Ultrasonic capture device including a protective film

Abstract

Ultrasonic capture device comprising a protective film. This description relates to an ultrasonic capture device (100) comprising at least one capture surface (102) configured so that at least one element is disposed upon it during capture by the ultrasonic capture device (100), and comprising a film (108) movable in the plane of the capture surface (102) such that a portion of the film (108) protected in a housing (104) of the ultrasonic capture device (100) prior to capture can be moved to form the capture surface (102) during capture. Figure for the abstract: Fig. 1

Description

Title of the invention: Ultrasonic capture device comprising a protective film. Technical field

[0001] This description relates generally to the field of capture devices based on reading and measuring information by ultrasonic transduction, finding applications for example in the fields of biometric identification, medicine, non-destructive testing, or even in other technical fields such as consumer fields. Previous technique

[0002] A biometric identification device is used to verify or determine the identity of a user of the device based on a measurement of at least one biometric characteristic of the user, such as a fingerprint, facial shape, iris pattern, retinal pattern, etc. The various techniques for measuring one or another of these characteristics each have advantages and disadvantages according to different criteria, including: error rate (more or less significant), ease or difficulty of stealing the template with which the measurements are compared, possibility of detecting a forgery, proof or not of life, ease and comfort of use, size of the sensor required, energy consumption required, etc.

[0003] In the case of a biometric identification device by ultrasonic transduction in which the measurement of a biometric characteristic involves contact between the device and the user, there arises the problem of possible contamination, cleanliness, and also the protection of the capture surface of the device on which the contact must be made.

[0004] These problems are also found in capture devices other than biometric identification devices, for example in the medical field, non-destructive testing, or other technical fields. Summary of the invention

[0005] There is a need to propose an ultrasonic capture device, or ultrasonic transduction capture device, which does not present at least some of the disadvantages of existing solutions.

[0006] An embodiment overcomes all or part of the drawbacks of known solutions and proposes an ultrasonic capture device comprising at least one capture surface configured so that at least one element is disposed on it during capture by the ultrasonic capture device, and comprising a movable film in the plane of the capture surface such that a portion of the film protected in a housing of the ultrasonic capture device prior to capture can be moved to form the capture surface during capture.

[0007] According to a particular embodiment, the film has a stripe form.

[0008] According to a particular embodiment, the ultrasonic capture device It also includes rollers arranged in the housing of the ultrasonic capture device and configured to move the film lengthwise prior to capture.

[0009] According to a particular embodiment, the rollers are configured to move the film as it unwinds from a first of the rollers and as it winds around a second of the rollers.

[0010] According to a particular embodiment, the rollers are configured to move the film as it unwinds from a first roller and winds around a second roller prior to capture, and as it unwinds from the second roller and winds around the first roller after capture.

[0011] According to a particular embodiment, the film forms a belt configured to be set in motion by the rollers.

[0012] According to a particular embodiment, the film comprises at least a first portion configured to form the capture surface during capture, and at least a second protective portion configured to take the place of the first portion after capture, and in which the first portion is protected in the housing after capture.

[0013] According to a particular embodiment, the film comprises several first portions and several second protective portions arranged alternately next to each other.

[0014] According to a particular embodiment, the ultrasonic capture device further comprises an ultrasonic transducer circuit and an acoustic coupling element disposed between the ultrasonic transducer circuit and the capture surface.

[0015] According to a particular embodiment, the acoustic coupling element comprises a liquid and / or a gel.

[0016] According to a particular embodiment, at least one face of the film intended to form the capture surface is pre-coated with lubricant.

[0017] According to a particular embodiment, the ultrasonic capture device further comprises at least one reservoir configured to store a lubricant and communicating with the capture surface such that the lubricant can be dispensed onto the capture surface through the film.

[0018] According to a particular embodiment, the ultrasonic capture device further comprises a lubricant storage compartment and / or a coating device lubricants configured to apply lubricant to at least one face of the film intended to form the capture surface when the portion of the film protected in the housing is moved to form the capture surface.

[0019] According to a particular embodiment, the ultrasonic capture device is configured to detect the presence of the element near the capture surface and to control the movement of the portion of the film protected in the housing when the element is detected near the capture surface.

[0020] According to a particular embodiment, the ultrasonic capture device corresponds to a biometric identification device configured to implement biometric identification from a part of a user's body intended to be placed on the capture surface. Brief description of the drawings

[0021] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0022] - Figure 1 schematically represents an ultrasonic capture device according to a first embodiment;

[0023] - Figure 2 schematically represents an ultrasonic capture device according to a first variant of the first embodiment;

[0024] - Figure 3 schematically represents an ultrasonic capture device according to a second variant of the first embodiment;

[0025] - Figure 4 schematically represents a lubricant coating device ultrasonic capture device;

[0026] - Figure 5 schematically represents an ultrasonic capture device according to a second embodiment;

[0027] - Figure 6 schematically represents an ultrasonic capture device according to a third embodiment;

[0028] - Figure 7 represents different positions of a protective film on a device ultrasonic capture according to a variant of the first embodiment. Description of the implementation methods

[0029] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0030] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, various elements (ultrasonic transducer circuit, moving film actuator, detector of The presence of an element near the capture surface, etc., and the various steps involved (image acquisition, image processing, minutiae determination, calculations performed, etc.) are not detailed. A person skilled in the art will be able to perform these steps in detail based on the functional description provided here.

[0031] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0032] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures in a normal position of use.

[0033] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0034] Throughout this document, the term "vasculature" is used interchangeably to refer to blood vessels or micro-blood vessels, of the artery and / or vein type, and is used as a synonym for the term "microvasculature".

[0035] An ultrasonic capture device 100 according to a first embodiment is described below in relation to [Fig.1].

[0036] In the various embodiments described below, the device 100 is configured to implement biometric identification by one or more measurements of at least one biometric characteristic of a part of the user's body. Furthermore, in the examples described below, this part of the user's body corresponds to a single finger of the user. Alternatively, several fingers of the user or other parts of the user's body can be used to perform biometric identification by the device 100.

[0037] The device 100 includes a capture surface 102 on which the finger of the user of the device 100 is intended to be placed during biometric identification.

[0038] The device 100 also includes a housing 104 in which various elements of the device 100 are arranged. In the embodiment shown in [Fig.1], the capture surface 102 is arranged at the level of an upper face 106 of the housing 104.

[0039] The device 100 further comprises a film, or a thin layer, 108, a portion of which forms the capture surface 102 during a measurement by the device 100. For example, the film 108 may comprise one or more of the following materials: polyethylene, polyethylene terephthalate (PET), polyolefin, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polybutadiene. Generally, the film 108 may comprise a single layer of a single material, or a stack of several materials. The thickness of the film 108 is, for example, between 20 µm and 150 µm. In the described embodiment, the film 108 is strip-shaped, that is, it is in the form of a film whose length is much greater than its width. Alternatively, the film 108 may have a shape other than a strip.In the described embodiment, the portion of the film 108 forming the capture surface 102 is accessible to the user through an opening 109 formed through the upper face 106 of the housing 104. Other configurations of the film 108 and the housing 104 are conceivable.

[0040] In the first embodiment as described here, the device 100 includes rollers arranged in the case 104 and configured to move the film 108 lengthwise prior to the implementation of a capture by the device 100. More particularly, in the first embodiment, the device 100 includes a first roller 110 and a second roller 112 configured to move the film 108 such that, when different captures are implemented, the film 108 unwinds from the first roller 110 and winds around the second roller 112.

[0041] At least one of the rollers 110, 112 can be motorized to allow the movement of the film 108. According to a first example, one of the rollers 110, 112 can be motorized and the other roller can include a mechanism applying a tensile force to the film 108. In this case, it is the rotation of the motorized roller combined with the tensile force of the other roller that allows the film 108 to unwind from the first roller 110, its movement in the plane of the capture surface 102, the maintenance of its tension and its winding around the second roller 112. According to a second example, both rollers 110, 112 can be motorized.

[0042] In the embodiment shown in [Fig.1], the device 100 also includes guides 114 (for example cylindrical as in [Fig.1]) allowing a portion of the film 108 to be held at the level of the upper face 106 of the housing 104. Thus, the film 108 is mobile in the plane of the capture surface 102, and a portion of the film 108 held at the level of the upper face 106 of the housing 104 forms the capture surface 102.

[0043] The device 100 further comprises at least one ultrasonic transducer circuit 116 configured to transmit and receive ultrasonic signals during the captures implemented by the device 100. In the embodiment shown on [Fig. 1], the part of the film 108 located opposite the circuit 116 forms the capture surface 102.

[0044] The circuit 116 may include a plurality of ultrasonic transducers configured to perform the image acquisitions required for biometric identification. The ultrasonic transducers are, for example, arranged in a matrix or in another manner adapted to the captures to be performed. The number of ultrasonic transducers in the circuit 116 may depend on the dimensions of the capture surface 102, the dimensions of each ultrasonic transducer, the resolution of the measurements intended to be performed by the device 100, etc. The circuit 116 may, for example, include CMUT (Capacitive Micromachined Ultrasonic Transducer) or PMUT (Piezoelectric Micromachined Ultrasonic Transducer) type transducers, or transducers of another type.

[0045] In the embodiment shown in [Fig. 1], the device 100 also includes an acoustic coupling element 118 disposed between the circuit 116 and the capture surface 102. For example, this acoustic coupling element 118 may comprise a liquid or a gel disposed in a cavity interposed between the circuit 116 and the capture surface 102. Such an element corresponds, for example, to water, an aqueous solution, or an aqueous gel, this element having in this case the advantage of exhibiting an acoustic velocity and impedance values ​​close to those of the biological tissues of the finger. Alternatively, a different acoustic coupling element 118 may be used and interposed between the circuit 116 and the capture surface 102.

[0046] The characteristics of the acoustic coupling element 118 can be such that they give it good acoustic properties to ensure good acoustic coupling (i.e., low attenuation in the transmission of acoustic waves) between the capture surface 102 and the circuit 116. Such acoustic coupling can be achieved by ensuring good acoustic impedance matching either between the circuit 116 and the target (the target corresponding to the user's finger in the example described), or between the circuit 116 and the acoustic impedance value with Za and Zb corresponding respectively to the acoustic impedances of circuit 116 and the target.

[0047] In the first embodiment described, most of the film 108 is initially wound around the first roller 110, and one end of the film 108 is attached to the second roller 112. Prior to a capture by the device 100, in particular before the emission of ultrasound by the circuit 116 and before the user's finger is placed against the capture surface 102, a displacement of the film 108 is triggered by the movement of the rollers 110, 112. so that the capture surface 102 is, at that moment, formed by a portion of the film 108 that was protected in the casing 104. Thus, this portion of the film 108 forming the capture surface 102 is free from any contamination to which the device 100 might have been exposed prior to this capture. This replacement of the portion of the film 108 present above the circuit 106, prior to the capture, with a "clean," or uncontaminated, portion of the film 108 can be performed for each capture, or after a certain number of captures made by the device 100 using the same portion of the film 108.

[0048] Furthermore, in the embodiment shown in [Fig. 1], at least one face of the film 108, which is intended to form the capture surface 102, is pre-coated with lubricant. Thus, replacing the portion of the film 108 forming the capture surface 102 obtained by partially unwinding the film 108 allows the lubricant to be renewed on the capture surface 102.

[0049] In a first embodiment, the device 100 may include at least one reservoir configured to store a lubricant and communicating with the capture surface 102 such that the lubricant can be dispensed onto the capture surface 102 through the film 108. For example, considering the configuration shown in [Fig. 1], the acoustic coupling element 118 may form this lubricant reservoir, for example, when the acoustic coupling element 118 comprises hydrogel, and the lubricant passes through the film 108 via pores and / or holes present in the film 108. For example, lubricant may pass through the film 108 when the user's finger is positioned on the capture surface 102, due to the pressure applied by the finger on the portion of the film 108 forming the capture surface 102.According to another configuration, the lubricant reservoir can be formed by one or more separate elements of the acoustic coupling element 118. In addition, the device 100 can include an actuator, for example a micropump, configured to control the extraction of the lubricant from the reservoir to the capture surface 102. Other types of actuator are possible.

[0050] In a second embodiment, the device 100 may include a lubricant storage compartment 120, or reservoir, configured to apply the lubricant at least to the face of the film 108 intended to form the capture surface 102 when the portion of the film 108 protected in the housing 104 is moved to form the capture surface 102. Figure 2 shows an example of an embodiment of the device 100 according to this second embodiment, the compartment 120 forming a lubricant bath in which the film 108 circulates before forming the capture surface 102. The thickness of liquid obtained on the film 108 after its circulation in the lubricant bath depends in particular on the viscosity of the lubricant and the surface tensions, or "wetting", of the film 108 and the lubricant. In this Alternatively, the application of the lubricating liquid to the film 108 corresponds to a dip coating process also known as "dip coating" in English.

[0051] In both variants above, the quantity of lubricant present in compartment 120 can be much greater than that dispensed on the capture surface 102 prior to each capture, which makes it possible to dispense lubricant many times on the capture surface 102 before the reservoir or compartment 120 is empty.

[0052] In a third embodiment, the device 100 may include a lubricant coating or dispensing device 122, configured to apply the lubricant at least to the face of the film 108 intended to form the capture surface 102 when the portion of the film 108 protected in the housing 104 is moved to form the capture surface 102. Figure 3 schematically represents an example of an embodiment of the device 100 according to this third embodiment, and Figure 4 represents in more detail an example of an embodiment of the lubricant coating device 122.

[0053] The different embodiment variants described above are not mutually exclusive and can be combined within the same device 100. In all cases, upon contact with the finger, the lubricant present on the capture surface 102 spreads and forms an interface improving the acoustic coupling between the finger and the capture surface 102.

[0054] Furthermore, in the various examples described above, the lubricant may correspond to a gel including a liquid ensuring the lubrication function, this liquid corresponding for example to water in the case of a hydrogel.

[0055] In this first embodiment, when the film 108 is fully unwound from the first roll 110, this film 108 can be replaced by another film which is again initially wound around the first roll 110. Alternatively, it is possible for the existing film 108 to be treated and / or cleaned and then repositioned so that it is wound again around the first roll 110 in its initial configuration.

[0056] In the embodiments described above, the film 108 is unwound from the first roll 110 and wound around the second roll 112 as the captures are made. Alternatively, the film 108 may be unwound from the second roll 112 and wound around the first roll as the captures are made.

[0057] An ultrasonic capture device 100 according to a second embodiment is described below in relation to [Fig.5].

[0058] Device 100 according to this second embodiment comprises all the elements of device 100 according to the first embodiment described above. However, unlike the first embodiment in which the rollers 110, 112 are configured to move the film 108, as captures are made by the device 100, as it unwinds from the first roller 110 and winds around the second roller 112, the rollers 110, 112 are configured, in this second embodiment, to move the film 108 as it unwinds from the first roller 110 and winds around the second roller 112 prior to capture, and as it unwinds from the second roller 112 and winds around the first roller 110 after capture.In another configuration of this second embodiment, the rollers 110, 112 can be configured to move the film 108 as it unwinds from the second roller 112 and winds around the first roller 110 prior to capture, and as it unwinds from the first roller 110 and winds around the second roller 112 after capture.

[0059] Furthermore, in the described embodiment, the film 108 comprises at least a first portion 124 configured to form the capture surface 102 during capture, and at least a second protective portion 126 configured to take the place of the first portion 124 after capture. Moreover, after capture, the first portion 124 is protected within the housing 104. In [Fig. 5], the film 108 comprises two first portions 124 between which a second protective portion 126 is arranged.

[0060] In [Fig. 5], the film 108 is shown in a position corresponding to a resting, or standby, configuration of the device 100, that is, a configuration in which no capture is performed. In this resting configuration, the second protective portion 126 is positioned opposite the circuit 116, and the first portion(s) 124 are protected within the housing 104. During a capture by the device 100, the rollers 110, 112 are actuated so that one of the first portions 124 is positioned opposite the circuit 116 and forms the capture surface 102. Thus, in this second embodiment, the first portion(s) 124 of the film 108 are exposed outside the housing 104 only when a capture is performed. In the example of [Fig.5] in which the film 108 comprises two first portions 124, they can alternatively be arranged opposite the circuit 116 to form the capture surface 102 at each capture implemented by the device 100. .

[0061] As an alternative to the embodiment described above, the film 108 may comprise a different number of first portions 124 and / or second portions 126.

[0062] As in the first embodiment, the faces of the first portions 124 of the film 108 intended to form the capture surface 102 can be pre-coated with lubricant. The embodiment variants previously described in connection with the first embodiment (reservoir configured to store a lubricant and communicating with the capture surface 102 through the film 108, lubricant storage compartment 120, lubricant coating device 122) can also be applied to this second embodiment.

[0063] An ultrasonic capture device 100 according to a third embodiment is described below in relation to [Fig.6].

[0064] The device 100 according to this third embodiment comprises all the elements of the device 100 according to the second embodiment described above. However, in this third embodiment, the film 108 forms a belt configured to be set in motion by the rollers 110, 112. In this configuration, it is possible for the rollers 110, 112 to be configured to move the film 108 in one direction and / or the other (for example, clockwise and / or counterclockwise, considering the view in [Fig. 6]).

[0065] Furthermore, in the described embodiment, the film 108 comprises several first portions 124 (two in the example in [Fig. 6]) configured to form the capture surface 102 during capture by the device 100, and several second protective portions 126 (two in the example in [Fig. 6]) configured to replace one of the first portions 124 after capture. Moreover, after capture, the first portions 124 are protected within the housing 104, and one of the second protective portions 126 is positioned opposite the circuit 116.

[0066] In [Fig. 6], the film 108 is in a position corresponding to a resting configuration during which no capture is performed, and in which one of the second protective portions 126 is positioned opposite the circuit 116. During a capture by the device 100, the rollers 110, 112 are actuated so that one of the first portions 124 is positioned opposite the circuit 116 and forms the capture surface 102. Thus, in this third embodiment and as in the second embodiment, the first portions 124 of the film 108 are only exposed outside the housing 104 when the captures are carried out.

[0067] As in the previous embodiments, the faces of the first portions 124 of the film 108 intended to form the capture surface 102 can be pre-coated with lubricant. The embodiment variants previously described in connection with the first embodiment (reservoir configured to store a lubricant and communicating with the capture surface 102 through the film 108, lubricant storage compartment 120, lubricant coating device 122) can also be applied to this third embodiment.

[0068] As an alternative to the embodiment described above, the film 108 may comprise a different number of first portions 124 and / or second portions 126.

[0069] In the configuration described in relation to [Fig. 6], the film 108 comprises several first portions 124 and several second protective portions 126 arranged alternately next to each other. Such a film 108 can be used in the device 100 according to the first and / or second embodiment.

[0070] Figure 7 schematically represents different positions of the film 108 with respect to the circuit 116 when this film 108, comprising several first portions 124 and several second protective portions 126 arranged alternately next to each other, is used in the device 100 according to the first embodiment. View a) of Figure 7 corresponds to the position of the film 108 during a first capture, during which one of the first portions 124 forms the capture surface 102.

[0071] After the first capture, the film 108 is set in motion (symbolized by arrows on [Fig.7]) so that one of the second protective portions 126 adjacent to the first portion 124 forming the capture surface 102 is positioned above the circuit 116. View c) of [Fig.7] represents the configuration obtained after this movement, and view b) corresponds to an intermediate position through which the film 108 passes during this movement.

[0072] Then, prior to the implementation of a second capture, the film 108 is set in motion so that the first portion 124 adjacent to the second protective portion 126 positioned above the circuit 116 and which has not yet served as a capture surface 102 is positioned above the circuit 116 and forms the capture surface 102. View d) of [Fig.7] corresponds to the position of the film 108 during this second capture.

[0073] In all the modes and embodiments described, the device 100 can be configured to acquire at least one surface image of the user's finger placed on and in contact with the capture surface 102, i.e., to acquire at least one image of a fingerprint of the finger, formed of ridges and valleys present on the surface of the skin of the finger placed on the capture surface 102. In the device 100, the acquisition of a surface image of the user's finger placed on and in contact with the capture surface 102 is possible because the ultrasound emitted by the circuit 116 through the film 108 is reflected more significantly against the air present in the valleys of the finger than against the ridges.The difference between the signals received by circuit 116 that were reflected off the valleys and those that were reflected off the ridges can be exploited to reconstruct the image of the fingerprint of the user's finger present on the capture surface 102.

[0074] In addition, the device 100 can also be configured to acquire volume or depth information of the finger placed on the surface of capture 102 of device 100 and in contact with it, and from which it is possible, for example, to determine, by processing this volume information, global information on the vasculature of the finger, for example a global volume image of the vasculature of this finger, that is to say a capture of images of the blood vessels of the finger of the user of device 100. According to a particular example, the acquired volume information can correspond to volume, or depth, images of the finger placed on the capture surface 102. The global volume information obtained can be deduced from several volume information successively captured at non-zero depths (dimension substantially perpendicular to the capture surface 102) of the finger present on the capture surface 102.

[0075] Alternatively, it is possible that the device 100 is configured to perform only one of the two types of acquisition described above.

[0076] In the various examples and embodiments, the movement of the film 108 can be triggered by a preliminary detection to determine whether a finger is positioned near the upper face 106 of the housing 104. According to a first example, this detection can be achieved by the emission / reception of ultrasonic signals by the circuit 116 (only some of the detectors of the circuit 116 can be used to perform this detection). According to a second example, this detection can be achieved by a sensor (not visible in the figures) configured to detect the presence of the user's finger near the upper face 106 of the housing 104 and to trigger the movement of the film 108 when the user's finger is detected near this face 106.

[0077] The device 100 includes other elements which are not described in detail in this description, such as a control circuit for controlling the rollers 110, 112, a data processing circuit, etc., and which can be implemented from the general knowledge of a person skilled in the art.

[0078] Device 100 can implement additional functions to those previously described, such as a contribution to the detection of living things from the information captured.

[0079] In the various embodiments, the device 100 allows the user to have a clean and lubricated capture surface 102 when necessary. It also reduces the degradation over time of the film 108 due to its exposure to the ambient atmosphere, such as drying out, the presence of dust or contaminating particles, the effects of UV rays, etc. In addition, the second portions 126 can also have a decorative function.

[0080] In the different configurations, the possible lubrication of the film 108 allows the coupling between the element to be captured and the ultrasonic transducer circuit 116 to be optimized, and this without user intervention.

[0081] Furthermore, in the various embodiments described above, the tension and rigidity of the film 108 obtained make it possible to control the relative position of the finger with respect to the ultrasonic transducer circuit 116, in particular its distance from the circuit 116 in the direction perpendicular to the capture surface 102, as well as the shape of the contact obtained between the finger and the capture surface 102 in the plane of the capture surface 102. In addition, the tension and rigidity of the film 108 impart a reaction force when the finger is brought into contact with the capture surface 102, which makes it possible to obtain a slight compression of the biological tissues of the finger, facilitating, for example, the implementation of anti-hacking countermeasures such as a proof-of-life detection.

[0082] In the various embodiments described above, the ultrasonic capture device 100 corresponds to a biometric identification device. Alternatively, these various examples and embodiments can be applied to a device 100 performing ultrasonic capture that does not correspond to biometric identification, such as capture for medical purposes or for non-destructive testing of an object. In this case, the element intended to be placed on the capture surface of the device may correspond to something other than a part of the user's body, for example, a surface to be inspected by ultrasonic measurement.

[0083] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0084] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Ultrasonic capture device (100) comprising at least one capture surface (102) configured so that at least one element is disposed thereon during capture by the ultrasonic capture device (100), and comprising a film (108) movable in the plane of the capture surface (102) such that a portion of the film (108) protected in a housing (104) of the ultrasonic capture device (100) prior to capture can be moved to form the capture surface (102) during capture.

2. Ultrasonic capture device (100) according to claim 1, wherein the film (108) has a strip shape.

3. Ultrasonic capture device (100) according to claim 2, further comprising rollers (110, 112) arranged in the housing (104) of the ultrasonic capture device (100) and configured to move the film (108) lengthwise prior to capture.

4. Ultrasonic capture device (100) according to claim 3, wherein the rollers (110, 112) are configured to move the film (108) as it unwinds from a first of the rollers (110) and wraps around a second of the rollers (112).

5. Ultrasonic capture device (100) according to claim 3, wherein the rollers (110, 112) are configured to move the film (108) such that it unwinds from a first of the rollers (110, 112) and winds around a second of the rollers (110, 112) prior to capture, and such that it unwinds from the second of the rollers (110, 112) and winds around the first of the rollers (110, 112) after capture.

6. Ultrasonic capture device (100) according to claim 3, wherein the film (108) forms a belt configured to be set in motion by the rollers (110, 112).

7. Ultrasonic capture device (100) according to any one of the preceding claims, wherein the film (108) comprises at least a first portion (124) configured to form the capture surface (102) during capture, and at least a second protective portion (126) configured to take the place of the first portion (124) after capture, and wherein the first portion (124) is protected in the housing (104) after capture.

8. Ultrasonic capture device (100) according to claim 7, wherein the film (108) comprises several first portions (124) and several second protective portions (126) arranged alternately next to each other.

9. Ultrasonic capture device (100) according to any one of the preceding claims, further comprising an ultrasonic transducer circuit (116) and an acoustic coupling element (118) disposed between the ultrasonic transducer circuit (116) and the capture surface (102).

10. Ultrasonic capture device (100) according to claim 9, wherein the acoustic coupling element (118) comprises a liquid and / or a gel.

11. Ultrasonic capture device (100) according to any one of the preceding claims, wherein at least one face of the film (108) intended to form the capture surface (102) is pre-coated with lubricant.

12. Ultrasonic capture device (100) according to any one of the preceding claims, further comprising at least one reservoir configured to store a lubricant and communicating with the capture surface (102) such that the lubricant can be dispensed onto the capture surface (102) through the film (108).

13. Ultrasonic capture device (100) according to any one of the preceding claims, further comprising a lubricant storage compartment (120) and / or a lubricant coating device (122) configured to apply the lubricant to at least one face of the film (108) intended to form the capture surface (102) when the portion of the film (108) protected in the housing (104) is moved to form the capture surface (102).

14. Ultrasonic capture device (100) according to any one of the preceding claims, configured to detect the presence of the element near the capture surface (102) and to control the movement of the portion of the film (108) protected in the housing (104) when the element is detected near the capture surface (102).

15. Ultrasonic capture device (100) according to any one of the preceding claims, corresponding to a biometric identification device configured to implement identification biometric from a part of a user's body intended to be placed on the capture surface (102).

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