J. Eur. Opt. Society-Rapid Publ. 22, 36( 2026) 365
Figure 17. Movement of the fringes D / over the stage movement Dy. The fringe period p can be determined from the gradient m y of a linear fit of the measurement data.
Figure
18. Difference between the measured fringe movement D / in nanometer and the y-interferometer signal Dy in order to evaluate the measurement accuracy of the fringe observation system.
Figure
19. Visualization of the z scan to generate the aerial images from the camera images via 2D volume cut. b ¼ arctan / p ¼ arctan m z p
2pz 2p ð22Þ
to b x = �1.894 °. However, it should be noted here that the period must be redetermined for each change in the tilt of the writing pattern in order to determine the phase offset in nanometers accurately and thus the actual tilt. The fringe pattern tilt calibration can then be repeated for the other tilt direction b y.
4.4 Evaluation of positioning errors
In a last step of calibration, the positioning error occuring during the scan-and-stitch process is characterized. The platform is translated such that the entire camera field of view is illuminated. Within an area of 14 14 lm 2, scanning is performed along the x-axis at a velocity of 10 lm / s, followed by stitching with an offset of three fringe periods. The FrObSy is mounted on the platform with a 45 ° rotation, resulting in the fringes being imaged at an angle of approximately 45 °, too( see Fig. 23, left). Every 10 ms, an image of the current position of the writing point is captured on the camera and the recorded image stack is combined into a single image. The recorded pattern is subsequently analyzed using the carrier-frequency method, as illustrated in Figure 10. A Zernike polynomial fit is then applied to the inner circle of the reconstructed wavefront to remove remaining tip and tilt components. The resulting positioning error is shown in Figure 23, right. Positioning errors of approx. 75 nm peak-to-valley with an RMS of 15.6 nm can be observed. The errors are caused by vibrational errors of the positioning stage with a frequency of approx. 20 Hz. These errors lead to observable deviations in each individual scan line.
4.5 Exposure results
To evaluate the previously achieved alignment and calibration, exposure tests were performed in positive photo resist( AZ MIR 701 from MicroChemicals) with a fiber output