在正弦相位调制(SPM)干涉仪中,若调制频率或者采样频率发生变化将使干涉信号出现频谱泄漏,减小了谐波分量的幅值,在测量结果中引入了误差。对频谱泄漏的产生及其对测量精度的影响进行了理论分析,获得了频谱泄漏引入测量误差的计算方法。实验测得频率漂移量在-0.3～0.3 Hz内,得到的频谱泄漏引入的误差为0.3～7.9 nm,当超出这个范围时,频谱泄漏误差将迅速增长。实验结果与模拟分析结果一致。

In sinusoidal phase modulating (SPM) interferometry, the spectrum leakage is generated due to the frequency variation of modulating signal or sampling signal. The spectrum leakage induces errors in the measurement result by reducing values of harmonic components. The spectrum leakage in a SPM interferometer and its influence on measurement accuracy are analyzed theoretically with the discrete Fourier transform method. The mathematical expression of the measurement error induced by frequency leakage is obtained. In experiments, when the frequency shift is -0.3～0.3 Hz, the induced measurement error is 0.3～7.9 nm. Beyond the range, the measurement error increases obviously. The experimental and theoretical data agree well with each other.