1 research outputs found
A Simple Distortion Calibration method for Wide-Angle Lenses Based on Fringe-pattern Phase Analysis
A distortion calibration method for wide-angle lens is proposed based on
fringe-pattern phase analysis. Firstly, according to the experimental result of
the radial distortion of the image not related to the recording depth of field,
but depending on the field of view angle of the wide-angle lens imaging system,
two-dimensional image distortion calibration is need to be considered. Four
standard sinusoidal fringe-patterns with phase shift step of , which are used
as calibration templates, are shown on a Liquid Crystal Display screen, and
captured by the wide-angle lens imaging system. A four-step phase-shifting
method is employed to obtain the radial phase distribution of the distorted
fringe-pattern. Wavelet analysis is applied for the analysis of the
instantaneous frequency to show the fundamental frequency of the fringe-pattern
in the central region being unchanged. Performing numerical calculation by the
central 9 points of the central row of the fringe-pattern, we can get the
undistorted radial phase distribution, so, the radial modulated phase is
computed. Finally, the radial distortion distribution is determined according
to the radial modulated phase. By employing a bilinear interpolation algorithm,
the wide-angle lens image calibration is achieved. There is no need to
establish any kind of image distortion model for the proposed method. There is
no projecting system in the experimental apparatus, which avoids projection
shadow problems, and no need to align with the center of the template for
distortion measurement for the proposed method. Theoretical description,
numerical simulation and experimental results show that the proposed method is
simple, automatic and effective