Method for exploring viewpoint and focal length of camera
First Claim
1. A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises:
- providing a calibration target with a test pattern composed of at least one geometric figure;
aiming the center of the test pattern at an optic axis of a lens in the camera; and
searching a pinpoint along the optic axis to enable at least one image height on an image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model.
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Abstract
The present invention is a method for exploring the viewpoint and focal length of a fisheye lens camera (FELC). It employs the characteristic of the central symmetry of the distortion of the fisheye lens (FEL) to set its optic axis by means of a calibration target with a plurality of symmetrically homocentric figures. Once the optic axis is fixed, further disclose the viewpoint (VP) of the FELC along the optic axis through a trail-and-error procedure and calculate its effective focal length and classify it to the primitive projection mode. Because the invention is capable of finding out both the internal and external parameters of the FELC and the calibration method is easy, low-cost, suitable to any projection model, and has greater sensitivity corresponding to an increasing in image distortion, the distortive images can be transformed easily to normal ones which fit in with a central perspective mechanism. Furthermore, the invention is also practicable and excellent in its applications in the fields of quality identification of the FEL and wide-view 3-D metering.
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Citations
21 Claims
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1. A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises:
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providing a calibration target with a test pattern composed of at least one geometric figure;
aiming the center of the test pattern at an optic axis of a lens in the camera; and
searching a pinpoint along the optic axis to enable at least one image height on an image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for exploring viewpoint and focal length of camera that has an axis-symmetrical nonlinear-distortive lens, the method comprises:
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providing a calibration target with a test pattern composed of at least one geometric figure;
placing the calibration target in the field of view of the camera to let the test pattern form a corresponding image on an image plane;
changing the position of the calibration target to make the image similar to the test pattern, then connecting both the centers of the calibration target and the image to locate an optic axis; and
searching a pinpoint along the optic axis to enable at least one image height on the image plane which is related to the geometric figure and the corresponding zenithal angle between the incident rays of light and the optic axis both fit in with a projection model. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification