Method for Measuring Lens Distortion by Using Pinhole Lens
- CTU in Prague, Civil Engineering Faculty, Dept. of Geomatics, Thakurova 7, 166 29 Prague 6, Czech Republic
Keywords: Metrology, Vision, Camera, Calibration, Correlation, Distortion, Pinhole
Abstract. In photogrammetric applications, the measurements are conducted on images given by optical imaging systems (cameras). In order to ensure the demanded accuracy, those cameras have to be well calibrated geometrically. A new method for measuring glass lens distortion based on using distortion-free pinhole lens is proposed, where the measure of the distortion progress is derived by comparing two images of the calibration field, given by pinhole lens and glass lens. Presented approach to measuring the lens distortion provides directly the deviations of corresponding target images given by the pinhole lens and the glass lens, therefore the method is not limited by pre-defined functional model describing the distortion progress. The modelling of the distortion can be done a posteriori, by using tabulated distortion values. The proposed method for measuring lens distortion is applied in an experimental investigation leading to the confirmation of the validity of the theoretical development. The result of the investigation derives a promising new possibility for accurate lens calibration.