An enhanced homodyne laser vibrometer based on an auto-gain module

This study presents an enhanced homodyne laser vibrometer with adaptability to reflectivity. The reflectivity could be quite different when measuring different target, which caused the variation of the intensity of the interference signals. In order to enhance the measurement range for the reflectivity of the target, an auto-gain module, which could enlarge the interference signals to an optimal range of the analog-to-digital converter, is implemented in the signal-processing card. The intensity of the interference signals could be calculated in the auto-gain module, and then amplified according to a predetermined rule by using programmable gain amplifiers. The experimental results indicated that the laser vibrometer proposed is capable of measuring vibration with surface reflectivity down to 0.08%.