基于光谱型白光干涉仪的绝对距离测试研究

Absolute distance measurement with spectral domain white-light interferometer

采用微型光纤光谱仪记录宽波段(450～900nm)下的光谱干涉图,提出一种解包络线的方法来提取相位主值,同时由总光程差与棱镜折射率成正比的关系进行相位解包裹.由线性关系的斜率和截距分别求解得到棱镜的等效厚度和两参考镜之间的绝对距离.利用该方法测试了参考镜在不同位置处的距离,结果与千分尺数值之间的偏差小于1%,同时获得了99.9%的线性度.还测试了BK7玻璃的厚度,与其他方法相比,其精度达0.21%.分析了影响测试精度的因素,并对测距范围进行了讨论.

A fiber-optic spectrometer was employed for recording spectral interferograms over a wide wavelength range （450 ～ 900 nm）.A new method was presented for retrieving the wrapped phase function by the envelope method.The unwrapped phase was obtained by a simple procedure based on linear dependence of optical path difference between interferometer beams on the refractive index of optical elements.The effective thickness of the beam splitter was given by the slope of the linear dependence,and the absolute distance was determined by the intercept.The method was applied to measure the distances when displacing mirror to different positions.The measured results deviated less than 1% from those of vernier caliper and presented a linearity of 99.9%.The thickness of a BK7 glass plate was also measured.An accuracy of 0.21% was obtained compared with other methods.The reasons that affected the measurement accuracy were analyzed,and the range of measurable distance was discussed.