Photon-level speckle interferometric vibration imaging

Non-contact vibration measurement is essential for structural health monitoring and precision manufacturing, but traditional speckle interferometry fails under extreme low-light conditions when echo signals attenuate to the single-photon level. To overcome this fundamental limitation, we propose and experimentally demonstrate a photon-level speckle interferometric vibration imaging method. By encoding the dynamic speckle field waveform directly into the probability distribution of sparse single-photon arrival time sequences, we enable high-fidelity signal reconstruction from extremely weak optical fields. Experimental results demonstrate that our system can accurately reconstruct a 1 MHz vibration waveform, with a frequency-estimation repeatability better than 0.04 Hz for stable single-frequency signals and nanometer-scale displacement resolution even at an ultra-low photon count rate of 6 kcps. This approach provides a robust solution for vibration monitoring in extreme environments, significantly extending the operational boundaries of non-contact optical sensing.