Precipitation sensor

• US 20020121972A1
• Filed: 01/29/2002
• Published: 09/05/2002
• Est. Priority Date: 10/30/1997
• Status: Active Grant

• Current Assignee: Brent J. Bos, Kenneth Schofield, Mark L. Larson, Niall R. Lynam
• Original Assignee: Brent J. Bos, Kenneth Schofield, Mark L. Larson, Niall R. Lynam
• Inventors: Schofield, Kenneth, Lynam, Niall R., Larson, Mark L., Bos, Brent J.
• Granted Patent: US 6,768,422 B2
• Time in Patent Office: Days
• US Class Current: 340/438
• CPC Class Codes: B60H 1/00785 by the detection of humidity or frost
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60N 2210/24 Cameras
• CPC Class Codes: B60R 2001/1223 with sensors or transducers
• 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 1/0837 with a particular arrangement of the optical elements
• 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: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A vehicular rain sensor system for detecting precipitation on an exterior surface of a window including a illumination sensor that is decoupled from the window. The illumination sensor is preferably an imaging array sensor which communicates a signal to a control which further determines whether rain is present on the window. The control preferably includes an edge detection function for detecting edges of precipitation droplets on the window and activating the windshield wipers of the vehicle when the number of edges detected exceeds a predetermined threshold value. A smoothing algorithm or filter is provided to account for surface irregularities on the window, thereby substantially precluding such irregularities from being erroneously detected as rain droplets by the edge detection function. The rain sensor system may further include a polarizing filter and an illumination source, such that the rain sensor system may not only prevent false signals of rain when only fog is present on an interior surface of the window, but also allows the rain sensor system to actually detect fog particles on an interior surface of the window, thereby allowing the control to further be connected to a ventilation blower within the vehicle for the purpose of activating the blower to eliminate the fog.

Claims

1. A vehicular rain sensor which senses at least one of rain and fog on a vehicle window, said vehicular sensor comprising:

an imaging array sensor directed at the vehicle window from inside the vehicle; and

a control which responds to an output of said imaging array sensor in order to indicate precipitation on a surface of the window.

2. The vehicular sensor in claim 1, wherein said surface of the window is an exterior surface exposed to weather conditions and the precipitation indicated is rain.

3. The vehicular sensor in claim 1, wherein said surface of the window is an interior cabin surface and the precipitation indicated is fog.

4. The vehicular sensor in claim 1, wherein said control comprising a computer programmed with an edge detection algorithm.

5. The vehicular sensor in claim 4, wherein said edge detection algorithm detects edges of particles of precipitation on the window, said control responding when a threshold amount of said particles is detected by said edge detection algorithm.

6. The vehicular sensor in claim 5, wherein said edge detection algorithm analyzes a quantity of edges present on the window.

7. The vehicular sensor in claim 6, wherein said edge detection algorithm further analyzes a size of the edges present on the window.

8. The vehicular sensor in claim 5, wherein the vehicle has a windshield wiper, said control controlling said windshield wiper when said threshold amount is detected.

9. The vehicular sensor in claim 8, wherein the control varies a rate at which the windshield wiper is wiped according to a level of edges detected by said edge detection algorithm.

10. The vehicular sensor in claim 1 further including a polarizing filter between the window and said imaging array sensor.

11. The vehicular sensor in claim 1 including an optic between said imaging array sensor and the window, said optic establishing a small depth of field, thereby focusing on an area at or immediately adjacent to the vehicle window.

12. The vehicular sensor in claim 11, wherein said imaging array sensor and said optic are oriented relative the window according to the Scheimpflug condition.

13. The vehicular sensor in claim 1 including an illumination device for illuminating the window.

14. The vehicular sensor in claim 13, wherein said illumination device provides illumination having an illumination wavelength approximately that of an infrared wavelength.

15. The vehicular sensor in claim 13, wherein said illumination device provides illumination having an illumination wavelength approximately within a range between 820 and 880 nanometers.

16. The vehicular sensor in claim 13 further including an illumination device control for at least occasionally activating said illumination device.

17. The vehicular sensor in claim 16, wherein said illumination device is pulsed on and off by said illumination device control.

18. The vehicular sensor in claim 17, wherein during low light conditions, said illumination sensor is exposed to the vehicle window when said illumination device is pulsed on and not exposed to the window when said illumination device is pulsed off.

19. The vehicular sensor in claim 16, wherein said illumination device control operates said illumination device during low light conditions.

20. The vehicular sensor in claim 19, wherein said illumination device control senses ambient light and operates said illumination device in low ambient light conditions.

21. The vehicular sensor in claim 19, wherein said imaging array sensor includes an array of imaging pixels, said illumination device control determines a level of ambient light by monitoring light received by said pixels on said imaging array, said illumination device control switching to said active mode when light received by said pixels is below a predetermined threshold value.

22. The vehicular sensor in claim 20, wherein said control comprising a computer programmed with an edge detection algorithm, said control responding to control a windshield wiper on the vehicle when a threshold level of particles of precipitation on the window is detected.

23. The vehicular sensor in claim 22, wherein said threshold level varies according to a level of ambient light present on the window.

24. The vehicular sensor in claim 20, wherein said illumination device control operates said illumination device when the ambient light conditions are below approximately 250 lux.

25. The vehicular sensor in claim 20, wherein said illumination device control operates said illumination device when the ambient light conditions are below approximately 150 lux.

26. The vehicular sensor in claim 20, wherein said illumination device control operates said illumination device when the ambient light conditions are below approximately 100 lux.

27. The vehicular sensor in claim 20, wherein said illumination device control operates said illumination device in response to when a vehicle'"'"'s headlamps are activated.

28. The vehicular sensor in claim 13 including a polarizing filter along an optic path between said illumination device and said imaging array sensor.

29. The vehicular sensor in claim 28, wherein said polarizing filter is oriented to filter out light signals radiating from fog particles on an interior surface of the window.

30. The vehicular sensor in claim 1, wherein said imaging array sensor is a CMOS sensor.

31. The vehicular sensor in claim 1, wherein the window is a vehicle windshield and the vehicle includes a windshield wiper and a rear window wiper, wherein said control causes the rear window wiper to cycle for every N cycles of the windshield wiper, wherein N is greater than one.

32. The vehicular sensor in claim 31, wherein the value of N varies as a function of the speed of the windshield wiper.

33. The vehicular sensor in claim 1, wherein said control comprising a micro-computer having one of an embedded control application, a custom digital logic circuit and a digital signal processor circuit.

34. The vehicular sensor in claim 33, wherein said control is adaptable to be positioned substantially adjacent a rear view mirror housing.

36. The rain sensor in claim 35, wherein said polarizing filter is at least occasionally not in said at least one optical path and wherein said control responds to an electrical characteristic of said at least one illumination sensor in order to indicate moisture on an interior surface of the window by comparing a signal from said at least one illumination sensor when said polarizing filter is not in said at least one optical path to a signal from said at least one illumination sensor when said polarizing filter is in said at least one optical path.

37. The rain sensor in claim 35, wherein said polarizing filter is at least occasionally in said at least one optical path between said at least one illumination source and the window.

38. The rain sensor in claim 35, wherein said polarizing filter is occasionally in said at least one optical path between the window and said at least one illumination sensor.

39. The rain sensor in claim 35, wherein said at least one illumination source and said at least one illumination sensor are oriented at a range of approximately 80 to 100 degrees with respect to each other along said at least one optical path.

40. The rain sensor in claim 35, wherein said at least one illumination source and said at least one illumination sensor are oriented at approximately 90 degrees with respect to each other along said at least one optical path.

41. The rain sensor in claim 35, wherein said at least one illumination sensor is an integrating sensor.

42. The rain sensor in claim 35, wherein said at least one illumination sensor is an imaging array sensor.

43. The rain sensor in claim 42, wherein said control is a computer which is programmed with an edge detection algorithm to detect edges of precipitation particles.

44. The rain sensor in claim 42, wherein said at least one illumination sensor is a CMOS sensor.

45. The rain sensor in claim 35, wherein the vehicle includes a windshield wiper and a rear window wiper, wherein said control causes the rear window wiper to cycle for every N cycles of the windshield wiper, wherein N is greater than 1.

46. The rain sensor in claim 45, wherein the value of N varies as a function of the speed of the windshield wiper.

47. The rain sensor in claim 35 including an illumination control which measures a level of ambient light that is present on the window and switches said rain sensor from an active mode, where said illumination source is on and provides light to the window, to a passive mode, where said illumination source is off and ambient light provides illumination to said illumination sensor, said illumination control being in said passive mode when said ambient light level is greater than a predetermined threshold value.

48. The rain sensor in claim 35, wherein said polarizing filter is fixed along said optical path, said polarizing filter being oriented to filter out a plurality of illumination signals radiating from fog particles on an interior surface of the window.

50. The vehicular sensor of claim 49, wherein said at least one illumination sensor is an imaging array sensor.

51. The vehicular sensor of claim 50, wherein said control comprising a computer programmed with an edge detection algorithm.

52. The vehicular sensor of claim 49, wherein said control functions to control a windshield wiper control if said at least one illumination sensor detects a precipitation level on said exterior surface of the window.

53. The vehicular sensor of claim 49, wherein said control functions to control a blower control if said at least one illumination sensor senses a fog level on said interior surface of the window.

54. The vehicular sensor of claim 53, wherein said control further functions to control a windshield wiper control if said at least one illumination sensor detects a precipitation level on said exterior surface of the window.

55. The vehicular sensor of claim 49, wherein said at least one illumination sensor is a single element integrating sensor.

56. The vehicular sensor of claim 49, further including an illumination control whereby said illumination control determines a level of ambient light in the vicinity of the vehicle and deactivates said at least one illumination source when said level of ambient light is above a predetermined threshold value.

57. The vehicular sensor of claim 49, wherein said at least one illumination source comprises at least two illumination sources, said polarizing filter being positioned between one of said illumination sources and the vehicle window defining a polarized beam having a polarized optic path between said one of said illumination sources and said at least one illumination sensor, other of said illumination sources defining a non-polarized beam having a non-polarized optic path between said other of said illumination sources and said at least one illumination sensor.

58. The vehicular sensor of claim 57, wherein said one of said illumination sources and said one of said at least one illumination sensor being oriented within a range of approximately 80 to 100 degrees relative one another along said polarized optic path.

59. The vehicular sensor of claim 57, wherein said one of said illumination sources and said one of said at least one illumination sensor being oriented at approximately 90 degrees relative one another along said polarized optic path.

60. The vehicular sensor of claim 57, wherein said control compares a signal received from said one of said illumination sources to a signal received from said other of said illumination sources to determine if at least one of fog and rain is present on the window.

61. The vehicular sensor of claim 60, wherein said control activates a blower in the vehicle if fog is detected and activates a windshield wiper on a windshield of the vehicle if rain is detected.

62. The vehicular sensor of claim 49, wherein said at least one illumination sensor comprises at least two illumination sensors.

63. The vehicular sensor of claim 62, wherein said polarizing filter is positioned between one of said illumination sensors and the vehicle window, said one of said sensors and said at least one illumination source defining a polarized optic path and the other of said illumination sensors and said at least one illumination source defining a non-polarized optic path.

64. The vehicular sensor of claim 63, wherein said one of said illumination sensors and said at least one illumination source are oriented within a range of approximately 80 to 100 degrees relative one another along said polarized optic path.

65. The vehicular sensor of claim 63, wherein said one of said illumination sensors and said at least one illumination source are oriented approximately 90 degrees relative one another along said polarized optic path.

66. The vehicular sensor of claim 63, wherein said control compares a signal received by said one of said illumination sensors to a signal received by said other of said illumination sensors to determine if at least one of fog and rain is present on the window.

67. The vehicular sensor of claim 66, wherein said at least two illumination sensors are imaging array sensors, and said control is programmed with an edge detection algorithm to detect precipitation particles.

68. The vehicular sensor of claim 66, wherein said control controls a windshield wiper on the vehicle in response to detection of precipitation particles on the window.

69. The vehicular sensor of claim 66, wherein said control controls a blower in the vehicle in response to detection of fog on an interior surface of the window.

70. The vehicular sensor of claim 69, wherein said control controls a windshield wiper on the vehicle in response to detection of precipitation particles on the window.

71. The vehicular sensor of claim 62, wherein said polarizing filter is positioned between said at least one illumination source and the vehicle window.

72. The vehicular sensor of claim 71, wherein one of said illumination sensors and said at least one illumination source define a first optic path and the other of said illumination sensors and said at least one illumination source define a second optic path.

73. The vehicular sensor of claim 72, wherein said one of said illumination sensors and said at least one illumination source are oriented within a range of approximately 80 to 100 degrees relative to one another along said first optic path, said polarizing filter oriented with a pass axis substantially perpendicular to a segment of said first optic path that is between the 5 vehicle window and said one of said illumination sensors.

74. The vehicular sensor of claim 72, wherein said one of said illumination sensors and said at least one illumination source are oriented approximately 90 degrees relative to one another along said first optic path, said polarizing filter oriented with a pass axis substantially perpendicular to a segment of said first optic path that is between the vehicle window and said one of said illumination sensors.

75. The vehicular sensor of claim 73, wherein said other of said illumination sensors and said at least one illumination source are oriented approximately 90 degrees relative to one another along said second optic path, said polarizing filter oriented with said pass axis substantially parallel to a segment of said second optic path that is between the vehicle window and said other of said illumination sensors.

76. The vehicular sensor of claim 75, wherein said other of said illumination sensors and said one of said illumination sensor are positioned such that said first optic path between said one of said illumination sensors and the vehicle window and said second optic path between said other of said illumination sensors and the vehicle window are generally perpendicular.

77. The vehicular sensor of claim 76, wherein said control compares a signal received by said one of said illumination sensors to a signal received by said other of said illumination sensors to determine if there is rain or fog present on the vehicle window.

78. The vehicular sensor of claim 77, wherein said control controls a windshield wiper on the vehicle in response to detection of precipitation particles present on the window.

79. The vehicular sensor of claim 78, wherein said one of said illumination sensors and said other of said illumination sensors are imaging array sensors, and said control is programmed with an edge detection algorithm.

80. The vehicular sensor of claim 78, wherein said control controls a blower in the vehicle in response to detection of fog present on an interior surface of the window.

81. The vehicular sensor of claim 80, wherein said control controls a windshield wiper on the vehicle in response to detection of precipitation particles present on the window.

35. A vehicular rain sensor which senses at least one of rain and fog on a vehicle window, comprising:

at least one illumination source and at least one illumination sensor defining at least one optical path from said at least one illumination source to the window and from the window to said at least one illumination sensor;

a polarizing filter at least occasionally in said at least one optical path in a manner that polarized light from the window is more attenuated than is nonpolarized light from the window; and

a control which responds to an electrical characteristic of said at least one illumination sensor in order to indicate precipitation on an exterior surface of the window independent of moisture on an interior surface of the window.

49. A vehicular sensor for detecting rain or fog on a vehicle window comprising:

at least one illumination source;

at least one illumination sensor;

said at least one illumination source and said illumination sensor defining at least one optic path therebetween, said at least one optic path defined between said at least one illumination source and the vehicle window, and further between the vehicle window and said at least one illumination sensor;

a polarizing filter positioned along said at least one optic path; and

a control, wherein said control responds to an output of said at least one illumination sensor in order to indicate at least one of precipitation on an exterior surface of the window and fog on an interior surface of the window.

82. A vehicular sensor for detecting rain or fog on a vehicle window, said vehicular sensor comprising:

a first illumination source;

a second illumination source;

an illumination sensor, said first illumination source and said illumination sensor defining a first optic path between said first illumination source and the vehicle window and between the vehicle window and said illumination sensor;

said second illumination source and said illumination sensor defining a second optic path between said first illumination source and the vehicle window and between the vehicle window and said illumination sensor;

a polarizing filter positioned along one of said first and second optic paths; and

a control, wherein said control responds to an output of said illumination sensor in order to indicate at least one of precipitation on an exterior surface of the window and fog on an interior surface of the window.

83. The vehicular sensor of claim 82, wherein said polarizing filter is positioned along said first optic path between said first illumination source and the window, said polarizing filter including a pass axis that is oriented generally parallel a portion of said first optic path between said illumination sensor and the vehicle window.

84. The vehicular sensor of claim 83, wherein said first illumination source and said illumination sensor are oriented within a range of approximately 80 to 100 degrees relative one another along said first optic path.

85. The vehicular sensor of claim 83, wherein said first illumination source and said illumination sensor are oriented approximately 90 degrees relative one another along said first optic path.

86. The vehicular sensor of claim 82, wherein said control responds to an output of said illumination sensor and determines whether precipitation is present on an exterior surface of the window or if fog is present on an interior surface of the window.

87. The vehicular sensor of claim 86, wherein said control activates a windshield wiper on the vehicle when precipitation is detected on the window, and activates a blower in the vehicle when fog is detected on the window.

88. The vehicular sensor of claim 87, wherein the vehicle includes a windshield wiper and a rear window wiper, said control activates the windshield wiper and the rear window wiper when precipitation is detected, said control causing the rear window wiper to cycle for every N cycles of the windshield wiper, wherein N is greater than 1.

89. The vehicular sensor of claim 88, wherein the value of N varies as a function of the speed of the windshield wiper.

90. A vehicular sensor for detecting rain or fog on a vehicle window, said vehicular sensor comprising:

an illumination source;

a first illumination sensor;

a second illumination sensor, said illumination source and said first illumination sensor defining a first optic path between said illumination source and the vehicle window and between the vehicle window and said first illumination sensor, said illumination source and said second illumination sensor defining a second optic path between said illumination source and the vehicle window and between the vehicle window and said second illumination sensor;

a polarizing filter positioned along one of said first and second optic paths; and

a control, wherein said control responds to an output of said illumination sensor in order to indicate at least one of precipitation on an exterior surface of the window and fog on an interior surface of the window.

91. The vehicular sensor of claim 90, wherein said polarizing filter is positioned along said first optic path between said first illumination sensor and the window, said polarizing filter including a pass axis that is oriented parallel a portion of said first optic path between said illumination source and the vehicle window.

92. The vehicular sensor of claim 91, wherein said illumination source and said first illumination sensor are oriented within a range of approximately 80 to 100 degrees relative one another along said first optic path.

93. The vehicular sensor of claim 91, wherein said illumination source and said first illumination sensor are oriented approximately 90 degrees relative one another along said first optic path.

94. The vehicular sensor of claim 90, wherein said control responds to an output of said first illumination sensor and an output of said second illumination sensor and indicates at least one of precipitation on an exterior surface of the window and fog on an interior surface of the window.

95. The vehicular sensor of claim 94, wherein said control activates a windshield wiper on the vehicle when precipitation is detected, and activates a blower in the vehicle when fog is detected.

96. The vehicular sensor of claim 95, wherein the vehicle includes a windshield wiper and a rear window wiper, said control activating the windshield wiper and the rear window wiper when precipitation is detected, said control causing the rear window wiper to cycle for every N cycles of the windshield wiper, wherein N is greater than 1.

97. The vehicular sensor of claim 96, wherein the value of N varies as a function of the speed of the windshield wiper.