弹光调制傅里叶变换光谱相位校正及DSP实现

摘要

弹光调制傅里叶变换光谱仪(PEM-FTS)具有调制速度快、信息量大的特点,但采样位置偏差会导致干涉图存在相位误差,影响复原光谱的准确性.因此,必需采用一种运算速度高的相位校正方案.以300 K黑体为辐射源,通过弹光调制干涉具产生干涉数据,并在TM S320C6713DSP芯片上,采用Mertz法对弹光调制干涉图进行相位校正.首先提取出一幅完整周期的双边干涉图,经过切趾处理后,以零光程差点为中心计算小双边干涉图的相位误差,再通过插值补零得到整幅干涉图的相位误差,求出整体干涉图的频谱并进行相位修正.采用二范数定义校正后反演光谱的精度,以计算定时器周期寄存器值的方法设置DS P定时器,以统计代码的运行时间,并通过观察链接命令文件.cmd中程序与数据的分配存储情况,来对比分析Mertz法与模平方法的校正结果.实验结果表明,在DSP上实现相位校正时,Mertz法相位校正方案具有运算速度快、占用存储空间少、误差较小等特点,并且Mertz相位校正法的运算时间较模平方法快20倍,适用于对PEM-FTS干涉图进行高速准确的相位校正.%Photo-elastic modulation Fourier transform spec trum (PEM-FTS) has the characteristics of fast modulation speed and large amoun t of information.However,because of the sampling position error and other reas ons,there exists phase difference in the output interference data,which affect s the accuracy of the reconstructed spectrum.Therefore,a phase correction sche me with high computing speed must be adopted.The 300K infrared blackbody was us ed as the radiant source in the experiment,and interference data were generated by the photo-elastic modulation interferometer.Mertz method is used to correc t the phase of photo-elastic modulation interference data on the TMS320C6713 DS P (digital signal processor) chip.First a complete double interference data is extracted befroe the apodization processing to calculate the phase error of smal l double interference data,which takes the zero optical path as the center.The n a whole interference figure error phase is acquired with interpolating zero an d the spectrum of the complete interference data and correcting phase are obtain ed at last.With two-norm to define the accuracy of corrected spectrum ,and us ing the method of calculating timer period register to count code running time,a nd observing program and data memory space in the file of command.The correct ion results of Mertz method and modulus square method were analysed comparativel y.Experimental results show that Mertz method has advantages of fast speed,occu pying less storage space and less correction error when implement phase correcti on on the DSP.And the operation time of Mertz phase correction method is 20 tim es faster than that of modulus square method.Consequently,it is suitable for hi gh speed and accurate phase correction of PEM-FTS interference data.