S/PDIF Signal Decoding-Based Heterodyne Interferometry Used for Determining the Sensitivities of Low-Frequency Analog and Digital Vibration Sensors

The low-frequency vibration sensors have been widely utilized in different applications of precision motion control and measurement. In order to guarantee the performance of these applications, the heterodyne laser interferometry (TLI) recommended by the International Organization for Standard (ISO) is commonly applied to determine the sensitivities of these sensors. However, the original heterodyne interference signal acquisition has to require a high sampling rate, which results in the vibration calibration in low frequency is significantly difficult to be accomplished. Although the direct output displacement signal of the interferometer can be utilized for calibrating the sensitivity magnitude, it involves a phase delay that inevitably reduces the calibration accuracy of the sensitivity phase. In this study, a new TLI that based on the Sony/Philips digital interconnect format (S/PDIF) signal is investigated to simultaneously calibrate the low-frequency analog and digital vibration sensors. This investigated method determines the sensitivity magnitude and phase of the sensors by adopting the high-accuracy S/PDIF decoding and signal alignment methods. Comparison experiments with the current monocular vision (MV) and linear grating (LG) methods as well as the conventional TLI demonstrate that the investigated method has the ability to accurately calibrate the sensitivity magnitude and phase of the analog and digital sensors with a high repeatability in the range from 0.05 to 20 Hz.