Detection of Raindrops on a Pane by Means of a Camera and Lighting

• US 20130235381A1
• Filed: 09/20/2011
• Published: 09/12/2013
• Est. Priority Date: 11/30/2010
• Status: Active Grant

• Current Assignee: Conti Temic Microelectronic GmbH (Continental AG)
• Original Assignee: Conti Temic Microelectronic GmbH (Continental AG)
• Inventors: Kroekel, Dieter, Chivukula, Radhakrishna
• Granted Patent: US 9,335,264 B2
• Time in Patent Office: Days
• US Class Current: 356/445
• CPC Class Codes: B60S 1/0844 including a camera
• CPC Class Codes: G01N 2021/435 Sensing drops on the contact surface
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

The invention relates to a device or a method for detecting rain (4), said device or method comprising a camera (1) and a lighting source (3). The camera (1) is disposed behind a pane (2), in particular in the interior of a vehicle behind a windscreen, and focused onto a far range that lies in front of the pane (2). The lighting source (3) for generating at least one light beam (h; n) that is directed at the pane (2) directs the at least one light beam (h; n) towards the pane (2) such that at least one beam (r2; r2′) that is reflected from the outer face (2.2) of the pane impinges on the camera (1).

The light quantity of the at least one beam (r2; r2′) that impinges on the camera (1) can be measured by the camera (1).

Claims

1. A device for detecting rain (4) comprising

a camera disposed behind a pane (2), wherein the camera (1) is focused onto a far range that lies in front of the pane (2), and

a lighting source (3) for generating at least one light beam (h;

n) directed towards the pane, wherein the lighting source (3) directs the at least one light beam (h;

n) towards the pane (2) such that at least one beam (r2;

r2′

) that is reflected from the outer face (2.2) of the pane (2) impinges on the camera (1) and that the light quantity of at least one beam (r2;

r2′

) impinging on the camera (1) can be measured by the camera (1).

2. The device according to claim 1, wherein the angle of incidence of the light beam (h;

n) generated by the lighting source (3) is set up such that the beam (t1), which impinges on the outer face (2.2) of the pane (2), is more reflected than decoupled (t2) out of the pane, when there is no rain (4) on the outer face (2.2) of the pane (2).

3. A device according to claim 1, wherein the device comprises an evaluation unit, which determines from the measured light quantity of the beam (r2;

r2′

) that is reflected at the outer face (2.2) of the pane (2) whether there is rain (4) on the outer face (2.2) of the pane (2).

4. A device according to claim 3, wherein the evaluation unit compares the measured light quantity of the beam (r2;

r2′

) that is reflected at the outer face (2.2) of the pane (2) with a threshold value.

5. A device according to claim 3, wherein the evaluation unit determines a time variation of the light values, measured by an image sensor (5) of the camera (1), of the beam (r2;

r2′

) that is reflected at the outer face (2.2) of the pane (2).

6. A device according to claim 1, wherein the lighting source (3) directs the at least one light beam (h;

n) towards the pane (2) such that respective beams (r1;

r2 or r2′

) that are reflected from the inner face (2.1) and outer face (2.2) of the pane impinge as at least two spatially separated beams (r1;

r2 or r2′

) on the camera (1) and the light quantities of the at least two beams (r1;

r2 or r2′

) impinging on the camera (1) can be measured by the camera (1).

7. A device according to claim 1, wherein the lighting source (3) is structurally integrated into a housing of the camera (1).

8. A device according to claim 7, wherein the lighting source (3) is arranged below a view shield (11) of the camera (1).

9. A device according to claim 8, wherein the lighting source (3) generates light in the infrared wavelength range and the view shield (11) is permeable in the infrared wavelength range at least in a portion, which is located above the lighting source (3).

10. A device according to claim 7, wherein the lighting source (3) is arranged on a circuit carrier (12) of the camera (1).

11. A device according to claim 1, wherein the lighting source (3) generates only light with a wavelength in a specific wavelength range, and in the beam path of the camera (1) a first spectral filter is arranged in the region, in which the at least one beam (r2;

r2′

) that is reflected at the outer face (2.2) of the pane (2) is passing through, wherein the first spectral filter is permeable to light having a wavelength in the specific wavelength range.

12. A device according to claim 11, wherein a second spectral filter is arranged in the region of the beam path, in which the at least two spatially separated reflected beams (r1;

r2 or r2′

) do not pass through, wherein the second spectral filter blocks light having a wavelength in the specific wavelength range.

13. A device according to claim 12, wherein the camera (1) comprises an image sensor (5) and the first or both spectral filters are applied directly on pixels of the image sensor (5).

14. A device according to claim 1, wherein the lighting source (3) generates a focused light beam (h).

15. A device according to claim 1, wherein the light beam (h) generated by the lighting source (3) is directed by means of a light guide (13) towards the pane (2).

17. A method for detecting rain (4) on the outer face (2.2) of a pane (2) by a device according to claim 1, comprising the steps:

with the camera, recording a first image with the lighting source (3) turned off,

with the camera, recording a second image with the lighting source (3) turned on,

forming a difference image from the second and first images, and

in the difference image, evaluating a light quantity of the at least one beam (r2;

r2′

) that is reflected from the outer face (2.2) of the pane (2) to detect whether there is rain (4) on the outer face (2.2) of the pane.

16. A method for detecting rain (4) on the outer face (2.2) of a pane (2), comprising the steps:

providing a camera (1) disposed behind the pane (2) and focused onto a far range in front of the pane,

with a lighting source (3), generating at least one light beam (h;

n), and directing the at least one light beam (h;

n) towards the pane (2) such that at least one beam (r2;

r2′

) that is reflected from the outer face (2.2) of the pane (2) impinges on the camera (1),

using the camera, measuring the light quantity of the at least one beam (r2;

r2′

) that is reflected from the outer face (2.2) of the pane (2), and

evaluating the measured light quantity of the at least one beam (r2;

r2′

) that is reflected from the outer face (2.2) of the pane (2) to detect whether there is rain (4) on the outer face (2.2) of the pane (2).