Differential imaging rain sensor

• US 6,603,137 B2
• Filed: 04/16/2001
• Issued: 08/05/2003
• Est. Priority Date: 04/16/2001
• Status: Expired due to Fees

• Current Assignee: Valeo Electrical Systems Incorporated (Valeo SE)
• Original Assignee: Valeo Electrical Systems Incorporated (Valeo SE)
• Inventors: Hochstein, Peter A.
• Primary Examiner(s): Pyo, Kevin
• Assistant Examiner(s): Sohn, Seung C.
• Application Number:
  US09/835,755
• Publication Number:
  US 20020148986A1
• Time in Patent Office: 841 Days
• Field of Search: 250/573, 250/574, 250/208.1, 250/214.R, 250/214.AL, 250/214.B, 250/341.8, 250/349, 250/227.25, 318/443, 318/444, 318/480, 318/483, 318/DIG.2, 15D/IG.15, 152/500.01, 152/500.1, 152/501.2, 340/602, 340/604
• US Class Current: 250/573
• 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: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

A method and assembly for sensing moisture on the exterior surface of a sheet of glass (16) by capturing an ambient image (A) of light rays passing through the glass (16) from the exterior to the interior surfaces thereof under ambient light conditions. The invention is characterized by illuminating (18) the glass with pulses of light rays, capturing an illuminated image of the glass containing the ambient image (A) plus the illuminated image (B) containing the reflected light from the illuminating (18) of the glass (16) between the ambient images (A), and subtracting each ambient image (A) from the next adjacent illuminated image (B) to produce a moisture signal (30).

Claims

1. A method for sensing moisture on the exterior surface of a sheet of glass comprising the steps of;

capturing an ambient image of light rays made up of a first plurality of pixel light intensity with each value derived from at least one of a plurality of pixels to represent the ambient image of light rays passing through the glass from the exterior to the interior surfaces thereof under ambient light conditions,

said method characterized illuminating the glass with rays, capturing an illuminated image made up of a second plurality of pixel light intensity values with each value derived from the same grouping of the plurality of pixels to represent an illuminated image of the glass containing the ambient image plus the illuminated image containing the reflected light pixel light intensity values from the second series of pixel light intensity values to produce a moisture signal in response to increased light intensity values captured by corresponding pixels.

2. A method as set forth in claim 1 including measuring the moisture signal and producing an actuation signal in response to said moisture signal reaching a predetermined level.

3. A method as set forth in claim 1 wherein the step illuminating the glass is further defined as pulsing light rays toward the glass to provide pulses of light separated by ambient images.

4. A method as set forth in claim 2 further defined as capturing an illuminated image during said pulses and capturing an ambient image immediately adjacent each of the illuminated images to define a differential pair of images which are subtracted from one another on a pixel by pixel basis to provide a series of moisture signals.

5. A method as set forth in claim 2 wherein the step of pulsing is further defined as producing at least sixty pulses per second.

6. A method as set forth in claim 1 wherein the step of illuminating the glass with light rays is further defined as illuminating the glass with light rays at wave lengths invisible to the human eye.

7. A method as set forth in claim 1 further including the step of positioning an imaging device adjacent to the interior surface of the sheet of glass to capture the images, optically filtering the ambient light to the imaging device to wavelengths in a predetermined range including the wavelength of the illuminating light rays.

8. An assembly for sensing moisture on an exterior surface of a sheet of glass from a position adjacent the sheet of glass, said assembly comprising;

a light source (18) for illuminating the sheet of glass with light rays,

an imager device including a plurality of pixels and adapted for disposition adjacent to the interior surface of the sheet of glass for capturing an ambient image of light rays made up of a first plurality of pixel light intensity values each derived from at least one of said pixels to represent an ambient image of light rays passing through the sheet of glass from the exterior to the interior surface thereof under ambient light conditions and for capturing an illuminated image made up of a second plurality of pixel light intensity values each derived from corresponding grouping of pixels to represent an illuminated image of the sheet of glass containing the reflected light from the illuminating of the sheet of glass, pixel light intensity values from the second series of pixel light intensity values to produce a moisture signal in response to increased light intensity values captured by corresponding pixels.

9. An assembly as set forth in claim 8 wherein said controller includes a moisture signal detector for measuring said moisture signals and producing an actuation signal in response to said moisture signal reaching a predetermined level.

10. An assembly as set forth in claim 8 wherein said light source (18) includes a pulse generator for pulsing light rays toward the glass to provide pulses of light separated by ambient images.

11. An assembly as set forth in claim 10 wherein said controller includes a synchronizing device for controlling said imager device for capturing the illuminated image during said pulses and capturing the ambient image immediately adjacent each capture of the illuminated images to define a differential pair of images which are subtracted from one another on a pixel by pixel basis to provide a series of moisture signals.

12. An assembly as set forth in claim 8 wherein said light source (18) emits light rays at wavelengths invisible to the human eye.

13. An assembly as set forth in claim 8 including a filter for optically filtering the ambient light to the imager device to wavelengths in a predetermined range including the wavelength of the illuminating light rays.