Fast full-field profilometry using a repetition-rate-scanned femtosecond laser

Liheng Shi; Jinxu Zhang; Guanhao Wu

doi:10.1117/12.2686542

29 November 2023 Fast full-field profilometry using a repetition-rate-scanned femtosecond laser

Liheng Shi, Jinxu Zhang, Guanhao Wu

Proceedings Volume 12769, Optical Metrology and Inspection for Industrial Applications X; 1276915 (2023) https://doi.org/10.1117/12.2686542
Event: SPIE/COS Photonics Asia, 2023, Beijing, China

Conference Poster

Abstract

We present a coherence scanning interferometer based on a mode-locked femtosecond laser, enabling precise pulse alignment for cross-correlation interferogram acquisition. However, Nyquist's law necessitates step lengths below 1/8 of the central wavelength, while area-array detectors face limitations in pixel density and frame rate due to communication throughput. To overcome these challenges, we propose downsampling methods that preserve interferometric contrast. The simultaneous exposure method maintains a stationary state for exposure at each sampling point, mitigating contrast loss from phase shifts. The phase compensation technique reduces carrier frequency through acousto-optic modulators, preserving high-contrast interference signals without altering the scanning mechanism. Leveraging our optimized frequency domain analysis algorithm, both methods achieved nm-level measurement accuracy with μm-level scanning intervals, facilitating efficient profilometry.

Citation Download Citation

Liheng Shi, Jinxu Zhang, and Guanhao Wu "Fast full-field profilometry using a repetition-rate-scanned femtosecond laser", Proc. SPIE 12769, Optical Metrology and Inspection for Industrial Applications X, 1276915 (29 November 2023); https://doi.org/10.1117/12.2686542

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