Yuan Ke, Zhu Zhonghua, Chen Wei, Zhu Weidong
Department of Mechanical Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
OmniSensing Photonics LLC, Columbia, MD 21046, USA.
Sensors (Basel). 2024 Aug 13;24(16):5230. doi: 10.3390/s24165230.
Developing a miniatured laser vibrometer becomes important for many engineering areas, such as experimental and operational modal analyses, model validation, and structural health monitoring. Due to its compact size and light weight, a miniatured laser vibrometer can be attached to various mobilized platforms, such as an unmanned aerial vehicle and a robotic arm whose payloads can usually not be large, to achieve a flexible vibration measurement capability. However, integrating optics into a miniaturized laser vibrometer presents several challenges. These include signal interference from ghost reflectance signals generated by the sub-components of integrated photonics, polarization effects caused by waveguide structures, wavelength drifting due to the semiconductor laser, and the poorer noise characteristics of an integrated laser chip compared to a non-integrated circuit. This work proposes a novel chip-based high-precision laser vibrometer by incorporating two or more sets of quadrature demodulation networks into its design. An additional set of quadrature demodulation networks with a distinct reference arm delay line length can be used to conduct real-time compensation to mitigate linear interference caused by temperature and environmental variations. A series of vibration measurements with frequencies ranging from 0.1 Hz to 1 MHz were conducted using the proposed laser vibrometer to show its repeatability and accuracy in vibration and ultrasonic vibration measurements, and its robustness to test surface conditions. The proposed laser vibrometer has the advantage of directly measuring the displacement response of a vibrating structure rather than integrating its velocity response to yield the measured displacement with a conventional laser Doppler vibrometer.
开发微型激光振动计对于许多工程领域都很重要，例如实验模态分析和运行模态分析、模型验证以及结构健康监测。由于其尺寸紧凑、重量轻，微型激光振动计可以附着在各种移动平台上，如无人机和通常负载不大的机械臂，以实现灵活的振动测量能力。然而，将光学元件集成到微型激光振动计中存在若干挑战。这些挑战包括集成光子学子组件产生的鬼反射信号引起的信号干扰、波导结构导致的偏振效应、半导体激光器引起的波长漂移，以及与非集成电路相比集成激光芯片较差的噪声特性。这项工作通过在设计中纳入两组或更多组正交解调网络，提出了一种新型的基于芯片的高精度激光振动计。一组具有不同参考臂延迟线长度的额外正交解调网络可用于进行实时补偿，以减轻温度和环境变化引起的线性干扰。使用所提出的激光振动计进行了一系列频率范围从0.1 Hz到1 MHz的振动测量，以展示其在振动和超声振动测量中的重复性和准确性，以及其对测试表面条件的鲁棒性。所提出的激光振动计的优点是直接测量振动结构的位移响应，而不是像传统激光多普勒振动计那样对其速度响应进行积分以得到测量的位移。
