- Number
- 9641830
- Published
- 2017-05-02
- Filed
- 2014-04-08
- Assignee
- LUCASFILM ENTERTAINMENT COMPANY LTD.
- Inventors
- Mallet; Ronald, Snell; Jason, Saltzman; Jeff, Moore; Douglas, Warner; Paige
- CPC
- H04N17/002; G06T7/80
- Verdict
- Low Notable software
- Source
- Google Patents · FreePatentsOnline
The keeper's note
Calibrates a camera using a calibration target apparatus with distinguishable fiducial markings on a planar surface to infer camera parameters.
Abstract
Methods and systems are disclosed for calibrating a camera using a calibration target apparatus that contains at least one fiducial marking on a planar surface. The set of all planar markings on the apparatus are distinguishable. Parameters of the camera are inferred from at least one image of the calibration target apparatus. In some embodiments, pixel coordinates of identified fiducial markings in an image are used with geometric knowledge of the apparatus to calculate camera parameters.
Background
BRIEF DESCRIPTION OF THE DRAWINGS(1) FIG. 1 is a simplified perspective view of a calibration target according to an embodiment of the invention that can be used to automatically calibrate a camera.(2) FIG. 2 is a top plan view of a first planar componentof the calibration target shown in FIG. 1.(3) FIG. 3 is a top plan view of a second planar component of the calibration target shown in FIG. 1.(4) FIG. 4 is a top plan view of a third planar component of the calibration target shown in FIG. 1.(5) FIG. 5 is a top plan view of a fourth planar component of the calibration target shown in FIG. 1.(6) FIG. 6 is asimplified perspective view showing the separated first, second, third and fourth planar components shown in FIGS. 2-5 oriented for assembly to form calibration target 100 shown in FIG. 1.(7) FIGS. 7A-7C are simplified illustrations of fiducial markings that can be incorporated onto a calibration target according to embodiments of the invention.(8) FIG. 8 is a simplified view of the calibration target located in a three dimensional space being imaged by a camera.(9) FIG. 9A is a flowchart of a method for calibrating a camera according to an embodiment of the invention.(10) FIG. 9B is a flowchart of a method for calibrating a virtual camera according to an embodiment of the invention.(11) FIG. 10 is a schematicdiagram of a computing system that can be used in connection with computer-implemented methods described in this document.DETAILED DESCRIPTION OF THE INVENTION(12)
Claims
1. A computer-implemented method of determining parameter values of a camera comprising: receiving an image of a 3-dimensional (3D) physical scene obtained from the camera, the image of the 3D physicalscene including a calibration target comprising a plurality of unique fiducial markings; comparing, by the computer, the calibration target in the image to a computer model of thecalibration target using at least one uniquely identified fiducial marking of the plurality of unique fiducial markings; for the at least one of the uniquely identified fiducial marking, estimating corresponding 3D coordinates in the 3D physical scene based on the comparison; and determining at least one parameter value of the camera using the estimated corresponding 3D coordinates; wherein the calibration target comprises a plurality of trihedral sections arranged around a central axis, each trihedral section having first, second and third surfaces with a window formed through at least one of the surfaces, each surface having at least one unique fiducial marker arranged on the surface.
9. A system for calibrating a camera comprising: one or more processors; memory communicatively linked with the one or more processors and comprising computer-readable instructions that when executed cause the one or more processors to implement a method comprising: receiving an image of a 3-dimensional (3D) physical scene obtained from the camera, the image of the 3D physical scene including a calibration target comprising planar components arranged to project substantially into three dimensions and a plurality of unique fiducial markings on the planar components; comparing, by the one or more processors, the calibration target in the image to a computer model of the calibration target using at least one uniquely identified fiducialmarking of the plurality of unique fiducial markings; for the at least one of the uniquely identified fiducial marking, estimating corresponding 3D coordinates in the 3D physical scene based on the comparison; and determining a set of parameter values of the camera using the estimated corresponding 3D coordinates; wherein the calibration target comprises a plurality of trihedral sections arranged around a central axis, each trihedral section having first, second and third surfaces with a window formed through at least one of the surfaces, each surface having at least one unique fiducial marker arranged on the surface. 12.A method of placing a virtual camera in a computer graphics scene, the method comprising:capturing an image of a calibration target in a physical scene with a physical camera, the calibration target comprising planar surfaces configured to project substantially into three dimensions (3D) forming a plurality of trihedral sections arranged around a central axis, each trihedral section having first, second and third surfaces with a window formed through at least one of the surfaces, each surface having at least one unique fiducial marker arranged on the surface; comparing, with a processor, the captured image to a computer graphics model of the calibration target stored in a computer-readable memory operatively coupled to the processor; mapping, with the processor, at least one visible unique fiducial marker in the captured image to the computer graphics model; determining, with the processor, at least one parameter for the physical camera in relation to the calibration target; and setting a virtual camera in a computer graphics environment based on the determined parameter of the physical camera.
17. A system for placing a virtual camera in a computer graphics scene, comprising: one or more processors; memory communicatively linked with theone or more processors and comprising computer-readable instructions that when executed cause the one or more processors to implement a method comprising: capturing an image of a calibration target in a physical scene with a physical camera, the calibration target comprising planar surfaces configured to project substantially into three dimensions (3D) forming a plurality of trihedral sections arranged around a central axis, each trihedral section having first, second and third surfaces with a window formed through at least one of the surfaces, each surface having at least one unique fiducial marker arranged on the surface; comparing, with a processor, the captured image to a computer graphics model of the calibration target stored in a computer-readable memory operatively coupled to the processor;mapping, with the processor, at least one visible unique fiducial marker in the captured image to the computer graphics model; determining, with the processor, at least one parameter for the physical camera in relation to the calibration target; and setting a virtual camera in a computer graphics environment based on the determined parameter of the physicalcamera.
19. A computer-implemented method of determining parameter values of a camera comprising: receiving an image of a 3-dimensional (3D) physical scene obtained from the camera, the image of the 3D physical scene including a calibration target comprising a plurality of unique fiducial markings and windows such that for any given image of the calibrationtarget taken by a camera there is only one position, rotation, distortion value and focallength for the camera; performing, with the computer, an identification process on the image to identify a plurality of different parts of the image that are likely to correspond to fiducial markings of the calibration target; comparing, by the computer, each individual part of the image in the plurality of different parts of the image identified as likely corresponding to a fiducial marking to a computer model of the calibration target to identify a unique fiducial marking that is the source for the individual part of the image; forat least one identified unique fiducial marking, estimating corresponding 3D coordinates in the 3D physical scene based on the comparison; and determining a position, rotation, distortion and focal length of the camera using the estimated corresponding 3D coordinates.