Abstract
Precise determination of the refractive index and surface spacing in multi-lens system is essential for ultra-precision system performance, such as lithography objectives with strict requirements for each lens fabrication and assembly position. Generally, the nominal value of the refractive index at a given wavelength must be known before resolving the geometric thickness of multi-lens using conventional methods, which leads to inaccurate and inconvenient measurements. We propose a method to simultaneously measure the refractive index and surface spacing in multi-lens system based on dual-comb ranging method. The precision of the thickness measurement is better than 0.18 µm, and the refractive index is better than 1.6 × 10−4. This study provides a potential solution for realizing the real-time, fast, and precise measurement of the geometric thickness and assembly position of multi-lens in lithography objectives.
Funder
National Natural Science Foundation of China
Subject
Atomic and Molecular Physics, and Optics
Cited by
2 articles.
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