When Mobile ToF Meets Micro-Vibration: Multi-Point kHz-Frequency Sensing using Laser Speckle

Abstract

Sensing micro-vibration plays a critical role in diverse industrial applications, including structural health monitoring and machinery diagnostics. However, most existing vibration sensing technologies rely on physical contact with the target object or demand complex installation procedures, making them intrusive and costly. This paper presents PocketVib, the first cost-effective, portable smartphone-based laser speckle vibrometry system for multi-point kHz-frequency microvibration sensing. PocketVib integrates built-in smartphone sensors, i.e., Time-of-Flight (ToF) depth cameras and rolling shutter cameras, to achieve non-contact micron-level vibration sensing. The design features three key innovations: 1) emitter-imager synchronization, which ensures stable speckle pattern acquisition, 2) a dual-lens enhanced imager that stretches speckle patterns to improve their limited coverage on the rolling shutter camera, and 3) a reference-free algorithm that leverages temporal correlations across rolling shutter image rows for precise vibration extraction. We implement PocketVib on commodity smartphones with a custom hardware kit. Extensive experimental results demonstrate that PocketVib enables fast and accurate vibration frequency estimation on mobile devices, achieving frequency measurements of up to 1 kHz with an average error of only 0.6 Hz at just 30 fps, while supporting simultaneous measurements at seven points. The project page is available at https://shangchengjin.github.io/PocketVibWeb.