激光干涉条纹锁定系统测量地面低频振动谱

Low-frequency seismic spectrum measured by a laser interference fringe locking system

地面振动噪声是在地面高精度实验中一个重要的误差来源,安静环境下地面振动噪声水平的幅度为纳米量级,通常干涉仪无法直接测量。设计并制作用于了纳米精度测量的激光干涉仪反馈控制系统,该系统由激光器及稳频装置、干涉系统、检测及控制电路和位移反馈执行机(压电陶瓷)组成。采用一个长周期的折叠摆对水平方向0.3 Hz以下的振动频率进行隔振,利用该系统对0.3~3 Hz的低频地面水平振动谱密度进行测量了。测量结果表明在1 Hz处,水平地脉动噪声为10-9m/(Hz)^(1/2)量级。

Seismic noise is one of the crucial problems for terrestrial precision experiment.It can not be measured by the general interferometric method because the seismic noise usually has the level of nanometer.A laser in interferometer control system,which consists of a laser interferometer,a detector,a control circuit,and a displacement feedback actuator（piezoelectric ceramic）,has been built up.The low-frequency（0.3~3 Hz） seismic noise level is measured using the lock-in laser interferometer combined with a long period folded pendulum.The results show that the maximum vibration noise level is 10-9m/（Hz）^（1/2） at 1 Hz.