Method and system to calibrate a camera system using phase demodulation sensing
First Claim
1. A calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate a camera system that acquires a camera-captured image definable in pixel (xi,yi) coordinates, the calibration target including:
- a target pattern including intensity levels that change continuously in any pattern direction such that when captured by said camera system at a known distance Z said target pattern produces an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in the camera-captured image of said target pattern.
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Abstract
A preferably parametrically defined calibration target pattern definable in real-world coordinates (Xi,Yi) is used to spatially calibrate a camera system acquiring images in pixel coordinates (xi,yi). The calibration target pattern is used to produce a unique 1:1 mapping enabling the camera system to accurately identify each point in the calibration target pattern point mapped to each pixel in the acquired image. Preferably the calibration target pattern is pre-distorted and includes at least two sinusoids that create a pattern of distorted wavefronts that when imaged by the camera system will appear substantially linearized. Since wavefront locations on the calibration target pattern were known, a mapping between those wavefronts and the substantially linearized wavefront pattern on the camera system captured image can be carried out. Demodulation of the captured image enables recovery of the continuous wave functions therein, using spectral analysis and iteration.
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Citations
30 Claims
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1. A calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate a camera system that acquires a camera-captured image definable in pixel (xi,yi) coordinates, the calibration target including:
a target pattern including intensity levels that change continuously in any pattern direction such that when captured by said camera system at a known distance Z said target pattern produces an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in the camera-captured image of said target pattern. - View Dependent Claims (2, 3, 4, 5)
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6. A calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate a camera system that acquires a camera-captured image definable in pixels having pixel (xi,yi) coordinates, the calibration target including:
a pre-distorted target pattern defined in terms of at least a first frequency and a second frequency, said first frequency and said second frequency selected to produce a pattern in said camera-captured image exhibiting wavefronts having a wavelength greater than two and less than twenty pixels, said target pattern when captured by said camera system at a known distance Z producing an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in said camera-captured image of said target pattern. - View Dependent Claims (7, 8, 14)
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9. A method of spatially calibrating a camera system that captures an image definable in pixel coordinates (xi,yi) on an image plane, the method comprising:
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(a) providing a calibration target containing a pattern including intensity levels that change continuously in any Pattern direction, said pattern recognizable by said camera system and definable in real-world (Xi,Yi) coordinates, such that when imaged by said camera system, said pattern enables said camera system to discern by identifying and locating real-world coordinates of said pattern to pixel coordinates in said image captured by said camera system; and (b) using said camera system to capture an image of said pattern on said calibration target; wherein a unique 1;
1 mapping between pixel coordinates and real-world coordinates is obtainable. - View Dependent Claims (10, 11, 12, 13, 15, 16, 17, 18, 19, 26)
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20. A camera system including an image plane definable in pixels, upon which an image of a target may be captured, said camera system including:
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storage, associated with said camera system, to store data used during calibration of said camera system; said camera system having been calibrated by using one of (a) a calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate said camera system during acquisition of a camera-captured image definable in pixel (xi,yi) coordinates, the calibration target including a target pattern including intensity levels that change continuously in any pattern direction such that when captured by said camera system at a known distance Z said target pattern produces an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in the camera-captured image of said target pattern; and
(b) a calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate said camera system during acquisition of a camera-captured image definable in pixels having pixel (xi,yi) coordinates, the calibration target including a pre-distorted target pattern defined in terms of at least a first frequency and a second frequency, said first frequency and said second frequency selected to produce a pattern in said camera-captured image exhibiting wavefronts having a wavelength greater than two and less than twenty pixels, said target pattern when captured by said camera system at a known distance Z producing an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in said camera-captured image of said target pattern. - View Dependent Claims (21, 22, 23, 24, 25)
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27. A method of spatially calibrating a camera system that captures an image definable in pixel coordinates (xi,yi) on an image plane, the method comprising:
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(a) providing a calibration target definable in real-world (Xi,Yi) coordinates usable to spatially calibrate a camera system that acquires a camera-captured image definable in pixels having pixel (xi,yi) coordinates, the calibration target including; a pre-distorted target pattern defined in terms of at least a first frequency and a second frequency, said first frequency and said second frequency selected to produce a pattern in said camera-captured image exhibiting wavefronts having a wavelength greater than two and less than twenty pixels, said target pattern when captured by said camera system at a known distance Z producing an image that enables said camera system to discern real-world coordinates of any point in said target pattern with respect to pixel locations in said camera-captured image of said target pattern; and (b) using said camera system to capture an image of said pattern on said calibration target. - View Dependent Claims (28, 29, 30)
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Specification