Homodyne and heterodyne rolling shutter laser speckle acoustic sensing in bio-photonics

We present an innovative approach for remote sensing and measuring (human) biological signals arising from vibrating speckle patterns using a low-cost and low frame rate rolling shutter (RS) CMOS camera. The advantage of the proposed configuration is its capability to sense high-frequency signals with a low FPS camera. By applying a dedicated correlation algorithm on the acquired speckle pattern frames, we can reconstruct a carotid phonocardiogram (PCG), lung sounds, and human speech with remarkable clarity. Furthermore, we show how our method can be applied in a traditional self-beating optical configuration (homodyne setup) as well as in an interferometric configuration (heterodyne setup). The heterodyne setup notably enhances the signal-to-noise ratio (SNR) by 12.83 dB and eliminates the need for a lens system.