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EP-4363798-B1 - HYPER CAMERA WITH SHARED MIRROR

EP4363798B1EP 4363798 B1EP4363798 B1EP 4363798B1EP-4363798-B1

Inventors

  • BESLEY, JAMES, AUSTIN
  • TARLINTON, Mark, Harold
  • BLEADS, David, Arnold

Dates

Publication Date
20260506
Application Date
20210628

Claims (15)

  1. An imaging system, comprising: a first camera (102) configured to capture a first set of oblique images along a first scan path (180) on an object area; a second camera (102) configured to capture a second set of oblique images along a second scan path (180) on the object area; a scanning mirror structure (122) including at least one mirror surface; and a drive (120) coupled to the scanning mirror structure (122) and configured to rotate the scanning mirror structure (122) about a scan axis based on a scan angle, wherein the first camera (102) has an optical axis (106) set at an oblique angle to the scan axis and includes a lens (104) to focus a first imaging beam (160) reflected from the scanning mirror structure (122) to an image sensor (144) of the first camera (102), the second camera (102) has an optical axis (106) set at an oblique angle to the scan axis and includes a lens (104) to focus a second imaging beam (160) reflected from the scanning mirror structure (122) to an image sensor (144) of the second camera (102), at least one of an elevation and azimuth of the first imaging beam (160) and at least one of an elevation and azimuth of the second imaging beam (160) vary according to the scan angle, the image sensor (144) of the first camera (102) captures the first set of oblique images along the first scan path (180) by sampling the first imaging beam (160) at values of the scan angle, and the image sensor (144) of the second camera (102) captures the second set of oblique images along the second scan path (180) by sampling the second imaging beam (160) at values of the scan angle, characterized by a geometry of the at least one mirror surface is determined based on, at least partially, at least one of one or more predetermined orientations of the image sensor (144) of the first camera (102) and one or more predetermined orientations of the image sensor (144) of the second camera (102); and a set of scan angles of the scanning mirror structure (122).
  2. The imaging system according to claim 1, wherein the at least one mirror surface includes a first mirror surface and a second mirror surface that is substantially opposite the first mirror surface, and the first imaging beam (160) is reflected from the first mirror surface and the second imaging beam (160) is reflected from the second mirror surface.
  3. The imaging system according to claim 1, wherein a first scan angle for the first camera (102) is the same as a first scan angle for the second camera (102).
  4. The imaging system according to claim 1, wherein the image sensor (144) of the first camera (102) and the image sensor (144) of the second camera (102) capture respective images of the first set of oblique images and the second set of oblique images simultaneously.
  5. The imaging system according to claim 1, wherein the scanning mirror structure (122) is symmetric about the scan axis.
  6. The imaging system according claim 1, wherein the scan angle is a tilt angle of the scanning mirror structure (122).
  7. The imaging system according to claim 6, wherein steps of the tilt angle are determined based on sizes of the image sensors (144) and focal lengths of the first and second camera (102).
  8. The imaging system according to claim 1, wherein the first camera (102) and the second camera (102) are inclined towards the scanning mirror structure (122) at predetermined angles.
  9. The imaging system according to claim 1, wherein the first scan path (180) and the second scan path (180) are symmetric.
  10. The imaging system according to claim 1, wherein an azimuth of the first camera (102) is substantially 180 degrees from an azimuth of the second camera (102).
  11. The imaging system according to claim 1, wherein the first scan path (180) and the second scan path (180) are curved.
  12. The imaging system according to claim 1, further comprising: at least one third camera (102) configured to capture vertical images; and at least one mirror configured to direct a third imaging beam, corresponding to the vertical images, to the at least one third camera (102).
  13. The imaging system according to claim 1, further comprising: a third camera (102) configured to capture a third set of images; and a second scanning mirror structure configured to direct a third imaging beam, corresponding to the third set of images, to be received by the third camera.
  14. The imaging system according to claim 13, further comprising: a fourth camera (102) configured to capture a fourth set of images; and a third scanning mirror structure configured to direct a fourth imaging beam, corresponding to the fourth set of images, to be received by the fourth camera.
  15. An imaging method comprising: reflecting a first imaging beam (160) from an object area using a scanning mirror structure (122) having at least one mirror surface to a first image sensor (144) of a first camera (102) to capture a first set of oblique images along a first scan path (180) of the object area, the first camera (102) comprising a first lens (104) to focus the first imaging beam (160) to the first image sensor (144); reflecting a second imaging beam (160) from the object area using the scanning mirror structure (122) to a second image sensor (144) of a second camera (102) to capture a second set of oblique images along a second scan path (180) of the object area, the second camera (102) comprising a second lens (104) to focus the second imaging beam (160) to the second image sensor (144); rotating the scanning mirror structure (122) about a scan axis based on a scan angle, wherein at least one of an elevation and azimuth of the each of the first and second imaging beams (160) vary according to the scan angle; setting an optical axis (106) of each of the first and second cameras (102) at an oblique angle to the scan axis; sampling the first and second imaging beams (160) at values of the scan angle, characterized by a geometry of the at least one mirror surface is determined based on, at least partially, at least one of one or more predetermined orientations of the image sensor (144) of the first camera (102) and one or more predetermined orientations of the image sensor (144) of the second camera (102); and a set of scan angles of the scanning mirror structure (122).

Description

FIELD OF THE INVENTION The present invention relates to efficient aerial camera systems and efficient methods for creating orthomosaics and textured 3D models from aerial photos. BACKGROUND The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Prior art document US20211051311 discloses a scanning camera for capturing images along a curved path within an area of interest. Accurately georeferenced mosaics of orthophotos, referred to as orthomosaics, can be created from aerial photos. In such a case, these photos can provide useful images of an area, such as the ground. The creation of an orthomosaic requires the systematic capture of overlapping aerial photos of the region of interest (ROI), both to ensure complete coverage of the ROI, and to ensure that there is sufficient redundancy in the imagery to allow accurate bundle adjustment, orthorectification and alignment of the photos. Bundle adjustment is the process by which redundant estimates of ground points and camera poses are refined. Bundle adjustment may operate on the positions of manually-identified ground points, or, increasingly, on the positions of automaticallyidentified ground features which are automatically matched between overlapping photos. Overlapping aerial photos are typically captured by navigating a survey aircraft in a serpentine pattern over the area of interest. The survey aircraft carries an aerial scanning camera system, and the serpentine flight pattern ensures that the photos captured by the scanning camera system overlap both along flight lines within the flight pattern and between adjacent flight lines. Though such scanning camera systems can be useful in some instances, they are not without their flaws. Examples of such flaws include: (1) difficulty fitting several long focal length lenses and matched aperture mirrors in configured spaces on a vehicle for capturing vertical and oblique imagery; (2) a camera hole in an aerial vehicle is generally rectangular, but yaw correction gimbal space requirements are defined by a circle, so inefficiencies in spacing are present; and (3) low quality images (e.g. blurry, vignetting). SUMMARY The present disclosure is directed towards an imaging system, comprising: a first camera configured to capture a first set of oblique images along a first scan path on an object area; a second camera configured to capture a second set of oblique images along a second scan path on the object area; a scanning mirror structure including at least one mirror surface; and a drive coupled to the scanning mirror structure and configured to rotate the scanning mirror structure about a scan axis based on a scan angle, wherein the first camera has an optical axis set at an oblique angle to the scan axis and includes a lens to focus a first imaging beam reflected from the scanning mirror structure to an image sensor of the first camera, the second camera has an optical axis set at an oblique angle to the scan axis and includes a lens to focus a second imaging beam reflected from the scanning mirror structure to an image sensor of the second camera, at least one of an elevation and azimuth of the first imaging beam and at least one of an elevation and azimuth of the second imaging beam vary according to the scan angle, the image sensor of the first camera captures the first set of oblique images along the first scan path by sampling the first imaging beam at first values of the scan angle, and the image sensor of the second camera captures the second set of oblique images along the second scan path by sampling the second imaging beam at second values of the scan angle. The present disclosure is directed to an imaging method comprising: reflecting a first imaging beam from an object area using a scanning mirror structure having at least one mirror surface to a first image sensor of a first camera to capture a first set of oblique images along a first scan path of the object area, the first camera comprising a first lens to focus the first imaging beam to the first image sensor; reflecting a second imaging beam from the object area using the scanning mirror structure to a second image sensor of a second camera to capture a second set of oblique images along a second scan path of the object area, the second camera comprising a second lens to focus the second imaging beam to the second image sensor; rotating the scanning mirror structure about a scan axis based on a scan angle, wherein at least one of an elevation and azimuth of the each of the first and second imaging beams vary according to the scan angle; setting an optical axis of each of the first and second c