FR3090822A1 - Glass and light device for obstacle detection system - Google Patents

Abstract

The invention relates to a closing glass (2) for a vehicle lighting device (1) comprising two faces, an outer face (21) and an inner face (20), it is characterized in that it comprises at least one coating anti-reflective (22) on at least one side. The anti-reflective coating makes it possible to reduce the repair on the treated face and therefore to increase the quantity of effective waves of the detection system, thus gaining up to 18% of range of the detection system between the transmission and reception of the signals. electromagnetic waves. Figure for the abstract: Figure 2]

Description

Description

Title of the invention: Glass and light device for obstacle detection system

The invention relates to the field of light devices with obstacle detection system of a motor vehicle and more particularly the closing glass fitted to said device.

Motor vehicles in particular, autonomous vehicles, are now equipped with obstacle detection systems consisting of an emitter of electromagnetic waves and a receiver. The emitted electromagnetic waves will reflect on the obstacle and be picked up by the receiver. These detection systems are not very aesthetic, they are most often hidden in the front light devices of the vehicle.

However, these light devices include a closing glass at the front which disturbs the propagation of electromagnetic waves. Indeed, the ice by the effect of the Eresnel reflection of the electromagnetic waves on the ice, there is a loss of about 4% per diopter or 8 to 9% of the waves emitted and 8% to 9% for the waves reflected by the obstacle, for a total of 16 to 18%. Due to this loss, the detection system cannot, for example, the detection distance could be reduced by at least 10m compared to placement outside.

This loss is all the more critical when the climatic conditions are bad (temperature, frost, rain, ...).

The detection system uses electromagnetic waves which are located in the infrared zone so as not to interfere with the vision of the driver of the vehicles coming opposite because the eye does not perceive these wavelengths while being able to scan the entire front periphery of the vehicle, while the lighting consists of waves located in the visible spectrum, in particular white with a wavelength between 400 and 630nm.

To cope with these various constraints, the current solution consists in increasing the power of the detection system to keep the same range, but this increases its consumption all the more.

An object of the present invention is to overcome the drawbacks of the prior art mentioned above and by proposing a suitable lens and a light device as well as the method for manufacturing said lens.

The closing glass of a vehicle light device according to the invention has two faces, an outer face and an inner face, it is characterized in that it comprises at least one anti-reflective coating on at least part of a face. The anti-reflective coating makes it possible to reduce the repair on the treated face and therefore to increase the quantity of effective waves of the detection system, thus gaining up to 18% of the range of the detection system between the emission and the reception of the electromagnetic waves.

According to a particular provision, the anti-reflective coating covers only a portion of the face. The detection system being placed relatively close to the ice, its radiation is localized, it is therefore not necessary to treat the entire surface of the ice, only the area facing the system is treated. The cost of processing the ice is thus reduced.

According to another arrangement, the glass comprises at least one anti-reflective coating on each of the faces. To further reduce the reflection, both sides of the glass are treated. Preferably, the coatings will be identical on each side.

According to a particular characteristic, the anti-reflective coating has a thickness of between 10 and 250 nm (nanometers). The coating preferably has a thickness of around 155nm for centering at 850nm, 145nm for centering at 800nm, 162nm for centering at 900nm and 250nm for centering at 1400nm. In general, we allow +/- 10% error for a monolayer on the thickness error.

According to a first embodiment, the coating comprises only a single anti-reflective layer of low refractive index in the infrared zone, on the outer face. The layer limits the reflection of electromagnetic waves emitted by the detection system.

According to a particular arrangement of the first embodiment, the anti-reflective layer is made of MgF ₂ . MgF ₂ has a refractive index of 1.37 for a wavelength of 850 nm, the infrared zone being between 700 and 2500nm.

According to a second embodiment, the coating comprises several superimposed layers. The superposition of several layers makes it possible to choose the wavelengths which will have the least reflection in a wider spectrum by playing on the material used and / or their thickness.

According to a particular characteristic of the second embodiment, each layer is made of a material with a different refractive index. The combination of materials with different refractive indices allows you to choose the waves that will be the least reflected.

According to another characteristic, the coating comprises 2 to 10 layers. This number of layers is sufficient to have a limited reflection in the lighting and infrared wavelengths.

According to a particular arrangement, the coating alternates layers of materials of high and low refractive index in the infrared zone. This makes it possible to adapt the treatment of the glass to the desired result and in particular to widen the spectral range of function of the anti-reflective coating.

The invention also relates to a vehicle light device comprising an obstacle detection system by emission and reception of electromagnetic waves, it is characterized in that it comprises a lens with at least one of the preceding characteristics and that the detection system is arranged opposite at least one anti-reflective coating.

The invention also relates to a method for treating a light device closing lens having at least one of the preceding characteristics, said method comprises a step of laying at least one anti-reflective coating on at least one face of ice.

Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, of several embodiments of the invention given by way of nonlimiting example and illustrated by the appended drawings, wherein :

[Fig.l] shows the principle of an obstacle detection system arranged in a light device of a motor vehicle;

[Fig-2] is a section through a light device according to the invention;

[Fig.3] shows the refractive indices of the ice according to the different embodiments of the invention compared to the state of the art;

[Fig-4] is a section of the ice according to a second embodiment of the invention.

In the following description, it will be considered that the outside corresponds to the outside of the lighting device and the inside inside of said device, in the same way the front will correspond to the direction of emission of light outside the corresponding light device, which corresponds in the case of a headlamp to the front of the vehicle.

[Fig.l] The operating principle of the detection system illustrated in the, is as follows:

the obstacle detection system 3 comprises a transmitter 30 and a receiver 31, the transmitter 30 transmits electromagnetic waves 32 towards the front of the vehicle,

- when these electromagnetic waves 32 encounter an obstacle 7, they are reflected,

the reflected waves 33 are then picked up by a sensor 31,

- a computer then determines the distance between the vehicle and the obstacle 7.

The emitted electromagnetic waves are preferably in the infrared region.

In the invention, the detection system 3 is arranged in a light device 1 comprising a closing glass 2.

When the electromagnetic waves 32 emitted through the closing glass 2 some are reflected by the inner surface 20 of the closing glass 2, thereby limiting the amount of electromagnetic waves which actually pass through the closing glass 2 and therefore the accuracy of the detection system 3.

Similarly, the reflected electromagnetic waves 33 do not all pass through the outer surface 21 of the closing glass 2.

As can be seen in [fig.2], the light device 1 is mounted on a vehicle 6. In this example, it is a headlight of the vehicle. It comprises, in known manner, a lighting system 4 comprising a high beam 40 and a low beam 41. The obstacle detection system 3 is placed behind the closing glass 2.

The closing glass 2 is partially covered with an anti-reflective coating 22 facing the detection system 3. In the example illustrated in [fig.2], the coating 22 is disposed on the face outer 21 but it can be arranged on the inner face 20 or on both sides of the closing glass 2.

The closing glass 2 may have a coating with a single anti-reflective layer 22 (or monolayer) or of several superimposed layers 23 (or multilayer).

As can be seen in [fig.3], the reflection value 10 of the closing glass 2 is substantially constant throughout the wavelength range.

The reflection value 11 of a coating with a single anti-reflective layer 22 is lower in the infrared region which is between 830nm and 905nm and thus the amount of electromagnetic waves 32, 33 passing through the ice of closure 2 increases.

The reflection value 12 of a coating with six layers 23 is lower both in the infrared region and in the visible waves. Thus not only the quantity of electromagnetic waves 32, 33 passing through the closing glass 2 increases in these two zones but also the visible waves emitted by the lighting system.

The reflection index 13 of a coating with seven layers 23 is lower throughout the area between the infrared and the visible waves which are between 380nm and 780nm. This improves the whole quantity of useful electromagnetic waves passing through the closing glass 2.

Thus, for a polycarbonate lens, the refractive index is approximately 1.59 for a wavelength at 550 nm, ie approximately 5.5% of reflection by diopter.

For example, an anti-reflective monolayer 22 made of MgF ₂ has a refractive index of 1.37 for a wavelength of 850 nm. The centering depends on the thickness of the layer: if you are not well centered the reflection will be higher.

In the case of the illustrated multilayer [fig.4], they consist of a superposition of thin layers of different materials with different refractive indices. Preferably, the layers of high (H) and low (L) refractive indices will be alternated.

The materials of high refractive index are for example: TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , Nb ₂

05, SiO, and those with a low refractive index are for example: SiO ₂ , A1 ₂ O ₃ , MgF ₂ .

For a monolayer, the thickness could, for example, be 154.6 nm for a material with a low refractive index such as MgF ₂ .

For example, for a multilayer of 6 layers, it is possible to alternate layers of high and low refractive index with a majority of low index materials, for example:

- a first layer of high refractive index and thickness 19.5nm,

- a second layer of low refractive index and thickness 27.3nm,

- a third layer of high refractive index and thickness 91.4nm, - a fourth layer of low refractive index and thickness lOnm, - a fifth layer of high refractive index and thickness 46.9nm, - a sixth layer of low refractive index and thickness 106.3nm.

For a multilayer of 7 layers, it is possible to alternate layers of high and low refractive index, for example:

- a first layer of low refractive index and thickness lOnm - a second layer of high refractive index and thickness 24.7nm, - a third layer of low refractive index and thickness 26.2nm, - a fourth layer high refractive index and thickness 94.8nm, - a fifth layer of low refractive index and thickness 13.6nm, - a sixth layer of high refractive index and thickness 33.9nm, - a seventh layer of low index of refraction and thickness 116.6nm.

The number and thickness of the layers depend on the materials used.

The monolayer being optimized for the wavelength of the infrared, it is less efficient for the visible spectrum, it will therefore be used rather in the part opposite the obstacle detection system 3.

The multilayer covering a wider spectrum can more easily be used on the entire surface of the closing glass 2.

It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention defined by the appended claims. In particular, the example illustrated relates to a front headlight of a vehicle but could be applied to other vehicle light devices, such as in particular signaling devices, in particular a rear signaling light, such as a brake light. or a rear position lamp.]

Claims (1)

Claims [Claim 1] [Closing glass (2) of a light device (1) of a vehicle having two faces, an outer face (21) and an inner face (20), characterized in that it comprises at least one anti-reflective coating (22, 23) on at least part of a face (20, 21). [Claim 2] Closing glass (2) according to claim 1 characterized in that the anti-reflective coating (22, 23) covers only a portion of the face (20, 21). [Claim 3] Closing glass (2) according to one of the preceding claims, characterized in that it comprises an anti-reflective coating (22, 23) on each of the faces (20, 21). [Claim 4] Closing glass (2) according to one of the preceding claims, characterized in that the anti-reflective coating (22, 23) has a thickness of between 10 and 250 nanometers. [Claim 5] Closing glass (2) according to one of the preceding claims, characterized in that the coating comprises only a single anti-reflective layer (22) of low refractive index in the infrared zone, on the external face (21). [Claim 6] Closing glass (2) according to the preceding claim, characterized in that the anti-reflective layer (22) is made of MgF ₂ . [Claim 7] Closing glass (2) according to one of claims 1 to 3, characterized in that the coating comprises several superposed layers (23). [Claim 8] Closing glass (2) according to the preceding claim, characterized in that each layer (23) is made of a material with a different refractive index. [Claim 9] Closing glass (2) according to one of claims 7 or 8, characterized in that the coating comprises 2 to 10 layers (23). [Claim 10] Closing glass (2) according to one of claims 7 to 9, characterized in that it alternates layers of materials of high and low refractive index in the infrared zone. [Claim 11] Vehicle lighting device comprising an obstacle detection system by emission and reception of electromagnetic waves characterized in that it comprises a closing glass (2) according to one of the preceding claims and that the detection system (3) is arranged opposite at least one anti-reflection layer (22, 23). [Claim 12] Method for treating a closing glass for a light device according to one of claims 1 to 10, characterized in that it comprises a step of laying at least one anti-reflective coating (22, 23) on at least part of a face (20, 21) of the closing glass (2).