Vehicle vision system with lens pollution detection

1. A vision system for a vehicle, said vision system comprising:

a camera disposed at a vehicle and having a field of view exterior of the vehicle;

wherein said camera comprises a lens and an imaging array comprising an array of photosensing elements having multiple columns of photosensing elements and multiple rows of photosensing elements;

said multiple columns of photosensing elements being generally vertically orientated relative to ground when said camera is disposed at the vehicle;

said multiple rows of photosensing elements being generally horizontally orientated relative to ground when said camera is disposed at the vehicle;

said multiple rows of photosensing elements comprising top rows, middle rows and bottom rows;

wherein, with said camera disposed at the vehicle, top rows are higher above ground than middle and bottom rows;

wherein, with said camera disposed at the vehicle, middle rows are higher above ground than bottom rows and are lower above ground than top rows;

wherein, with said camera disposed at the vehicle, middle rows are between top rows and bottom rows;

a processor operable to process image data captured by said camera;

wherein, when the vehicle is moving, top row brightness values at top rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, middle row brightness values at middle rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, bottom row brightness values at bottom rows are determined by processing of captured image data by said processor;

wherein contrast of middle row brightness values compared to bottom row brightness values or top row brightness values is determined; and

wherein, based on determined contrast of middle row brightness values compared to bottom row brightness values or top row brightness values, an at least partial blockage of said camera is detected.

2. The vision system of claim 1 , wherein said processor is incorporated in circuitry of said camera.

3. The vision system of claim 1 , wherein said processor is incorporated in circuitry of a control of the vehicle.

4. The vision system of claim 1 , wherein said processor is operable to read a selected set of imager register values and compare a contrast of auto exposure control zones, and wherein, responsive to a determination that a range of contrast levels is less than a threshold level, said processor determines that there are contaminants at said lens of said camera.

5. The vision system of claim 4 , wherein said processor is operable to compare a contrast of auto exposure control zones when an auto exposure function of said camera is enabled.

6. The vision system of claim 4 , wherein said processor compares contrast levels between a generally middle zone and an upper or lower zone.

7. The vision system of claim 4 , wherein said processor is incorporated in circuitry of said camera.

8. The vision system of claim 1 , wherein the vehicle moving comprises the vehicle being driven forward on a road.

9. The vision system of claim 8 , wherein determining contrast of middle row brightness values compared to bottom row brightness values or top row brightness values comprises determining the difference of middle row brightness values to bottom row brightness values or top row brightness values in the same column compared to in a different column.

10. The vision system of claim 8 , wherein said processor is incorporated in circuitry of a control of the vehicle.

11. The vision system of claim 1 , wherein, when an at least partial blockage of said camera is detected, said system at least one of (i) generates an alert, (ii) adapts processing of captured image data to at least partially accommodate for the at least partial blockage and (iii) cleans said lens.

12. The vision system of claim 1 , wherein said camera comprises a CMOS camera.

13. The vision system of claim 12 , wherein said imaging array comprises at least 640 columns of photosensing elements and at least 480 rows of photosensing elements.

14. The vision system of claim 13 , wherein said camera is part of a multi-camera birds-eye surround view system of the equipped vehicle.

15. A vision system for a vehicle, said vision system comprising:

a camera disposed at a vehicle and having a field of view exterior of the vehicle;

wherein said camera comprises a lens and an imaging array comprising an array of photosensing elements having at least 640 columns of photosensing elements and at least 480 rows of photosensing elements;

said at least 640 columns of photosensing elements being generally vertically orientated relative to ground when said camera is disposed at the vehicle;

said at least 480 rows of photosensing elements being generally horizontally orientated relative to ground when said camera is disposed at the vehicle;

said at least 480 rows of photosensing elements comprising top rows, middle rows and bottom rows;

wherein, with said camera disposed at the vehicle, top rows are higher above ground than middle and bottom rows;

wherein, with said camera disposed at the vehicle, middle rows are higher above ground than bottom rows and are lower above ground than top rows;

wherein, with said camera disposed at the vehicle, middle rows are between top rows and bottom rows;

a processor operable to process image data captured by said camera;

wherein, when the vehicle is moving, top row brightness values at top rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, middle row brightness values at middle rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, bottom row brightness values at bottom rows are determined by processing of captured image data by said processor;

wherein contrast of middle row brightness values compared to bottom row brightness values or top row brightness values is determined;

wherein, based on determined contrast of middle row brightness values compared to bottom row brightness values or top row brightness values, an at least partial blockage of said camera is detected; and

wherein, when an at least partial blockage of said camera is detected, said system at least one of (i) generates an alert, (ii) adapts processing of captured image data to at least partially accommodate for the at least partial blockage and (iii) cleans said lens.

16. The vision system of claim 15 , wherein said processor is incorporated in circuitry of said camera.

17. The vision system of claim 15 , wherein said processor is incorporated in circuitry of a control of the vehicle.

18. A vision system for a vehicle, said vision system comprising:

a camera disposed at a vehicle and having a field of view exterior of the vehicle;

wherein said camera comprises a lens and an imaging array comprising an array of photosensing elements having at least 640 columns of photosensing elements and at least 480 rows of photosensing elements;

said at least 640 columns of photosensing elements being generally vertically orientated relative to ground when said camera is disposed at the vehicle;

said at least 480 rows of photosensing elements being generally horizontally orientated relative to ground when said camera is disposed at the vehicle;

said at least 480 rows of photosensing elements comprising top rows, middle rows and bottom rows;

wherein, with said camera disposed at the vehicle, top rows are higher above ground than middle and bottom rows;

wherein, with said camera disposed at the vehicle, middle rows are higher above ground than bottom rows and are lower above ground than top rows;

wherein, with said camera disposed at the vehicle, middle rows are between top rows and bottom rows;

a processor operable to process image data captured by said camera;

wherein, when the vehicle is moving, top row brightness values at top rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, middle row brightness values at middle rows are determined by processing of captured image data by said processor;

wherein, when the vehicle is moving, bottom row brightness values at bottom rows are determined by processing of captured image data by said processor;

wherein contrast of middle row brightness values compared to bottom row brightness values or top row brightness values is determined;

wherein, based on determined contrast of middle row brightness values compared to bottom row brightness values or top row brightness values, an at least partial blockage of said camera is detected;

wherein, when an at least partial blockage of said camera is detected, said system at least one of (i) generates an alert, (ii) adapts processing of captured image data to at least partially accommodate for the at least partial blockage and (iii) cleans said lens;

wherein said camera comprises a CMOS camera; and

wherein said camera is part of a multi-camera birds-eye surround view system of the equipped vehicle.

19. The vision system of claim 18 , wherein said processor is incorporated in circuitry of said camera.

20. The vision system of claim 18 , wherein said processor is incorporated in circuitry of a control of the vehicle.