Double stereoscopic sensor

1. A stereoscopic sensor comprising:

a first camera pair for capturing a first and second image, wherein the stereoscopic sensor is adapted to monitor and define a main surveillance zone in a surveillance plane at a predetermined distance from the stereoscopic sensor, said main surveillance zone comprising a first and a second surveillance zone, and

the first camera pair defines the first surveillance zone with a primary coverage in a first direction and a secondary coverage in a second direction, wherein the stereoscopic sensor further comprises a second camera pair for capturing a first and a second image, said images being processable into a height image, wherein the coverage of the second camera pair defines the second surveillance zone with a primary coverage in the surveillance plane in the second direction and a secondary coverage in the first direction,

wherein said secondary coverage of the first and the second camera pairs overlap the primary coverage of the other camera pair respectively, wherein said stereoscopic sensor is arranged above said overlap.

2. The stereoscopic sensor according to claim 1 , wherein said overlap comprises about 10-30% of the primary coverage.

3. The stereoscopic sensor according to claim 1 , wherein said surveillance plane comprises a projected mounting position that corresponds to a position of a region of the overlap as seen in a direction X.

4. The stereoscopic sensor according to claim 1 , wherein each one of the camera pairs is directed towards the surveillance plane with an angle being different than an angle of an imaginary line perpendicular arranged to the surveillance plane.

5. The stereoscopic sensor according to claim 1 , wherein the first direction and the second direction extend in opposite directions from a projected mounting position in said surveillance plane.

6. The stereoscopic sensor according to claim 1 , wherein said stereoscopic sensor is provided with a control unit and is adapted to process images captured by the first and second camera pairs to produce the height image.

7. The stereoscopic sensor according to claim 6 , wherein the control unit is configured to combine a first height image, being processed from images from the first camera pair, and a second height image, being processed from images from the second camera pair, into one combined height image, whereby said combined height image comprises the overlapping area.

8. A system for surveillance comprising:

a stereoscopic sensor; and

a central system including a central control unit,

said stereoscopic sensor comprising:

a first camera pair for capturing a first and a second image wherein the stereoscopic sensor is adapted to monitor and define a main surveillance zone in a surveillance plane at a predetermined distance from the stereoscopic sensor, said main surveillance zone comprising a first and a second surveillance zone and the first camera pair defines the first surveillance zone with a primary coverage in a first direction and a secondary coverage in a second direction wherein the stereoscopic sensor further comprises a second camera pair for capturing a first and a second image, said images being processable into a height image, wherein the coverage of the second camera pair defines the second surveillance zone with a primary coverage in the surveillance plane in the second direction and a secondary coverage in the first direction, wherein said secondary coverage of the first and the second camera pairs overlap the primary coverage of the other camera pair respectively, wherein said stereoscopic sensor is arranged above said overlap.

9. The system according to claim 8 , wherein said system further comprises one or more additional stereoscopic sensors.

10. The system according to claim 8 , wherein the stereoscopic sensor is mounted upon a gantry and defines the surveillance plane upon a road surface below the gantry.

11. The system according to claim 10 , wherein the stereoscopic sensor is arranged at the predetermined distance perpendicular from the overlap region.

12. A method for controlling a system comprising at least one stereoscopic sensor and a central system including a central control unit that performs the method to control the system, the method comprising:

capturing a first and a second image with the first camera pair, the first camera pair included in the at least one stereoscopic sensor and configured for capturing a first and a second image, wherein the stereoscopic sensor is adapted to monitor and define a main surveillance zone in a surveillance plane at a predetermined distance from the stereoscopic sensor, said main surveillance zone comprising a first and a second surveillance zone, wherein the first camera pair defines the first surveillance zone with a primary coverage in a first direction and a secondary coverage in a second direction, wherein the stereoscopic sensor further comprises a second camera pair configured for capturing a first and a second image, said images being processable into a height image, wherein the coverage of the second camera pair defines the second surveillance zone with a primary coverage in the surveillance plane in the second direction and a secondary coverage in the first direction, wherein said secondary coverage of the first and the second camera pairs overlap the primary coverage of the other camera pair respectively, wherein said stereoscopic sensor is arranged above said overlap,

capturing a first and a second image with the second camera pair, and

processing said first and second images from the first and second camera pair into a combined height image disclosing both said first surveillance zone and said second surveillance zone, wherein an average value of said first and second height images is used in an overlapping area.

13. The method according to claim 12 , the method further comprising:

detecting a pixel having a height corresponding to said surveillance plane in the first height image in the overlapping area,

comparing the height in a pixel, corresponding to the detected pixel, in the second height image in the overlapping area, and

adjusting the height in said second height image to the surveillance plane in response to the pixel in the second height image being classified with a height above the surveillance plane.

14. The method according to claim 12 , the method further comprising:

sending the first and second image pairs from the stereoscopic sensor to the central system, wherein the central system processes the first and the second image pairs to a respective height image.

15. The method according to claim 12 , the method further comprising:

compressing the first and the second image pairs, and thereafter

sending the first and second image pairs to the central system, wherein the first and second image pairs are compressed such that they become a higher resolution in the overlapping area.

16. The method according to claim 12 , the method further comprising:

processing the first and second image pairs into a respective height image;

sending the first and the second height images to the central system.

17. The method according to claim 12 , the method further comprising:

processing the first and second image pairs into a respective height image;

processing the first and second height images into a combined height image, and thereafter

sending the combined height image to the central system.