在激光二极管(LD)正弦相位调制(LD-SPM)干涉仪中,通过注入电流调制激光二极管波长的同时,光源输出的光强也被调制,成为测量误差的主要来源之一。提出一种新的消除激光二极管正弦相位调制干涉仪中光强调制影响的干涉仪,给出了具体的理论分析。该干涉仪采用全光纤结构,有效减小外界干扰对干涉测量的影响;采用容易实现的前置信号处理电路和实时相位检测器对干涉信号进行处理,消除了激光二极管光强调制产生的测量误差;同时实现了物体微小位移的高精度实时测量,测量的重复精度达到1 nm。实验结果与其他消除光强调制影响的方法测得的结果基本一致,验证了该方法的实用性。

In a laser-diode (LD) sinusoidal phase-modulating (SPM) interferometer, the wavelength of the LD is modulated by varying its injection current, but at the same time the intensity of the LD is modulated too, which causes a major measurement error. To decrease the effect of the intensity modulation of the LD on measurement accuracy, a novel LD-SPM fiber-optic interferometer is presented, and the theory of the interferometer is analyzed. The all fiber-optic structure decreases the influence of extermal perturbation on interference measurement effectively. Using this interferometer with simple pre-signal process circuit and real-time phase detector, the measurement error caused by LD intensity modulation is eliminated, and the displacements are measured with a higher accuracy (a few nanometers). And the measurement repeatability is less than 1 nm. The experimental results are consistent with those with other methods to eliminate influence of intensity modulation. The validity of the new interferometer is proved.