Optical system for a vehicle equipped with a camera

Abstract

The invention relates to an optical system (1) for a vehicle (2), the optical system (1) for the vehicle (2) comprising: - a camera (10) configured to acquire an image (11) 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), the inner surface (11.2) of the protective outer lens (11) being characterized by having a local radius of curvature R2 defined such that the protective outer lens (11) has a focal length (f) with a tendency to be directed towards infinity.

Description

Technical Field

[0001] The present invention relates to an optical system for a vehicle equipped with a camera. It can be applied in particular to motor vehicles, but is not limited thereto.

Summary of the Invention

[0002] In the field of motor vehicles, optical systems for vehicles known to those skilled in the art comprise the following: - A camera configured to acquire an image of the environment outside the vehicle, - A protective outer lens configured to be arranged facing the camera, the protective outer lens comprising an outer surface facing the outside of the vehicle and an inner surface facing the camera.

[0003] The protective outer lens is configured to hide the camera so that it cannot be seen from outside the vehicle.

[0004] The drawback of this prior art is that due to the curved shape and / or the semi-transparency or opacity of the protective outer lens, the protective outer lens affects the performance of the camera.

[0005] In this regard, the present invention intends to propose an optical system for a vehicle equipped with a camera that solves the described drawbacks.

[0006] For this purpose, the invention comprises - A camera configured to acquire an image of the environment outside the vehicle, and - A protective outer lens configured to be arranged facing the camera, the protective outer lens comprising an outer surface facing the outside of the vehicle and an inner surface facing the camera, and The inner surface of the protective outer lens has a local radius of curvature R2 defined such that the protective outer lens has a focal length tending towards infinity, characterized in that An optical system for a vehicle is proposed.

[0007] Thus, as will be explained in detail below, defining the local radius of curvature such that the focal length of the protective outer lens tends towards infinity provides an optically neutral protective outer lens and thus does not degrade the performance level of the camera.

[0008] According to a non-limiting embodiment, the optical system can further include one or more of the following additional features, implemented alone or in any technically possible combination.

[0009] According to a non-limiting embodiment, the local radius of curvature R2 is given by R2 = R1 - (n - 1)d / n, where R1 is the local radius of curvature of the outer surface, d is the local thickness of the protective outer lens, and n is the refractive index of the protective outer lens.

[0010] According to a non-limiting embodiment, the camera is an RGB or infrared camera.

[0011] According to a non-limiting embodiment, the outer surface has a set of local radii of curvature R1.

[0012] According to a non-limiting embodiment, the inner surface has a set of local radii of curvature R2.

[0013] A vehicle protective outer lens configured to be arranged facing a camera mounted on the vehicle is also proposed, the protective outer lens comprising an outer surface facing the outside of the vehicle and an inner surface facing the camera. The inner surface of the protective outer lens is characterized by having a local radius of curvature R2 defined such that the protective outer lens has a focal length tending towards infinity.

[0014] According to non - limiting embodiments, the protective outer lens can further include one or more of the following additional features, implemented alone or in any technically possible combination.

[0015] According to a non - limiting embodiment, the local radius of curvature R2 is given by R2 = R1-(n - 1)d / n, where R1 is the local radius of curvature of the outer surface, d is the local thickness of the protective outer lens, and n is the refractive index of the protective outer lens.

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

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

[0018] The invention and its various applications will be better understood by reading the following description and considering the accompanying drawings:

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0020] Elements that are structurally or functionally identical and appear in multiple figures are given the same reference numeral unless otherwise noted.

[0021] The optical system 1 for a vehicle according to the invention will be described with reference to FIGS. 1 to 5. In a non-limiting embodiment, the vehicle 2 is an automotive vehicle. An automotive vehicle means any type of motor vehicle. This embodiment is considered as a non-limiting example in the remainder of the specification. Thus, in the remainder of the specification, the vehicle 2 is also referred to as the automotive vehicle 2. The automotive vehicle 2 comprises the optical system 1.

[0022] As shown in FIG. 1, the optical system 1 comprises: - a camera 10 configured to acquire an image I1 of the environment outside the automotive vehicle 2, the acquisition of the image I1 being performed at an image focus f' of the optical system 100 of the camera 10, the camera 10, - a protective lens 11 configured to be disposed facing the camera 10.

[0023] In a non-limiting embodiment, the optical system 1 is incorporated in: - a logo, - a rotating logo, - a rearview mirror, - a third brake light called a center high mount stop lamp (CHSML), - in a trunk bar, - in a front-end grille of the automotive vehicle 2, - at the rear of the automotive vehicle 2.

[0024] When the optical system 1 is incorporated into a logo or a rotating logo, the protective outer lens 11 forms part of the logo or the rotating logo.

[0025] In a non-limiting embodiment, the camera 10 is an RGB camera or an infrared camera. In one non-limiting embodiment, the camera 10 is a FishEye TM camera. In a non-limiting example, a light ray L1 (illustrated in FIG. 1) from an external light source such as natural light illuminates a scene outside the motor vehicle 2 and enables the scene to be viewed using the optical system of the camera 10 that acquires an image I1 of the scene.

[0026] In a non-limiting embodiment, the camera 10 is used for the following: - A parking assistance function known as "Rear View" or "Surround View" (in a non-limiting example in the range of 0 to 30 meters), - A rearview mirror function (in a non-limiting example in the range of approximately 80 to 200 meters).

[0027] The protective outer lens 11 is configured to conceal the camera 10 from the outside of the motor vehicle 2, but it is also possible to define a standardized shape specific to the motor vehicle manufacturer. In a non-limiting embodiment, it is translucent or opaque or transparent.

[0028] The protective outer lens 11 has a focal point F, a focal length f, and a field of view FOV (illustrated in FIG. 2). The protective outer lens 11 also has a thickness d. The protective outer lens 11 includes an outer surface 11.1 disposed to face the outside of the motor vehicle 2 and an inner surface 11.2 disposed to face the camera 10.

[0029] In a non-limiting embodiment, the outer surface 11.1 is convex while the inner surface 11.2 is concave, or vice versa. In another non-limiting embodiment, both the outer surface 11.1 and the inner surface 11.2 are convex, or both the outer surface 11.1 and the inner surface 11.2 are concave.

[0030] In a non-limiting embodiment, the protective outer lens 11 is made of polycarbonate (PC). Different from PMMA (polymethyl methacrylate), PC provides a robust outer surface that does not break. In another non-limiting embodiment, the protective lens 11 is made of PMMA.

[0031] By the standardized shape of the protective outer lens 11, it means that its outer surface 11.1 has a set of multiple local radii of curvature R1 defined by the standardized shape. And the inner surface 11.2 has a set of multiple local radii of curvature R2 that conform to the various multiple local radii of curvature R1 of the outer surface 11.1.

[0032] The thickness d of the protective outer lens 11 and the radius of curvature R2 of the inner surface 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. Therefore, the focal length f tends to be infinite so as to avoid the incoming light ray L1 from being deflected onto the camera 10. In fact, if the light ray L1 is deflected, this will distort the image I1 acquired by the camera 10, which results in a low sharpness image I1.

[0033] The definition of the focal length f is as follows:

Equation

[0034] Based on the formula of [[Calculation 1]], when the focal length f tends to infinity, the inner surface 11.2 of the protective outer lens 11 has a local radius of curvature R2 such that R2 = R1 - (n - 1)d / n. Therefore, the internal local radius of curvature R2 is always smaller than the external local radius of curvature R1.

[0035] This provides an optically neutral protective outer lens 11, and since the outer surface 11.1 of the optically neutral protective outer lens 11 is not modified, it retains the manufacturer's standardized shape.

[0036] In a non - limiting example, the protective outer lens 11 has the following characteristics: - The refractive index of light for the n - polycarbonate protective outer lens 11 is equal to 1.58, - The thickness d is 2.5 mm (millimeters), - At the bottom of the protective outer lens 11, the external local radius of curvature R1 is equal to 150 mm, - At the center of the protective outer lens 11, the external local radius of curvature R1 is equal to 177 mm, and - At the top of the protective outer lens 11, the external local radius of curvature R1 is equal to 195 mm.

[0037] By applying the formula to the internal local radius of curvature R2, the following is obtained: - At the bottom of the protective outer lens 11, the internal local radius of curvature R2 is equal to 149.08 mm, - At the center of the protective outer lens 11, the internal local radius of curvature R2 is equal to 176.08 mm, and - At the top of the protective outer lens 11, the internal local radius of curvature R2 is equal to 194.08 mm.

[0038] Drawing (a) in Fig. 2 shows a prior art protective outer lens 31 having a focal length f0 and a focal point F0. Drawing (b) in Fig. 2 shows a protective outer lens 11 having a focal length f, wherein the inner surface 11.2 has a local radius of curvature R2 = R1 - (n - 1)d / n. As shown, the focal length f is greater than the focal length f0. Further, the field of view FOV of the protective outer lens 11 is smaller than the field of view FOV0 of the prior art protective outer lens 31, which means that the light ray L1 is less deflected and thus converges further away towards the focal point F. Therefore, f > f0.

[0039] Figs. 3 to 5 show the optical transfer function (OTF) curves for the following respectively: - Camera 10 without a protective outer lens, - Camera 10 arranged to face a protective outer lens 11 defined by an inner radius of curvature R2 adapted to have a focal length f that tends towards infinity, - Camera 10 arranged to face a prior art protective outer lens 31 defined by an unadapted radius of curvature R2.

[0040] Those curves correspond to various angles of incidence (0° to 97°) of the light ray L1 reaching the optical system 100 of the camera 10.

[0041] The optical transfer function curve of Fig. 2 is used as a reference.

[0042] The optical transfer function curve is used to evaluate the ability of elements of an optical system, such as a camera with or without a protective outer lens, to restore contrast based on the sharpness of details of an object, i.e., its ability to transmit the spatial frequency of the object. It is used to evaluate the quality of the optical system 100. Therefore, it can be used to evaluate the ability of the protective outer lens 11 not to degrade the performance level of the camera 10 as compared to a camera 10 without a protective outer lens or with the prior art protective outer lens 31.

[0043] The contrast between 0 and 1 is plotted on the Y-axis of the curve (referred to as ct). The spatial frequency of the object is plotted on the X-axis in cycles per millimeter (referred to as Spf (cy / mm)). This represents the sharpness of the details of the object.

[0044] As shown in FIG. 4, due to the optimized protective outer lens 11, that is, due to the adapted inner radius of curvature R2, the optical transfer function (OTF) does not deteriorate at any of the considered angles of incidence. Almost the same curve as in the case of FIG. 3, that is, in the case without a protective outer lens, is obtained. On the other hand, as shown in FIG. 5, this does not apply to the non-optimized protective outer lens 31 according to the prior art, that is, in the case of a non-adapted inner radius of curvature R2, and the resulting curve is completely different from the curve of FIG. 3.

[0045] Thus, the protective outer lens 11 of the optical system 1 achieves the same performance level with respect to the camera 10 arranged in the same orientation as the camera 10 without the protective outer lens. Therefore, the protective outer lens 11 does not interfere with the camera 10.

[0046] Of course, the description of the invention is not limited to the above-described embodiments and the above-described fields.

[0047] The invention thus described has the following advantages in particular: - It enables the camera 10 to be incorporated behind the protective outer lens 11 without degrading the performance level of the camera 10. - Since it does not change its outer surface 11.1, it enables the standardized shape given to the protective outer lens 11 by the automobile vehicle manufacturer to be retained. - It provides an optically neutral protective outer lens 11 by locally adapting the inner surface 11.2 of the protective outer lens 11. - It is easy to implement.

Claims

1. An optical system (1) for a vehicle (2), comprising: - A camera (10) configured to acquire an image (I1) of the environment outside the vehicle (2); - A protective outer lens (11) configured to be disposed facing the camera (10), the protective outer lens (11) having an outer surface (11.1) facing the outside of the vehicle (2) and an inner surface (11.2) facing the camera (10). The optical system (1) is characterized in that: The inner surface (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 towards infinity. An optical system (1) for a vehicle (2).

2. The optical system (1) according to claim 1, wherein the local radius of curvature R2 is given by R2 = R1 - (n - 1)d / n, where R1 is the local radius of curvature of the outer surface (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) according to claim 1 or 2, wherein the camera (10) is an RGB camera or an infrared camera.

4. The optical system (1) according to any one of claims 1 to 3, wherein the outer surface (11.1) has a set of local radii of curvature R1.

5. The optical system (1) according to any one of claims 1 to 4, 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), configured to be disposed facing a camera (10) mounted on the vehicle (2), the protective outer lens (11) having an outer surface (11.1) facing the outside of the vehicle (2) and an inner surface (11.2) facing the camera (10). The protective outer lens (11) is characterized in that the inner surface (11.2) has a local radius of curvature R2 defined such that the protective outer lens (11) has a focal length (f) tending towards infinity. A protective outer lens (11) for a vehicle (2).

7. The local radius of curvature R2 is R2 = R1 - (n - 1)d / n, where R1 is the local radius of curvature of the outer surface (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), the protective outer lens (11) according to claim 6.

8. The outer surface (11.1) has a set of a plurality of local radii of curvature R1, the protective outer lens (11) according to claim 6 or claim 7.

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

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