Shabahang Farzaneh, Smith Stuart T
Appl Opt. 2022 Apr 1;61(10):2768-2774. doi: 10.1364/AO.453951.
This paper presents design and operation of a multi-axis optical probe for independently measuring the relative displacements of external surfaces. Displacement is measured by mechanically modulating the optical cavity formed by an internal surface and the external surfaces, each of which comprise a Fabry-Perot interferometer. Multiple sensing axes are created using a beam splitter, and these sensing axes are separated by modulating the measurement paths at different frequencies. Two probes have been fabricated and tested; the first uses a single laser source with axes monitored by shuttering; the second probe uses two source wavelengths with beam splitting achieved using dichroic mirrors. Experimental results are presented for mirrors moving independently over distances of 1 to 2 µm with displacement noise less than 10-nm rms that is higher than the noise floor of 2.8 nm for stationary mirrors. Currently, the bandwidth is limited to the modulation frequencies ranging between 200 Hz and 2.43 kHz.
本文介绍了一种用于独立测量外表面相对位移的多轴光学探头的设计与操作。位移是通过机械调制由内表面和外表面形成的光学腔来测量的，内表面和外表面均包含法布里-珀罗干涉仪。使用分束器创建多个传感轴，并通过在不同频率下调制测量路径来分离这些传感轴。已经制造并测试了两个探头；第一个探头使用单个激光源，通过快门监测轴；第二个探头使用两个源波长，通过二向色镜实现光束分离。给出了镜子在1至2 µm距离上独立移动的实验结果，位移噪声均方根小于10 nm，高于静止镜子2.8 nm的本底噪声。目前，带宽限于200 Hz至2.43 kHz的调制频率范围。
