The low-frequency vibration measurement has been increasingly used in the aspects of earthquake warning, bride and building construction healthy monitoring, marine monitoring, etc. Currently, the linear and rotary vibrations are commonly measured by laser interferometry; however, this method usually requires a high-cost and complex operation system, and its measurement accuracy at low-frequencies is affected the weak collimation and speckle noise. In this study, a monocular vision method is investigated to accurately and flexibly measure the low-frequency linear and rotary vibrations simultaneously. This method mainly consists of two steps: the template matching and the linear segment detection (LSD). The matching with a series of circular templates is applied to correctly determine the region of interest (ROI) in the image captured at different rotation positions and distances. The LSD is used to extract the motion feature edge in the ROI and achieve the vibration measurement. Comparison experiments with the laser interferometry and circular grating method demonstrate that the investigated method can accomplish the high-accuracy linear displacement and rotary angle measurements in the low-frequency range.

Monocular vision,LSD,Template matching,Low-frequency vibration,Laser interferometry