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A distortion calibration method for wide-angle lens is proposed based onfringe-pattern phase analysis. Firstly, according to the experimental result ofthe 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. Fourstandard sinusoidal fringe-patterns with phase shift step of , which are usedas calibration templates, are shown on a Liquid Crystal Display screen, andcaptured by the wide-angle lens imaging system. A four-step phase-shiftingmethod is employed to obtain the radial phase distribution of the distortedfringe-pattern. Wavelet analysis is applied for the analysis of theinstantaneous frequency to show the fundamental frequency of the fringe-patternin the central region being unchanged. Performing numerical calculation by thecentral 9 points of the central row of the fringe-pattern, we can get theundistorted radial phase distribution, so, the radial modulated phase iscomputed. Finally, the radial distortion distribution is determined accordingto the radial modulated phase. By employing a bilinear interpolation algorithm,the wide-angle lens image calibration is achieved. There is no need toestablish any kind of image distortion model for the proposed method. There isno projecting system in the experimental apparatus, which avoids projectionshadow problems, and no need to align with the center of the template fordistortion measurement for the proposed method. Theoretical description,numerical simulation and experimental results show that the proposed method issimple, automatic and effective.

A Simple Distortion Calibration method for Wide-Angle Lenses Based on Fringe-pattern Phase Analysis