentication system may be a biometric authentication system. The material authentication system may be integrated into a mobile computing device, for example a smartphone, a tablet, a smartwatch or a laptop, into a vehicle, for example a car, a truck, a motorcycle, a train, an airplane, into an access system for a building or a gate.

[0017] The term "object” may refer to any object which can be measured with light. An object can be a living body, for example a human, or a non-living object. An object may refer to a complete object or a small piece thereof, for example a sample extracted from the object. In case of a living body, the object may refer to a body part, for example face or hand.

[0018] The term "biometric authentication” may refer to any procedure which uses a characteristic of a human to identify if a real human is present, i.e. in front of the biometric authentication system, or not. In the context of the present disclosure, the characteristic of the human is a material. The material may be any material which is found in a human body, for example skin, hair, or cornea tissue. Biometric authentication may be combined with biometric recognition, i.e. the determination which person is present. Biometric recognition may include optical biometric recognition like face recognition, iris scan, palm scan or fingerprint scan; or acoustic recognition like voice recognition. Optical biometric recognition may be passive, i.e. an image is recorded of the user or part of the user to be recognized, wherein the user is only under irradiation of ambient light. Optical biometric recognition may be active, i.e. an image is recorded of the user or part of the user to be recognized, wherein the user is only under irradiation of light emitted by a projector. The term "light” may refer to electromagnetic radiation in one or more of the infrared, the visible and the ultraviolet spectral range. Herein, the term "ultraviolet spectral range”, generally, refers to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably of 100 nm to 380 nm. Further, in partial accordance with standard ISO- 21348 in a valid version at the date of this document, the term "visible spectral range”, generally, refers to a spectral range of 380 nm to 760 nm. The term "infrared spectral range” (IR) generally refers to electromagnetic radiation of 760 nm to 1000 m, wherein the range of 760 nm to 1.5 pm is usually denominated as "near infrared spectral range” (NIR) while the range from 1.5 p to 15 pm is denoted as "mid infrared spectral range” (MidlR) and the range from 15 pm to 1000 pm as "far infrared spectral range” (FIR). Preferably, light used for the typical purposes of the present disclosure is light in the infrared (IR) spectral range, more preferred, in the near infrared (NIR) and / or the mid infrared spectral range (MidlR), especially the light having a wavelength of 1 pm to 5 pm, preferably of 1 pm to 3 pm.

[0019] The material authentication system may comprise a projector. The term "projector” may refer to a device configured for generating or providing light in the sense of the above-mentioned definition. The projector may be a pattern projector, a floodlight projector or both either simultaneously or the projector may repeatedly switch from illuminating patterned light to floodlight.

[0020] The term "pattern projector” may refer to a device configured for generating or providing at least one light pattern, in particular at least one infrared light pattern. The term "light pattern” may refer to at least one pattern comprising a plurality of light spots. The light spot may be at least partially spatially extended. At least one spot or any spot may have an arbitrary shape. In some cases, a circular shape of at least one spot or any spot may be preferred. The spots may be arranged by considering a structure of a display comprised by a device that is further comprising the optoelectronic apparatus. Typically, an arrangement of an OLED-pixel-structure of the display may be considered. The term "infrared light pattern” may refer to a light pattern comprising spots in the infrared spectral range. The infrared light pattern may be a near infrared light pattern. The infrared light may be coherent. The infrared light pattern may be a coherent infrared light pattern.

[0021] The pattern projector may be configured for emitting monochromatic light, e.g. in the near infrared region. The term "monochromatic” may refer to light with a wavelength accuracy of less or equal to ± 2 % or less or equal to ± 1 %. The wavelength accuracy may be the maximum difference of emitted wavelength relative to the mean wavelength. In other embodiments, the pattern projector may be adapted to emit light with a plurality of wavelengths, e.g. for allowing additional measurements in other wavelengths channels.

[0022] The infrared light pattern may comprise at least one regular and / or constant and / or periodic pattern such as a triangular pattern, a rectangular pattern, a hexagonal pattern or a pattern comprising further convex tilings. For example, the infrared light pattern is a hexagonal pattern, preferably a hexagonal infrared light pattern. The illumination pattern may comprise a number of rows on which the illumination features are arranged in equidistant positions with distance d. The rows may be orthogonal with respect to the epipolar lines. A distance between the rows may be constant. A different offset may be applied to each of the rows in the same direction. The offset may result in that the illumination features of a row are shifted. The offset 5 may be 5= a / b, wherein a and b are positive integer numbers such that the illumination pattern is a periodic pattern. For example, 5 may be 1 / 3 or 2 / 5. Using a periodical pattern with said offset can allow distinguishing between artefacts and usable signal.

[0023] The light pattern may comprise less than 4000 spots, for example less than 3000 spots or less than 2000 spots or less than 1500 spots or less than 1000 spots. The light pattern may comprise patterned coherent infrared light of less than 4000 spots or less than 3000 spots or less than 2000 spots or less than 1500 spots or less than 1000 spots.

[0024] At least one of the infrared light spots may be associated with a beam divergence of 0.2° to 0.5°, preferably 0.1 ° to 0.3°. The term "beam divergence” may refer to at least one measure of an increase in at least one diameter and / or at least one diameter equivalent, such as a radius, with a distance from an optical aperture from which the beam emerges. The measure may be an angle or an angle equivalent. In the context of the present disclosure, typically, a beam divergence may be determined at 1 / e2.

[0025] The pattern projector may comprise at least one pattern projector configured for generating the infrared light pattern. The pattern projector may comprise at least one emitter, in particular a plurality of emitters. The term "emitter” may refer to at least one arbitrary device configured for providing at least one light beam. The light beam may generate the infrared light pattern. The emitter may comprise at least one element selected from the group consisting of at least one laser source such as at least one semi-conductor laser, at least one double heterostructure laser, at least one external cavity laser, at least one separate confinement heterostructure laser, at least one quantum cascade laser, at least one distributed Bragg reflector laser, at least one polariton laser, at least one hybrid silicon laser, at least one extended cavity diode laser, at least one quantum dot laser, at least one volume Bragg grating laser, at least one Indium Arsenide laser, at least one Gallium Arsenide laser, at least one transistor laser, at least 50 one diode pumped laser, at least one distributed feedback lasers, at least one quantum well laser, at least one interband cascade laser, at least one semiconductor ring laser, at least one vertical cavity surface emitting laser (VCSEL); at least one non-laser light source such as at least one LED or at least one light bulb. For example, the pattern projector comprises at least one least one VCSEL, preferably a plurality of VCSELs. The plurality of VCSELs may be arranged in at least one array, e.g. comprising a matrix of VCSELs. The VCSELs may be arranged on the same substrate, or on different substrates. The term "vertical-cavity surface-emitting laser” may refer to a semiconductor laser diode configured for laser beam emission perpendicular with respect to a top surface. Examples for VCSELs can be found e.g. in en.wikipedia.org / wikiA / erticalcavity_surface-emitting_laser. VCSELs are generally known to the skilled user such as from WO 2017 / 222618 A. Each of the VCSELs is configured for generating at least one light beam. The plurality of generated spots may be associated with the infrared light pattern. The VCSELs may be configured for emitting light beams at a wavelength range from 800 to 1000 nm. For example, the VCSELs may be configured for emitting light beams at 808 nm, 850 nm, 940 nm, and / or 980 nm. Preferably the VCSELs emit light 940 nm, since terrestrial sun radiation has a local minimum in irradiance at this wavelength, e.g. as described in CIE 085-1989 „Solar spectral Irradiance”.

[0026] The pattern projector may comprise at least one optical element configured for increasing, e.g. duplicating, the number of spots generated by the pattern projector. The pattern projector, particularly the optical element, may comprises at least one diffractive optical element (DOE) and / or at least one meta surface element. The DOE and / or the meta surface element may be configured for generating multiple light beams from a single incoming light beam. Further arrangements, particularly comprising a different number of projecting VCSEL and / or at least one different optical element configured for increasing the number of spots may be possible. Other multiplication factors are possible. For example, a VCSEL or a plurality of VCSELs may be used and the generated laser spots may be duplicated by using at least one DOE.

[0027] The pattern projector may comprise at least one transfer device. The term "transfer device”, also denoted as "transfer system” may refer to one or more optical elements which are adapted to modify the light beam, particularly the light beam used for generating at least a portion of the infrared light pattern, such as by modifying one or more of a beam parameter of the light beam, a width of the light beam or a direction of the light beam. The transfer device may comprise at least one imaging optical device. The transfer device specifically may comprise one or more of: at least one lens, for example at least one lens selected from the group consisting of at least one focus-tunable lens, at least one aspheric lens, at least one spherical lens, at least one Fresnel lens; at least one diffractive optical element; at least one concave mirror; at least one beam deflection element, preferably at least one mirror; at least one beam splitting element, preferably at least one of a beam splitting cube or a beam splitting mirror; at least one multi lens system; at least one holographic optical element; at least one meta optical element. Specifically, the transfer device comprises at least one refractive optical lens stack. Thus, the transfer device may comprise a multi-lens system having refractive properties.

[0028] The pattern projector may be configured for emitting modulated or non-modulated light. In case a plurality of emitters is used, the different emitters may have different modulation frequencies, e.g. which can be used for distinguishing the light beams.

[0029] The light beam or light beams generated by the pattern projector may propagate parallel to an optical axis. The pattern projector may comprise at least one reflective element, preferably at least one prism, for deflecting the illuminating light beam onto the optical axis. As an example, the light beam or light beams, such as the laser light beam, and the optical axis may include an angle of less than 10°, preferably less than 5° or even less than 2°. Other embodiments, however, are feasible. Further, the light beam or light beams may be on the optical axis or off the optical axis. As an example, the light beam or light beams may be parallel to the optical axis having a distance of less 10 than 10 mm to the optical axis, preferably less than 5 mm to the optical axis or even less than 1 mm to the optical axis or may even coincide with the optical axis. The term "flood projector” may refer to at least one device configured for providing substantially continuous spatial illumination. The flood projector may illuminate a measurement area, such as a user, a portion of the user and / or a face of the user, with a spatially constant or essentially constant illumination intensity. The term "flood light” may refer to substantially continuous spatial illumination, in particular diffuse and / or uniform illumination. The flood light has a wavelength in the infrared range, in particular in the near infrared range. The flood projector may comprise at least one least one VCSEL, preferably a plurality of VCSELs, for example an array of VCSELs. The term "substantially continuous spatial illumination” may refer to uniform spatial illumination, wherein areas of non-uniform are possible.

[0030] A relative distance between the flood projector and the pattern projector may be below 3.0 mm. The relative distance between the flood projector and the pattern projector may be below 2.5 mm, preferably below 2.0 mm. The pattern projector and the flood projector may be combined into one module. For example, the pattern projector and the flood projector may be arranged on the same substrate, in particular having a minimum relative distance. The minimum relative distance may be defined by a physical extension of the flood projector and the pattern projector. Arranging the pattern projector and the flood projector having a relative distance below 3.0 mm can result in decreased space requirement of the two projectors. In particular, said projectors can even be combined into one module. Such a reduced space requirement can allow reducing the transparent area(s) in a display necessary for operation of the projector(s) behind the display.

[0031] In an embodiment, the pattern projector and the flood projector may comprise at least one VCSEL, preferably a plurality of VCSELs, for example an array of VCSELs. The pattern projector may comprise a plurality of first VCSELs mounted on a first platform. The flood projector may comprise a plurality of second VCSELs mounted on a second platform. The second platform may be beside the first platform. The optoelectronic apparatus may comprise a heat sink. Above the heat sink a first increment comprising the first platform may be attached. Above the heat sink a second increment comprising the second platform may be attached. The second increment may be different from the first increment. Thus, the first platform may be more distant to the optical element configured for increasing, e.g. duplicating, the number of spots. The second platform may be closer to the optical element. The beam emitted from the second VCSEL may be defocused and thus, form overlapping spots. This leads to a substantially continuous illumination and, thus, to flood illumination.

[0032] The projector may be positioned such that it can illuminate light through the transparent display. Hence, light emitted by the projector may cross the transparent display before it impinges on the user. From the user's view, the projector may be placed behind the transparent display.

[0033] The material authentication system may comprise a camera. The term "camera” may refer to at least one unit of the optoelectronic apparatus configured for generating at least one image. The image may be generated via a hardware and / or a software interface, which may be considered as the camera. The term "image generation” may refer to capturing and / or generating and / or determining and / or recording at least one image by using the camera. The image generation may comprise imaging and / or recording the image. The image generation may comprise capturing a single image and / or a plurality of images such as a sequence of images. For generating an image via a hardware and / or a software interface, the capturing and / or generating and / or determining and / or recording of the image may be caused and / or initiated by the hardware and / or the software interface. For example, the image generation may comprise recording continuously a sequence of images such as a video or a movie. The image generation may be initiated by a user action or may automatically be initiated, e.g. once the presence of at least one object or user within a field of view and / or within a predetermined sector of the field of view of the camera is automatically detected.

[0034] The camera may comprise at least one optical sensor, in particular at least one pixelated optical sensor. The camera may comprise at least one CMOS sensor or at least one CCD chip. For example, the camera may comprise at least one CMOS sensor, which may be sensitive in the infrared spectral range. The term "image” may refer to data recorded by using the optical sensor, such as a plurality of electronic readings from the CMOS or CCD chip. The image may comprise raw image data or may be a pre-processed image. For example, the pre-processing may comprise applying at least one filter to the raw image data and / or at least one background correction and / or at least one background subtraction.

[0035] For example, the camera may comprise a color camera, e.g. comprising at least color pixels. The camera may comprise a color CMOS camera. For example, the camera may comprise black and white pixels and color pixels. The color pixels and the black and white pixels may be combined internally in the camera. The camera may comprise a color camera (e.g. RGB) or a black and white camera, such as a black and white CMOS. The camera may comprise a black and white CMOS chip. The camera generally may comprise a one-dimensional or two-dimensional array of image sensors, such as pixels.

[0036] The color camera may be an internal and / or external camera of a device comprising the optoelectronic apparatus. The internal and / or external camera of the device may be accessed via a hardware and / or a software interface comprised by the optoelectronic apparatus, which is used as the camera. In case, the device is or comprises a smartphone the image generating unit may be a front camera, such as a selfie camera, and / or back camera of the smartphone.

[0037] The camera may have a field of view between 10°x10° and 75°x75°, preferably 55°x65°. The camera may have a resolution below 2 megapixel (MP), for example 0.3 to 1 .8 MP, such as 0.5 MP and 1 .6 MP or 1 .0 to 1 .5 MP.

[0038] The camera may comprise further elements, such as one or more optical elements, e.g. one or more lenses. As an example, the optical sensor may be a fix-focus camera, having at least one lens which is fixedly adjusted with respect to the camera. Alternatively, however, the camera may also comprise one or more variable lenses which may be adjusted, automatically or manually. Other cameras, however, are feasible. The term "pattern image” may refer to an image generated by the camera while illuminating the infrared light pattern, e.g. on an object and / or a user. The pattern image may comprise an image showing a user, in particular at least parts of the face of the user, while the user is being illuminated with the infrared light pattern, particularly on a respective area of interest comprised by the image. The pattern image may be generated by imaging and / or recording light reflected by an object and / or user which is illuminated by the infrared light pattern. The pattern image showing the user may comprise at least a portion of the illuminated infrared light pattern on at least a portion the user. For example, the illumination by the pattern illumination source and the imaging by using the optical sensor may be synchronized, e.g. by using at least one control unit of the optoelectronic apparatus.

[0039] The term "flood image” may refer to an image generated by the camera while illumination source is illuminating infrared flood light, e.g. on an object and / or a user. The flood image may comprise an image showing a user, in particular the face of the user, while the user is being illuminated with the flood light. The flood image may be generated by imaging and / or recording light reflected by an object and / or user which is illuminated by the flood light. The flood image showing the user may comprise at least a portion of the flood light on at least a portion the user. For example, the illumination by the flood illumination source and the imaging by using the optical sensor may be synchronized, e.g. by using at least one control unit of the optoelectronic apparatus.

[0040] The camera may be configured for imaging and / or recording the pattern image and the flood image at the same time or at different times. The camera may be configured for imaging and / or recording the pattern image and the flood image at at least partially overlapping measurement areas or equivalents of the measurement areas.

[0041] The material authentication system may comprise a transparent display. The camera or the projector may be placed behind the transparent display in order maximize the display area of a device. The term "display” may refer to an arbitrary shaped device configured for displaying an item of information. The item of information may be arbitrary information such as at least one image, at least one diagram, at least one histogram, at least one graphic, text, numbers, at least one sign, or an operating menu. The display may be or may comprise at least one screen. The display may have an arbitrary shape, e.g. a rectangular shape. The display may be a front display of the device.

[0042] The display may be or may comprise at least one organic light-emitting diode (OLED) display. The term "organic light emitting diode” may refer to a light-emitting diode (LED) in which an emissive electroluminescent layer is a film of organic compound configured for emitting light in response to an electric current. The OLED display may be configured for emitting visible light. The display, particularly a display area, may be covered by glass. In particular, the display may comprise at least one glass cover.

[0043] The transparent display may be at least partially transparent. The term "at least partially transparent” may refer to a property of the display to allow light, in particular of a certain wavelength range, e.g. in the infrared spectral region, in particular in the near infrared spectral region, to pass at least partially through. For example, the display may be semitransparent in the near infrared region. For example, the display may have a transparency of 20 % to 50 % in the near infrared region. The display may have a different transparency for other wavelength ranges. For example, the display may have a transparency of > 80 % for the visible spectral range, preferably > 90 % for the visible spectral range. The transparent display may be at least partially transparent over the entire display area or only parts thereof. Typically, it is sufficient if only those parts of the display area are at least partially transparent trough which light needs to pass from the projector or to the camera.

[0044] The display comprises a display area. The term "display area” may refer to an active area of the display, in particular an area which is activatable. The display may have additional areas such as recesses or cutouts. The display may have a first area associated with a first pixel per inch (PPI) value and a second area associated with a second PPI value. The first PPI value may be lower than the second PPI value, preferably first PPI value is equal to or below 400 PPI, more preferably the second PPI value may be equal to or higher than 300 PPI. The first PPI value may be associated with the at least one continuous area being at least partially transparent.

[0045] Biometric authentication may comprise identifying the object based on the flood image. The term "identifying” may refer to identity check and / or verifying an identity of the object. The identifying of the object may comprise analyzing the flood image. The analyzing of the flood image may comprise performing a face verification of the imaged face to be the user's face. The identifying the object may comprise matching the flood image, e.g. showing a contour of parts of the user, in particular parts of the user's face, with a template. Determining if the imaged face is the face of the user may comprise identifying the user, in particular determining if the imaged face corresponds to at least one image of the user's face stored in at least one memory, e.g. of the device.

[0046] The analyzing may comprise one or more of the following: a filtering; a selection of at least one region of interest; a formation of a difference image between the flood image and at least one offset; an inversion of flood image; a background correction; a decomposition into color channels; a decomposition into hue; saturation; and brightness channels; a frequency decomposition; a singular value decomposition; applying a Canny edge detector; applying a Laplacian of Gaussian filter; applying a Difference of Gaussian filter; applying a Sobel operator; applying a Laplace operator; applying a Scharr operator; applying a Prewitt operator; applying a Roberts operator; applying a Kirsch operator; applying a high-pass filter; applying a low-pass filter; applying a Fourier transformation; applying a Radon- transformation; applying a Hough-transformation; applying a wavelet-transformation; a thresholding; creating a binary image. The region of interest may be determined manually by a user or may be determined automatically, such as by recognizing the user within the image. In particular, the analyzing of the flood image may comprise using at least one image recognition technique, in particular a face recognition technique. An image recognition technique comprises at least one process of identifying the user in an image. The image recognition may comprise using at least one technique selected from the technique consisting of: color-based image recognition, e.g. using features such as hue, saturation, and value (HSV) or red, green, blue (RGB); template matching, for example as illustrated on https: / / www.mathworks.com / help / vision / ug / pattern-matching.html; image segment and / or blob analysis e.g. using size, color, or shape; machine learning and / or deep learning e.g. using at least one convolutional neural network. The neural network may be trained by the user, such as in a training procedure, in which the user is indicated to take at least one or a plurality of pictures showing himself.

[0047] The analyzing of the flood image may comprise determining a plurality of facial features. The analyzing may comprise comparing, in particular matching, the determined facial features with template features. The template features may be features extracted from at least one template. The template may be or may comprise at least one image generated in an enrollment process, e.g. when initializing the authentication system. Template may be an image of an authorized user. The template features and / or the facial feature may comprise a vector. Matching of the features may comprise determining a distance between the vectors. The identifying of the user may comprise comparing the distance of the vectors to a least one predefined limit, wherein the user is successfully identified in case the distance is smaller than or equal to the predefined limit at least within tolerances. The user declining and / or rejected otherwise.

[0048] For example, the image recognition may comprise using at least one model, in particular a trained model comprising at least one face recognition model. The analyzing of the flood image may be performed by using a face recognition system, such as FaceNet, e.g. as described in Florian Schroff, Dmitry Kalenichenko, James Philbin, "FaceNet: A Unified Embedding for Face Recognition and Clustering”, arXiv: 1503.03832. The trained model may comprises at least one convolutional neural network. For example, the convolutional neural network may be designed as described in M. D. Zeller and R. Fergus, "Visualizing and understanding convolutional networks”, CoRR, abs / 1311.2901, 2013, or C. Szegedy et al., "Going deeper with convolutions”, CoRR, abs / 1409.4842, 2014. For more details with respect to convolutional neural network for the face recognition system reference is made to Florian Schroff, Dmitry Kalenichenko, James Philbin, "FaceNet: A Unified Embedding for Face Recognition and Clustering”, arXiv: 1503.03832. As training data labelled image data from an image database may be used. Specifically, labeled faces may be used from one or more of G. B. Huang, M. Ramesh, T. Berg, and E. Learned-Miller, "Labeled faces in the wild: A database for studying face recognition in unconstrained environments”, Technical Report 07-49, University of Massachusetts, Amherst, October 2007, the Youtube® Faces Database as described in L. Wolf, T. Hassner, and I. Maoz, "Face recognition in unconstrained videos with matched background similarity”, in IEEE Conf, on CVPR, 2011, or Google® Facial Expression Comparison dataset. The training of the convolutional neural network may be performed as described in Florian Schroff, Dmitry Kalenichenko, James Philbin, "FaceNet: A Unified Embedding for Face Recognition and Clustering”, arXiv: 1503.03832.

[0049] Image artifacts caused by diffraction of the light when passing the transparent display may be corrected. The term "correct” may mean partially or fully remove the artifacts or tag them so they can be excluded from further processing, in particular from determine if the imaged user is an authorized user. Correcting image artifacts may take into account the information about the transparent display, in particular the dimensions of the pixels or the distance of repeating features to each other. This information can facilitate identifying artifacts as diffraction patterns can be calculated and compared to the image. Correcting image artifacts may comprise identifying reflection features, sorting them by brightness and selecting the locally brightest features. For determining a distance around a feature in the image which qualifies as local, the information of the transparent display may be used, in particular a distance in the image by which a light beam may be displaced by diffraction on the transparent display may be calculated based on the information about the transparent display. This method can be particularly useful for pattern images. Further details are disclosed in WO 2021 / 105265 A1.

[0050] The term "image data” may refer to data associated with one or more images recorded with a camera. The image data may comprise one or more images as received from a camera, or it may comprise data derived from one or more images received from a camera. The term "derived” may mean adjustments to the image, for example change of contrast or brightness, cropping, for example removal of background sections, division into multiple partial images, transformation into a different format, for example into a feature vector. Image data may comprise one or more pattern images and / or one or more flood images. Image data may comprise multiple partial images derived from an image, for example from a pattern image. In particular, image data may comprise multiple partial images, where a partial image obtained from a pattern image by cropping around a pattern feature. A partial image may comprise one pattern feature or a subset of image features of the pattern image, for example one pattern features and its neighboring pattern features.

[0051] The material authentication may comprise determining region data from the image data. The term "region data” may refer to data indicative for the probability that the object exposes its expected material in a region of the image. Hence, the region data comprises data indicating for various regions or parts of the image if the object presumably exposes its expected material, for example by assigning a probability that the object exposes its expected material to the regions. The region data may comprise at least one region of the object, preferably at least two regions of the object, more preferably at least three regions of the object, for example at least five regions of the object or at least ten regions of the object. The region data may for example comprise a vector or an array of values indicative for the probability that the object exposes its expected material in the respective region. A region may refer to one pixel or to a range of pixels in the image, in particular a contiguous range of pixels in the image. Generally, a region may be smaller than the object in the image. The value may be a Boolean value or a float value, for example a float value between 0 and 1, wherein 0 indicates that the object is very likely occluded in this region and a 1 indicates that the object is very likely exposing its expected material in this region. Alternatively, the region data may comprise a list of those regions for which the probability that the object exposes its expected material in a region of the image exceeds a threshold value. Hence, the presence in the list indicates for the respective region a high probability and the absence a low probability.

[0052] The determination of the region data may comprise an image segmentation algorithm. Image segmentation may comprise a global or local thresholding algorithm, i.e. replacing each pixel in an image with a black pixel if the image intensity is less than a threshold value or white otherwise. An example for a thresholding algorithm is the Otsu's method. Image segmentation may comprise clustering methods, for example K-means clustering based on pixel color, intensity, texture, and location, or a weighted combination of these factors. Image segmentation may comprise motion and interactive segmentation, i.e. by comparing a pair of images and identifying a segment based on the same differences. Image segmentation may comprise a compression-based method, i.e. a segmentation by minimizing the coding length of the image data. Image segmentation may comprise a histogram-based method, i.e. using peaks and valleys in the histogram to locate segments in the image. Image segmentation may comprise edge detection, for example the Canny edge detection algorithm. Image segmentation may comprise isolated point detection, for example using the Laplacian operator. Image segmentation may comprise a dual clustering method, a region-growing method, a partial differential equation-based method like parametric methods, level-set methods or fast marching methods, a variational method like the Potts model, a graph partitioning method like Markov random fields, normalized cuts, random walker, minimum cut, isoperimetric partitioning, minimum spanning tree-based segmentation, or segmentation-based object categorization, a watershed transformation, a model-based segmentation, a multi-scale segmentation, semi-automatic segmentation, trainable segmentation like a Kohonen map, pulse-coupled neural networks, convolutional neural networks, autoencoders. Image segmentation may comprise an active appearance model or an active shape model.

[0053] The determination of the region data may comprise attributing the regions an indicator indicating if the object appears to expose its expected material. Such attribution may comprise applying a model representing the typical topology of the object associated with the probability that an object exposes its expected material at a given region. For example, for a face, the model may represent a high probability that the face exposes skin for the front, the nose, the cheeks and the ears, but a low probability for the hair, the eyes and a beard.

[0054] Region data is determined from the image data. Image data may comprise a pattern image and a flood image. Region data may be determined from a flood image of the image data. Determination of region data preferably does not comprise material determination to make sure that the region data can increase reliability of the material determination.

[0055] The material authentication comprises generating a feature vector from the image data. A feature vector may be generated from the pattern image, for example the whole pattern image or for a part thereof. The pattern image may be cropped according to the region data, for example for each segment of the region data the pattern image may be cropped to generate a partial image for a segment. The pattern image may be cropped into multiple partial images around a pattern feature as described above. Feature vector may be generated for the partial images, for example one feature vector for each partial image.

[0056] The feature vector represents an interaction of patterned light with the object. Such interaction may correlate with the material of the object, hence the feature vector may represent one or more than one material property of the object. This may mean that the feature vector may contain one or more values which correlate with one or more material properties, i.e. an interaction with patterned light which is characteristic for the material. The interaction with patterned light usually takes place at the surface of the object or near the surface of the object, for example within 100 to 200 m from the surface. Hence, the feature vector may represent an interaction of the surface of the object with patterned light. Examples for the interaction of patterned light with the object or material properties are reflectance, absorbance, transmittance, refractive index, scattering, polarization, gloss, surface roughness, optical anisotropy, penetration depth, diffuse or specular reflectivity, translucence. In general, a pattern image mostly comprises information about the interaction of patterned light with the object, so the feature vector generated therefrom will represent said interaction. Such representation may be improved by attenuating or removing other pieces of information, for example geometric information about the object. An effective way of doing this is the cropping as described above. By such cropping, geometric information about the object may be attenuated or even gets completely lost, hence a feature vector generated from partial images essentially only represents the interaction of patterned light with the object.

[0057] A feature vector may be generated from image data by using an encoder. The term "encoder” may refer to an algorithm which uses the image data as input and output a feature vector representing features in the image data. The encoder may be or may comprise a convolutional neural network (CNN), an autoencoder, a histogram of oriented gradients (HOG), a scale-invariant feature transform (SIFT), speeded-up robust features (SURF) or bag-of- visual-words (BoVW). The image data may comprise multiple images, for example a set of partial images, wherein each partial image is obtained by cropping a pattern image around a pattern feature. The encoder may encode each partial image into a corresponding feature vector, so multiple feature vectors are obtained.

[0058] The encoder may be trained using a training dataset, for example by minimizing a loss function indicative for how well the predicted class labels match the labels of the training dataset and for the certainty of excluding other class labels. The loss function may be minimized by gradient descent including stochastic gradient descent (SGD), minibatch gradient descent, or adaptive gradient descent algorithms like Adam or RMSprop. The loss function may be a triplet loss or an anchor-based loss.

[0059] The feature vector is compared with a reference obtained from an enrollment process. The term "enrollment process” may refer to a process of obtaining reference data from the authentic object. Enrollment may comprise an authentication of the object, for example by a trusted authority. The authentication in the context of enrollment may be performed by a method different from image analysis to mitigate the risk of fraud, for example by entering a passcode or by checking an identity card, for example a passport or a digital identity. Enrollment may comprise recording or capturing image data comprising one or more than one pattern image of an object under patterned illumination. Illumination and recording may be performed with the material authentication system or with a different apparatus. Enrollment may comprise generating a feature vector from the image data as described above. The reference obtained from an enrollment process may be a reference feature vector or a reference pattern image. In the latter case, the material authentication system may generate a reference feature vector from the reference pattern image, for example by using the encoder. The reference feature vector or reference image may be an aggregation of several feature vectors or of several images, for example by averaging.

[0060] The feature vector may be compared to the reference feature vector in various ways, for example by determining a Euclidean distance, cosine similarity, Manhattan distance, Minkowski distance, Hamming distance, Jaccard similarity, Mahalanobis distance, Pearson correlation coefficient, or combinations thereof. The comparison may yield a similarity score indicating the similarity between the feature vector and the reference feature vector. The object is authenticated using the comparison result. For example, the object may be authenticated if the similarity score exceeds a threshold.

[0061] Several feature vectors may be generated from the image data, for example by cropping the pattern image to multiple partial images and generating feature vectors for the partial images. The several feature vectors may be compared to a reference. The comparison may involve aggregating the several feature vectors into one feature vector, for example by averaging, and determining the difference between the aggregated feature vector and the reference feature vector. The comparison may involve determining the difference between each feature vector with a corresponding reference feature vector and aggregating the differences, for example by averaging. The comparison may use region data, for example by weighing the similarity according to the segment of the object. Alternatively, the similarity within a segment may be determined for several or all segments and subsequently aggregated, for example by weighing according to the segment of the object.

[0062] In case more than one feature vectors are generated, the feature vector comparison may comprise a mechanism for positional encoding. For example, the feature vectors may be encoded according to the position of a partial images in the original images. In this way correlations between feature vectors can be used, for example the spatial relationships between the partial images the feature vectors are generated from. Positional encoding may be implemented by adding or multiplying the feature vectors with a value characteristic for the position, for example sine or cosine functions. The positional encoding may involve region data, for example by adding a value according to the segment in addition to the position in the original image.

[0063] A self-attention mechanism may be used for the comparison of feature vectors. The self-attention mechanism may enable identifying correlations between partial images from which the feature vectors are generated. For example, a vision transformer may be used for the comparison of feature vectors. In particular, a patterned image may be cropped into partial images according to the pattern, for example each partial image comprises a pattern feature and at least parts of its nearest neighbors. These partial images may be used to generate feature vectors subject to positional encoding and a self-attention mechanism. In this way, the object can be more reliably compared to the enrolled object, in particular for complex objects like a face in which different parts are of different skin or hair types. The material authentication system comprises a processor. The term "processor” may refer to a logic circuitry configured for performing basic operations of a computer or system, and / or, generally, to a device which is configured for performing calculations or logic operations. In particular, the processor may be configured for processing basic instructions that drive the computer or system. As an example, the processor may comprise at least one arithmetic logic unit (ALU), at least one floating-point unit (FPU), such as a math co-processor or a numeric coprocessor, a plurality of registers, specifically registers configured for supplying operands to the ALU and storing results of operations, and a memory, such as an L1 and L2 cache memory. In particular, the processor may be a multi-core processor. Specifically, the processor may be or may comprise a central processing unit (CPU). Additionally or alternatively, the processor may be or may comprise a micro-processor, thus specifically the processor's elements may be contained in one single integrated circuitry (IC) chip. Additionally or alternatively, the processor may be or may comprise one or more application-specific integrated circuits (ASICs) and / or one or more field-programmable gate arrays (FPGAs) and / or one or more tensor processing unit (TPU) and / or one or more chip, such as a dedicated machine learning optimized chip, or the like. The processor specifically may be configured, such as by software programming, for performing one or more evaluation operations. At least one or any component of a computer program configured for performing the authentication process may be executed by the processing device. Alternatively or in addition, the processor may be or may comprise a connection interface. The connection interface may be configured to transfer data from the device to a remote device; or vice versa. At least one or any component of a computer program configured for performing the authentication process may be executed by the remote device.

[0064] The processor may be configured, such as by software programming, for performing one or more evaluation operations. At least one or any component of a computer program configured for performing the authentication process may be executed by the processing device. Alternatively or in addition, the processor may be or may comprise a connection interface. The connection interface may be configured to transfer data from the device to a remote device; or vice versa. At least one or any component of a computer program configured for performing the authentication process may be executed by the remote device.

[0065] The method of the present disclosure comprises receiving image data. The term "receiving” may refer to reading the image information from a file, a database or from an interface to a camera. The image data may be received from a component of the same device, for example a camera of a portable computing device, or from a remote device, for example from a camera in an access terminal of a building.

[0066] An authentication signal may be output based on the object authentication, wherein the authentication signal is indicative whether the object is identified or not. The term "outputting” may relate to writing the authentication signal on a non-transitory data storage medium, for example into a file or database, display it on a user interface, for example a screen, or both. It is also possible to output the authentication signal through an interface to a cloud system for storage and / or further processing. The present disclosure further relates to a non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to the present disclosure. The term "computer-readable data medium" may refer to any suitable data storage device or computer readable memory on which is stored one or more sets of instructions (for example software) embodying any one or more of the methodologies or functions described herein. The instructions may also reside, completely or at least partially, within the main memory and / or within the processor during execution thereof by the computer, main memory, and processing device, which may constitute computer-readable storage media. The instructions may further be transmitted or received over a network via a network interface device. Computer-readable data medium include hard drives, for example on a server, USB storage device, CD, DVD or Blue-ray discs. The computer program may comprise all functionalities and data required for execution of the method according to the present disclosure or it may provide interfaces to have parts of the method processed on remote systems, for example on a cloud system.

[0067] The disclosure further relates to a method for granting a user access to a device or application. A device can be a mobile device, for example smartphone, a tablet computer, a laptop computer or a smartwatch, or it can be a stationary device such as a payment terminal or an access control system, for example to control access to a building, a subway train station, an airport gate, a production facility, a car rental site, an amusement park, a cinema, or a supermarket for registered customers. The access control system may further be integrated into a vehicle, for example a car, a train, an airplane, or a ship. An application may refer to a local program, for example installed on a smartphone or a laptop, or a remote service, for example a service on a cloud system to be accessed via internet. The application may serve several purposes, for example to authorize a payment, identify the user for a transaction with the public administration, for example to renew a driver's license, or authorize the user for high-security communication. For example, a request for access to a device of application may be submitted, for example by a user of the device or application. In response to the request for access, the user may be authenticated with the method of the disclosure. The authentication method may output an authentication signal indicative for the authenticity of the user. Access to the device or application may be granted based on the authentication signal, i.e. if the user is authenticated. Otherwise, access may be denied.

[0068] In one aspect the disclosure relates to a computer-implemented method for authentication an object comprising: a. receiving a request for access to a device or application, b. in response to the request, triggering the acquisition of image data comprising a flood image of the object under flood illumination and a pattern image of the object under pattern illumination, c. determining the identity of the object from the flood image, d. generating a feature vector from the pattern image, wherein the feature vector represents an interaction of patterned light with the object, e. comparing the feature vector with a reference obtained from an enrollment process, and f. granting access to the device or application depending on the determined identify of the object and the result of the comparison result of the feature vector with the reference.

[0069] Brief Description of the Figures

[0070] Figure 1 illustrates an example for a material authentication system.

[0071] Figure 2 illustrates an example for preprocessing image data.

[0072] Figure 3 illustrates an example of the method for authentication an object.

[0073] Figure 4 illustrates another example of the method for authentication an object.

[0074] Figure 5 illustrates an example for a biometric authentication system.

[0075] Description of Embodiments

[0076] Figure 1 illustrates an example for a material authentication system. The material authentication system 100 may be integrated into a portable device, for example a smartphone, a tablet computer, a laptop computer or a smartwatch. It may comprise a projector 101 which projects light 111 onto a user 110. The light may be infrared light, for example with a wavelength of 940 nm, which is invisible to the user 110. The projected light 111 may be floodlight or patterned light, for example a hexagonal point pattern. The projected light 111 may impinge on the face of the user 110, but it may also impinge on the whole head including hair, the upper part of the body including head neck and shoulders or even the complete body. Alternatively, the light may impinge on any object, for example a leather sample. The reflected light 112 may be recorded by a camera 102 which thereby captures an image of the user 110 illuminated by the projected light. The camera 102 may generate an image in the optical range matching the wavelength emitted by projector 101, for example in the infrared range. The image may be a grayscale image, i.e. each pixel comprises only the total intensity information, or an RGB image, i.e. different pixels indicate the intensity in a particular wavelength. The image may be passed to processor 103. The processor 103 may be a microcontroller, i.e. comprising memory and IO controller functionalities, or it may be a CPU which is connected to memory and IO controllers. The processor 103 may execute program code which determines if the user 110 is an authorized user 110. Such determination may involve vectorizing the image into features. Such feature vector may be compared to a stored template. If the difference between the feature vector and the stored template is below a predefined threshold, the processor may determine that the user 110 in the vehicle is authorized. The processor 103 may further determine if the image really shows a human rather than a spoofing mask. This may be accomplished by classifying the material of the face in the image by evaluating reflection characteristics in the reflected light. If no skin is detected, the processor may determine that the user 110 in front of the transparent display is not authorized. The processor 103 may be communicatively coupled to memory 104. The memory 104 may be transient memory, for example random access memory (RAM), or persistent memory, for example flash memory. The memory 104 may comprise program code configured to determines if the user 110 is an authorized person as well as templates for registered authorized users.

[0077] The processor 103 may generate a signal 105 indicating that the user 110 is authorized. The signal 105 may be forwarded to an access control for unlocking the device, granting access to an application, or effecting a secure payment, for example via a wireless communication interface. Alternatively, the signal may be forwarded to a program, for example a payment app, or to a user interface, for example on the display 106, where the result is shown.

[0078] The material authentication system 100 may comprise a display 106. The display 106 may be transparent for the projected light 111 and the reflected light 112, such that the projector 101 and the camera 102 may be placed behind the display 106. The display 106 may only be transparent at the positions at which the projected light 111 and the reflected light 112 passes the display 106. Transparent may mean that at least 30 % or at least 50 % of the incident light passes through the transparent display 106.

[0079] Figure 2 illustrates an example for preprocessing image data. Pattern image 211 may be obtained from a camera which has recorded a face under illumination of hexagonally patterned infrared light. The pattern image 211 may be cropped into multiple partial images, for example pattern patches 212. A pattern patch 212 may comprise in its center one pattern feature, for example a light spot, and parts of at least some of its next nearest neighbors. The pattern patches 212 may be labelled with the corresponding segment 202 extracted from the flood image 201 or its probability that skin is exposed. The labelled pattern patches 212 may be used as input for a material model, for example for classifying the material for each pattern patch 212.

[0080] Figure 3 illustrates an example of the method for authentication an object. A reference pattern image 301 may originate from an enrollment process in which an authentic object has been illuminated with patterned light, for example with a periodic point pattern of infrared light. The enrollment process may be performed with the material authentication system, so the same hardware is used for both reference pattern image 301 and pattern image 311. Reference pattern image 302 may be used to generate a reference feature vector 302, for example by using an encoder which has been trained to generate feature vectors representing material properties of the object. The encoder may be a convolutional neural network. A pattern image 311 of the object may be received, for example from the camera of the material authentication system. The pattern image 311 may be obtained from the object under illumination with patterned light, preferably under the same illumination as the used to capture the reference pattern image 301. The pattern image 311 may be used to generate a feature vector 312, preferably with the same encoder used to generate reference feature vector 302. A comparison 320 between feature vector 312 and reference feature vector 302 may yield a similarity score 330, for example a float value between 0 and 1 , wherein 0 means completely different and 1 means identical. The similarity score 330 may be used to authenticate the object 340, for example the object may be authenticated if the similarity score 330 is above a certain value, such as 0.9 or higher. Figure 4 illustrates another example of the method for authentication an object. Image data obtained from a camera may comprise a flood image of the object 411 and a pattern image of the object 401 . The flood image 411 may be used to determine region data 412, for example, the flood image 411 may be subject to a segmentation algorithm which may identify contiguous segments or regions of the object. The segmentation algorithm may be an active appearance model or an active shape model. The pattern image 401 may be cropped into partial images 402, for example as described for figure 2. A partial image may be annotated with region data 413, for example a partial image may be located in a segment and hence annotated with the probability that the object exposes the expected material in this segment. A feature vector for each partial image may be generated 403, for example by a material encoder, for example a convolutional neural network. The feature vectors may be compared 405 with reference feature vectors 404. The comparison may yield a set of similarity scores 406, for example for the similarity in each segment or a part of the image. The similarity scores 406 may be used to authenticate the object 406, for example by aggregating the similarity scores. Aggregation may mean an average value or a weight average, for example based on the region data 412, wherein the weight may depend on the region on the object. For example, in case of a face, the cheeks and the forehead may have a higher weight than the chin which may be covered by a beard. The authentication 406 may yield an authentication signal 407 indicating if the object is authenticated. Such authentication signal 407 may be output, for example to an application having requested authentication.

[0081] Figure 5 illustrates an example for a biometric authentication. The biometric authentication system may be a face authentication system which verifies if a face in front of a camera is really the claimed person, so neither a different person nor a spoofing mask. The biometric authentication system may be integrated into a portable device such as a smartphone, or in an access system, for example a door opening system of a building or a vehicle.

[0082] The face of the person may be illuminated with patterned illumination 501. A camera may record a pattern image 502 of the face under patterned illumination. The pattern image 502 may be used to authenticate the material 503 of the face as described for figure 3 and 4. The material authentication may yield a similarity score. If the similarity score is below a threshold, the authentication may be rejected 530. The face may be illuminated with flood light 511, for example shortly before or after illuminating the face with patterned light 501. A camera may record a flood image 512 of the face under flood illumination 511. The flood image 512 may be used to recognize the identity of the person, for example by extracting features of the flood image and compare them with a reference database. If recognition yields an incorrect person, for example a person without access rights, the authentication may rejected 530. If both the correct person is identified and the material authentication yields a similarity score above the threshold, the person may be authenticated 520.

[0083] The present disclosure has been described in conjunction with preferred embodiments and examples as well. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the claims. Any steps presented herein can be performed in any order. The methods disclosed herein are not limited to a specific order of these steps. It is also not required that the different steps are per-formed at a certain place or in a certain computing node of a distributed system, i.e. each of the steps may be performed at different computing nodes using different equipment / data processing.

[0084] As used herein ..determining" also includes ..initiating or causing to determine", "generating" also includes ..initiating and / or causing to generate" and "providing” also includes "initiating or causing to determine, generate, select, send and / or receive”. "Initiating or causing to perform an action” includes any processing signal that triggers a computing node or device to perform the respective action.

[0085] In the claims as well as in the description the word "comprising” does not exclude other elements or steps and the indefinite article "a” or "an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. In the claims as well as in the description the word "comprising” or "including” or similar wording does not exclude other elements or steps and shall not be construed limiting to the elements or steps lined out. The indefinite article "a” or "an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation or further elements may be included.

[0086] Providing in the scope of this disclosure may include any interface configured to provide data. This may include an application programming interface, a human-machine interface such as a display and / or a software module interface. Providing may include communication of data or sub-mission of data to the interface, in particular display to a user or use of the data by the receiving node, entity or interface.

[0087] Various units, circuits, entities, nodes or other computing components may be described as "con-figured to” perform a task or tasks. Configured to shall recite structure meaning "having circuitry that” performs the task or tasks on operation. The units, circuits, entities, nodes or other computing components can be configured to perform the task even when the unit / circuit / component is not operating. The units, circuits, entities, nodes or other computing components that form the structure corresponding to "configured to” may include hardware circuits and / or memory storing program instructions executable to implement the operation. The units, circuits, entities, nodes or other computing components may be described as performing a task or tasks, for convenience in the description. Such descriptions shall be interpreted as including the phrase "configured to.” Any recitation of "configured to” is expressly intended not to invoke 35 U.S.C. § 112(f) interpretation. In general, the methods, apparatuses, systems, computer elements, nodes or other computing components described herein may include memory, software components and hardware components. The memory can include volatile memory such as static or dynamic random-access memory and / or nonvolatile memory such as optical or magnetic disk storage, flash memory, programmable read-only memories, etc. The hardware components may include any combination of combinatorial logic circuitry, clocked storage devices such as flops, registers, latches, etc., finite state machines, memory such as static random-access memory or embedded dynamic random-access memory, custom designed circuitry, programmable logic arrays, etc.

[0088] Any disclosure and embodiments described herein relate to the methods, the systems, apparatuses, devices, chemi- cals, materials, computer program elements lined out above and vice versa. Advantageously, the benefits provided by any of the embodiments and examples equally apply to all other embodiments and examples and vice versa. All terms and definitions used herein are understood broadly and have their general meaning.

Claims

Claims1 . A material authentication system comprising: a. an input configured to receive image data comprising a pattern image of an object under patterned illumination, b. a processor configured to generate a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, comparing the feature vector with a reference obtained from an enrollment process and authenticating the object using the comparison result.

2. The material authentication system according to claim 1 , wherein the feature vector contains one or more values which correlate with at least one of reflectance, absorbance, transmittance, refractive index, scattering, polarization, gloss, surface roughness, optical anisotropy, penetration depth, diffuse or specular reflectivity, or translucence of the object.

3. The material authentication system according to claim 1 or 2, wherein the object is a human face.

4. The material authentication system according to any of the claims 1 to 3, wherein the processor is configured to determine the identity of the object from the image data.

5. The material authentication system according to any of the claims 1 to 4, wherein the material authentication system is integrated into a portable computing device.

6. The material authentication system according to any of the claims 1 to 5, wherein the pattern is a periodic dot pattern.

7. The material authentication system according to any of the claims 1 to 6, wherein the material authentication system comprises a projector emitting light with a wavelength in the range of 760 nm to 1000 pm.

8. The material authentication system according to any of the claims 1 to 7, wherein the material authentication system comprises a projector and a camera positioned behind a transparent display.

9. Use of the material authentication system according to any of the claims 1 to 8 for controlling access to a mobile computing device.

10. A method for authentication an object comprising: a. receiving image data comprising a pattern image of the object under patterned illumination,b. generating a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, c. comparing the feature vector with a reference obtained from an enrollment process, and d. authenticating the object using the comparison result.

11. The method according to claim 10, wherein the pattern image is cropped into partial images and wherein a feature vector is generated for each partial image.

12. The method according to claim 10 or 11, wherein the image data further comprises a flood image of the object under flood illumination, wherein region data is determined from the flood image, wherein region data refers to data indicative for the probability that the object exposes its expected material in a region of the image, and wherein region data is used for authentication.

13. The method according to any of the claims 10 to 12, wherein an authentication signal is output based on the object authentication, wherein the authentication signal is indicative whether the object is identified or not.

14. The method according to any of the claims 10 to 13, wherein the method is executed in response to receiving a request for access to a device or application.

15. A non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform a method comprising: a. receiving image data comprising a pattern image of an object under patterned illumination, b. generating a feature vector from the image data, wherein the feature vector represents one or more than one material property of the object, c. comparing the feature vector with a reference obtained from an enrollment process and d. authenticating the object using the comparison result.

Images