消除光强调制影响的双波长正弦相位调制干涉仪

Two-Wavelength Sinusoidal Phase-Modulating Interferometer Insensitive to Intensity Modulation

在双波长半导体激光（LD）正弦相位调制（SPM）干涉仪中,通过注入电流调制LD波长的同时,光源的输出光强也被调制,影响了测量精度。提出了一种新的双波长LD SPM干涉仪,通过对干涉信号进行处理,得到与干涉信号相位相关的线性方程组,利用该方程组精确计算相位,消除了光源光强调制的影响,使测量误差由6μm减小至1μm,并利用该干涉仪与波长扫描技术相结合实现了绝对距离的测量,当待测距离为60~280 mm时,测量结果的重复性为1μm。

In a two-wavelength laser-diode（LD） sinusoidal phase modulating（SPM） interferometer,wavelength of LD is modulated by variation of its injection current（IC）.However,the IC modulation results in both wavelength modulation and intensity modulation,which will cause a measurement error.A novel two-wavelength LD SPM interferometer is proposed.In order to eliminate the error caused by intensity modulation,phase of interference signal is calculated accurately by solving linear equations obtained with the interference signal processing.With the proposed method,measurement error decreases from 6 to 1 μm.Moreover,the proposed interferometer is combined with linear wavelength scanning interferometer（WSI） for absolute distance measurement.Experimental result indicates that an absolute distance measurement repeatability of 1 μm can be achieved over a range of 60 to 280 mm.