Authors:
Huixian Duan
;
Lin Mei
;
Yanfeng Shang
and
Chuanping Hu
Affiliation:
The Third Research Institute of Ministry of Public Security, China
Keyword(s):
Focal Length, Calibration, Paracatadioptric Camera, Circle Image.
Related
Ontology
Subjects/Areas/Topics:
Computer Vision, Visualization and Computer Graphics
;
Device Calibration, Characterization and Modeling
;
Image Formation and Preprocessing
Abstract:
Camera calibration from circles has great advantages, but for paracatadioptric camera, the estimation of intrinsic
parameters using circle images is still an open and challenging problem. Previous work proved that
the paracatadioptric projection of a circle is a quartic curve. But due to the partial occlusion, only part of the
quartic curve is visible on the image plane. Consequently, circle image cannot be directly estimated using image
points extracted from the visible part and camera parameters cannot be calibrated. To solve this problem,
In this paper, we study the properties of paracatadioptric circle image and application in calibrating the focal
length for the case that aspect ratio is 1 and skew is 0. Firstly, we derive the necessary and sufficient conditions
that must be satisfied by paracatadioptric circle image. Next, based on these conditions, a new object function
is presented to correctly estimate the circle image. Then, we show that the focal length can be computed
fro
m the estimated paracatadioptric circle image and the principal point that is estimated from the projected
contour of parabolic mirror. Experimental results on both simulated and real image data have demonstrated
the effectiveness of our method.
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