Rain detection apparatus and method

• US 8,781,155 B2
• Filed: 02/22/2012
• Issued: 07/15/2014
• Est. Priority Date: 07/16/2002
• Status: Active Grant

• Current Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Heenan, Adam John, Hazelden, Roger John, Thompson, Martin John, Buchanan, Alastair James
• Primary Examiner(s): TUCKER, WESLEY J
• Application Number:
  US13/402,438
• Publication Number:
  US 20120182424A1
• Time in Patent Office: 874 Days
• Field of Search: 382/100, 382104-106
• US Class Current: 382/100
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0844 including a camera
• CPC Class Codes: B60S 1/485 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like
• CPC Class Codes: B60S 1/603 the operation of at least a part of the cleaning means being controlled by electric means
• CPC Class Codes: G06T 7/254 involving subtraction of images
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

A rain detection apparatus includes a camera that views a surface and a processor that captures an image from the camera. The processor generates a signal indicative of rain on the surface from information contained in the captured image and optionally drives a surface cleaning apparatus in response thereto. The apparatus captures images focused at a plurality of distances. The processor includes an edge detector that detects edges visible in the captured image and a difference structure that calculates the difference between the number of edges visible between differing images. The edge detector disregards edges close to areas of light larger than the largest raindrop that is desired or expected to be detected. The apparatus optionally includes a backlight, and the difference in numbers of edges between frames with and without the backlight illuminated are used to distinguish between background features and rain on the surface.

Claims

1. A mist detection apparatus comprising:

a camera adapted to view a surface;

a processor adapted to capture at least one image from the camera and generate at least one signal indicative of the presence of mist on the surface from information contained in the at least one captured image, and

a backlight adapted to illuminate the surface,

wherein the processor is arranged to (1) distinguish a first area of the image, in which a specular reflection of the backlight is not found, from a second area of the image, in which a specular reflection of the backlight on the surface is found, (2) calculate a difference in intensity in the first area of the image between captured images in which the backlight is illuminated and in which the backlight is not illuminated, and (3) generate the at least one signal based upon the difference in intensity.

2. The mist detection apparatus of claim 1 wherein the processor is arranged to activate at least one from the group comprising a vehicle window heater, a vehicle heater, and a vehicle air conditioning system in response to the generation of the at least one signal.

3. The mist detection apparatus of claim 2 wherein the processor is arranged to activate a vehicle blower in response to the generation of the at least one signal.

4. The mist detection apparatus of claim 1 wherein the processor is arranged to determine average intensities in the first area of the image.

5. The mist detection apparatus of claim 1 wherein the processor is arranged to determine an average of the difference in intensities over the first area of the image.

6. The apparatus of claim 1 wherein the backlight is arranged to illuminate the surface with a range of frequencies of light, and wherein the apparatus comprises a filter which preferentially allows the range of frequencies to pass.

7. A method of detecting the presence of mist on a surface comprising the steps of:

capturing images of the surface with a backlight illuminated and not illuminated;

distinguishing a first area of the image, in which a specular reflection of the backlight is not found, from a second area of the image, in which a specular reflection of the backlight on the surface is found;

calculating a difference in intensity of the first area of the image between captured images in which the backlight is illuminated and in which the backlight is not illuminated; and

generate at least one signal based upon the difference in intensity generate the at least one signal based upon the difference in intensity.

8. The method of claim 7 further comprising the steps of activating at least one of the group comprising a vehicle window heater, a vehicle heater, and a vehicle air conditioning system in response to the generation of the at least one signal.

9. The method of claim 7 further comprising the step of activating a vehicle blower in response to the generation of the at least one signal.

10. The method of claim 7further comprising the step of determining average intensities in the first area of the image.

11. The method of claim 7 further comprising the step of determining an average of the difference in intensities over the first area of the image.

12. The method of claim 7 further comprising the steps of using the backlight to illuminate the surface with a range of frequencies of light using a filter to preferentially allows the range of frequencies to pass.