Rain sensor with fractal capacitor(s)

• US 8,009,053 B2
• Filed: 05/21/2009
• Issued: 08/30/2011
• Est. Priority Date: 01/10/2006
• Status: Expired due to Fees

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Veerasamy, Vijayen S.
• Primary Examiner(s): Bugg; George
• Assistant Examiner(s): Labbees; Edny
• Application Number:
  US12/453,755
• Publication Number:
  US 20090223288A1
• Time in Patent Office: 831 Days
• Field of Search: 340601-604, 731/701.7, 733/350.4, 733/350.8
• US Class Current: 340/602
• CPC Class Codes: B32B 17/10036 comprising two outer glass sheets
• CPC Class Codes: B32B 17/10174 Coatings of a metallic or dielectric material on a constituent layer of glass or polymer
• CPC Class Codes: B32B 17/10761 containing vinyl acetal
• CPC Class Codes: B60S 1/0818 including control systems responsive to external conditions, e.g. by detection of moisture, dirt or the like
• CPC Class Codes: B60S 1/0822 characterized by the arrangement or type of detection means
• CPC Class Codes: B60S 1/0825 Capacitive rain sensor
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

A system and/or method for sensing the presence of moisture (e.g., rain) and/or other material(s) on a window such as a vehicle window (e.g., vehicle windshield, sunroof or backlite). In certain example embodiments of the invention, at least one sensing capacitor is supported by a window such as a vehicle windshield, the capacitor(s) having a field that is affected by moisture (e.g., rain) on a surface of the window. The at least one sensing capacitor may have a fractal geometry in certain example embodiments of this invention. The sensing circuit may output an analog signal that is based on and/or related to the sensing capacitor(s). The analog output of the circuit may be converted to a digital signal, and subjected to processing (e.g., correlation) for determining whether moisture (e.g., rain, dew, fog, etc.) or the like is present on the surface of the window.

Claims

1. A moisture sensor comprising:

a sensing circuit comprising at least a first sensing capacitor supported by a window, the first sensing capacitor being sensitive to moisture on an external surface of the window;

the first sensing capacitor having first and second spaced apart capacitor electrodes that are substantially coplanar;

wherein the first and second capacitor electrodes of the first sensing capacitor each have a meandering shape and are substantially parallel to each other; and

means for autocorrelating data relating to and/or from the sensing capacitor to obtain autocorrelated data, and means for determining based at least on said autocorrelated data whether moisture is present on the external surface of the window.

2. The moisture sensor of claim 1, wherein the first sensing capacitor comprises a geometry so that lateral flux caused by the geometry of the meandering shapes allows the capacitor to be sensitive to moisture on the external surface of the window that is not located directly over the first sensing capacitor.

3. The moisture sensor of claim 1, wherein the window is a vehicle window.

4. The moisture sensor of claim 3, wherein the moisture sensor is a rain sensor, and wherein the moisture sensor comprises at least first and second sensing capacitors of approximately the same size that are sensitive to moisture on the external surface of the vehicle window, and wherein the second sensing capacitor includes first and second capacitor electrodes having meandering shapes.

5. The moisture sensor of claim 1, wherein the moisture sensor includes a plurality of sensing capacitors arranged in an array around a centrally located contact pad.

6. The moisture sensor of claim 1, wherein the overall length of the first sensing capacitor is from about 25 to 200 mm, more preferably from about 30 to 90 mm.

7. The moisture sensor of claim 1, wherein the window is a vehicle windshield, and wherein the first and second spaced apart capacitor electrodes are electrically conductive and are supported by an interior glass sheet of the vehicle windshield, wherein the vehicle windshield comprises both the interior glass sheet and an exterior glass sheet.

8. The moisture sensor of claim 7, wherein the first and second spaced apart capacitor electrodes are located on the surface of the interior glass sheet closest to an interior of the vehicle.

9. The moisture sensor of claim 1, wherein the first sensing capacitor is a fractal.

10. The moisture sensor of claim 1, wherein the at least one sensing capacitor is part of the sensing circuit, the sensing circuit further comprising at least one mimicking capacitor that mimics at least charging and/or discharging of the first sensing capacitor, wherein a writing pulse causes at least the first sensing capacitor to be charged and an erasing pulse causes each of the first sensing capacitor and the mimicking capacitor to substantially discharge;

wherein presence of moisture on the external surface of the window in a sensing field of the first sensing capacitor causes a voltage at an output electrode of the mimicking capacitor to fluctuate in a manner proportional to fluctuation of voltage at an output electrode of the first sensing capacitor, even though the rain is not present in a field of the mimicking capacitor; and

wherein moisture is detected based on an output signal from the output electrode of the mimicking capacitor, wherein the output signal is read at least between an end of the writing pulse and a beginning of the erase pulse.

11. The moisture sensor of claim 1, wherein the first capacitor electrode of the sensing capacitor receives a charging signal and the second capacitor electrode of the sensing capacitor is spaced apart from the first capacitor electrode;

and

wherein the second capacitor electrode is floating so that the sensing capacitor is isolated from ground.

12. A moisture sensor comprising:

a sensing circuit comprising at least a first sensing capacitor supported by a window, the first sensing capacitor being sensitive to moisture on an external surface of the window;

the first sensing capacitor having first and second spaced apart capacitor electrodes that are substantially coplanar;

wherein the first and second capacitor electrodes of the first sensing capacitor each have a meandering shape and are substantially parallel to each other; and

programmable logic circuitry for autocorrelating data relating to and/or from the sensing capacitor to obtain autocorrelated data, and for determining based at least on said autocorrelated data whether moisture is present on the external surface of the window.

13. The moisture sensor of claim 12, wherein the first sensing capacitor comprises a geometry so that lateral flux caused by the geometry of the meandering shapes allows the capacitor to be sensitive to moisture on the external surface of the window that is not located directly over the first sensing capacitor.

14. The moisture sensor of claim 12, wherein the window is a vehicle window.

15. The moisture sensor of claim 12, wherein the moisture sensor is a rain sensor, and wherein the moisture sensor comprises at least first and second sensing capacitors of approximately the same size that are sensitive to moisture on the external surface of the vehicle window, and wherein the second sensing capacitor includes first and second capacitor electrodes having meandering shapes.

16. The moisture sensor of claim 12, wherein the overall length of the first sensing capacitor is from about 25 to 200 mm, more preferably from about 30 to 90 mm.

17. The moisture sensor of claim 12, wherein the first sensing capacitor is a fractal.

18. The moisture sensor of claim 12, wherein the at least one sensing capacitor is part of the sensing circuit, the sensing circuit further comprising at least one mimicking capacitor that mimics at least charging and/or discharging of the first sensing capacitor, wherein a writing pulse causes at least the first sensing capacitor to be charged and an erasing pulse causes each of the first sensing capacitor and the mimicking capacitor to substantially discharge;

wherein presence of moisture on the external surface of the window in a sensing field of the first sensing capacitor causes a voltage at an output electrode of the mimicking capacitor to fluctuate in a manner proportional to fluctuation of voltage at an output electrode of the first sensing capacitor, even though the rain is not present in a field of the mimicking capacitor; and

wherein moisture is detected based on an output signal from the output electrode of the mimicking capacitor, wherein the output signal is read at least between an end of the writing pulse and a beginning of the erase pulse.

19. The moisture sensor of claim 12, wherein the first capacitor electrode of the sensing capacitor receives a charging signal and the second capacitor electrode of the sensing capacitor is spaced apart from the first capacitor electrode;

and

wherein the second capacitor electrode is floating so that the sensing capacitor is isolated from ground.

20. A moisture sensor comprising:

a sensing circuit comprising at least a first sensing capacitor supported by a window, the first sensing capacitor being sensitive to moisture on an external surface of the window;

the first sensing capacitor having first and second spaced apart capacitor electrodes that are substantially coplanar;

wherein the first and second capacitor electrodes of the first sensing capacitor each have a meandering shape and are substantially parallel to each other;

at least one mimicking capacitor that mimics at least charging and/or discharging of the first sensing capacitor, wherein a writing pulse causes at least the first sensing capacitor to be charged and an erasing pulse causes each of the first sensing capacitor and the mimicking capacitor to substantially discharge;

wherein presence of moisture on the external surface of the window in a sensing field of the first sensing capacitor causes a voltage at an output electrode of the mimicking capacitor to fluctuate in a manner proportional to fluctuation of voltage at an output electrode of the first sensing capacitor, even though the rain is not present in a field of the mimicking capacitor; and

wherein moisture is detected based on an output signal from the output electrode of the mimicking capacitor, wherein the output signal is read at least between an end of the writing pulse and a beginning of the erase pulse.