Single-Shot Microvibration Detection and Its Application in Spatial Multipoints Vibration Sensing

Extraction of microvibration information from a single-shot speckle image is realized based on the row-by-row exposure mechanism of a rolling shutter camera and the high intensity of laser speckle. Normalized cross-correlation and cubic spline interpolation algorithm is first used between nonoverlapping gray scales of adjacent rows to infer microdisplacement information. With the number of rows set as 342, a wide frequency range from 300 Hz to 20 kHz sinusoid signals are recovered with relative errors smaller than 2%. For low-frequency signals from 40 to 300 Hz, the relative errors of the extracted frequency are smaller than 5%. The effects of the number of sampling cycles (NSC) and sampling points in a unit period on the system performance are investigated and high accuracy is obtained with an NSC of 4 and sampling points of 3 per signal period. In a single-shot image, a spatial multipoints vibration detection scheme is presented and experimentally realized. The representative signals of 5, 10, and 20 kHz are successfully extracted in the multidimensional scenes of 1-D, 2-D, and 3-D, respectively, and the relative errors are all within 0.5%. This scheme can be potentially used in air surveillance for wide-range remote sensing of interested object or sounding.