基于FPGA的插频式外差干涉信号处理方法

摘要

In order to measure the phase displacement of a heterodyne interferometer, namely Doppler frequency shift, an interpolation processing method of the heterodyne interferometer based on field programmable gate array( FPGA )was introduced.Based on zero-crossing detection, it starts to interpolate pulses at the rising edges of measurement and reference signals respectively and the phase displacement can be calculated by counting the interpolated pulses.In the experiment, the light source is He-Ne laser with beat frequency of 2.2MHz, measurement device is Michelson' s interferometer, and the inserting pulse frequency is 100MHz.The following calculating work, such as counting, multiplication and division, was accomplished by FPGA.From theoretical analysis, the measurement resolution can achieve,(11/1000)λ, about 6.9608nm.The result indicates that is of high value for practical application.%为了测得外差干涉仪的相位移,采用插频法对外差干涉仪的参考信号与测量信号进行了处理,从而测得两个信号的相位差即多普勒频移.插频法基于过零检测原理,即在测量信号与参考信号上升沿来临时,分别对两信号插入脉冲,通过对插入的脉冲计数,实现相位差的测量.外差干涉仪光源是拍频为2.2MHz的He-Ne激光,使用迈克尔逊干涉仪测量系统,插入脉冲频率为100MHz,计数及乘除等相关运算用现场可编程门阵列实现,理论分析测量分辨率可以达到11/1000λ,约为6.9608nm.结果表明,该方法具有很强的实际应用价值.