Optical wedge element for glazing with optical sensors - Patents.com

Abstract

The present invention relates to a glazing including an optical sensor facing its inner surface. An optical wedge element having an optimized wedge angle is placed on the inner surface of the glazing between the glazing and the optical sensor. The present invention also relates to the use of a glazing including an optical wedge element and a method for determining an optimal wedge angle γ of such an optical wedge element.

Description

[Technical field]

[0001] The present invention relates to the field of optical sensors placed behind a sloped glazing. In particular, it relates to an optical wedge element placed on the inner surface of the sloped glazing. The present invention also relates to a method for rescaling the field of view of an optical sensor placed behind a sloped glazing, in particular behind a sloped glazing of a vehicle. [Background technology]

[0002] Nowadays, vehicles are equipped with an increasing number of optical sensors. Vehicles include cars, vans, lorries, motorbikes, buses, trams, trains, drones, planes, helicopters, etc. In addition to vehicles, there is also an increasing requirement to install optical sensors behind the glazing of buildings (including wind turbines, oil rigs, road signs, etc.).

[0003] Among the optical sensors used on vehicles, there is an ever-increasing demand for emitting and receiving (E / R) optical sensors, which means optical sensors that first emit a signal from the vehicle towards the outside of the vehicle and then receive the signal reflected by some obstacle outside the vehicle. Lidar is a representative example of such an E / R optical sensor. Both the expressions "emitting / receiving" or "E / R" may be used throughout this specification, and both refer to the same concept.

[0004] The trend is towards integrating such E / R optical sensors behind the glazing of the vehicle. Since the E / R optical sensors are placed behind the glazing, significant signal losses arise from reflection of the emitted signal on the inner surface of the glazing (meaning the surface of the glazing that faces the inside of the vehicle). Such reflections occur at the air / glazing interface when the light beam is emitted towards the outside. This attenuation impairs the detection by the E / R optical sensor, so that accurate distance measurements are no longer possible.

[0005] If the E / R optical sensor is placed behind the inclined glazing of the vehicle, the signal is attenuated even more. For example, in the case of a windshield, the E / R optical sensor is placed at an angle of 25° to 40° with the horizontal plane. Since the E / R optical sensor is usually placed in the upper part of the windshield, which may be curved more in its upper part, the angle between the glazing and the horizontal plane is even smaller (usually 20° to 35°). Therefore, if the E / R optical sensor is placed horizontally, this means an incidence angle of the signal on the glazing (complement of the angle between the glazing and the horizontal plane) of 55° to 70°. Thus, considering a field of view (FOV) of the E / R optical sensor of 30°, this leads to an incidence angle on the glazing that may be as large as 85°, resulting in a significant portion of the signal being reflected.

[0006] One way to reduce such reflections is to coat the inner surface of the glazing with an antireflective (AR) coating. An AR coating can be applied on the glazing, for example, by physical vapor deposition (PVD). The AR coating is only required on a small area of ​​the glazing (which means "on a part of the glazing inside the field of view (FOV) of the optical sensor"). However, local deposition is quite complicated. Thus, rather full coverage is applied, leading to an AR coating on areas that do not require an AR coating. Masking is required on the whole glass surface except on the dedicated areas for the AR coating, which leads to manufacturing constraints. Local deposition can be performed by techniques other than PVD, but these techniques usually do not reach a high level of optical quality in terms of roughness, uniformity and durability. Moreover, standard AR coatings are usually optimized for normal incidence. The performance of such AR coatings decreases with increasing incidence angle of the incident light. Specially designed AR coatings can be optimized for large angles of incidence, but such AR coatings are more complex, more expensive and challenging to install. AR coatings obviously increase manufacturing difficulties and costs. Furthermore, AR coatings can reduce the mechanical, chemical and thermal resistance of the glazing to which they are applied.

[0007] Another way to reduce such reflections is to place prismatic elements with appropriate refractive index and absorption level on the inner surface of the glazing to adapt the angle of incidence of the beam, as disclosed in WO 9419705. Such optical wedge elements will reduce reflections. However, optical wedge elements can be large pieces of material with significant weight and size, complicating their integration on the glazing of the vehicle or leading to difficulties in bonding the optical wedge elements to the glazing. Furthermore, due to the thickness of the optical wedge elements, the optical wedge elements will absorb part of the signal, thus causing signal attenuation.

[0008] The use of the optical wedge element also leads to a modification of the field of view (FOV) of the optical sensor. Usually, for a vehicle that includes an optical sensor behind one of the vehicle's glazings, the manufacturer requires a specific field of view of the optical sensor when the optical sensor is placed behind the glazing. This specific FOV is required not only so that the optical sensor can detect objects outside the vehicle, but also so that it can measure the distance between such objects and the vehicle. Thus, the FOV of the optical sensor is designed based on the FOV specification from the manufacturer. However, when the optical sensor is placed facing the optical wedge element (and the glazing), its FOV is modified. This modified FOV no longer corresponds to the required FOV.

[0009] WO2018087223 also discloses the use of a light guide (active in the visible wavelength range) in the camera. Such a light guide can also act as an optical prism and be assimilated as an optical wedge element. However, the purpose of this optical wedge element is to deflect the radiation passing through the vehicle window from the outside and detected by the sensor in such a way that the working angle of the sensor is enlarged. The area of ​​the vehicle window used for detection is then reduced. It is thus possible to use a less transparent masking print to hide the sensor, leading to an improvement in the total light transmittance and aesthetic appearance of the vehicle window. As stated in this patent document, the larger the wedge angle, the stronger the deflection of the radiation and the more noticeable its effect, but the wedge angle is limited by space requirements. However, the larger the wedge angle, the thicker the optical wedge element and the higher the absorption of light due to the optical wedge element, thus leading to less accurate measurements since the camera receives less light.

[0010] Therefore, there is a need for an optical wedge element that corrects the shortcomings of the optical wedge elements known from the prior art and that answers the requirements from vehicle manufacturers. Summary of the Invention [Means for solving the problem]

[0011] The present invention relates to a glazing having an inner and an outer surface. The glazing includes an E / R optical sensor facing the inner surface of the glazing. The E / R optical sensor has a unique field of view α. The glazing also includes an optical wedge element also having an inner and an outer surface. The optical wedge element is located between the inner surface of the glazing and the E / R optical sensor. The outer surface of the optical wedge element faces the inner surface of the glazing. The inner and outer surfaces form a wedge angle γ. The glazing is located at an installation angle τ with respect to a horizontal plane in the area where the E / R optical sensor faces the inner surface of the glazing. The scaling factor is TIFF2024524062000002.tif11170, where β is the field of view of the E / R optical sensor placed on the inner surface of the glazing. The maximum angle of incidence ι of the signal emitted by the E / R optical sensor on the inner surface of the optical wedge elementmax is set to a value of 60°, more preferably 50°, and even more preferably 40°. The wedge angle γ is determined such that the intersection of the field of view α of the E / R optical sensor with the inner surface of the optical wedge element is at a maximum incidence angle ι max The following incidence angles ι L+ , ι L- is equal to the value that forms the

[0012] The present invention also relates to the use of glazing that includes optical wedge elements, as well as to a method for determining the optimum wedge angle γ of such optical wedge elements. [Brief description of the drawings]

[0013] The present invention will be further described, by way of example only, with reference to the accompanying drawings, in which like reference numerals refer to like elements in the various drawings. These examples are provided by way of illustration and not by way of limitation. The accompanying drawings are schematic and not to scale. The accompanying drawings do not limit the invention in any manner. Further advantages will be illustrated by some examples.

[0014] [Figure 1] 1 shows a 3D view of an optical wedge element according to the present invention placed behind the windshield of a vehicle. [Figure 2a] Figure 2b shows a 2D view of an optical wedge element according to the present invention placed behind a vehicle glazing; [Figure 2b] FIG. 2b is an enlarged view of FIG. 2a showing a 2D view of an optical wedge element according to the present invention placed behind a vehicle glazing. [Figure 2c] 13 illustrates an embodiment in which the E / R optical sensor is tilted compared to the horizontal plane. [Diagram 3] 1 is a graph of the scaling factor S as a function of wedge angle for various values ​​of installation angle. [Figure 4] 1 shows the reflectance based on the Fresnel equation at the interface between a material having a refractive index of 1.5 and air. [Diagram 5] 1 illustrates the positive impact of using an optical wedge element according to the present invention for a given configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

[0016] Although some embodiments described herein include some features included in other embodiments and not others, combinations of features of the various embodiments are intended to form various embodiments within the scope of the invention, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments may be used in any combination.

[0017] The present invention proposes a glazing that includes an emitter / receiver optical (E / R) sensor and an optical wedge element placed between the glazing and the E / R sensor. Although the following description focuses on the case of vehicle glazing, the present invention can be applied to optical wedge elements placed on any kind of glazing.

[0018] Vehicle glazing refers to any conventional window of a vehicle, such as windshield, rear light or side light (including triangular window). Essentially, such vehicle glazing is provided to separate the vehicle interior from the outside environment. However, such vehicle glazing can also refer to any other external part of the vehicle, as long as it is transparent to the wavelength range of the E / R optical sensor. For example, the E / R optical sensor may be placed inside the headlight compartment. In this case, the glazing refers to the transparent part that forms the headlight. Another example would be an E / R optical sensor placed behind one of the pillars of a motorized vehicle. In this case, the glazing refers to the part placed in front of the E / R optical sensor as the pillar cover.

[0019] The vehicle glazing includes at least one window frame. A surface of the at least one window frame that faces the vehicle's exterior envelope in the installed position is referred to as the "exterior surface." A surface of the at least one window frame that faces the vehicle's interior in the installed position is referred to as the "interior surface." The same terminology is used to describe the surfaces of the optical wedge element: "exterior surface" refers to the surface in contact with the interior surface of the glazing, while "interior surface" refers to the surface in front of the E / R optical sensor.

[0020] Vehicle glazing can be made of glass (single glass) or plastic, or a combination thereof (such as laminated glass), as long as it is transparent in the operating wavelength range of the E / R optical sensor. The glazing can be flat or curved. Vehicle glazing (such as, for example, an automobile windshield) can also exhibit a different curvature at the top than at the bottom.

[0021] E / R optical sensor refers to an emitting / receiving optical sensor such as a lidar or radar. In the case of a lidar, the lidar first emits IR light from inside the vehicle towards the outside of the vehicle. The IR light is then reflected by an object outside the vehicle back to the sensor, which can then assess the distance between the vehicle and said object.

[0022] The optical wedge element may be made of glass or plastic, such as polyvinyl butyral (PVB), polyurethane (PU), polymethyl methacrylate (PMMA), polycarbonate (PC) or optical silicon. The optical wedge element may also be made of a combination of these materials. Basically, the optical wedge element may be made of any material as long as it is transparent in the operating wavelength range of the E / R optical sensor. The optical wedge element must also exhibit a refractive index close to that of the glazing for the purposes of the present invention. The optical wedge element may also be coated with an anti-reflection coating to reduce the reflection on its surface. Applying such an anti-reflection coating on the optical wedge element is easier and cheaper than applying it on the entire surface of the glazing as discussed, compared to the prior art. Furthermore, a standard AR coating designed for normal incidence may be used so that the angle of incidence is kept below a defined value (described later in this specification). Additional features may be added to this optical wedge element, such as heat coating or silver printing. The optical wedge element may be attached to the vehicle glazing by gluing, autoclaving, mechanical clipping, laser welding, optical bonding, or any other method known to one of ordinary skill in the art.

[0023] The wedge angle γ is the angle formed by the outer and inner surfaces of the optical wedge element.

[0024] The installation angle τ is the angle formed by the vehicle glazing and a horizontal plane in the area of ​​the glazing where the E / R optical sensor faces the inner surface of the glazing.

[0025] FOV Scaling Typically, for a vehicle that includes an E / R optical sensor behind at least one of its glazings, the manufacturer requires a specific field of view (FOV) of the E / R optical sensor when the optical sensor is placed behind the glazing. This specific FOV is required not only for the E / R optical sensor to be able to detect objects outside the vehicle, but also to be able to measure the distance between such objects and the vehicle. This required FOV is different from the intrinsic FOV of the E / R optical sensor, since the light rays have to pass through the glazing and thus encounter refraction. Therefore, the required FOV is always larger than the intrinsic FOV of the E / R optical sensor. A scaling factor S determines the ratio between the intrinsic FOV and the required FOV: TIFF2024524062000003.tif15170

[0026] The intrinsic FOV is specific to the E / R optical sensor. Using a ray tracing simulation method, it is possible to determine the scaling factor S based on the installation angle, wedge angle, and refractive index of the glazing and optical wedge elements.

[0027] Basically, the intrinsic FOV of the E / R optical sensor should be as small as possible. In this way, the sensor zone on the glazing (meaning the zone within the glazing): the zone through which the light rays travel from or to the E / R optical sensor (and which is transparent for the working wavelength range of the E / R optical sensor) can be relatively small. Because this sensor zone is small, the optical wedge element thickness can also be reduced, which leads to less absorption on the glazing as well as easier integration.

[0028] The inherent FOV of the optical sensor needs to be scaled and the signal distribution needs to be redistributed so that the required FOV (behind the vehicle glazing with the optical wedge element) follows the required configuration from the vehicle manufacturer. Usually, the required FOV can be adjusted to the required configuration by only manipulating the tilt of the E / R optical sensor and the wedge angle of the optical wedge element. However, additional corrective optical elements such as distorting lenses may also be added between the E / R optical sensor and the optical wedge element to rescale the size and signal distribution of the inherent FOV.

[0029] Maximum angle of incidence on the inner surface of the optical wedge element The angle of incidence ι is the angle of incidence of the E / R optical sensor signal on the inner surface of the optical wedge element. As known by those skilled in the art, the smaller the angle of incidence, the less reflection occurs and the higher the transmittance of the light beam.

[0030] Based on the Fresnel equations and knowing the refractive indices of both the glazing and the optical wedge, the reflectance can be calculated as a function of the angle of incidence. Depending on the minimum transmittance required for the E / R optical sensor to operate with sufficient accuracy, the maximum reflectance can be estimated. This maximum reflectance is given by the maximum angle of incidence ι on the inner surface of the optical wedge. max Corresponds to.

[0031] maximum angle of incidence ι max is set to a value of 60°, more preferably 50°, and even more preferably 40°.

[0032] Minimum Wedge Angle The intersection of the inner surface of the optical wedge element and the inherent FOV of the E / R optical sensor is the maximum incidence angle ι max A wedge angle γ is determined that produces an angle of incidence of: Selecting the minimum wedge angle γ will make the optical wedge element as thin as possible, thus leading to less absorption from the material of the optical wedge element and in turn to a higher transmission.

[0033] The present invention also relates to the use of glazing that includes an optical wedge element to reduce reflection of a signal from an E / R optical sensor at the inner surface of the glazing.

[0034] The present invention also relates to a method for determining an optimum wedge angle for an optical wedge element placed on an inner surface of a glazing, the inner surface of the optical wedge element facing an E / R optical sensor. EXAMPLES

[0035] In the following examples, the invention will be described in detail with reference to the accompanying drawings (exemplary embodiments), which are schematic and not to scale, and which do not limit the invention in any way.

[0036] Figure 1 shows a 3D view of a vehicle glazing (1) (in this case a windshield) with an E / R optical sensor (2) facing the vehicle glazing (1). An optical wedge element (3) is placed between the vehicle glazing (1) and the E / R optical sensor (2). As can be seen, both the intrinsic FOV (α) and the required FOV (β) are conical. However, for clarity of explanation, the following explanation will be based on a 2D view, but the reasoning remains the same.

[0037] 2a depicts a vehicle glazing (1) with an E / R optical sensor (2) facing an inner surface (1i) of the vehicle glazing (1). An optical wedge element (3) is placed between the vehicle glazing (1) and the E / R optical sensor (2). The outer surface (3e) of the optical wedge element (3) and the inner surface (1i) of the glazing (1) are aligned with each other. In this example, both the glazing (1) and the optical wedge element (3) have the same refractive index of 1.5.

[0038] The required FOV (β) is the limit ray (L- b , L+ b In this example, the required FOV (β) is equal to 30°. b , L+ b ) are respectively at −15° and +15° symmetrically relative to the center of the desired FOV (β), which is horizontal in this example.

[0039] Figure 2b depicts the same vehicle glazing (1) with the same E / R optical sensor (2) and including the same optical wedge element (3) at a higher magnification for clarity of illustration. Figure 2b also shows the installation angle (τ) corresponding to the angle formed by the horizontal plane and the vehicle glazing (1) in the area where the E / R optical sensor (2) is placed close to the vehicle glazing (1). In this example, the E / R optical sensor (2) is placed horizontally, but may be tilted compared to the vehicle glazing (1) as shown in Figure 2c.

[0040] The intrinsic FOV (α) of the E / R optical sensor (2) is also determined by its limiting ray (L- a ,L+ a The limit ray (L- a ,L+ a ) incidence angle (ι L- , ι L+ ) is also depicted.

[0041] The wedge angle (γ) is the angle formed by the outer surface (3e) and the inner surface (3i) of the optical wedge element (3).

[0042] The scaling factor is given by: TIFF2024524062000004.tif13170

[0043] FIG. 3 shows the scaling factor S as a function of the wedge angle (γ) for various values ​​of the installation angle (τ). As the installation angle (τ) increases, the scaling factor S increases as well. For a fixed installation angle (τ)≦40°, the scaling factor S decreases with increasing wedge angle (γ) (up to 30°): the larger the wedge angle (γ), the smaller the intrinsic FOV (α). Moreover, for a fixed installation angle (τ)>40°, the scaling factor S reaches a minimum value for a wedge angle (γ)<30°. This means that the design should be as close as possible to this wedge angle (γ) in order to have the smallest intrinsic FOV (α).

[0044] The maximum angle of incidence (ι) on the inner surface (3i) of the optical wedge element (3) max ) is 60°, more preferably 50°, and even more preferably 40°. Based on the Fresnel equation, FIG. 4 shows the reflection at the interface between a material with a refractive index of 1.5 and air. It is assumed that the maximum reflection value is fixed at 5%. This value is chosen as an example and may therefore vary depending on the E / R optical sensor sensitivity. This value is set at angles of incidence (ι) lower than 40°. max ), which means that the E / R optical sensor receives enough transmitted signal for accurate measurement as long as the angle of incidence (ι) on the inner surface (3i) of the optical wedge element (3) is less than 40°.

[0045] Table 1 shows the angle of incidence (L+ a ,L- a ) and the corresponding incidence angle (ι L+ ,ι L- ) values. For this example, values ​​below 40° as defined previously have been highlighted in bold.

[0046] TIFF2024524062000005.tif230170

[0047] The minimum wedge angle (γ) is the angle at which the intersection of the inner surface (3i) of the optical wedge element (3) with the intrinsic FOV (α) of the E / R optical sensor (2) is smaller than the previously defined maximum incidence angle (ι max ) (40° in this example) L+ ,ι L- ) is equal to the value that forms the

[0048] Table 2 shows the optimum values ​​of the wedge angle (γ) depending on the installation angle (τ). The minimum values ​​of the wedge angle (γ) were selected from Table 1 among the highlighted bold values.

[0049] TIFF2024524062000006.tif46170

[0050] Comparative Example Based on the previous example, both the glazing (1) and the optical wedge element (3) have a very low absorption coefficient (0.01 cm -1 Based on the fact that the required FOV (β) has a wedge angle (γ) of 15° for an installation angle (τ) of 30°, FIG. 5 shows the total transmittance within the required FOV (β) with and without the optical wedge element (3) having a wedge angle (γ) of 15°. Thanks to the optical wedge element (3) with the optimum value of the wedge angle (γ) defined before, the transmittance can be increased by up to 10%, which is very meaningful in the automotive industry.

[0051] While the present invention has been illustrated and described in detail in the accompanying drawings and the foregoing specification, such illustrations and descriptions are to be considered as illustrative or exemplary and therefore not restrictive. The foregoing specification details several embodiments of the present invention. However, no matter how detailed the foregoing specification appears in text, it should be understood that the invention can be practiced in many ways. The present invention is not limited to the disclosed embodiments.

Claims

1. A glazing (1) having an inner surface (1i) and an outer surface (1e), said glazing (1) comprising: a. an emission / reception optical sensor (2) facing the inner surface (1i) of the glazing (1) and having a specific field of view (α); b. an optical wedge element (3) having an inner surface (3i) and an outer surface (3e) placed between the inner surface (1i) of the glazing (1) and the emitting / receiving optical sensor (2), the outer surface (3e) of the optical wedge element (3) facing the inner surface (1i) of the glazing (1), the inner surface (3i) and the outer surface (3e) forming a wedge angle (γ); Including; said glazing (1) is placed at an installation angle τ to a horizontal plane in the area where said emission / reception optical sensor (2) faces said inner surface (1i) of said glazing (1); where the scaling factor is and β is the required field of view of the emission / reception optical sensor (2) placed on the inner surface (1i) of the glazing (1), i. The maximum angle of incidence ι of the signal emitted by the emission / reception optical sensor (2) on the inner surface (3i) of the optical wedge element (3). ｍａｘ is set to a value of 60°, more preferably 50°, and even more preferably 40°; ii. The wedge angle (γ) is determined by the intersection of the field of view (α) of the emitting / receiving optical sensor (2) with the inner surface (3i) of the optical wedge element (3) at the maximum incidence angle (ι ｍａｘ ) or less incidence angle (ι Ｌ＋ ,ι Ｌ－ ) is equal to the value that forms the The glazing (1) is characterized by:

2. The wedge angle (γ) is determined by the angle at which the intersection of the field of view (α) of the emitting / receiving optical sensor (2) with the inner surface (3i) of the optical wedge element (3) is greater than the maximum incidence angle (ι ｍａｘ ) or less incidence angle (ι Ｌ＋ ,ι Ｌ－ 2. The glazing (1) according to claim 1, wherein the minimum value forming the glazing (1) is 0.015 μm.

3. 3. The glazing (1) according to any one of claims 1 to 2, wherein the optical wedge element (3) is made of glass or plastic, such as polyvinyl butyral (PVB), polyurethane (PU), polymethyl methacrylate (PMMA), polycarbonate (PC) or optical silicon, or a combination thereof.

4. 3. The glazing (1) according to any one of claims 1 to 2, wherein the inner surface (3i) of the optical wedge element (3) is coated with an anti-reflection coating.

5. The glazing (1) according to any one of claims 1 to 2, wherein the optical wedge element (3) is fixed to the glazing (1) by gluing, autoclaving, mechanical clipping, laser welding or optical bonding.

6. The glazing (1) according to any one of claims 1 to 2, wherein the emitting / receiving optical sensor (2) is a Lidar.

7. 3. The glazing (1) according to claim 1, further comprising an additional corrective optical element, such as a distortion lens, between the emission / reception optical sensor (2) and the optical wedge element (3), adapted to rescale the size and signal distribution of the eigenfield (α) of the emission / reception optical sensor (2).

8. The glazing (1) according to any one of claims 1 to 2, wherein the glazing (1) is an automobile glazing.

9. The glazing (1) according to claim 8, wherein the glazing (1) is a windscreen or a rear light.

10. The glazing (1) according to any one of claims 1 to 2, wherein the glazing (1) is made of glass or plastic or a combination thereof.

11. The glazing (1) according to any one of claims 1 to 2, wherein the glazing (1) is a laminated glazing.

12. 3. The glazing (1) according to any one of claims 1 to 2, wherein the glazing (1) has a transmittance value of 90% or more in the operating wavelength range of the emitting / receiving optical sensor.

13. 3. Glazing (1) according to any one of claims 1 to 2, wherein the optical wedge element (3) has a transmittance value of 90% or more in the operating wavelength range of the emitting / receiving optical sensor.

14. Use of a glazing (1) according to any one of claims 1 to 2 for reducing the reflection of the signal from the emitting / receiving optical sensor (2) at the inner surface (1i) of the glazing (1).

15. 1. A method for determining an optimal wedge angle (γ) formed by an inner surface (3i) and an outer surface (3e) of an optical wedge element (3), comprising the steps of: - said optical wedge element (3) is placed on the inner surface (1i) of a glazing (1) having an inner surface (1i) and an outer surface (1e), said outer surface (3e) of said optical wedge element (3) facing said inner surface (1i) of said glazing (1); - the inner surface (3i) of the optical wedge element (3) faces a transmission / reception optical sensor (2), the transmission / reception optical sensor having a specific field of view (α); - said vehicle glazing (1) forms an installation angle (τ) with respect to the horizontal plane in the area where said emission / reception optical sensor (2) is placed near said glazing (1); The method comprises: determining a scaling factor S based on said installation angle (τ), and β is the field of view of the emitting / receiving optical sensor (2) placed on the inner surface (1i) of the vehicle glazing (1); b. The maximum angle of incidence (ι) at the inner surface (3i) of the optical wedge element (3) based on the maximum defined reflection ｍａｘ ) to determine; c. The intersection of the field of view (α) of the emitting / receiving optical sensor (2) with the inner surface (3i) of the optical wedge element (3) is within the maximum angle of incidence (ι) defined in step b). ｍａｘ ) or less incidence angle (ι Ｌ＋ ,ι Ｌ－ ) to determine the minimum wedge angle (γ) that will form A method comprising:

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