Apparatus and method for detecting precipitation for a motor vehicle

Abstract

An apparatus and a method are for detecting precipitation on a windscreen of a motor vehicle. A camera device records a first image and thereafter a second image. A comparison device produces a first comparison image by comparing the first image with the second image. An image detection device identifies objects on the first comparison image, and determines motion of the objects, to detect whether there is precipitation on the windscreen.

Claims

1. An apparatus for detecting precipitation on a windscreen of a motor vehicle, the apparatus comprising: a camera device configured to record a first image and thereafter a second image; a comparison device configured to produce a first comparison image by comparing the first image with the second image; and an image detection device configured to detect objects in the first comparison image, and to determine a respective apparent motion and a respective apparent motion direction of moving objects among the detected objects, and to classify some of the moving objects respectively as being either precipitation drops on the windscreen or non-precipitation objects in an outside environment of the motor vehicle based on consideration of at least the respective motion direction thereof; wherein the moving objects include first moving objects of which the respective motion direction includes a lateral or horizontal motion component, and second moving objects of which the respective motion direction does not include a lateral or horizontal motion component, and wherein the image detection device is further configured so that the classifying of the moving objects based on consideration of the respective motion direction thereof comprises ignoring or filtering-out the first moving objects and further classifying only the second moving objects as being either the precipitation drops or the non-precipitation objects.

2. The apparatus according to claim 1, wherein the comparison device is further configured to produce a difference image as the first comparison image.

3. The apparatus according to claim 1, wherein: the camera device is further configured to record a third image following the second image; the comparison device is further configured to produce a second comparison image by comparing the second image with the third image; and the image detection device is further configured to determine the respective apparent motion and the respective apparent motion direction of the moving objects by comparing the first comparison image with the second comparison image.

4. The apparatus according to claim 1, wherein the image detection device is further configured to determine the respective apparent motion and the respective apparent motion direction of the moving objects by comparing the first image with the second image.

5. The apparatus according to claim 1, wherein the image detection device is further configured to classify the detected objects other than the moving objects in the first comparison image.

6. The apparatus according to claim 1, wherein the image detection device is further configured to classify the detected objects based on consideration of respective shapes of the detected objects.

7. The apparatus according to claim 1, wherein the image detection device is further configured to classify the detected objects based on consideration of respective local frequencies of the detected objects in the first comparison image.

8. The apparatus according to claim 1, wherein the camera device is further configured to record the images with a predefined depth of field, and the image detection device is further configured to classify the detected objects based on consideration of whether a respective one of the detected objects lies within or outside the predefined depth of field.

9. The apparatus according to claim 1, wherein the camera device is further configured to record the images without the apparatus applying any active lighting.

10. The apparatus according to claim 1, wherein the camera device is further configured to record the images and the image detection device is further configured to perform the classifying when the motor vehicle is stationary.

11. The apparatus according to claim 1, wherein the camera device is further configured to record the images and the image detection device is further configured to perform the classifying when the motor vehicle is moving with a vehicle motion, and to filter out motion components of the respective apparent motion of the moving objects caused by the vehicle motion before the classifying of the moving objects.

12. A method of detecting precipitation on a windscreen of a motor vehicle, the method comprising the following steps performed with a driver assistance system of the vehicle: with a camera of the driver assistance system recording a first image and thereafter a second image; producing a comparison image from the first image and the second image; identifying objects in the comparison image; determining a respective apparent motion and a respective apparent motion direction of moving objects among the identified objects, wherein the moving objects include first moving objects of which the respective motion direction includes a lateral or horizontal motion component, and second moving objects of which the respective motion direction does not include a lateral or horizontal motion component; and classifying some of the moving objects based on consideration of at least the motion direction thereof, comprising ignoring or filtering-out the first moving objects and then further classifying the second moving objects to determine whether the second moving objects represent environment objects in an outside environment in front of the motor vehicle or represent precipitation drops on the windscreen.

13. A method of detecting precipitation on a windscreen of a motor vehicle, the method comprising the following steps performed with a driver assistance system of the motor vehicle: a) with a camera of the driver assistance system having a field of view directed through the windscreen and focused in an outside environment in front of the motor vehicle, recording a first image and thereafter a second image; b) evaluating the images and detecting therein moving objects that have moved in the second image relative to the first image; c) determining a respective motion direction of the moving objects; d) among the moving objects, determining first moving objects of which the respective motion direction is horizontal and determining second moving objects of which the respective motion direction does not include a lateral or horizontal motion component; and e) performing a rain detection procedure on the second moving objects, and ignoring or filtering-out the first moving objects from the rain detection procedure, wherein the rain detection procedure comprises classifying the second moving objects to determine whether the second moving objects represent physical objects in the outside environment in front of the motor vehicle or represent precipitation drops on the windscreen.

14. The method according to claim 13, wherein the step d) further includes determining, among the moving objects, third moving objects of which the respective motion direction is a diagonal motion direction; and wherein the step e) further involves ignoring or filtering-out the third moving objects from the rain detection procedure.

15. The method according to claim 13, performed when the motor vehicle is stationary.

16. The method according to claim 13, performed when the motor vehicle is moving with a vehicle motion, wherein the method further comprises filtering-out motion components caused by the vehicle motion in the respective motion directions of the moving objects before performing the steps d) and e).

17. The apparatus according to claim 1, wherein the image detection device is configured to detect the detected objects in the first comparison image by detecting new objects that are present in the second image but are not present in the first image, whereby the new objects appear in the first comparison image.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The enclosed drawings shall provide further understanding of the embodiments of the invention. The enclosed drawings demonstrate the embodiments and serve in context with the description of the explanation of concepts of the invention.

(2) Other embodiments and many of the mentioned advantages result from the drawings. The shown elements of the drawings are not necessarily shown to scale.

(3) FIG. 1 shows a schematic view of an apparatus for detecting precipitation according to an embodiment of the invention;

(4) FIG. 2 shows a schematic view of a flow chart of a method for detecting precipitation for a motor vehicle according to a further embodiment of the invention; and

(5) FIG. 3 shows a schematic view of a windscreen for explaining the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) In the figures of the drawings identical and/or functionally identical elements, parts, components or method steps are referred to by the same reference numerals, unless otherwise indicated.

(7) FIG. 1 shows a schematic view of an apparatus for detecting precipitation according to an embodiment of the invention.

(8) An apparatus 100 for detecting precipitation for a motor vehicle comprises for example a camera device 101, a comparison device 102, and an image detection device 103.

(9) The camera device 101 can be designed for example such that it records a first image at a first moment and a second image at a second moment following the first moment.

(10) The camera device 101 can be embodied as an optical camera and is disposed for example behind a pane or windscreen 20, in particular in the interior of a vehicle, e.g. behind a windscreen, and focused onto a remote region that lies in front of the pane or windscreen 20. The camera preferably comprises an objective used for focusing and an image sensor, e.g. a CCD sensor or CMOS sensor and can record images within an image angle region or spatial angle referred to as image angle 11.

(11) The comparison device 102 can be designed for example such that it produces a first comparison image by comparing the first image with the second image.

(12) The image detection device 103 can be designed such that it identifies objects on the first comparison image.

(13) The camera device 101 can be designed such that it records the images with a predefined depth of field and the image detection device 103 can be designed such that it identifies the objects within and outside the predefined depth of field.

(14) For example the depth of field or focal depth can be defined as a measure for the expansion of the sharp region in the object space of a copied optical system, the camera device. The focal depth describes the quantity of the distance range, within which an object appears sufficiently sharp in the image of the camera optics.

(15) For example a large depth of field is obtained by small camera apertures or objectives with short focal lengths.

(16) In this case the focal depth of the camera device 101 can reach from approx. 5 m to 100 m or from 8 m to 200 m or from 12 m to infinity.

(17) FIG. 2 shows a schematic view of a flow chart of a method for detecting precipitation for a motor vehicle according to a further embodiment of the invention.

(18) The method for detecting precipitation for a motor vehicle comprises the following steps:

(19) A first step of the method comprises recording S1 of a first image at a first moment and recording of a second image at a second moment following the first moment.

(20) A second step of the method comprises producing S2 a comparison image from the first image and the second image.

(21) A third step of the method comprises identifying S3 of objects on the comparison image.

(22) The method steps can be repeated iteratively or recursively and in any sequence.

(23) FIG. 3 shows a schematic view of a windscreen for explaining the invention. FIG. 3 shows in particular a simplified representation of the drop distribution with light or moderate rain. With a precipitation intensity of up to 0.2 millimeters per hour one can speak of a light drizzle, with 0.2 to 0.5 millimeters per hour of a moderate drizzle, and with over 0.5 millimeters per hour of a heavy drizzle.

(24) A detection surface 40 of a comparative LED-based detection apparatus is shown on the windscreen 20 in FIG. 3 for purposes of comparison and explanation.

(25) The raindrops 31 outside the detection surface 40 remain undetected by the LED-based detection method. With a light to moderate rain it can happen that the windscreen 20 overall is uniformly wetted with drops, whereas no drops fall onto the detection surface 40 as is shown in FIG. 3.

(26) For a stable rain detection in particular with light precipitation it is, therefore, desirable to increase the size or area of the detection surface.

(27) The increased detection surface 11 of the camera device 101, which is defined by the field of view or image angle 11 of the camera device 101, makes it possible to detect raindrops 31 even with a light or low precipitation intensity.

(28) Although the present invention was described above on the basis of preferred exemplary embodiments, it is not restricted thereto, but is modifiable in many ways. In particular, the invention can be changed or modified in various ways without deviating from the core of the invention.

(29) In addition, it may be pointed out that including and comprising do not exclude other elements or steps and one does not exclude a plurality.

(30) Further, it may be pointed out that the features or steps, which were described with reference to one of the above exemplary embodiments, can be used also combined with other features and steps of other exemplary embodiments described above. Reference numerals in the claims are not to be considered as restrictions.