Moisture sensor and windshield fog detector

• US 6,495,815 B1
• Filed: 06/12/2001
• Issued: 12/17/2002
• Est. Priority Date: 09/16/1997
• Status: Expired due to Fees

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Roberts, John K., Stam, Joseph S., Bechtel, Jon H.
• Primary Examiner(s): Allen, Stephone B.
• Application Number:
  US09/878,799
• Time in Patent Office: 553 Days
• Field of Search: 250/208.1, 250/227.25, 250/341.7, 250/339.1, 250/574, 15D/IG.15, 219/203, 318/DIG.2, 318/444, 318/483, 340/602
• US Class Current: 250/208.1
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0833 Optical rain sensor
• CPC Class Codes: B60S 1/0844 including a camera
• CPC Class Codes: B60S 1/0885 the sensor being integrated in a rear-view mirror module
• CPC Class Codes: B60S 1/0888 characterized by the attachment of the elements in a unit
• CPC Class Codes: G06T 2207/20056 Discrete and fast Fourier transform, [DFT, FFT]
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/42 using transform domain methods
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: Y10S 15/15 Moisture responsive
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A system for automatically detecting moisture on the windshield of a vehicle includes an optical system for imaging a portion of the windshield on to an image array sensor, such as a CMOS active pixel sensor. The voltage of each of the pixels which represents the illumination level is converted to a corresponding gray scale value by an analog digital converter. The gray scale values corresponding to the image are stored in memory. The spatial frequency composition of the gray scale values is analyzed to determine the amount of rain present in order to provide a control signal to control the operation of the windshield wipers of the vehicle as a function of the amount of moisture present. The system is also adapted to detect the level of fog both on the interior of the windshield as well as the exterior of the windshield. By providing a system for automatically detecting the presence of fog on the interior and exterior of the windshield, serious performance limitations of known automatic rain sensors are eliminated.

Claims

1. A system for detecting moisture on a surface comprising:

an image sensor;

an optical system operative to image at least a portion of the surface onto the image sensor; and

a processing system in communication with the image sensor and operative to analyze images from the image sensor to detect moisture using an edge detection algorithm.

2. The system of claim 1 and further including an illuminator for providing supplemental illumination across substantially all of the imaged portion of the windshield surface.

3. The system of claim 1 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein said image sensor is supported by said rearview mirror assembly.

4. The system of claim 1 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein at least a portion of said processing system is supported by said rearview mirror assembly.

5. The system of claim 1, wherein said processing system is further operative to detect operation of a windshield wiper and to obtain a baseline image of the windshield immediately after it has been wiped by the windshield wiper, said processing system utilizing the baseline image to distinguish moisture from bugs, cracks, dirt, and other debris on the windshield.

6. The system of claim 1, wherein said image sensor mounted in said vehicle such that said imaging surface is inclined with respect to vertical.

7. The system of claim 1, where said processing system determines a spatial frequency component of the moisture on the windshield and generates control signals to control the time intervals at which the windshield wipers are activated.

8. The system of claim 1, wherein said processing system analyzes images from the image sensor to detect the presence of a windshield wiper moving across the imaged portion of the surface.

9. A system for detecting moisture on a vehicle windshield comprising:

an image sensor having an imaging surface, said image sensor mounted in said vehicle such that said imaging surface is inclined with respect to vertical;

an optical system operative to image at least a portion of the vehicle windshield onto the image sensor; and

a processing system in communication with the image sensor and operative to analyze images from the image sensor to detect moisture.

10. The system of claim 9 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein said image sensor is supported by said rearview mirror assembly.

11. The system of claim 9 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein at least a portion of said processing system is supported by said rearview mirror assembly.

12. The system of claim 9, wherein said image sensor is inclined at an angle of at least about 10 degrees relative to vertical.

13. A system for detecting moisture on a surface comprising:

a lens;

an image sensor inclined relative to an imaging plane of said lens, said lens positioned to image at least a portion of the surface onto said image sensor; and

a processing system in communication with the image sensor and operative to analyze images from the image sensor to detect moisture.

14. The system of claim 13, wherein said image sensor is inclined at an angle of at least about 10 degrees relative to an imaging plane of said lens.

15. The system of claim 13 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein said image sensor is supported by said rearview mirror assembly.

16. The system of claim 13 and further including a rearview mirror assembly adapted for attaching to a vehicle, wherein at least a portion of said processing system is supported by said rearview mirror assembly.