Direction-resolved homodyne laser-Doppler vibrometry by analyzing space-time fringes created by the successive 1D intensity profiles of the interference fringes

In this Letter, we introduce a simple direction-resolved homodyne Laser-Doppler Vibrometry method, by sewing successive one-dimensional images of the interference pattern recorded by a linear array detector, and creating a two-dimensional space-time fringes pattern. A space-time fringes pattern visualizes the vibration form and it can be used for characterizing vibration of the object. We measure the vibration of a harmonically driven loudspeaker as a known source to demonstrate the capability of the method. We also employ the method to characterize the vibrational properties of the resonator elements of a thin-disk laser. The method reveals the environmental and instrumental sources of the vibration. The use of an array detector in the detection system simplifies the fringe chasing procedure and optical setup, and by the aid of space-time image, the vibration waveform is directly determined with no requirement to a time consuming SPS algorithm.