Wide-area aerial camera systems

• US 9,706,117 B2
• Filed: 05/21/2015
• Issued: 07/11/2017
• Est. Priority Date: 06/20/2014
• Status: Active Grant

• Current Assignee: NearMap Pty Ltd.
• Original Assignee: NearMap Pty Ltd.
• Inventors: Lapstun, Paul, Tarlinton, Mark Harold, Bleads, David Arnold
• Primary Examiner(s): Perkey, W B
• Application Number:
  US14/718,528
• Publication Number:
  US 20150373267A1
• Time in Patent Office: 782 Days
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G03B 15/006 Apparatus mounted on flying objects
• CPC Class Codes: G03B 37/04 with cameras or projectors providing touching or overlapping fields of view
• CPC Class Codes: G06T 3/4038 Image mosaicing, e.g. composing plane images from plane sub-images
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 23/90 Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

A system for capturing aerial images, the system comprising at least one camera unit, the at least one camera unit comprising at least one detail camera, the pointing direction of the at least one detail camera time-multiplexed via a steerable mirror to implement a virtual array of cameras with overlapping fields of view, thereby to allow the at least one detail camera to capture an extended field of view.

Claims

1. A system for capturing aerial images, the system comprising:

at least one camera unit, the at least one camera unit comprising at least one detail camera mounted to substantially vertically orient an optical path thereof;

a first steerable mirror configured to time-multiplex a pointing direction of the at least one detail camera to implement a virtual array of cameras with overlapping fields of view, thereby to allow the at least one detail camera to capture an extended field of view;

an inertial measurement unit (IMU) configured to measure angular motion of the aircraft;

a second steerable mirror configured to compensate, at least partially, for bending of the optical path of the at least one detail camera by the first steerable mirror; and

an angular motion compensation unit (AMC), responsive to the measurement reported by the IMU, configured to control the second steerable mirror to compensate for the angular motion of the aircraft, thereby to ensure that the at least one detail camera points in a consistent direction over time.

2. The system of claim 1, wherein the at least one camera unit is attachable, above a camera hole, to at least one of:

a floor of an aircraft and a floor of a pod carried by an aircraft, thereby providing the at least one detail camera with a view of the ground below the aircraft through the camera hole.

3. The system of claim 1, comprising a plurality of camera units, each camera unit mounted at a different angle so that the extended fields of view of the camera units overlap to form a larger extended field of view.

4. The system of claim 1, wherein the at least one camera unit comprises at least one overview camera, the at least one detail camera having a longer focal length than the at least one overview camera.

5. The system of claim 4, wherein the ratio of the focal length of the at least one detail camera to the focal length of the at least one overview camera is between 4 and 8.

6. The system of claim 1, wherein at least one detail camera has a lens selected from the group comprising:

a dioptric lens, a catoptric lens, and a catadioptric lens.

7. The system of claim 1, further comprising a computer configured to automatically trigger exposure of the at least one detail camera during flight according to a stored flight plan and the real-time position of the aircraft.

8. The system of claim 7 further comprising at least one Global Navigation Satellite System (GNSS) receiver, the computer configured to receive and store position data from the at least one GNSS receiver in real time.

9. The system of claim 7, wherein the computer is configured to receive and store orientation data from the IMU in real time.

10. The system of claim 1 further comprising at least one forward motion compensation (FMC) mechanism, the at least one FMC mechanism configured to correct the effect, on the at least one detail camera, of forward motion of the aircraft, thereby to reduce motion blur in photos captured by the camera.

11. The system of claim 10, wherein FMC is provided via a mechanism selected from the group comprising:

translating the image sensor of the at least one detail camera, rotating the image sensor of the at least one detail camera, translating the at least one detail camera, rotating the at least one detail camera, rotating a mirror in the optical path of the at least one detail camera, and time delayed integration of adjacent lines of pixels in the image sensor of the at least one detail camera.

12. The system of claim 10, wherein FMC is provided via a steerable mirror in the optical path of the at least one detail camera.

13. The system of claim 12, wherein the steerable FMC mirror is oscillated and exposure of the at least one detail camera is synchronised with the oscillation.

14. The system of claim 1, wherein the pointing direction of the at least one camera unit, relative to nadir, is selected from the group comprising:

zero degrees and 45 degrees.

15. The system of claim 3, wherein the pointing direction of each camera unit, relative to nadir, is selected from the group comprising:

zero degrees and 45 degrees.

16. The system of claim 1, wherein the image sensor of the at least one detail camera is tilted to reduce perspective foreshortening in photos captured by the camera.

17. The system of claim 12, wherein the steerable FMC mirror is the second steerable mirror.