Patent Publication Number: US-2019171004-A1

Title: Device for protecting an optical sensor and driver assistance system comprising an optical sensor

Description:
The present invention relates to the driving aid field and in particular to the driving assistance systems that are installed on certain vehicles, the assistance system being able to include an optical sensor such as, for example, a camera comprising a lens. More particularly, the invention relates to a protection device of such a driving assistance system comprising means for cleaning the optic thereof. 
     Currently, front, rear or even side vision cameras equip a large number of motor vehicles. They form in particular part of the driving assistance systems, such as parking aid systems, or even lane departure detection systems. 
     There are cameras installed inside the interior of a motor vehicle as an aid to parking. These cameras are well protected from random climatic factors such as smears linked to organic or mineral pollutants. However, the viewing angle for such cameras, installed inside the interior, is not optimal, particularly for aid to parking because they do not make it possible to see the obstacles located in proximity to the rear of the vehicle for example. 
     Preference is therefore given to installing these driving assistance systems, and in particular their cameras, on the outside of the vehicles at different points depending on the desired use. In such a case, the driving assistance system, and in particular the camera of such a system, is therefore greatly exposed to random climatic factors and to smear sprays which can reduce its effectiveness, even render it inoperative. 
     To counter the deposition of smears on the driving assistance system, it is known practice to arrange a device for cleaning the optic of the camera, generally a cleaning liquid spray nozzle in proximity thereto in order to eliminate the pollutant elements which are deposited over time. 
     Also, the optic of the camera, generally formed by a lens, is a relatively fragile device. It is therefore necessary to protect it from spray which could damage it. It is therefore commonplace to find such cameras housed inside protection casings comprising a protection window arranged facing the lens. However, the cleaning of the lens or of the window of the casing protecting the latter is an important criterion in ensuring the optimal operation of the camera. 
     The document US2014/0036084 discloses a camera mounting inside a protection casing in which there is a piezoelectric vibrator which makes it possible to vaporize water droplets present on the lens of the camera and thus clean them when the vehicle is running. 
     However, such a system does not make it possible to clean the organic or mineral smears, or even traces of water filled with various pollutants which would have been deposited on the lens and would have had time to dry because, for example, of the prolonged parking of the vehicle. 
     Also known from the document US2012/0243093 is a casing comprising a camera and equipped with a piezoelectric device and a cover protecting the lens of the camera. The piezoelectric device makes it possible to vibrate the assembly composed of the casing and the camera, and thus prevent organic or mineral smears from adhering to a cover protecting the lens. 
     However, such vibration of the assembly greatly increases the risks of breaks and/or cracks of the material forming the lens or the cover covering the latter so as to close a casing in which the optical sensor is arranged. To form the lens, it is therefore necessary to use glasses or plastics that are highly resistant to vibrations and impacts which are generally costly. Also, such vibrations can damage the internal system of the camera, in particular its electronic components. 
     In order to be able to clean the lenses of cameras having organic or mineral smears, without risking damaging the lens or the optical sensor, the document FR2841488 discloses a casing enclosing a camera with means for cleaning the casing composed of a spray nozzle and means for vibrating the window facing the camera. This casing also comprises de-icing and demisting means. Furthermore, to limit the traces of water, this window is produced in a hydrophobic material which has undergone a catalytic treatment in order to reduce the adherence of water and of the organic pollutants thereon. 
     However, this device can in some cases be too bulky, particularly when it is intended to be installed at the level of the registration plate of the vehicle, on the front or rear bumpers, or even on the rearview mirrors. Moreover, this device allows only the runoff of the cleaning liquid over the glass, its effectiveness for tenacious and embedded smears can be limited despite the vibration of the glass and the catalytic treatment that the latter has undergone. Also, the presence of a spray nozzle requires cleaning liquid intake ducts to be formed on the casing. These ducts must generally be formed by the manufacturer and require a more complex initial design within the vehicle. 
     The present invention sets out to at least partially remedy the drawbacks of the prior art mentioned above by presenting a protection device protecting an optical sensor which ensures a good protection thereof and in which the cleaning of the optic is rapid, efficient, and without necessarily requiring a cleaning liquid, both for the traces of water and for organic or mineral smears which would have had the time to adhere strongly to the optic of the optical sensor included in the driving assistance system. 
     To this end, the subject of the invention is a protection device protecting an optical sensor for a motor vehicle comprising a protection casing in which is formed a housing configured to house an optical sensor, characterized in that said device also comprises:
         a support movably mounted on the protection casing and bearing a membrane fixed by its periphery to the support and intended to be arranged facing the optical sensor, the membrane comprising an optically transparent and elastically deformable material; and   at least one actuator borne by the protection casing and configured to move the support bearing the membrane;
 
and in that the support, under the effect of the moving of the support by the actuator, is configured to deform the membrane between a position of rest in which the membrane is in a first state of tension and at least one active position in which the membrane is in a second state of tension. In the second state of tension the membrane is more taut than in the first state of tension.
       

     Thus, if the smears come to be deposited on the membrane situated in front of the optical sensor housed in the protection casing, the mobile support bearing the membrane will be able to allow the elastic deformation of the latter upon the movement of said support. 
     When the membrane is in its second state of tension, the smears will be able to drop from the membrane because the surface of contact of the smears on the membrane is reduced. The membrane exhibits a greater elasticity than the smears which adhere to the membrane. Because of this, the adhesion links between the smears and the membrane will be broken when the membrane is in its second state of tension and thus allow the smears to drop. 
     The device for protecting the optical sensor according to the invention can also comprise one or more of the following features taken alone or in combination: 
     The optically transparent and elastically deformable material of the membrane is an elastomer. 
     The protection casing has a substantially central opening allowing the passage of an optic of the optical sensor and at least one first guiding member configured to cooperate with a complementary second guiding member borne by the support. 
     The support comprises a plate secured to at least one second guiding member and comprising an opening in which the membrane is placed, the plate being intended to be oriented substantially at right angles to the optical axis of the optical sensor. 
     The support comprises a fixing ring for the membrane surrounding the opening in which the membrane is placed. 
     The complementary guiding members are oriented so as to allow a translational movement of the support along an axis substantially at right angles to the plate of the support. 
     The opening of the plate is configured to accommodate the optic in such a way that it protrudes from the opening and is in contact with the elastic membrane. 
     The complementary guiding members are formed by a rod/cylinder system. 
     The actuator of the support comprises at least one of the elements chosen from the following list: a piezoelectric transducer, an electromagnet, a mechanical system comprising a toothed wheel and a rack. 
     According to a variant, the actuator is arranged inside the protection casing. 
     According to another variant, the actuator is arranged outside the protection casing. 
     The actuator is configured to move the support at a frequency lying within the ultrasound range. 
     The formulation of the elastomer forming the membrane exhibits properties of resistance to ultraviolet radiations and/or non-stick properties. 
     Another subject of the invention is a driving assistance system comprising an optical sensor and comprising a protection device as described previously. 
     Thus, the driving assistance system can be directly installed on any kind of vehicle. The optical sensor comprises at least one camera which will thus be protected from external abuses, thus avoiding having the field of view of the camera being altered by traces of water or by the smears linked to organic or mineral pollutants. The optical sensor will therefore have optimized operation. 
     The driving assistance system can also comprise one or more of the following features taken alone or in combination: 
     The actuator is configured to move the support along the optical axis of the optical sensor. 
     The optic of the optical sensor protrudes through an opening of the plate of the support and is in contact with the elastic membrane arranged on the plate. 
    
    
     
       Other advantages and features will become apparent on reading the description of the invention, and from the attached drawings in which: 
         FIG. 1  is a schematic view of the driving assistance system according to the invention, 
         FIG. 2  is an exploded view of the driving assistance system of  FIG. 1 , 
         FIG. 3  is a schematic view of the driving assistance system when the membrane is in a position of rest, 
         FIG. 4  is a longitudinal cross-sectional view of the driving assistance system when the membrane is in position of rest, 
         FIG. 5  is a schematic view of the driving assistance system when the membrane is in an active position, 
         FIG. 6  is a longitudinal cross-sectional view of the driving assistance system when the membrane is in active position. 
     
    
    
     In these figures, the elements that are the same bear the same numeric references. 
     The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments can also be combined or interchanged to provide other embodiments. 
     In the following description, reference is made to first guiding members and to second guiding members. This relates to a simple indexing for differentiating and naming elements that are similar but not identical. This indexing does not imply a priority of one element over another and such denominations can easily be interchanged without departing from the scope of the present invention. Nor does this indexing imply an order in time, for example for assessing the movement of the support. 
     Referring to  FIGS. 1 and 2 , the invention relates to a driving assistance system  1  comprising an optical sensor  11  for a motor vehicle and a protection device  2  protecting the optical sensor  11 . 
     The protection device  2  comprises, on the one hand, a protection casing  13  in which is formed a housing  26  configured to house the optical sensor  11 , such as a camera, and, on the other hand, a membrane support  15  movably mounted on the protection casing  13 . 
     The protection casing  13  has a substantially central opening  25  configured to allow the passage of an optic  4  of the optical sensor  11 . Furthermore, the protection casing  13  bears at least one first guiding member  22  configured with a complementary second guiding member  23  borne by the support  15 . 
     According to the embodiment described here, the protection casing  13  comprises two guiding members  22  of cylinder type and the second guiding members  23  borne by the support  15  are of rod type. 
     The protection casing  13  also comprises at least one actuator  21  configured to move the support  15  along the optical axis  50  of the optical sensor  11 . According to the embodiment described here, the protection casing comprises two actuators  21  situated on either side of the substantially central opening  25  of the protection casing  13 . These actuators  21  are situated inside the guiding members  22  of cylinder type to enter into contact with the second guiding members  23 . 
     Moreover, according to this nonlimiting exemplary embodiment, the actuators  21  are linear piezoelectric transducers. Thus, the actuator  21  has a small bulk and is protected from external abuses which can be linked to random climatic factors or even to organic or mineral pollutants, which could prevent it from operating correctly. 
     The support  15  bears the membrane  19  which is fixed by its periphery thereto. According to the embodiment described here, the support  15  comprises a plate  16  secured to the second guiding members  23 . To this plate  16  there is fixed a fixing ring  17  for the membrane  19  and in which is an elastically deformable membrane  19  intended to be arranged facing the optical sensor  11 , 
     The plate  16  is intended to be oriented substantially at right angles to the optical axis  50  of the optical sensor  11  and comprises an opening  18  configured to accommodate the optic  4  of the optical sensor  11  in such a way that it protrudes from the opening and is in contact with the membrane  19 . The substantially central opening  25  of the protection casing  13  and the opening  18  of the plate  16  of the support  15  are therefore centered relative to the optical axis  50  of the optical sensor  11  and concentric. 
     The support  15 , under the effect of its movement by the actuator  21 , is configured to be displaced between a position of rest in which the membrane  19  is in a first state of tension (represented in  FIGS. 3 and 4 ), and an active position in which the membrane  19  is in a second state of tension (represented in  FIGS. 5 and 6 ). In the second state of tension, the membrane  19  is more taut than in the first state of tension. 
     The membrane  19  is elastically deformable and comprises an optically transparent material. The use of an elastomer in the formulation of the membrane  19  allows the latter to exhibit the elastic deformation sought. According to the embodiment described here, the membrane  19  is an elastomer exhibiting properties of resistance to ultraviolet radiation and non-stick properties. Because of its potential installation on the outside of a motor vehicle, it is advantageous for the properties of the membrane  19 , in particular of elasticity and of transparency, not to be altered by ultraviolet radiations. For example, it is best to avoid it becoming tarnished or opaque, or even it becoming embrittled because of exposure to the sun, in particular because of the UV radiation, that it will intrinsically be subjected to in its use. 
     According to this particular embodiment, silicon is introduced into the formulation of the elastomer. That makes it possible to confer on the elastomer a good resistance to ultraviolet radiations. The use of silicon in the formulation of the elastomer forming the membrane  19  also makes it possible to confer a hydrophobic character thereon. Drops of water will therefore be able to adhere to the membrane  19  only with difficulty and the traces that they would allow through their runoff would be almost invisible. Also, to limit the possibilities of adherence of the traces of water or of pollutants, the membrane  19 , preferably, has non-stick properties. Furthermore, according to this embodiment, the membrane  19  is fixed in the ring  17  by its periphery. 
     The complementary guiding members  22  and  23  are oriented so as to allow a translational movement of the support  15  along an axis substantially at right angles to the plane defined by the plate  16  and more particularly along the optical axis  50  of the optical sensor  11 . 
     Referring to  FIGS. 3 and 4 , the membrane  19  is in a position of rest, that is to say that it is in a first state of tension. 
     The arrows  32  directed toward the center illustrate the movement of the guiding members  23  under the effect of the actuator  21  when the support  15  is displaced in order for the membrane  19  to reach its position of rest. “Movement of the guiding members  23 ” should be understood to mean the displacement of the mobile support  15  relative to the protection casing  13 . 
     The arrows  34  show the direction of deformation of the membrane  19  in response to the moving of the support  15 . According to this representation, the direction of deformation of the membrane  19  is toward the interior thereof. This deformation of the membrane  19  occurs in response to the displacement of the support  15 . In this position of rest, the membrane  19  is in its first state of tension. In this position, the smears  30 , such as organic or mineral pollutants as well as traces of water, can be deposited on the membrane  19  and thus be detrimental to the correct operability of the driving assistance system  1 . 
     According to  FIG. 4 , the actuator  21  is configured to move the support  15  along the optical axis  50  of the optical sensor  11 . This type of translation avows the membrane  19  to undergo similar pulling forces over all of its surface when it switches to active position. 
     The movement of the support  15  is possible by virtue of gaps  40 ,  42  and  43  present between the support  15  and the protection casing  13 . These gaps  40 ,  42  and  43  each define a spacing between the support  15  and the protection casing  13  which is maximal ( FIG. 4 ) when the membrane  19  is in position of rest and minimal ( FIG. 6 ) when the membrane  19  is in its active position. 
     According to the representation in  FIG. 4 , the gap  40  corresponds to the space present between the protection casing  13  and the support  15  at the level of the guiding members  22 . The gap  42  corresponds to the space between the ring  17  and the rim of the objective  6  bearing the lens  4  of the camera  11 . The gap  43 , for its part, corresponds to the space between the support  15  and the surface of the protection casing  13  having the substantially central opening  25  intended to accommodate the lens  4  of the camera  11 . According to this embodiment, it will be noted that the lens  4  protrudes through the opening  18  of the plate of the support  15 . According to this representation, it will be observed that the lens  4  is partially in contact with the membrane  19  arranged on the plate  16  when the membrane  19  is in position of rest. It will also be noted, according to this representation, that the elastic membrane  19  is arranged coaxially with the optical axis  50  of the optical sensor  11 . 
     The contact between the membrane  19  and the lens  4  of the camera  11  will make it possible to tension the membrane  19  when the latter switches from its position of rest, that is to say its first state of tension, to its active position, that is to say its second state of tension, under the effect of the moving of the support  15 . For this change of position to be possible, it is necessary for the membrane  19  to be facing the lens  4  of the optical sensor  11 . 
       FIGS. 5 and 6  represent the membrane  19  in its active position, that is to say that it is in the second state of tension. When the membrane  19  is in this second state of tension, it is more taut than when it is in its first state of tension. 
     The arrows  33  directed outward from the center illustrate the movement of the guiding members  23  under the effect of the actuator  21  when the support  15  is displaced in order for the membrane  19  to reach its active position. These arrows  33  are opposed to the arrows  32  represented in  FIGS. 3 and 4 . 
     The arrows  35  illustrate the direction of deformation of the membrane  19 . According to this representation, the deformation of the membrane  19  corresponds to an extension thereof when the membrane  19  switches to its second state of tension. This deformation therefore takes place toward the outside of the membrane  19 . These arrows  35  are opposed to the arrows  34  represented in  FIGS. 3 and 4 . This tension will allow the smears  30  to drop from the surface of the membrane  19 . 
     According to  FIG. 6 , the gap  41  between the support  15  and the protection casing  13  corresponds to the minimum possible space between these two elements. This gap  41  corresponds to the gap  40  represented in  FIG. 4  when the membrane  19  is in its position of rest. It will be noted that the gaps  42  and  43  initially present in  FIG. 4  between the support  15  and the base of the objective  6  of the optical sensor  11  have disappeared because of the moving of the support  15  relative to the protection casing  13  under the effect of the actuator  21 . 
     In this active position, the elastic membrane  19  is, according to this embodiment, fully in contact with the lens  4  of the optical sensor  11  which protrudes through the opening of the plate  16  of the support  15  which bears the ring  17 . The contact between the membrane  19  and the lens  4  will serve as bearing point. Moreover, since the membrane  19  is fixedly mounted in the ring  17  borne by the support  15 , the membrane  19  will be able to stretch to reach its active position when the support  15  approaches the protection casing  13  or to shrink to reach its position of rest when the support  15  moves away from the protection casing  13 . Thus, the membrane  19  will tighten and switch to active position when the support  15  approaches the protection casing  13  under the effect of the actuator  21 . 
     During the operation of the protection device  2  according to the invention, the support  15  will perform several reciprocal movements at a predefined frequency. According to this embodiment, the frequency of displacement of the support  15  relative to the protection casing  13  lies within the ultrasound range. 
     When the membrane  19  is in active position, the contact surface between the membrane  19  and the smears  30  is reduced. Thus, links between the smears  30  and the membrane  19  will be broken thus allowing the latter to drop. Also, the membrane  19  exhibits a greater elasticity than the smears  30  which adhere thereto. Because of this, by stretching the membrane  19 , there is also a tendency to stretch the smears  30 , which is not possible because of their lesser elasticity. These two combined actions linked to the tension of the membrane  19  will allow the smears to drop therefrom. Moreover, when the membrane  19  is in its second IS state of tension, the latter will allow links to be broken within the smears  30  and thus facilitate the disintegration thereof. 
     According to this particular embodiment, by using piezoelectric transducers as actuator  21 , a deformation of the membrane  19  lying between 0.5% and 5% makes it possible to obtain an effective dropping of the smears  30 . 
     According to this particular embodiment, the moving of the support  15  by the actuators  21  is controlled automatically by the vehicle at the end of a predefined period of use thereof. 
     Alternatively, the actuators  21  of the support  15  can be replaced by electromagnets. In this case, the second guiding members  23  of rod type borne by the support  15  are made of a ferromagnetic material. 
     According to another embodiment, the actuators  21  can be mechanical systems comprising a toothed wheel and a rack for example. 
     The use of a piezoelectric transducer as actuator  21  makes it possible to have a fairly small and very rapid movement of the support  15  bearing the membrane  19  relative to the protection casing  13 . The use of an electromagnet or of a mechanical system as actuator  21  will require a longer travel of the support  15  bearing the membrane  19  relative to the protection casing  13 . The use of these second systems will allow a greater elongation of the membrane  19 . For such actuators  21 , an elongation of the membrane  19  lying between 5% and 15% makes it possible to obtain an effective dropping of the smears  30 . 
     According to another embodiment, the actuator  21  can be placed outside of the protection casing  13 . In this case, the actuator  21  can be located behind the protection casing  13 , in front of it, or even above or below it. 
     According to another embodiment, the complementary first and second guiding members  22 ,  23  borne by the protection casing  13  and by the mobile support  15  can be systems with complementary form structure. 
     According to an alternative embodiment, the guiding members  23  borne by the support  15  can be of cylinder type. In this case, the complementary guiding members  22  borne by the support  15  will be of rod type. In this particular embodiment, the actuator  21  will be borne by the support  15 . 
     According to another embodiment, it is possible to modify the times of activation of the moving of the support  15 . It is for example possible to move the support  15  when the vehicle is started up. 
     Alternatively it is possible to command the moving of the support  15  when a detector measures a fouling state that might be detrimental to the correct operation of the optical sensor  11 . 
     According to another embodiment, the moving of the support  15  can be commanded by the user. This is particularly advantageous when the protection device  2  is used to protect optical sensors  11  used in parking aid systems. The user can therefore activate the actuator  21 , and thus allow the moving of the support  15 , when he or she observes that the membrane  19  is fouled, for example when using the driving assistance system  1  as parking aid. Moreover, in this configuration, the presence of the detector is not necessary. 
     According to another embodiment, the membrane  19  can be directly fixed by its periphery to the plate  16  of the support  15  without requiring the use of the ring  17 . 
     Optionally, it is possible to place a cleaning product spray nozzle in proximity to the membrane  19  so as to spray cleaning product onto the latter. The spray nozzle can be incorporated or not in the protection casing  13 . 
     These exemplary embodiments are provided in an illustrative and nonlimiting manner. In fact, it is perfectly possible for the person skilled in the art. without departing from the scope of the invention, to replace the actuators  21  described here with any other actuator making it possible to move the support  15  by a translation substantially at right angles to the plate  16  of said support  15 . Also, the person skilled in the art will be able to use any other compound exhibiting a resistance to UV and/or having hydrophobic properties and whose physical and mechanical properties are compatible with the use described above in the formulation of the elastomer forming the membrane  19  without departing from the scope of the invention. Finally, he or she will be able to replace the guiding members  22  and  23  described here with any other type of complementary guiding members without departing from the scope of the invention. 
     The rapid and effective cleaning, without necessarily requiring cleaning product, of the optic  4  of an optical sensor  11 , possibly a camera for example, intended to equip a motor vehicle, is thus possible by virtue of the subject of the present invention which comprises an optically transparent and elastically deformable membrane  19  mounted on a mobile support  15 . The support  15  cooperates with a protection casing  13  which accommodates the camera. The moving of the support  15  uses complementary first and second guiding members  22  and  23  borne respectively by the protection casing  13  and by the support  15 . The support  15  is moved using one or more actuators  21 , for example borne by the protection casing  13 . The moving of the support  15  allows the membrane  19  to switch from its position of rest to its active position in order to allow the smears  30  to drop away.