Laser confocal vibration measurement method with high dynamic range

A new laser confocal vibration measurement method (LCVM) is proposed to meet the requirements of high precision and high dynamic range measurements in micro and nano electromechanical systems. The proposed method uses different measurement modes to ensure that the amplitude solution interval of the out-of-plane is always in the optimal test interval of a confocal curve with the highest sensitivity to axial displacement, and thereby achieving the high-precision extraction of large-scale frequency and the high-precision measurement of large-scale amplitude. Using a 100×, NA=0.9 objective lens with a working distance of 1 mm, the theoretical analysis and preliminary experimental results indicate that the maximum measurable amplitude is 500 µm, the displacement resolution of the amplitude is 4 nm, and the measurable frequency range limited by electrical design is 0-120 MHz. The LCVM provides a novel approach for out-of-plane vibration measurements.