Evaluation of positioning errors during the scan-and-stitch process. The fringe observation system is moved with 10 μm/s in x-direction and is stitched with an overlap of three fringes in y-direction. The recorded image stack is combined into a single image. The wavefront error of the recorded pattern is calculated by using the carrier-frequency method. A Zernike polynomial fit is applied to the inner circle of the reconstructed wavefront error to remove remaining tip and tilt components.