DEVICE FOR CLEANING AN OPTICAL SURFACE

Abstract

The invention relates to a device (5) comprising: an optical surface (10); a cleaning unit (15) for cleaning the optical surface, comprising at least one wave transducer (70) acoustically coupled to the optical surface, the wave transducer having a piezoelectric layer (80) and electrodes (85) of opposite polarity in contact with the piezoelectric layer, and being configured to generate at least one surface ultrasonic wave (W.sub.S) or a Lamb wave (W.sub.L) propagating in the optical surface; the optical surface having at least one region of optical interest (100) not superposed on the wave transducer, the device comprising an apparatus (20) configured to sense and/or to emit radiation (R) through the region of optical interest (100).

Claims

1. A device comprising: an optical surface; a unit for cleaning the optical surface including at least one wave transducer acoustically coupled to the optical surface, the wave transducer including a piezoelectric layer and electrodes of opposite polarity in contact with the piezoelectric layer, and being configured to generate at least one ultrasound surface wave or Lamb wave propagating in the optical surface, the optical surface having at least one region of optical interest not superimposed with the wave transducer; and an item of equipment configured to detect and/or emit radiation through the region of optical interest.

2. The device as claimed in claim 1, the wave transducer being arranged outside the optical field of the item of equipment.

3. The device as claimed in claim 1, further comprising: a processing unit configured to analyze only the radiation detected by the optical apparatus through the region of optical interest.

4. The device as claimed in claim 1, the transducer being arranged at the periphery of the optical surface.

5. The device as claimed in claim 1, 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. The device as claimed in claim 1, 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. The device as claimed in claim 1, the piezoelectric layer forming at least one strip extending over one face of the optical surface.

8. The device as claimed in claim 1, the piezoelectric layer forming a surround at least partially framing the region of optical interest.

9. The device as claimed in claim 1, including several wave transducers which share the same piezoelectric layer.

10. The device as claimed in claim 1, the wave transducer being in contact with the optical surface, and the transducer being fixed to the optical surface, for example bonded by a polymeric adhesive which acoustically couples the transducer to the optical surface or by molecular adhesion or by a thin metallic layer providing adhesion between the optical surface and the piezoelectric layer, or by a process including a step of melting a portion of the piezoelectric layer and/or a portion of the optical surface followed by compressing the piezoelectric layer and the optical surface together, the respective melted portions of the optical surface and the piezoelectric layer being in contact with each other.

11. The device as claimed in claim 1, the optical surface including an acoustically conducting portion made of glass, the wave transducer being acoustically coupled to the acoustically conducting portion, and preferably being in contact with the acoustically conducting portion.

12. The device as claimed in claim 11, the optical surface including a stack including an acoustically insulating portion and the acoustically conducting portion, these being stacked one on the other.

13. The device as claimed in claim 12, the acoustically conducting portion being removably mounted on the acoustically insulating portion.

14. The device as claimed in claim 1, the item of equipment including the optical surface which is a lens, or the optical surface is a protective member of the item of equipment.

15. The device as claimed in claim 1, the thickness of the piezoelectric layer being less than or equal to 0.5*, notably for an ultrasonic surface wave with a frequency comprised between 0.1 MHz and 60 MHz.

16. The device as claimed in claim 1, the piezoelectric layer having a thickness of between 1 m and 300 m.

17. An automated vehicle, including a device as claimed in claim 1.

Description

[0087] The invention may be understood more clearly on reading the following detailed description of nonlimiting implementation examples thereof, and on examining the appended drawing, in which:

[0088] FIG. 1 schematically depicts, in cross section, an example of a device according to the invention,

[0089] FIG. 2 schematically depicts another example of a device,

[0090] FIG. 3 schematically depicts, in front view, a portion of an example of a device according to the invention,

[0091] FIG. 4 schematically depicts, in front view, a portion of another example of a device according to the invention,

[0092] FIG. 5 schematically depicts, in cross section, a portion of an example of a device according to the invention,

[0093] FIG. 6 schematically depicts, in cross section, a portion of another example of a device according to the invention, and

[0094] FIG. 7 schematically depicts, in cross section, an example of a device according to the invention.

[0095] For the sake of clarity, the elements that make up the drawings have not always been drawn to scale.

[0096] FIG. 1 illustrates a first example of a device 5 according to the invention.

[0097] The device includes an optical surface 10, an optical surface cleaning unit 15 and an item of equipment 20.

[0098] The item of equipment 20 includes a sensor 25 to detect radiation R and a lens 30 to direct the radiation R toward the sensor. As a variant or in addition, it may include an emitter to emit radiation. For example, the equipment includes a lidar which is configured to emit laser radiation and in return detect that part of this laser radiation that has been reflected by an object.

[0099] Moreover, the lens 30 is optional. In an implementation example not shown, the item of equipment does not have one.

[0100] The item of equipment defines an optical field Co which corresponds to the portion of space from which it is able to detect radiation. Outside of this optical field, even though the radiation may be able to reach the sensor, the latter is not able to detect it.

[0101] The optical surface 10 completely covers the sensor 25 and is thus a protective member 35 of the item of equipment. For example, the device is mounted on a motor vehicle that may move in an X direction, 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.

[0102] Moreover, the optical surface is transparent to the radiation received by the sensor. The optical surface is, for example, made of glass. However, it may be made of a material that is opaque to radiation in the visible range but transparent to the wavelengths of the radiation that the sensor is capable of detecting.

[0103] In the illustrated example, the optical surface is in the form of a disk whose thickness e.sub.p is, for example, between 0.5 mm and 5 mm. In a variant, the optical surface may be curved, and may, for example, have the shape of a lens.

[0104] The device may, as illustrated, include a housing 50 which defines a chamber 55 housing the sensor. The chamber 55 may notably 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 against the weather.

[0105] In particular, the optical surface may close off the housing. For example, the optical surface is mounted on a ring 65 which is screwed onto the housing 50.

[0106] The optical surface is thus removable, which allows for simple replacement thereof when, for example, it has been damaged by a projectile.

[0107] The optical surface cleaning unit 15 includes two transducers 70 which are arranged in contact with and acoustically coupled to the optical surface. The cleaning unit also includes a current generator 75 electrically powering the transducers. The number of transducers is nonlimiting. Notably, the device may include a single transducer.

[0108] The transducers moreover each include a piezoelectric layer 80 and electrodes 85 of opposite polarity arranged on the piezoelectric layer. Such layered transducers thus allow the manufacture of particularly compact devices. They may also be easily arranged on curved optical surfaces.

[0109] The transducers may each generate an ultrasound surface wave W.sub.S or a Lamb wave W.sub.L that propagates in the optical surface. In the example illustrated in FIG. 1, the transducers are arranged on the face 90 of the optical surface 10 opposite to the face 45 that is to be cleaned. They are preferably configured to generate a Lamb wave that reaches the face 45 that is to be cleaned.

[0110] Moreover, the transducers delimit a region of optical interest 100 which is not superposed with the transducers.

[0111] Preferably, part of the region of optical interest is contained within the optical field of the item of equipment In other words, the transducers are positioned outside of the optical field of the equipment so that they create almost no interference with the radiation passing through the region of optical interest and detected by the sensor.

[0112] In order to reduce the bulk, as illustrated in FIG. 1, the transducers are preferably arranged at the periphery of the optical surface. Thus, it is possible to maximize the area of the region of optical interest by offsetting the transducers to the periphery. Each wave transducer may notably extend from an edge of the optical surface over a distance less than 10%, or even less than 5% of the length of the optical surface.

[0113] In the example shown, the transducers extend on the face 90 directly from the edge 105.

[0114] The device of FIG. 2 differs from that shown in FIG. 1 in that the transducers 70 are arranged on the face 45 to be cleaned of the optical surface 10 that is opposite the face 90 facing the sensor 25.

[0115] The transducers are preferably configured to generate an ultrasound surface wave W.sub.S propagating along the face 45 to be cleaned so as to move a body in contact with said face.

[0116] As illustrated, optionally, the housing 50 has a shoulder 115 that forms a cover and covers the transducers 70, so as to protect them from the weather.

[0117] FIG. 3 illustrates part of a device 5 according to the invention according to a view perpendicular to one of the faces 45, 90 of the optical surface.

[0118] Two transducers are arranged in contact with one of the faces of the optical surface. They each include a piezoelectric layer 80 which is in contact with the optical surface and which extends in a band B between two opposite edges 120 and parallel to a third edge 125 which connects these two opposite edges. Electrodes 85 of opposite polarity and including interdigitated combs are arranged on the piezoelectric layer, and are arranged so as to generate a Lamb W.sub.L or surface W.sub.S ultrasound wave that propagates through the region of optical interest, so as to clean the bodies 40 deposited thereon.

[0119] The portion of the device depicted in FIG. 4 differs from the one illustrated in FIG. 3 in that the transducers 70 share the same piezoelectric layer 80 which delimits a surround 130 which frames the region of optical interest 100. The surround is, for example, rectangular. The surround has an exterior contour 135 which coincides with the contour of that face of the optical surface on which the piezoelectric layer is applied. In addition, the device may include a larger number of transducers, for example arranged evenly around the surround. To facilitate the manufacture of such a device, the electrodes 85 may be printed on the piezoelectric layer. An arrangement of the transducers as described in FIGS. 3 and 4 may, of course, be implemented in the examples shown in FIGS. 1, 2 and 7.

[0120] FIG. 5 is a view in cross section of part of the device of FIG. 3. The optical surface 10 includes an acoustically conducting portion 150, for example made of glass, and a coating 155 completely covering one face 160 of the acoustically conducting portion and made up of a stack of an antireflection layer 165 and a hydrophobic layer 170 so as, for example, to prevent raindrops from spreading over the optical surface and to make them easier to remove. The transducer 70 is positioned in contact with the coating opposite the acoustically conducting portion. The coating preferably has a thickness that is small enough with respect to the wavelength of the surface wave generated by the transducer. Thus, the acoustically conducting portion and the transducer are acoustically coupled.

[0121] The device illustrated in FIG. 6 differs from the device illustrated in FIG. 5 in that the transducer 70 is sandwiched between the hydrophobic layer 170 and the acoustically conducting portion 150. Thus, the hydrophobic layer protects the transducer.

[0122] Finally, FIG. 7 illustrates yet another exemplary 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 including an acoustically conducting portion 150 and an acoustically insulating portion 180 stacked on top of each other.

[0123] In addition to its ability to modify the path of radiation passing through it, the lens 178 also protects the sensor 25.

[0124] Moreover, the acoustically insulating portion is, for example, thicker than the acoustically insulating portion and can mechanically support the acoustically conducting portion. The transducer is acoustically coupled to the acoustically conducting portion.

[0125] The acoustically conducting portion may be removably mounted, for example, by means of a reversible adhesive layer arranged between the opposing faces of the acoustically insulating portion and the acoustically conducting portion. Thus, the acoustically insulating portion can be readily replaced.

[0126] The acoustically conducting portion 150 is arranged opposite the sensor 25 relative to the acoustically insulating portion 180. Thus, the cleaning unit can clean the face 45 of the acoustically conducting portion on which bodies 40, for example raindrops, may collect.

[0127] Needless to say, the invention is not limited to the implementation examples of the invention that have been presented as nonlimiting illustrations.