Rain sensor using statistical analysis

• US 6,144,022 A
• Filed: 03/15/1999
• Issued: 11/07/2000
• Est. Priority Date: 03/15/1999
• Status: Expired due to Term

• Current Assignee: Valeo Electrical Systems Incorporated (Valeo SE)
• Original Assignee: Valeo Electrical Systems Incorporated (Valeo SE)
• Inventors: Tenenbaum, Jeff, Hochstein, Peter A.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US09/268,387
• Time in Patent Office: 603 Days
• Field of Search: 250/208.1, 250/573, 318/483, 318/DIG. 2, 15/DIG. 15, 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 1/0844 including a camera
• CPC Class Codes: B60S 1/087 including an ambient light sensor control of vehicle lights B60Q
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: Y10S 15/15 Moisture responsive
• CPC Class Codes: Y10S 318/02 Windshield wiper controls

Abstract

A method and an assembly for sensing moisture (20) on the exterior surface (22) of a sheet of glass (14) by positioning an imaging lens (16) adjacent to the interior surface (18) of the sheet of glass (14), passing light rays from moisture (20) on the exterior surface (22) of the sheet of glass (14) through the imaging lens (16) and producing first and second successive images of the moisture (20) on the glass (14), and successively directing the first and second images from the lens (16) onto a focal plane detector (12). The focal plane detector (12) is divided into rows of pixels (24) which are ligned into columns. The assembly and method are characterized by scanning the pixels (24) of each row in a first scan (FIG. 4) and producing a reference value X for each pixel (24) in response to an initial image in that pixel (24), scanning the pixels (24) of each row in a second scan (FIG. 5) and producing a subsequent value Y different from the reference value in response to an subsequent image in that pixel (24). A correlation coefficient value r is developed for each row with a statistical formula from the reference and subsequent values to produce a wiper signal in response to the correlation coefficient value r deviating from a predetermined value. An additional condition to the wiper signal could be that the correlation coefficient values r differ from row to row.

Claims

1. A method for sensing moisture (20) on the exterior surface (22) of a sheet of glass (14) comprising the steps of;

positioning an imaging lens (16) adjacent to the interior surface (18) of the sheet of glass (14),

passing light rays from moisture (20) on the exterior surface (22) of the sheet of glass (14) through the imaging lens (16) and producing first and second successive images of the moisture (20) on the glass (14), and

successively directing the first and second images from the lens (16) onto a focal plane detector (12),

dividing each of the images into a plurality of elements (24),

said method characterized by scanning the elements in a first scan and producing an initial reference value for each element in response to an initial image in that element, scanning the elements in a second scan and producing a subsequent value different from the initial reference value in response to an initial image in that element, developing a correlation coefficient value from the reference and subsequent values, and producing a wiper signal in response to the correlation coefficient value deviating from a predetermined value.

2. A method as set forth in claim 1 further defined as developing the correlation coefficient value in accordance with a statistical formula.

3. A method as set forth in claim 1 further defined as developing the correlation coefficient value (r) in accordance with the following statistical formula:

##EQU3## wherein X equals the reference value, Y equals the subsequent value, and N equals the number of elements (24).

4. A method as set forth in claim 1 further defined as dividing the plurality of elements into first and second groups, developing a first correlation coefficient value for the first group, developing a second correlation coefficient value for the second group, and producing a wiper signal in response to either of the first and second correlation coefficient values deviating from said predetermined value.

5. A method as set forth in claim 1 further defined as dividing the plurality of elements into first and second groups, developing a first correlation coefficient value for the first group, developing a second correlation coefficient value for the second group, and producing a wiper signal in response to either of the first and second correlation coefficient values deviating from said predetermined value and differing from each other.

6. A method as set forth in claim 5 further defined as placing the first and second groups in first and second rows, and leading the reference and correlation integers in each row with a zero.

7. A method as set forth in claim 6 further defined as aligning the elements of the first and second rows in columns.

8. An assembly for sensing moisture (20) on a glass (14) surface from a position adjacent the glass (14), said assembly comprising;

a focal plane detector (12) adapted for disposition adjacent to the interior surface (18) of the sheet of glass (14), and

an imaging lens (16) adapted for disposition between said focal plane detector (12) and the interior surface (18) of the sheet of glass (14) for directing light rays from moisture (20) on the exterior surface (22) of the sheet of glass (14) through said imaging lens (16) to produce successive first and second images of the moisture (20) on said focal plane detector (12),

a plurality of pixels (24) for dividing the images into a plurality of elements,

said assembly characterized by a controller (28) for scanning the elements in a first scan and producing a reference value for each element in response to an initial image in that element, for scanning the elements in a second scan and producing a subsequent value different from the reference value in response to a subsequent image in that element, for developing a correlation coefficient value from the reference and subsequent values, and for producing a wiper signal in response to the correlation coefficient value deviating from a predetermined value.

9. An assembly as set forth in claim 8 wherein said controller (28) includes a storage unit for storing a statistical formula and developing the correlation coefficient value in accordance with said statistical formula.

10. An assembly as set forth in claim 8 wherein said controller (28) includes a storage unit for storing the statistical formula:

##EQU4## wherein X equals the reference value, Y equals the subsequent value, and N equals the number of pixels (24), and developing the correlation coefficient value r in accordance with said statistical formula.

11. An assembly as set forth in claim 8 wherein the plurality of pixels are arranged into first and second groups for developing a first correlation coefficient value for the first group and for developing a second correlation coefficient value for the second group to producing a wiper signal in response to either of the first and second correlation coefficient values deviating from said predetermined value.

12. An assembly as set forth in claim 8 wherein the plurality of pixels are arranged into first and second groups for developing a first correlation coefficient value for the first group and for developing a second correlation coefficient value for the second group to producing a wiper signal in response to either of the first and second correlation coefficient values deviating from said predetermined value and differing from each other.

13. An assembly as set forth in claim 12 wherein the first and second groups are arranged in first and second rows, and including constant integer means for leading the reference and correlation integers in each row with a zero.

14. An assembly as set forth in claim 13 wherein the pixels of the first and second rows are aligned in columns.