Lateral optical distortion is present in most optical imaging systems. In coherence scanning interferometry (CSI) [1,2], distortion may cause field-dependent systematic errors in the measurement of surface topography. Distortion, unlike optical aberrations such as spherical aberration, coma and astigmatism, is not responsible for a lack of sharpness of the image [3]; rather is related to the form of the image, and the degree of the distortion is dependent on the position in the image plane. Optical aberrations are usually suppressed for optimisation of the optical resolution in a commercial CSI system, but a significant amount of distortion can be present [4,5]. In areas such as computer vision, distortion in a camera system may cause errors in pattern analysis and recognition, dimensional and displacement measurement, 3D image reconstruction, etc. [6]. In a CSI system that measures the 3D topography of a surface, distortion may cause errors in the dimensional measurement in both lateral and height directions. Thus, distortion should be corrected in order to achieve a non-distorted image field and a uniform lateral sampling distance of the image projected on to the camera, such that the measurement accuracy can be improved.
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