提出并在实验上实现了一种以慢变化近似为基础的新型正弦相位调制半导体激光（ＳＰＭ－ＬＤ）干涉仪。原理上它不要求相位解调一次和二次谐波分量振幅在实验中必须保持相等，从而将动态范围提高了３～４个数量级且不损失精度。用压电陶瓷和微电机驱动位移。当压电陶瓷驱动位移大于半波长时，均方根误差为５ｎｍ。测量所得到的最大位移为１ｍｍ。系统能在噪声环境中进行自动实时位移测量。 A novel sinusoidal phase-modulated semiconductor laser (SPM-LD) interferometer based on slow-change approximation is proposed and experimentally implemented. In principle, it does not require phase demodulation. The amplitudes of the first and second harmonic components must be equal in the experiment, increasing the dynamic range by 3 to 4 orders of magnitude with no loss of accuracy. Piezoelectric ceramic and micro-motor-driven displacement. When the displacement of piezoelectric ceramics is more than half wavelength, the root mean square error is 5nm. The maximum displacement measured is 1 mm. The system can perform automatic real-time displacement measurement in a noisy environment.