Fiber-Based Rolling-Shutter Interferometric Laser Speckle Spectroscopy

Abstract

In this study, we present a fiber-based wearable interferometric laser speckle spectroscopy system, leveraging a rolling-shutter (RS) camera for sensing acoustic vibrations at high frame rate. We demonstrate the feasibility of using wearable fiber-coupled RS imaging to detect acoustic signatures from carotid artery blood flow and assess the signal-to-noise ratio (SNR) enhancement achieved through heterodyne interferometric detection. The system features a compact wearable probe with optical fibers that deliver laser light and collect backscattered signals from the skin surface, enabling localized acoustic measurements of the carotid artery. We further integrated an interferometric setup with a reference arm to enable heterodyne detection that enhances sensitivity to vibrations. Experimental results show that the interferometric system improves the SNR by approximately 24 dB when the detection fiber is positioned 7 mm above the skin. These findings underscore the potential of RS-camera-based speckle sensing in wearable platforms for noninvasive blood flow monitoring and broadband acoustic detection, with the interferometric enhancement significantly improving signal robustness and detectability.