Device for cleaning an optical surface

Abstract

Device for cleaning an optical surface. Device (5) comprising: - an optical surface (10), - a cleaning unit (15) for the optical surface comprising at least one wave transducer (70) acoustically coupled to the optical surface, the wave transducer comprising a piezoelectric layer (80) and electrodes (85) of opposite polarity in contact with the piezoelectric layer, and being configured to generate at least one ultrasonic surface wave (WS) or a Lamb wave (WL) propagating in the optical surface, - the optical surface having at least one region of optical interest (100) not superimposed on the wave transducer, the device comprising an apparatus (20) configured to capture and / or emit radiation (R) through the region of optical interest (100). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Device for cleaning an optical surface

[0001] The present invention relates to a device for cleaning a body in contact with an optical surface by means of ultrasonic waves.

[0002] In various fields, it is necessary to overcome the effects related to the accumulation of a body, in particular raindrops, frost or snow, on an optical surface.

[0003] It is known to rotate drops of a liquid to remove them from a surface. However, such a technique is not suitable for surfaces with an area greater than a few square centimeters.

[0004] The application of an electric field to control the hydrophobicity of a surface is also known, for example from KR 2018 0086173 AL. This technique, known by the acronym EWOD (for "Electro Wetting On Devices"), consists of applying a potential difference between two electrodes, so as to electrically polarize the surface and thus change its wetting properties. By controlling the location of the polarization, the droplet can then be moved. However, this technique can only be implemented with specific materials and requires particularly precise positioning of the electrodes over the entire surface where the wetting properties are to be controlled.

[0005] It is also well known to apply mechanical force to the liquid, for example by means of a windshield wiper on a motor vehicle's windshield. However, a windshield wiper limits the driver's field of vision. It also spreads the greasy particles deposited on the surface of the windshield. In addition, the wiper blades need to be replaced regularly.

[0006] Furthermore, autonomous vehicles have a large number of sensors to determine the distances and speeds of other vehicles on the road. Such sensors, for example lidars, are also subject to weathering and mud spray and require frequent cleaning. However, a windshield wiper is unsuitable for cleaning the small surface area of ​​such a sensor. In addition, these sensors need to be compact for easy integration into the vehicle. US 2016 / 0170203 A1 describes a device for cleaning a vehicle-mounted camera using ultrasonic waves.

[0007] There is always a need for a device that allows a body, especially a liquid, to be efficiently evacuated from an optical surface.

[0008] The invention aims to satisfy this need and proposes a device comprising: - an optical surface, - an optical surface cleaning unit comprising at least one transducer acoustically coupled wave transducer with the optical surface, comprising a piezoelectric layer and electrodes of opposite polarity in contact with the piezoelectric layer, and configured to generate at least one surface ultrasonic wave or a Lamb wave propagating in the optical surface, - the optical surface having at least one region of optical interest not superimposed on the wave transducer, the device comprising an apparatus configured to capture and / or emit radiation through the region of optical interest.

[0009] The device according to the invention thus makes it possible to efficiently clean the optical surface by means of the propagation of the ultrasonic surface wave, in such a way that a body, for example a raindrop, in contact with the optical surface does not prevent an efficient transmission of radiation through the optical surface.

[0010] Preferably, the transducer is located outside the optical field of the device. This limits the potential shadowing effects that the transducer can cause on the device. The capture and / or emission of radiation through the optical surface is optimized. The term "optical field" refers to the portion of space in the direction in which the device is capable of emitting radiation and / or from which it is capable of receiving radiation.

[0011] The radiation can be light radiation in the visible and / or infrared and / or ultraviolet range.

[0012] The device may include a processing unit configured to analyze, from all the radiation captured by the device, only the portion that has passed through the region of optical interest. In particular, such an analysis unit is adapted in a variant in which all or part of the transducer is contained within the optical field of the device.

[0013] Preferably, the transducer is located at the periphery of the optical surface. In this way, in addition to its minimal interaction with the operation of the device, the transducer can be easily protected, for example by a support bearing the optical surface.

[0014] Preferably, the wave transducer extends from an edge of the optical surface over a distance of less than 10%, or even less than 5%, of the length of the optical surface. "Length of the optical surface" means the distance between two opposite edges of the optical surface along one face of the optical surface.

[0015] Preferably, the transducer extends from an edge of the optical surface over a distance of less than 30 mm, preferably less than 20 mm, preferably less than 10 mm.

[0016] The transducer is preferably in contact with the optical surface.

[0017] The transducer can be fixed to the optical surface in different ways.

[0018] In particular, the transducer may be in the form of a foil that is transferred onto the optical surface. By "foil" is meant a flexible and thin film, in particular having a thickness of less than 100 pm.

[0019] It can be bonded to the optical surface, in particular by means of a polymer adhesive which also acoustically couples the transducer to the optical surface. The adhesive can be cross-linkable by illumination with ultraviolet radiation. It is, for example, an epoxy resin. The transducer can be fixed by molecular adhesion, or by means of a thin metallic layer ensuring adhesion between the optical surface and the piezoelectric layer. The layer can be made of a metal or alloy with a low melting point, i.e., having a melting point below 200 °C, for example, an indium alloy. Alternatively, the metallic layer can be made of a metal or alloy having a melting point above 200 °C, for example, an aluminum and / or gold alloy.

[0020] An example of attachment by molecular adhesion is described in "Glass-on-LiNbO 3 heterostructure formed via a two-step plasma activated low-temperature direct bonding method", J. Xu et al., Applied Surface Science 459 (2018) 621-629, doi: 10.1016 / j.apsusc.2018.08.031. According to another embodiment, the transducer can be attached to the optical surface by means of a process comprising a step of melting a portion of the piezoelectric layer and / or a portion of the optical surface followed by a step of compressing together the piezoelectric layer and the optical surface, the respective molten portions of the optical surface and the piezoelectric layer being in contact with each other.According to another variant, the transducer can be fixed to the optical surface by means of a process comprising the deposition of bonding layers of a low-melting-point alloy on a portion of the transducer and on a portion of the optical surface respectively, the at least partial melting of said bonding layers, and then the compression of the piezoelectric layer and the optical surface, the faces of the bonding layers opposite the optical surface and the piezoelectric layer being brought into contact with each other during the compression. The bonding layers can be deposited by sputtering, or by an evaporation technique implemented in the field of thin-film deposition.

[0021] The transducer can be positioned between the optical surface and the device. In this way, the transducer can be protected by the optical surface from weathering and / or splashes. Preferably, the transducer is then configured to generate a Lamb wave so as to reach the face opposite the device and against which a body, for example a raindrop, can be deposited.

[0022] In one embodiment, the optical surface can be arranged between the transducer and The device. Preferably, the transducer is then in contact with the face of the optical surface opposite the device. It can be configured to emit an ultrasonic surface wave propagating along this face. In particular, the device may include a cover superimposed on the transducer and shaped to define a protective housing for the transducer.

[0023] Preferably, the piezoelectric layer has the form of a band extending over one face of the optical surface. Preferably, the band extends along and preferably parallel to an edge of the optical surface.

[0024] In particular, the piezoelectric layer can form a frame surrounding at least partially, and in particular entirely, the region of optical interest. The outer contour and / or the inner contour of the frame can be homothetic to the contour of the face of the optical surface on which the piezoelectric layer is disposed.

[0025] The piezoelectric layer can have a thickness of between 1 pm and 100 pm. It can have a thickness of less than 50 pm, or even less than 10 pm.

[0026] The ratio of the thickness of the optical surface to the thickness of the piezoelectric layer is preferably greater than 2, preferably greater than 10, or even greater than 50.

[0027] It can be deposited on the optical surface by a process selected from physical vapor deposition, chemical vapor deposition, magnetron sputtering and electron cyclotron resonance.

[0028] The piezoelectric layer can be made of a material selected from the group formed by lithium niobate, aluminum nitride, zinc oxide, lead titano-zircanate, and mixtures thereof.

[0029] The piezoelectric layer can be opaque to light. In one variant, it can be transparent.

[0030] By "transparent" is meant transparency to light radiation in the visible and / or to radiation in the infrared and / or to radiation in the ultraviolet.

[0031] The electrodes are of opposite polarity, that is to say they are intended to be electrically supplied by electrical voltages of opposite signs.

[0032] Each polarity electrode may include a comb having a branch from which fingers extend. Preferably, the combs are interdigitated.

[0033] Each finger of a comb can have a width equal to the fundamental wavelength of the ultrasonic surface wave or the Lamb wave, divided by 4, and the spacing between two consecutive fingers of a comb can be equal to the fundamental wavelength of the ultrasonic surface wave or the Lamb wave, divided by 4. The spacing between the fingers determines the resonance frequency of the transducer that a person skilled in the art can easily identify. Applying alternating electrical voltage to electrodes of opposite polarity induces a mechanical response in the piezoelectric material, resulting in the generation of an ultrasonic surface wave or a Lamb wave that propagates in the optical surface.

[0034] The electrodes can be metallic. They can be made of chromium, or aluminium or a combination of an adhesion layer such as titanium and a conductive layer such as gold.

[0035] Alternatively, the electrodes may be made of a transparent conductive oxide, for example, indium tin oxide, aluminum-doped zinc oxide, and mixtures thereof. In particular, the transducer may be transparent and consist of such electrodes and a transparent piezoelectric layer of lithium niobate or zinc oxide. The transducer can thus be advantageously positioned within the optical field of the device, for example, to optimize the cleaning of the optical surface, without significantly disrupting the operation of the device through shadowing.

[0036] The electrodes can be deposited on the piezoelectric layer by an evaporation or spraying process and shaped by photolithography.

[0037] They can be printed, for example by inkjet printing. In particular, they can be printed on a foil, for example made of a flexible thermoplastic material, and applied by transferring the foil onto the piezoelectric layer.

[0038] The transducer can be configured to emit a surface ultrasonic wave or a Lamb wave whose fundamental frequency can be between 0.1 MHz and 1000 MHz, preferably between 10 MHz and 100 MHz, for example 40 MHz, and / or whose amplitude can be between 1 nanometer and 500 nanometers. The wave amplitude corresponds to the normal displacement of the face of the optical surface on which the ultrasonic surface wave propagates. It can be measured by laser interferometry.

[0039] The ultrasonic surface wave can be a Rayleigh wave when the optical surface has a thickness greater than the wavelength of the ultrasonic surface wave. A Rayleigh wave is preferred because a maximum proportion of the wave energy is concentrated on the face of the optical surface along which it propagates, and can be transmitted to a body, for example a raindrop, resting on the optical surface.

[0040] Preferably, the device comprises at least two transducers, for example more than five, or even more than ten transducers.

[0041] The transducers can be configured to emit surface acoustic waves propagating in parallel or intersecting directions. For example, the device comprises at least three transducers that are configured so that the The propagation directions of the waves that they are capable of generating intersect at a common point.

[0042] The transducers can be distributed regularly on the contour of the face of the optical surface on which they are arranged.

[0043] Preferably, the transducers share the same piezoelectric layer. In other words, the electrodes of the different transducers can be in contact with the same piezoelectric layer. Such a device is thus easy to manufacture, by successively implementing a step of depositing the piezoelectric layer followed by a step of depositing the electrodes to form the transducers.

[0044] The optical surface can be self-supporting, in the sense that it can deform, in particular elastically, without breaking under its own weight.

[0045] The face of the optical surface on which the ultrasonic surface wave or the Lamb wave propagates may be flat. It may also be curved, provided that the radius of curvature of the face is greater than the wavelength of the ultrasonic surface wave. This face may be rough. The roughness will preferably be less than the fundamental wavelength of the ultrasonic surface wave, in order to prevent it from significantly affecting its propagation.

[0046] The optical surface may be in the form of a flat plate, or one having at least one curvature in one direction. In particular, it may be a lens. The thickness of the plate may be between 100 µm and 5 mm. The length of the plate may be greater than 1 mm, or even greater than 1 cm, or even greater than 1 m.

[0047] By "optical surface thickness" is considered the smallest dimension of the optical surface measured along a direction perpendicular to the surface on which the ultrasonic surface wave or Lamb wave propagates.

[0048] The optical surface can be arranged flat with respect to the horizontal. Alternatively, it can be inclined with respect to the horizontal at an angle α greater than 10°, or even greater than 20°, or even greater than 45°, or even greater than 70°. It can be arranged vertically.

[0049] The optical surface is preferably optically transparent, in particular to light in the visible range or to radiation in the ultraviolet or infrared range.

[0050] Furthermore, the optical surface may include a single-layer or multi-layer coating which covers one face of the acoustically conductive portion.

[0051] The coating may include, in particular, a hydrophobic layer, an antireflective layer, or a stack of these layers. For example, the hydrophobic layer is made up of self-assembled OTS monolayers or may result from the deposition of a fluorine-based plasma. The coating may include one or more antireflective layers depending on the intended application (Visible, IR, etc.).

[0052] The transducer can be in contact with the acoustically conductive portion, and the hydrophobic layer can completely cover the transducer to protect it from contact with water. In one embodiment, the coating is positioned between the transducer and the acoustically conductive portion.

[0053] Preferably, the optical surface comprises an acoustically conductive portion, the transducer being acoustically coupled to, and preferably in contact with, the acoustically conductive portion.

[0054] The acoustically conductive portion is preferably transparent.

[0055] The acoustically conductive portion preferably has an attenuation length greater than the length of the optical surface, or even greater than 10 times the length of the optical surface, or even greater than 100 times the length of the optical surface.

[0056] The acoustically conductive portion can be made of any material suitable for propagating an ultrasonic surface wave or a Lamb wave. Preferably, it is made of a material having a modulus of elasticity greater than 1 MPa, for example greater than 10 MPa, or even greater than 100 MPa, or even greater than 10000 MPa. A material with such a modulus of elasticity exhibits a stiffness particularly well-suited to the propagation of an ultrasonic surface wave or a Lamb wave.

[0057] Preferably, the acoustically conductive portion is made of glass or poly(methyl methacrylate), also known by the trade name plexiglas®.

[0058] The optical surface may consist of the acoustically conductive portion.

[0059] In one embodiment, the optical surface may include an acoustically insulating portion, i.e., absorbing the surface ultrasonic wave or the Lamb wave over a distance less than the length of the optical surface, or even less than 0.1 times the length of the optical surface. The acoustically insulating portion is preferably superimposed, in particular completely superimposed, on the acoustically conductive portion. The acoustically insulating portion may completely cover the acoustically conductive portion. Preferably, the acoustically insulating portion is made of polycarbonate. Other rubbery or plastic materials may be considered.

[0060] The acoustically insulating portion is preferably transparent.

[0061] In particular, the acoustically insulating portion and the acoustically conductive portion can be stacked one on top of the other, and preferably in contact with each other. In particular, the acoustically conductive portion can have a thickness at least five times less than the thickness of the acoustically insulating portion. Thus, the acoustically insulating portion can provide mechanical resistance to the optical surface while the acoustically conductive portion enables the cleaning function by transporting the ultrasonic wave.

[0062] The acoustically conductive portion can be removably mounted on the acoustically insulating portion. Thus, it is possible to easily replace either portion when it is damaged, for example, following contact with a solid object, such as a pebble, during movement of the device.

[0063] In particular, the acoustically conductive portion can be glued to the acoustically insulating portion by means of a reversible adhesive.

[0064] The device is configured to capture and / or emit radiation. To this end, it includes a sensor and / or a radiation emitter.

[0065] In particular, the device can be chosen from an optical remote sensing device, for example a lidar, a photographic camera, a camera, a radar, an infrared sensor and an ultrasonic rangefinder.

[0066] The optical surface can be superimposed on the sensor and / or the emitter, in particular to protect the sensor. Preferably, the optical surface is located at a distance from the sensor and / or the emitter.

[0067] It can be a lens intended to deflect the radiation towards the sensor or from the emitter.

[0068] Alternatively, it can be an optical protection device, for example to protect the sensor and / or the emitter. An "optical protection device" is such that it does not deflect the optical path of radiation passing through it.

[0069] In particular, the device includes the optical surface which is a lens or the optical surface is a protective element of the device.

[0070] The device may be a motor vehicle and the apparatus is configured to acquire a quantity chosen from among the distance between the vehicle and an object, the speed of the vehicle, the positioning of the vehicle in relation to a traffic lane, as well as any additional information such as the nature of the vehicle (truck, bicycle...) or the nature of objects (civilians, animals...).

[0071] Alternatively, the optical surface can be a lab-on-a-chip substrate, particularly intended for microfluidic applications.

[0072] The optical surface can be a wall exposed to the condensation of a liquid that can solidify, for example a building window.

[0073] The device, in particular the apparatus, may include a housing in which the sensor and / or emitter are housed, and the optical surface may be removably mounted on the housing. In particular, the optical surface may be fixed to the housing so as to hermetically seal the housing, in order to protect the sensor and / or emitter. Specifically, the optical surface may be fixed to a mount, which may be screwed onto the housing. Thus, the optical surface can be easily replaced if it becomes damaged.

[0074] Furthermore, the cleaning unit may include an electric generator to electrically power the transducer, so that the transducer converts the electrical supply signal into a surface ultrasonic wave or a Lamb wave.

[0075] The invention further relates to the use of a device according to the invention, to evacuate a body in contact with the optical surface out of the region of optical interest.

[0076] The use may include powering the cleaning unit to melt the body when the body is in the solid state, and / or maintaining the body in the liquid state when the temperature of the optical surface is lower than the solidification temperature of the body.

[0077] The liquid substance may be in the form of at least one droplet or at least one film. The energy of the surface ultrasonic wave may be sufficient to induce the movement of the liquid substance on the face of the optical surface. The substance may be aqueous, in particular rainwater or dew. The temperature of the optical surface may be below 0°C. The substance is, for example, frost or snow.

[0078] The invention finally relates to a vehicle, preferably automated, or an organ of such a vehicle comprising a device according to the invention.

[0079] An automated vehicle is defined as a vehicle that can be driven on public roads without the intervention of a human driver. The vehicle is preferably a motor vehicle, in particular a car or a truck.

[0080] An organ of such a vehicle can be chosen from a headlight lighting module, a system containing a set of different sensors also called a "pod", at least one side window, a front window or a rear window and a driver assistance unit.

[0081] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the accompanying drawing, on which:

[0082] [fig. 1] Figure [fig. 1] schematically represents, in cross-section, an example of a device according to the invention,

[0083] [fig.2] Fig.2 schematically represents another example of a device,

[0084] [fig.3] Fig.3 schematically represents, in front view, part of an example of the device according to the invention,

[0085] [fig.4] The [fig.4] schematically represents, in front view, a part of another example of a device according to the invention,

[0086] [fig.5] Fig.5 schematically represents, in cross-section, a part of a example of a device according to the invention,

[0087] [fig.6] Fig.6 schematically represents, in cross-section, a part of a another example of a device according to the invention, and

[0088] [fig.7] Fig.7 schematically represents, in cross-section, a example of a device according to the invention.

[0089] The constituent elements of the design have not always been represented to scale for the sake of clarity.

[0090] A first example of device 5 according to the invention has been illustrated in [fig.1].

[0091] The device comprises an optical surface 10, a cleaning unit 15 of the optical surface and a device 20.

[0092] The device 20 includes a sensor 25 for capturing radiation R and a lens 30 for directing the radiation R towards the sensor. Alternatively or additionally, it may include an emitter for emitting radiation. For example, the device includes a lidar that is configured to emit laser radiation and capture the portion of this laser radiation reflected by an object.

[0093] Furthermore, lens 30 is optional. In an example embodiment not shown, the device is without it.

[0094] The device defines an optical field Co which corresponds to the portion of space from which it is able to acquire radiation. Outside this optical field, even if the radiation can reach the sensor, the latter is not able to acquire it.

[0095] The optical surface 10 completely covers the sensor 25 and is thus a protective element 35 of the device. For example, the device is mounted on a motor vehicle that can move in a direction X; the optical surface forms a barrier against bodies 40, such as dust, mud particles, and raindrops that come into contact with the face 45 of the optical surface opposite the sensor.

[0096] Furthermore, the optical surface is transparent to the radiation received by the sensor. The optical surface is, for example, made of glass. However, it can be made of a material opaque to visible radiation but transparent to the wavelengths of the radiation that the sensor is capable of acquiring.

[0097] In the illustrated example, the optical surface is in the form of a disk whose thickness ep is, for example, between 0.5 mm and 5 mm. In a variant, the optical surface can be curved, and for example have the shape of a lens.

[0098] The device may include, as illustrated, a housing 50 that defines a chamber 55 housing the sensor. The chamber 55 may, in particular, be delimited by a solid wall 60 of the housing and by the optical surface 10, so as to be airtight and watertight. The sensor is thus protected from the elements.

[0099] In particular, the optical surface can close off the housing. For example, the optical surface is mounted on a ring 65, which is screwed onto the housing 50.

[0100] The optical surface is thus removable, which allows for its simple replacement when, for example, it has been damaged by a projectile.

[0101] The optical surface cleaning unit 15 comprises two transducers 70 which are disposed in contact with the optical surface and are acoustically coupled to the optical surface. The cleaning unit further comprises a current generator 75 for supplying power to the transducers. The number of transducers is not limited. In particular, the device may comprise a single transducer.

[0102] The transducers each comprise a piezoelectric layer 80 and electrodes 85 of opposite polarity arranged on the piezoelectric layer. Such layer transducers thus allow the fabrication of particularly compact devices. They can also be easily arranged on curved optical surfaces.

[0103] The transducers can each generate either a surface ultrasonic wave WS or a Lamb wave WL that propagates through the optical surface. In the example shown in [Fig. 1], the transducers are arranged on face 90 of the optical surface opposite the face to be cleaned 45. They are preferably configured to generate a Lamb wave that reaches the face to be cleaned 45.

[0104] Furthermore, the transducers delimit a region of optical interest 100 which is not superimposed with the transducers.

[0105] Preferably, part of the region of optical interest is contained within the optical field of the device. In other words, the transducers are arranged outside the optical field of the device, so that they do not significantly interfere with the radiation passing through the region of optical interest and which is captured by the sensor.

[0106] In order to reduce the overall size, as illustrated in [Fig. 1], the transducers are preferably arranged on the periphery of the optical surface. This makes it possible to maximize the area of ​​optical interest by positioning the transducers at the periphery. In particular, the wave transducers can each extend from an edge of the optical surface over a distance of less than 10%, or even less than 5%, of the length of the optical surface.

[0107] In the illustrated example, the transducers extend over face 90 directly from edge 105.

[0108] The device of [fig.2] differs from that illustrated in [fig.1] in that the transducers 70 are arranged on the face to be cleaned 45 of the optical surface 10 which is opposite the face 90 opposite the sensor 25.

[0109] The transducers are preferably configured to generate an ultrasonic surface wave Ws propagating along the face to be cleaned 45 in order to move a body in contact with said face.

[0110] As illustrated, optionally, the 50 case features a shoulder 115 which forms a cover and covers the transducers 70, so as to protect them from the weather.

[0111] Fig. 3 illustrates part of a device 5 according to the invention from a view perpendicular to one of the faces 45, 90 of the optical surface.

[0112] Two transducers are arranged in contact with one face of the optical surface. Each transducer comprises a piezoelectric layer 80 in contact with the optical surface, extending in band B between two opposite edges 120 and parallel to a third edge 125 connecting these two opposite edges. Electrodes 85 of opposite polarity, each comprising interdigitated combs, are arranged on the piezoelectric layer and are positioned to generate an ultrasonic wave of Lamb WL or surface Ws, which propagates in the region of optical interest, in order to clean the bodies 40 deposited on them.

[0113] The portion of the device shown in [Fig. 4] differs from that shown in [Fig. 3] in that the transducers 70 share a common piezoelectric layer 80 which defines a frame 130 surrounding the region of optical interest 100. The frame is, for example, rectangular. It has an outer contour 135 which coincides with the contour of the face of the optical surface on which the piezoelectric layer is deposited. Furthermore, the device may include a larger number of transducers, arranged, for example, regularly around the frame. To facilitate the fabrication of such a device, the electrodes 85 can be printed onto the piezoelectric layer. An arrangement of the transducers as described in Figures 3 and 4 can obviously be implemented in the examples illustrated in Figures 1, 2, and 7.

[0114] Figure 5 illustrates a cross-sectional view of a portion of the device of Figure 3. The optical surface 10 comprises an acoustically conductive portion 150, for example made of glass, and a coating 155 completely covering one face 160 of the acoustically conductive portion. This coating consists of a stack of an antireflective layer 165 and a hydrophobic layer 170, for example, to prevent raindrops from spreading on the optical surface and to facilitate their removal. The transducer 70 is positioned in contact with the coating opposite the acoustically conductive portion. The coating preferably has a sufficiently small thickness with respect to the wavelength of the surface wave generated by the transducer. Thus, the acoustically conductive portion and the transducer are acoustically coupled.

[0115] The device illustrated in [fig.6] differs from that illustrated in [fig.5] in that the transducer 70 is sandwiched between the hydrophobic layer 170 and the acoustically conductive portion 150. Thus the hydrophobic layer protects the transducer.

[0116] Finally, [Fig. 7] further illustrates an example of an embodiment of a device 5 according to the invention. It differs from the example in [Fig. 2] in that the optical surface is a lens 178 comprising an acoustically conductive portion 150 and a portion acoustically insulating 180 stacked one on top of the other.

[0117] In addition to its ability to modify the path of radiation passing through it, the lens 178 also protects the sensor 25.

[0118] Furthermore, the acoustically insulating portion is, for example, thicker than the acoustically insulating portion and can mechanically support the acoustically conductive portion. The transducer is acoustically coupled to the acoustically conductive portion.

[0119] The acoustically conductive portion can be mounted removably, for example by means of a reversible adhesive layer placed between the facing surfaces of the acoustically insulating portion and the acoustically conductive portion. Thus, the acoustically insulating portion can be easily replaced.

[0120] The acoustically conductive portion 150 is arranged opposite the sensor 25 with respect to the acoustically insulating portion 180. Thus, the cleaning unit can clean the face 45 of the acoustically conductive portion on which bodies 40, for example raindrops, can accumulate.

[0121] Of course, the invention is not limited to the examples of embodiment of the invention presented by way of illustration and not limitation.

Claims

Demands

1. Device (5) comprising: - an optical surface (10), - an optical surface cleaning unit (15) comprising at least one wave transducer (70) acoustically coupled with the optical surface, the wave transducer comprising a piezoelectric layer (80) and electrodes (85) of opposite polarity in contact with the piezoelectric layer, and being configured to generate at least one ultrasonic surface wave (Ws) or a Lamb wave (WL) propagating in the optical surface, - the optical surface having at least one region of optical interest (100) not superimposed with the wave transducer, the device comprising an apparatus (20) configured to capture and / or emit radiation (R) through the region of optical interest (100).

2. Device according to claim 1, the wave transducer being disposed outside the optical field (Co) of the device.

3. Device according to any one of claims 1 and 2, comprising a processing unit configured to analyze, preferably only, the radiation captured by the optical device through the region of optical interest.

4. Device according to previous claims, the transducer being disposed at the periphery of the optical surface.

5. Device according to any one of the preceding claims, wherein the wave transducer extends from an edge of the optical surface over a distance of less than 10%, or even less than 5%, of the length of the optical surface.

6. Device according to any one of the preceding claims, the transducer extending from an edge of the optical surface over a distance of less than 30 mm, preferably less than 20 mm, preferably less than 10 mm.

7. Device according to any one of the preceding claims, the piezoelectric layer forming at least one band (B) extending over one face (45,90) of the optical surface.

8. Device according to any one of the preceding claims, the piezoelectric layer forming a frame (130) surrounding at least partially the region of optical interest.

9. Device according to any one of the preceding claims, comprising several wave transducers which share the same piezoelectric layer.

10. A device according to any one of the preceding claims, the wave transducer being in contact with the optical surface, in particular the transducer being fixed to the optical surface, for example glued by means of a polymeric adhesive which acoustically couples the transducer to the optical surface or by molecular adhesion or by means of a thin metallic layer ensuring adhesion between the optical surface and the piezoelectric layer, or by means of a process comprising a step of melting a portion of the piezoelectric layer and / or a portion of the optical surface followed by a step of compressing together the piezoelectric layer and the optical surface, the respective molten portions of the optical surface and the piezoelectric layer being in contact with each other.

11. Device according to any one of the preceding claims, the optical surface comprising an acoustically conductive portion (150), preferably made of glass, the wave transducer being acoustically coupled to the acoustically conductive portion, and being preferably in contact with the acoustically conductive portion.

12. Device according to claim 11, the optical surface comprising a stack comprising an acoustically insulating portion (180) and the acoustically conductive portion (150) stacked one on top of the other.

13. Device according to claim 12, the acoustically conductive portion being removably mounted on the acoustically insulating portion.

14. Device according to any one of the preceding claims, the apparatus comprising the optical surface which is a lens (178), or the optical surface is a protective element (35) of the apparatus.

15. Device according to any one of the preceding claims, the piezoelectric layer having a thickness between 1 pm and 100 pm.

16. Vehicle, preferably automated, comprising a device according to any one of the preceding claims.

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