Optical system for vehicle including camera

Abstract

The invention relates to an optical system (1) for a vehicle (2), the optical system comprising:-a camera (10) configured to acquire an image (11) of an outside environment of the vehicle (2),-a protective outer lens (11) configured to be arranged facing the camera (10), the protective outer lens (11) comprising an outer face (11.1) facing the outside of the vehicle (2) and an inner face (11.2) facing the camera (10), characterized in that the inner face (11.2) of the protective outer lens (11) has a local radius of curvature R2 defined such that the protective outer lens (11) has a focal length (f) tending to infinity.

Description

[0001] The present invention relates to an optical system for a vehicle, comprising a camera. The invention is particularly, but not exclusively, applicable to motor vehicles.

[0002] In the field of motor vehicles, an optical system for a vehicle known to those skilled in the art comprises:

[0003] - a camera configured to capture images of the environment outside the vehicle,

[0004] - a protective outer lens configured to be arranged facing the camera, the protective outer lens comprising an outer face facing the outside of the vehicle and an inner face facing the camera.

[0005] The protective outer lens is configured to conceal the camera so that the camera is not visible from outside the vehicle.

[0006] A disadvantage of this prior art is that the protective outer lens affects the performance of the camera due to the curved shape of the protective outer lens and / or the translucency or opacity of the protective outer lens.

[0007] In this context, the present invention aims to propose an optical system for a vehicle comprising a camera, thereby resolving the above-mentioned drawbacks.

[0008] To this end, the present invention proposes an optical system for a vehicle, the optical system comprising:

[0009] - a camera configured to capture images of the environment outside the vehicle,

[0010] a protective outer lens configured to be arranged facing the camera, the protective outer lens comprising an outer face facing the outside of the vehicle and an inner face facing the camera,

[0011] Characterized in that the inner face of the protective outer lens has a local radius of curvature R2, which is defined so that the protective outer lens has a focal length tending to infinity.

[0012] Therefore, as will be seen in detail below, limiting the local radius of curvature such that the focal length of the protective outer lens tends to infinity provides an optically neutral protective outer lens and therefore does not reduce the performance level of the camera.

[0013] According to non-limiting embodiments, the optical system may further comprise one or more of the following additional features implemented alone or in any technically possible combination.

[0014] According to one non-limiting embodiment, the local radius of curvature R2 is such that R2=R1-(n-1)d / n, where R1 is the local radius of curvature of the outer face, d is the local thickness of the protective outer lens, and n is the refractive index of the protective outer lens.

[0015] According to one non-limiting embodiment, the camera is an RGB camera or an infrared camera.

[0016] According to one non-limiting embodiment, the outer face has a set of local radii of curvature R1.

[0017] According to one non-limiting embodiment, the inner face has a set of local radii of curvature R2.

[0018] A protective outer lens for a vehicle is also proposed, the protective outer lens being configured to face a camera arrangement carried by the vehicle, the protective outer lens comprising an outer face facing the outside of the vehicle and an inner face facing the camera,

[0019] Characterized in that the inner face of the protective outer lens has a local radius of curvature R2, which is defined so that the protective outer lens has a focal length tending to infinity.

[0020] According to non-limiting embodiments, the protective outer lens may further include one or more of the following additional features implemented alone or in any technically possible combination.

[0021] According to one non-limiting embodiment, the local radius of curvature R2 is such that R2=R1-(n-1)d / n, where R1 is the local radius of curvature of the outer face, d is the local thickness of the protective outer lens, and n is the refractive index of the protective outer lens.

[0022] According to one non-limiting embodiment, the outer face has a set of local radii of curvature R1.

[0023] According to one non-limiting embodiment, the inner face has a set of local radii of curvature R2.

[0024] The present invention and its various applications will be better understood by reading the following description and studying the accompanying drawings:

[0025] [ Figure 1 ] shows an optical system for a vehicle according to a non-limiting embodiment of the present invention, the optical system comprising a camera and a protective outer lens arranged facing the camera, the protective outer lens comprising an outer face and an inner face,

[0026] [ Figure 2 ] shows a non-limiting embodiment of [ Figure 1] a comparison of the infinite focal length of the protective lens of the optical system in the prior art with the shorter focal length,

[0027] [ Figure 3 ] shows the optical transfer function curve of a camera with a prior art optical system without a protective outer lens,

[0028] [ Figure 4 ] shows the [ Figure 1 ] is the optical transfer function curve of the camera of the protective outer lens of the optical system,

[0029] [ Figure 5 ] shows the optical transfer function curves of a camera having a prior art optical system with a protective outer lens.

[0030] Unless otherwise stated, elements that are identical in structure or function and that appear in several figures retain the same reference numerals.

[0031] refer to Figures 1 to 5 An optical system 1 for a vehicle according to the invention is described. In a non-limiting embodiment, the vehicle 2 is a motor vehicle. A motor vehicle refers to any type of motorized vehicle. In the remainder of the description, this embodiment is considered by way of a non-limiting example. In the remainder of the description, the vehicle 2 is therefore also referred to as a motor vehicle 2. The motor vehicle 2 comprises the optical system 1.

[0032] like[ Figure 1 ] As shown, the optical system 1 comprises:

[0033] a camera 10 configured to capture an image I1 of the exterior environment of the motor vehicle 2 , the capture of the image I1 taking place at an image focus f′ of the optical system 100 of the camera 10 ,

[0034] A protective lens 11 , arranged to face the camera 10 .

[0035] In a non-limiting embodiment, the optical system 1 is built into:

[0036] - logo,

[0037] - Pivot logo,

[0038] -rearview mirror,

[0039] - Third brake light, (also known as center high mounted stop light (CHSML)),

[0040] - in the trunk crossbar,

[0041] - in a front grille of a motor vehicle 2,

[0042] At the rear of the motor vehicle 2 .

[0043] In case the optical system 1 is built into a sign or a pivoting sign, the protective outer lens 11 forms part of the sign or the pivoting sign.

[0044] In a non-limiting embodiment, the camera 10 is an RGB camera or an infrared camera. In a non-limiting embodiment, the camera 10 is a fisheye camera. TM ) camera. Light L1 (at [ Figure 1 ]) illuminates the scene outside the motor vehicle 2 so that the scene can be viewed using the optical system of the camera 10 which captures the image I1 of the scene.

[0045] In a non-limiting embodiment, the camera 10 is used to:

[0046] - an assisted parking function, called "Rear View" or "Surround View" (with a range of 0 to 30 meters in a non-limiting example),

[0047] - Rearview mirror function (having a range of about 80 to 200 meters in a non-limiting example).

[0048] The protective outer lens 11 is configured to hide the camera 10 from the outside of the motor vehicle 2 but at the same time allows to define a stylized shape specific to the motor vehicle manufacturer. In a non-limiting embodiment, the protective outer lens is translucent or opaque or transparent.

[0049] The protective outer lens 11 has a focal point F and a focal length f and a field of view FOV (in [ Figure 2 ]). The protective outer lens 11 also has a thickness d. The protective outer lens 11 comprises an outer face 11.1 arranged facing the outside of the motor vehicle 2 and an inner face 11.2 arranged facing the camera 10.

[0050] In a non-limiting embodiment, the outer face 11.1 is convex and the inner face 11.2 is concave, or vice versa. In another non-limiting embodiment, both the outer face 11.1 and the inner face 11.2 are convex, or both the outer face 11.1 and the inner face 11.2 are concave.

[0051] In one non-limiting embodiment, the protective outer lens 11 is made of polycarbonate (PC). PC provides a strong outer surface that will not break like polymethyl methacrylate (PMMA). In another non-limiting embodiment, the protective lens 11 is made of PMMA.

[0052] The stylized shape of the protective outer lens 11 means that its outer face 11.1 has a set of local radii of curvature R1 defined by the stylized shape. In turn, the inner face 11.2 has a set of local radii of curvature R2 adapted to the different local radii of curvature R1 of the outer face 11.1.

[0053] The thickness d of the protective outer lens 11 and the radius of curvature R2 of the inner face 11.2 are varied to maximize the focal length f of the protective outer lens 11. This provides an optically neutral protective outer lens 11. The focal length f therefore tends to infinity to avoid deflecting the light rays L1 coming from the outside onto the camera 10. In fact, if the light rays L1 were deflected, this would distort the image I1 captured by the camera 10, resulting in a less clear image I1.

[0054] The focal length f is defined as follows:

[0055] [Formula 1]

[0056]

[0057] in:

[0058] - R1 is the local radius of curvature of the outer surface 11.1 (also called the outer radius of curvature R1),

[0059] - R2 is the local radius of curvature of the inner surface 11.2 (also called the inner radius of curvature R2),

[0060] - d is the local thickness of the protective outer lens 11, and

[0061] -n is the refractive index of light of the protective outer lens 11 (also called refractive index n).

[0062] Based on the equation [Formula 1], if the focal length f tends to infinity, the local radius of curvature R2 of the inner face 11.2 of the protective outer lens 11 is such that R2=R1-(n-1)d / n[2]. Therefore, the inner local radius of curvature R2 is always smaller than the outer local radius of curvature R1.

[0063] Since the outer face 11 . 1 is not modified, this provides an optically neutral protective outer lens 11 that maintains the manufacturer's stylized shape.

[0064] In a non-limiting example, the protective outer lens 11 includes the following features:

[0065] - for the polycarbonate protective outer lens 11, the refractive index n of the light is equal to 1.58,

[0066] - thickness d is 2.5 mm (millimeters),

[0067] - at the bottom of the protective outer lens 11 , the outer local radius of curvature R1 is equal to 150 mm,

[0068] - at the centre of the protective outer lens 11, the outer local radius of curvature R1 is equal to 177 mm, and

[0069] - At the top of the protective outer lens 11 , the outer local radius of curvature R1 is equal to 195 mm.

[0070] Using formula [2] to adapt the internal local curvature radius R2, we get:

[0071] - at the bottom of the protective outer lens 11 , the inner local radius of curvature R2 is equal to 149.08 mm,

[0072] - at the centre of the protective outer lens 11 , the inner local radius of curvature R2 is equal to 176.08 mm, and - at the top of the protective outer lens 11 , the inner local radius of curvature R2 is equal to 194.08 mm.

[0073] [ Figure 2 ] shows a protective outer lens 31 with a focal length f0 and a focus F0 in the prior art. Figure 2 ] shows a protective outer lens 11 with a focal length f, wherein the inner surface 11.2 includes a local radius of curvature R2=R1-(n-1)d / n. As shown, the focal length f is greater than the focal length f0. In addition, the field of view FOV of the protective outer lens 11 is smaller than the field of view FOV0 of the protective outer lens 31 in the prior art, which means that the light L1 is deflected less and therefore converges toward the focal point F at a farther distance. Therefore, f>f0.

[0074] Figures 3 to 5 Optical Transfer Function (OTF) curves are shown for:

[0075] - a camera 10 without a protective outer lens,

[0076] a camera 10 arranged facing a protective outer lens 11 defining an inner radius of curvature R2 adapted to have a focal length f tending to infinity,

[0077] - A camera 10 arranged facing a prior art protective outer lens 31 defining an unadapted radius of curvature R2.

[0078] These curves correspond to different incident angles (between 0° and 97°) of the light ray L1 arriving at the optical system 100 of the camera 10 .

[0079] [ Figure 2 The optical transfer function curves in ] are used as reference.

[0080] The optical transfer function curve is used to evaluate the ability of an element of an optical system (such as a camera with or without a protective outer lens) to restore contrast in terms of the sharpness of details of a target object; in other words, its ability to transmit the spatial frequencies of the target object. The optical transfer function curve is used to evaluate the quality of the optical system 100. Therefore, the optical transfer function curve can be used to evaluate the ability of the protective outer lens 11 to not degrade the performance level of the camera 10 compared to a camera 10 without a protective outer lens or with a prior art protective outer lens 31.

[0081] The contrast between 0 and 1 is plotted on the y-axis of the curve (labeled ct). The spatial frequency of the target object in cycles / mm is plotted on the x-axis (labeled Spf(cy / mm)). This represents the sharpness of detail in the target object.

[0082] like[ Figure 4 ], with an optimized protective outer lens 11 (i.e., with an adapted inner radius of curvature R2), the optical transfer function (OTF) does not degrade at any incident angle considered. The curve obtained is almost the same as [ Figure 3 ] (i.e. without a protective outer lens). On the other hand, if [ Figure 5 ], this is not the case with a non-optimized protective outer lens 31 of the prior art (i.e., with an unadapted inner radius of curvature R2), the curve obtained is similar to [ Figure 3 ] are completely different.

[0083] Thus, the protective outer lens 11 of the optical system 1 enables a camera 10 arranged facing said protective outer lens to have the same performance level as a camera 10 without the protective outer lens. Thus, the protective outer lens 11 does not interfere with the camera 10.

[0084] Of course, the description of the present invention is not limited to the above-mentioned embodiments and the above-mentioned fields.

[0085] The invention thus described has in particular the following advantages:

[0086] - the invention allows the camera 10 to be incorporated behind a protective outer lens 11 without reducing the performance level of the camera 10,

[0087] - the invention allows to maintain the stylized shape of the protective outer lens 11 given by the motor vehicle manufacturer, since the invention does not modify the outer face 11 . 1 of the protective outer lens,

[0088] - the invention provides an optically neutral protective outer lens 11 by locally adapting the inner face 11 . 2 of the protective outer lens 11 ,

[0089] - The invention is simple to implement.

Claims

1. An optical system (1) for a vehicle (2), the optical system comprising: - a camera (10) configured to capture an image (I1) of the environment outside the vehicle (2), - a protective outer lens (11) configured to be arranged facing the camera (10), the protective outer lens (11) comprising an outer surface (11.1) facing the outside of the vehicle (2) and an inner surface (11.2) facing the camera (10), characterized in that the inner surface (11.2) of the protective outer lens (11) has a local curvature radius R2, and the local curvature radius is defined so that the protective outer lens (11) has a focal length (f) tending to infinity.

2. The optical system (1) according to claim 1, wherein: The local radius of curvature R2 is such that R2=R1-(n-1)d / n, wherein R1 is the local radius of curvature of the outer face (11.1), d is the local thickness of the protective outer lens (11), and n is the refractive index of the protective outer lens (11).

3. The optical system (1) as claimed in any one of the preceding claims, wherein: The camera (10) is an RGB camera or an infrared camera.

4. An optical system (1) as claimed in any one of the preceding claims, wherein: The outer surface (11.1) has a set of local radii of curvature R1.

5. The optical system (1) as claimed in any one of the preceding claims, wherein: The inner surface (11.2) has a set of local radii of curvature R2.

6. A protective outer lens (11) for a vehicle (2), the protective outer lens being arranged to face a camera (10) carried by the vehicle (2), the protective outer lens (11) comprising an outer surface (11.1) facing the outside of the vehicle (2) and an inner surface (11.2) facing the camera (10), It is characterized in that The inner face (11.2) of the protective outer lens (11) has a local radius of curvature R2 defined so that the protective outer lens (11) has a focal length (f) tending to infinity.

7. The protective outer lens (11) according to the preceding claim, wherein: The local radius of curvature R2 is such that R2=R1-(n-1)d / n, wherein R1 is the local radius of curvature of the outer face (11.1), d is the local thickness of the protective outer lens (11), and n is the refractive index of the protective outer lens (11).

8. A protective outer lens (11) as claimed in claim 6 or claim 7, wherein: The outer surface (11.1) has a set of local radii of curvature R1.

9. The protective outer lens (11) according to any one of claims 6 to 8, wherein The inner surface (11.2) has a set of local radii of curvature R2.

Images