Multi-view scanning aerial cameras

1. An aerial camera for capturing a set of images along at least two curved scan paths on an object plane within an area of interest, each image of the set of images associated with a viewing angle and a viewing direction relative to the object plane, the aerial camera comprising a scanning camera associated with each scan path, each scanning camera having a camera optical axis and comprising:

(a) an image sensor;

(b) a lens;

(c) a scanning mirror; and

(d) a drive coupled to the scanning mirror;

wherein:

(i) the drive is operative to rotate the scanning mirror about a spin axis according to a spin angle;

(ii) the spin axis is tilted relative to the camera optical axis;

(iii) the scanning mirror is tilted relative to both the camera optical axis and the spin axis, and is positioned to reflect an imaging beam into the lens, a viewing angle and a viewing direction of the imaging beam relative to the object plane varying with the spin angle and a pointing direction of the camera optical axis;

(iv) the lens is positioned to focus the imaging beam onto the image sensor; and

(v) the image sensor is operative to capture each image along the scan path by sampling the imaging beam at a value of the spin angle corresponding to the viewing angle and the viewing direction of the image.

2. The aerial camera of claim 1 , wherein each spin axis is substantially orthogonal to its respective camera optical axis.

3. The aerial camera of claim 1 , wherein each scanning mirror it tilted at approximately 45 degrees to its respective camera optical axis when its respective spin angle is zero.

4. The aerial camera of claim 1 , wherein the set of images comprises at least some oblique images with substantially orthogonal viewing directions.

5. The aerial camera of claim 1 , wherein the set of images comprises at least one image with a substantially nadir viewing angle and a plurality of images with substantially oblique viewing angles.

6. The aerial camera of claim 1 , wherein each scanning camera comprises a correction mirror positioned to bend its camera optical axis between its lens and its scanning mirror.

7. The aerial camera of claim 6 , wherein each correction mirror is tilted at approximately 45 degrees to its respective camera optical axis, thereby to bend the camera optical axis by approximately 90 degrees.

8. The aerial camera of claim 6 , further comprising a correction mirror stage coupled to each correction mirror, the correction mirror stage operative to rotate the correction mirror about at least one correction axis according to at least one correction angle.

9. The aerial camera according to claim 1 , wherein the camera optical axes of at least two of the scanning cameras point in opposite directions to each other.

10. The aerial camera according to claim 1 , wherein the camera optical axes of at least two of the scanning cameras point in directions that are perpendicular to each other.

11. The aerial camera according to claim 1 , the aerial camera comprising at least three scanning cameras, wherein the camera optical axes of a first two of the scanning cameras point in opposite directions to each other, and the camera optical axis of a third scanning camera points in a direction perpendicular to the first two pointing directions.

12. A method of capturing, using the aerial camera of claim 1 , the set of images along the at least two curved scan paths within the area of interest, the method comprising, for each scan path, rotating, using the respective drive, the respective scanning mirror about its spin axis according to a value of the spin angle corresponding to the viewing angle and the viewing direction of the image, and capturing, using the image sensor associated with the scan path, the image.

13. The method of claim 12 , wherein the set of images comprises at least some oblique images with substantially orthogonal viewing directions.

14. The method of claim 12 , wherein each spin axis is substantially orthogonal to its respective camera optical axis.

15. The method of claim 12 , wherein each scanning mirror it tilted at approximately 45 degrees to its respective camera optical axis when the spin angle is zero.

16. The method of claim 12 , the method further comprising moving the aerial camera along a survey path above the area of interest, and capturing, within each of a set of selected intervals along the survey path and using the aerial camera, a corresponding one of a plurality of the sets of images.

17. The method of claim 16 , wherein the camera optical axes of at least two of the scanning cameras point in opposite directions to each other, and the two pointing directions are parallel to a direction of movement.

18. The method of claim 16 , wherein the camera optical axes of at least two of the scanning cameras point in opposite directions to each other, and the two pointing directions are perpendicular to a direction of movement.

19. The method of claim 16 , the aerial camera comprising at least three scanning cameras, wherein the camera optical axes of a first two of the scanning cameras point in opposite directions to each other, the camera optical axis of a third of the scanning cameras points in a direction perpendicular to the first two pointing directions, and the first two pointing directions are perpendicular to a direction of movement.

20. The method of claim 16 , the method comprising using the first two scanning cameras to capture images with substantially oblique viewing angles, and using the third scanning camera to capture images with substantially nadir viewing angles.