A quality evaluation study for annular beams

The annular beam generated by an axicon-pair with laser beams is an important illumination method for optical inspection microscopies and Deep-Ultraviolet lithography off-axis illumination modes due to its variable-diameter flexibility, economic efficiency and accessibility. The annular ring beam quality is determined by the quality of the optical components, which depends on the manufacturing level. However, there is a lack of a comprehensive evaluation for such ring beams, as only the ring shape feature has been briefly mentioned with coherence factors in the pupil evaluation of lithography illumination systems. In this work, we established a comprehensive evaluation system for annular beams based on the far-field divergence angles, geometric characteristics and uniformity of the light intensity distribution. We aim to propose a comprehensive evaluation system for the annular beam quality which enables the analysis and improvement of ring beams quality to better meet various application requirements.