Extended range phase-sensitive swept source interferometer for real-time dimensional metrology

• Published in: Optics communications 2014-05, Vol.318, p.88-94
• Main Authors: Shen, Yi, Ding, Zhihua, Yan, Yangzhi, Wang, Chuan, Yang, Yaliang, Zhang, Yudong
• Format: Article
• Language: English
• Subjects: Dimensional metrology; Interferometers; Low coherence interferometry; Metrology; Noise levels; Phase unwrapping; Real time; Reference signals; Signal to noise ratio; Sweeping; Swept source
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2013.12.065

The measurement of center thicknesses and airgaps along its optical axis is crucial to a mounted optical system. Aiming to real-time dimensional metrology, an extended range phase-sensitive swept source interferometric system is developed. To yield high precision of measurement, reference interferometer sharing the same swept source with the measurement interferometer is introduced and a phase-sensitive approach based on phase-comparison between measurement signal and reference signal is exploited. The proposed phase-comparison method is theoretically developed and its merits over standard phase-sensitive approach are experimentally confirmed. In contrast to the standard phase-sensitive approach, the sensitivity under signal to noise ratio of 45dB achieved by the phase-comparison method is improved from 222nm to 25nm and the processing time is shorten by 90%. Measurements of glass plates are performed to evaluate the performance of the developed system. Submicron precision about a range of 30mm is realized by the developed system equipped by a commercial available swept source operating at a sweeping rate of 10kHz. The developed system holds potential application in real-time contact-free on-axis metrology for the fabrication and testing of complex optical systems.