An optical module including a camera and an opaque element that absorbs light

Abstract

The invention relates to an optical module (1) for a vehicle, said optical module (1) comprising: - a camera (10) having a set of optical lenses (100); - a housing (11) configured to receive said camera (10); and - a glass window (12) arranged facing said camera (10) and configured to hide said camera (10) from the outside of the vehicle, characterized in that said optical module (1) further comprises an opaque element (13) configured to absorb light (Lx) from the outside of the vehicle (2) so as to reduce stray light reflections of said light (Lx) at the set of optical lenses (100) of the camera (10).

Description

Technical Field

[0001] The present invention relates to an optical module for a vehicle. It is particularly applicable to motor vehicles, although not exclusively.

Summary of the Invention

[0002] As shown in FIG. 1, an example of an optical module 6 for a vehicle known to those skilled in the art comprises the following: - A camera 60 comprising a set of optical lenses 600, - A housing 61 configured to receive the camera 60, - An outer lens 62 arranged facing the camera 60.

[0003] The outer lens 62 is opaque, which makes it possible to hide the camera 60 from outside the vehicle. Thus, an observer outside the vehicle does not see the camera 60 when looking at the optical module 6. The camera 60 is used to monitor the external environment of the vehicle. It generates an image of the external environment of the vehicle and, in particular, generates an image useful to the driver of the vehicle when parking the vehicle. The vehicle displays the image from the camera 60 on its on-board screen.

[0004] One disadvantage of this prior art is that the light Lx coming from outside the vehicle, especially the light coming from above, is reflected towards the inner surface 620 of the outer lens 62 on the set of optical lenses 600, thereby causing a primary reflection r1 as shown in FIG. 1. These primary reflections r1 are reflections of order 1. These primary reflections r1 are then reflected by the inner surface 620 of the outer lens 62, thereby causing a secondary reflection r2 that is returned to the set of opaque lenses 600 as shown in FIG. 1. These secondary reflections r2 are reflections of order 2. These secondary reflections r2 cause parasitic diffusion of the light Lx inside the set of optical lenses 600, which is called flare. The driver will see these secondary reflections r2 on the image generated by the camera 60, which is visually disturbing to the driver looking at the image from the camera 60 on the in-vehicle screen. This makes it difficult for them to park the vehicle.

[0005] In connection with this, an object of the present invention is to provide an optical module that makes it possible to overcome the aforementioned drawbacks.

[0006] For this purpose, the invention proposes an optical module for a vehicle, said optical module comprising: - a camera comprising a set of optical lenses, - a housing configured to receive said camera, - an outer lens arranged facing said camera and configured to hide said camera from the outside of the vehicle, said optical module further comprising an opaque element configured to absorb light coming from the outside of the vehicle so as to reduce parasitic reflections of said light on the set of optical lenses of said camera.

[0007] According to a non-limiting embodiment, said optical module may further include one or more of the following additional features, implemented alone or in any technically possible combination.

[0008] According to a non-limiting embodiment, According to a non-limiting embodiment, According to a non-limiting embodiment, the parasitic reflection is caused by the reflection of light on the inner surface of the outer lens.

[0009] According to a non-limiting embodiment, the opaque element is the outer lens, and the outer lens includes a first portion and a second portion and is opaque in a non-uniform manner.

[0010] According to a non-limiting embodiment, the first portion of the outer lens is more opaque than the second portion.

[0011] According to a non-limiting embodiment, the first portion is darker than the second portion.

[0012] According to a non-limiting embodiment, the first portion has a greater thickness than the second portion.

[0013] According to a non-limiting embodiment, the first portion is made of a material that absorbs more light than the material of the second portion.

[0014] According to a non-limiting embodiment, the first portion of the outer lens has an opacity of 30% to 50%.

[0015] According to a non-limiting embodiment, the second portion of the outer lens has a transparency of 75% to 80%.

[0016] According to a non-limiting embodiment, the first portion of the outer lens is disposed at an angle of 11° or more with respect to the optical axis of the camera.

[0017] According to a non-limiting embodiment, the first portion of the outer lens is disposed at an angle of 21° or more with respect to the optical axis of the camera.

[0018] According to a non-limiting embodiment, the opaque element is an opaque cap disposed to protrude from the housing of the camera.

[0019] According to a non-limiting embodiment, the opaque element is an opaque cap disposed above the set of optical lenses of the camera.

[0020] According to a non-limiting embodiment, the housing comprises a non-reflective inner surface.

[0021] According to a non-limiting embodiment, the light is natural light or light from street lamps.

[0022] According to a non-limiting embodiment, the first portion of the outer lens has an opacity of 30% to 50%, and the second portion of the outer lens has a transparency of 75% to 80%.

[0023] According to a non-limiting embodiment, the first portion of the outer lens has an opacity of 50%, and the second portion of the outer lens has a transparency of 80%.

[0024] According to a non-limiting embodiment, the first portion of the outer lens is opaque in a variable manner.

[0025] According to a non-limiting embodiment, the first portion has a thickness greater than 2 mm, and the second portion has a thickness substantially equal to 2 mm.

[0026] According to a non-limiting embodiment, the first portion is disposed at an angle of 11° to 25° with respect to the optical axis of the camera.

Brief Description of the Drawings

[0027] The invention and its various applications will be better understood by reading the following description and considering the accompanying drawings, in which:

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DETAILED DESCRIPTION OF THE INVENTION

[0028] Elements that are identical in terms of structure or function and appear in various figures retain the same reference, unless otherwise specified.

[0029] The optical module 1 for the vehicle 2 according to the invention will be described with reference to FIGS. 2 to 8. In a non-limiting embodiment, the vehicle 2 is a motor vehicle. A motor vehicle is understood to mean any type of power-driven vehicle. This embodiment is taken as a non-limiting example throughout the remainder of the specification. Therefore, in the remainder of the specification, the vehicle 2 is referred to as the motor vehicle 2.

[0030] As shown in FIG. 2, the optical module 1 for the motor vehicle 2 comprises the following: - a camera 10, - a housing 11, - an outer lens 12, and - an opaque element 13.

[0031] The camera 10 comprises a set 100 of optical lenses. The set 100 of optical lenses includes one or more optical lenses. The camera 10 has a field of view Fov. The camera 10 generates an image i1 of the external environment of the motor vehicle 2. In other words, it generates an image i1 of a scene in the external environment. Thus, the camera 10 detects moving objects such as other vehicles, pedestrians, bicycles, or stationary objects such as sidewalks, road signs, buildings, trees. In a non-limiting example, the image i1 is displayed on the dashboard of the motor vehicle 2, enabling the driver of the motor vehicle 2 to perform an operation to park the motor vehicle 2. In another non-limiting example, the image i1 enables the driver to see vehicles at an intersection that may be coming from the right and left in order to determine whether they can safely cross the intersection. In another non-limiting example, the image i1 is an image from a reverse camera. This enables them to see pedestrians behind the motor vehicle 2 and thus enables the driver to perform a reverse operation completely safely without running over a pedestrian. The camera 10 further comprises an optical sensor 101 associated with the optical lens 100, and the optical sensor 101 has an integration time t1. The integration time t1 is the opening time of the cells of the optical sensor 101.

[0032] In a non-limiting embodiment, the camera 10 is an HDR, i.e., "High Dynamic Range", camera and has a plurality of integration times t1. The HDR camera enables the generation of a single final noise-free image by using three images of a scene acquired simultaneously, particularly at different integration times t1, and then reconstructing them. This also improves the light contrast of the final image so that it has more details.

[0033] In a non-limiting embodiment, the camera 10 is a wide-angle camera. In a non-limiting example, the camera 10 has a total horizontal angle of 170° with respect to the vehicle axis Ax. In a non-limiting embodiment, the camera 10 is arranged at the front, rear, or one side of the motor vehicle 2. In a non-limiting embodiment, the camera 10 is: - on the logo at the front of the motor vehicle 2, or - on the front headlamp, or - on the tail lamp, or - on the rear bumper, or - on the rearview mirror. arranged.

[0034] The housing 11 is configured to receive the camera 10. It is closed by an outer lens 12. In a non-limiting embodiment, the inner surface 11b of the housing 11 is black and non-reflective. In a non-limiting embodiment, it is covered with a matte paint to make it non-reflective. This makes it possible to hide the camera 10 from the outside of the motor vehicle 2. Thus, an observer outside the motor vehicle 2 cannot see the camera 10 even if they look at the optical module 1.

[0035] The outer lens 12, called the protective lens, is arranged facing the camera 10. It is configured to hide the camera 10 from outside the motor vehicle 2. Thus, the camera 10 is not visible to an observer outside the motor vehicle 2 looking at the optical module 1. Thus, the outer lens 12 is opaque. In one non-limiting embodiment, the outer lens 12 has an opacity substantially equal to 20% (in other words, a transparency substantially equal to 80%). The outer lens 12 has an inner surface 120 facing the camera 10 and an outer surface 121 facing the outside of the motor vehicle 2 on the opposite side of the inner surface 120. In one non-limiting embodiment, the outer lens 12 closes the housing 11.

[0036] The opaque element 13 is configured to absorb the light Lx coming from outside the motor vehicle 2 so as to significantly reduce or completely remove the parasitic reflection (r2, referenced in FIG. 1 showing the prior art) of the light Lx in the set 100 of optical lenses of the camera 10.

[0037] The light Lx coming from outside is called external light Lx. This light Lx can be natural light from the sun (otherwise called zenith light) or light from a street lamp. It is light coming from above with respect to the optical axis Aa of the camera 10. In one non-limiting embodiment, the optical axis Aa of the camera 10 corresponds to the optical center of the set 100 of optical lenses.

[0038] As can be seen below, the opaque element 13 is combined with or distinguished from the outer lens 12. In FIG. 2, the opaque element 13 is shown schematically separated from the outer lens 12.

[0039] In the non-limiting first embodiment shown in FIGS. 3 to 5, the opaque element 13 is the outer lens 12. Thus, the opaque element 13 and the outer lens 12 are combined. The outer lens 12 comprises a first part 12a, also called the upper part 12a, and a second part 12b, also called the lower part 12b, and it is opaque in a non-uniform way.

[0040] In a non-limiting embodiment, the first part 12a and the second part 12b are arranged to cover the field of view Fov of the camera 10.

[0041] The first part 12a is configured to directly receive the light Lx, while the second part 12b is configured to directly receive a small part of the light Lx or not to directly receive the light Lx. Thus, the upper part 12a is located above the lower part 12b along an axis Az perpendicular to the vehicle axis Ax. It is noted that the light Lx can be reflected at the ground where the motor vehicle 2 is located so as to reach especially the second part 12b. Thus, the second part 12b receives the light Lx, mainly or completely, indirectly via its reflection at the ground. It is noted that the reflection from the ground produces little flare. Thus, the sources of these reflections are street lights and the sun. Other sources may be other vehicles.

[0042] In a non-limiting embodiment, the upper part 12a thus extends from the upper part 110 of the housing 11 to approximately the middle height of the camera 10, in other words to approximately the optical axis Aa of the camera 10; the lower part 12b extends from the bottom part 111 of the housing 11 to approximately the middle height of the camera 10, in other words to approximately the optical axis Aa of the camera 10.

[0043] In a non-limiting embodiment, the upper part 12a and the lower part 12b are flat.

[0044] As shown in FIG. 8, in one non-limiting embodiment, the camera 10 focuses up to a maximum viewing distance D1 of 20 meters. In the worst case, the camera 10 may be dazzled by the light Lx coming from the street lamp 4 shown in FIG. 8 at an angle β = Arctan(D2 / D1), where D2 is the size of the street lamp 4 and h1 is the height of the camera 10 relative to the ground 5. In one non-limiting exemplary embodiment, the camera 10 is disposed at a height h1 of 1 meter relative to the ground 5. This is the case for the camera 10 for panoramic vision, which is called a "surround view camera". In one non-limiting embodiment, the street lamp 4 has a size D0 with a height of 5m to 9m. Thus, β = Arctan(4 / 20) = 11°, and 4 = 5m - 1m. Thus, in one non-limiting embodiment, the first portion 12a is disposed at an angle β of 11° or more with respect to the optical axis Aa of the camera 10. That is, the lower end of the first portion 12a stops beyond the angle β of 11°.

[0045] It should be noted that the illuminance of the street lamp 4 is approximately 500 lux or a luminous intensity of 40500 cd (candela) in the case of a street lamp with a height of 5m. At a viewing distance D1 of 20m, the illuminance is approximately equal to 100 lux, which is very small. On the other hand, at a viewing distance D1 of 10m, the illuminance is about 250 lux. Thus, the light Lx coming from such a street lamp 4 produces a stronger flare effect at a viewing distance D1 = 10m than at a viewing distance D1 = 20m. Further, in another non-limiting embodiment, the first portion 12a is disposed at an angle β of 21° or more with respect to the optical axis Aa of the camera 10.

[0046] In one non-limiting embodiment, the first portion 12a is disposed at an angle β of 11° to 25° with respect to the optical axis Aa of the camera 10.

[0047] Since the first portion 12a of the outer lens is more opaque than the second portion 12b, it absorbs more light Lx, while the second portion 12b is more transparent and thus captures more of the light Lx reflected especially from the ground and more direct light Lx when it receives the same.

[0048] In a non - limiting embodiment, the first part 12a has an opacity of 30% - 50% (in other words, a transparency of 70% - 50%), while the second part 12b has a transparency of 75% - 80% (in other words, an opacity of 20% - 25%). In a non - limiting alternative embodiment, the first part 12a has an opacity of 50% (in other words, a transparency of 50%), and the second part has a transparency of 80% (in other words, an opacity of 20%). This means that the first part 12a blocks up to 50% of the light Lx, and the second part 12b transmits 80% of the light Lx reaching the optical module 10.

[0049] In a non - limiting embodiment, the first part 12a is opaque in a variable manner. Thus, in a non - limiting example, the opacity of the first part 12a may gradually increase from bottom to top, in other words, from the end located near the optical axis Aa of the camera 10 to the end located near the top 110 of the housing 11. Similarly, in a non - limiting embodiment, the second part 12b is transparent in a variable manner. Thus, in a non - limiting example, the transparency of the second part 12b may gradually increase from top to bottom, in other words, from the end located near the optical axis Aa of the camera 10 to the end located near the bottom 111 of the housing 11.

[0050] The upper part 12a absorbs the light Lx such that it only partially passes through the outer lens 12 at this level and such that there are very few or no parasitic reflections on the inner surface 120 of the outer lens 12 that disrupt the image i1 from the camera 10. As shown in FIGS. 3 - 5, the upper part 12a absorbs most of the light Lx, Lx', and allows a small part Lx'' to pass through. The upper part 12a also significantly reduces or even eliminates other parasitic reflections, which are other secondary reflections on the set of optical lenses 100 and reflections of the external light Lx inside the outer lens 12, in other words, direct reflections on its inner surface 120, and which are returned to the set of optical lenses 100.

[0051] Three non-limiting alternative embodiments for making the first part 12a of the outer lens 12 more opaque than the second part 12b are described below.

[0052] In a non-limiting first alternative embodiment shown in FIG. 3, the first part 12a is darker than the second part 12b. This makes it more opaque. It is noted that in one non-limiting embodiment, in an industrial process, the upper part 12a is darkened. Thus, instead of an opacity of 20%, in one non-limiting example, the upper part 12a has an opacity of 30%. In another non-limiting embodiment, the lower part 12b is made more transparent. Thus, instead of a transparency of 70% like the upper part 12a, in one non-limiting example, the lower part 12b has a transparency of 90%. In one non-limiting example, a coloring paint may be used to darken the upper part 12a. In another non-limiting example, a 2K or 3K multi-shot injection molding process may be used.

[0053] In a non-limiting second alternative embodiment shown in FIG. 4, the first part 12a has a thickness e1 that is greater than the thickness e2 of the second part 12b. Making the material of the first part 12a thicker makes it more opaque, and thus it absorbs more light Lx. In one non-limiting embodiment, the thickness e1 is greater than 2 mm. In one non-limiting embodiment, it is equal to 3 mm to obtain an opacity of 50%. In one non-limiting embodiment, the thickness e2 is substantially equal to 2 mm.

[0054] The material absorbs light according to the linear absorption coefficient α, and the linear absorption coefficient α is such that P = P0×exp(-α×e), where e is the thickness of the material. In this case, e = e1 is the thickness of the material of the first part 12a. It should be noted that P is the luminous power of the light Lx, and P0 is the initial light power. Therefore, α = (4×π×k) / λ, where λ is the wavelength of the light Lx, and k is the attenuation coefficient specific to the material of the first part 12a. k depends on the refractive index and dielectric constant of the material. Since the formulation of k is known to those skilled in the art, k will not be described here.

[0055] In the non-limiting third alternative embodiment shown in FIG. 5, the first part 12a is made of a material m1 that absorbs more light Lx than the material m2 of the second part 12b. In a non-limiting example, the lower part 12b is made of a PMMA (polymethyl methacrylate) or PC (polycarbonate) material. In a non-limiting example, the upper part 12a is made of a PMMA or PC material having more coloring pigments (illustrated by dots) inside, which absorbs the light Lx, thereby making it more opaque.

[0056] In the non-limiting second embodiment shown in FIGS. 6 and 7, the opaque element 13 is an opaque cap, unlike the outer lens 12. Therefore, they are not combined. In this non-limiting second embodiment, in a non-limiting example, the outer lens 12 has an opacity of 20%, thereby taking in 80% of the light Lx coming from the outside of the motor vehicle 2. In a non-limiting embodiment, the opaque cap 13 is flat. The opaque cap 13 is arranged so as not to obstruct the field of view Fov of the camera 10.

[0057] In the non-limiting first alternative embodiment shown in FIG. 6, the opaque cap 13 is disposed to protrude from the housing 11 of the camera 10. It extends from the upper portion 110 of the housing 11 parallel to the optical axis Aa of the camera 10. As can be seen, the opaque cap 13 absorbs the light Lx. It absorbs the light partially or entirely. This depends on its opacity. In the non-limiting example shown, it absorbs the light completely. In a non-limiting example, the opaque cap 13 is adhesively bonded to the housing 11.

[0058] In the non-limiting second alternative embodiment shown in FIG. 7, the opaque cap 13 is disposed above the set 100 of the optical lenses of the camera 10. It extends parallel to the optical axis Aa of the camera 10. As can be seen, the opaque cap 13 absorbs the light Lx. It absorbs the light partially or entirely. This depends on its opacity. In the non-limiting example shown, it absorbs the light completely. In a non-limiting embodiment of this non-limiting second alternative embodiment, the opaque cap 13 is disposed in contact with the outer lens 12. In a non-limiting example, it is adhesively bonded to the outer lens 12.

[0059] It is noted that in a camera without the opaque element 13, the darker the scene, the longer the integration time t1 has to be to capture and generate the image i1 of the scene, and the brighter the scene, the shorter the integration time t1 has to be. Further, without the opaque element 13, multiple integration times t1 are required to reach the final image i1 having a strong contrast between the various regions of the image where details can be clearly seen in all regions of the imaged scene. For example, a short integration time t1 is required to image the empty sky brighter than the road (the dark elements of the image are darkened), and a long integration time t1 is required to image the steps of the road darker than the sky (the sky is saturated and thereby becomes almost white).

[0060] In the image i1, the light intensity of the scene becomes larger towards the upper part (at the sky level) than the part on the optical axis Aa of the camera 10 and the part towards the ground. The opaque element 13 makes it possible to compensate for this difference in light intensity. The light intensity becomes more uniform over the entire image i1 generated by the camera 10. The opaque element 13 makes it possible to darken the upper part of the image i1. In the image i1, at a single integration time t1, instead of using a plurality of integration times t1, it is possible to clearly see details in all regions of the image i1, particularly in the upper part of the scene being imaged and in the lower part of the scene being imaged. In this way, the contrast between various elements in the image i1 is reduced by the opaque element 13.

[0061] Also, it should be noted that in a camera without the opaque element 13, by increasing the contrast in the image i1, the signal-to-noise ratio of the optical sensor 101 decreases. Specifically, without the opaque element 13, for a given integration time t1, an image with larger quantification errors towards the extreme values of the light intensity is obtained. When the opaque element 13 is used, the quantification noise at the extreme values of the light intensity is reduced, so the signal-to-noise ratio is improved. Therefore, the conventional HDR that uses a plurality of images with different integration times t1 is not necessary.

[0062] In this way, by using the opaque element 13, the contrast of the image i1 is reduced, the signal-to-noise ratio is improved, and as a result, it becomes possible to see more details in the image i1. Therefore, a driver looking at the image i1 from the camera 10 can see the details more clearly, which for example makes the operation during parking easier.

[0063] Of course, the description of the invention is not limited to the above-described embodiments and the above-described fields. Thus, in one non-limiting embodiment, the set of optical lenses 100 may be treated by an anti-reflection treatment. Thus, in another non-limiting embodiment, instead of extending from the top of the housing 11 to approximately the mid-height of the camera 10, the upper portion 12a may extend from the top 110 of the housing 11 to one-third of the camera 10.

[0064] Thus, the described invention has the following advantages in particular: - It is possible to significantly reduce or even eliminate parasitic reflections in the set of optical lenses, the parasitic reflections caused by the light Lx; thus, it is possible to reduce or even eliminate flare, whereby the driver of the vehicle 2 does not feel bothered when viewing the image from the camera. - It makes it possible to hide the camera 10 from an observer looking at the optical module 1 from outside the motor vehicle 2. - It makes it possible to obtain a more homogeneous image, and thus to reduce the contrast in the image i1, whereby it is possible to obtain better image rendering quality. - It is possible to increase the signal-to-noise ratio, especially in the dark areas located generally towards the lower part of the image i1.

Claims

1. An optical module (1) for a vehicle (2), wherein the optical module (1) comprises: - A camera (10) comprising a set of optical lenses (100); - A housing (11) configured to receive the camera (10); - An outer lens (12) disposed facing the camera (10) and configured to hide the camera (10) from the outside of the vehicle (2); An opaque element (13) configured to absorb light (Lx) coming from the outside of the vehicle (2) so as to reduce parasitic reflection of the light (Lx) at the set of optical lenses (100) of the camera (10); Comprising; The opaque element (13) is the outer lens (12), and the outer lens (12) includes a first part (12a) and a second part (12b), and is opaque in a non-uniform manner; The first part (12a) of the outer lens (12) is more opaque than the second part (12b); The first part (12a) of the outer lens (12) has an opacity of 30% to 50%; Optical module (1).

2. The parasitic reflection is caused by reflection of the light (Lx) on the inner surface (120) of the outer lens (12), the optical module (1) according to claim 1.

3. The first part (12a) is darker than the second part (12b), the optical module (1) according to claim 1 or 2.

4. The first part (12a) has a greater thickness than the second part (12b), the optical module (1) according to claim 1 or 2.

5. The first part (12a) is made of a material (m1) that absorbs more light (Lx) than the material (m2) of the second part (12b), the optical module (1) according to claim 1 or 2.

6. The second part (12b) of the outer lens (12) has a transparency of 75% to 80%, the optical module (1) according to claim 1 or 2.

7. The first part (12a) of the outer lens (12) is disposed at an angle (β) of 11° or more with respect to the optical axis (Aa) of the camera (10), the optical module (1) according to claim 1 or 2.

8. The first part (12a) of the outer lens (12) is disposed at an angle (β) of 21° or more with respect to the optical axis (Aa) of the camera (10), the optical module (1) according to claim 1 or 2.

9. The optical module (1) according to claim 1 or 2, wherein the opaque element (13) is an opaque cap positioned to protrude from the housing (11) of the camera (10).

10. The optical module (1) according to claim 1 or 2, wherein the opaque element (13) is an opaque cap positioned above the set (100) of the optical lenses of the camera (10).

11. The optical module (1) according to claim 1 or 2, wherein the housing (11) has a non-reflective inner surface (11b).

12. The optical module (1) according to claim 1 or 2, wherein the light (Lx) is natural light or light from a street lamp.

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