Mechanics-free speckle contrast optical spectroscopy with liquid-lens-based adaptive illumination

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Zhang, Yuanzhe and Pan, Mingliang and Li, Chenxu and Qin, Ding and Chen, Yi-Chieh and Li, David Day-Uei (2026) Mechanics-free speckle contrast optical spectroscopy with liquid-lens-based adaptive illumination. Optics Letters, 51 (9). pp. 2524-2527. ISSN 0146-9592 (https://doi.org/10.1364/OL.591744)

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Abstract

Speckle contrast optical spectroscopy (SCOS) is often limited by short exposure bias and a reduced dynamic range at a long exposure time. We present a mechanics-free SCOS approach that simultaneously adjusts the exposure time and illumination spot size using an electrically tunable liquid lens (−3 to +3 dpt), redistributing photons across a broader exposure range. Using independently the measured field autocorrelation functions g1(τ), we validate the SCOS model and identify a reliable operating range of the normalized mean intensity between 0.2 and 0.5. Measurements acquired under different optical conditions are normalized by their respective speckle contrast factor β and combined into a single composite dataset, enabling joint analysis across multiple exposure times. The extracted correlation time ( ) agrees with the reference value to within <1%. These results show that adaptive spot control with unified data combination enables a robust multi-exposure-time SCOS analysis.

ORCID iDs

Zhang, Yuanzhe ORCID logoORCID: https://orcid.org/0009-0004-5107-3856, Pan, Mingliang ORCID logoORCID: https://orcid.org/0009-0001-9732-8963, Li, Chenxu, Qin, Ding, Chen, Yi-Chieh ORCID logoORCID: https://orcid.org/0000-0002-8307-0666 and Li, David Day-Uei ORCID logoORCID: https://orcid.org/0000-0002-6401-4263;
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