差分白光干涉法测量极薄金属带材厚度时，为了克服传统极值法在白光干涉谱数据处理中抗噪声能力差的缺点，提出了一种基于最小均方差(MMSE)意义下的小波变换处理方法。该方法首先对干涉谱测量值进行归一化处理，消除低频光强变化的影响，并用极值法求得光程差(OPD)的初值。然后求归一化后的干涉谱与基于初值的理想干涉谱之间的均方差，当干涉谱的光程差的某个估计值与实际值最接近时，对应的干涉谱的均方差最小。通过逼近法获得均方差最小时对应的估计值。数值仿真和实验结果表明，利用该方法处理差分白光干涉谱数据，可以获得优于极值法的更高的数据精度，而且有效地提高了信噪比。

During measuring the thickness of metallic foil with tandem differential white light interferometry, a new data processing method for white light interference spectrum based on the Minimum Mean-square Error (MMSE) was proposed to overcome the poor anti-noise capability of traditional extremum method. In the new method, the spectrum measured value was firstly normalized to eliminate the intensity modulation, and an initial value of Optical Path Difference (OPD) was calculated by extremum method. The mean square deviation between the normalized measured spectrum and the theoretical spectrum from the initial value was calculated. When the estimated value of OPD is closest to the actual one, the mean square deviation will be minimum. The optimal estimated value was obtained by means of iteration. Emulation and experiments show that the data processing method has higher precision and better Signal-to-noise Ratio (SNR) than the traditional extremum method.