Focal length measurement of large-aperture optical systems based on defocus wavefront sensing.

Authors

Yongqiang Luo, Kewei E, Xun Xue, Liude Tian, Fang Feng, Shangkuo Liu, Zhengfeng Wang

Published in

Applied optics. Volume 65. Issue 28. Pages 9749-9756. Oct 01, 2026.

Abstract

We present a method for measuring the focal length of large-aperture optical systems based on defocus wavefront sensing. A 4D dynamic interferometer acquires Zernike defocus coefficients at different axial positions, from which the focal length is derived via a simplified expression. The method is validated on three optical system models and an off-axis system with a nominal focal length of 50,000 mm. The measured focal length of 49,964 mm agrees well with the design value. The uncertainty analysis yields a total relative uncertainty of 0.184%. The method provides a cost-effective alignment solution requiring no additional large collimators or precision goniometric instruments.

PMID:
42837557
Bibliographic data and abstract were imported from PubMed on 07 Oct 2026.

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