Measurement Method Of Iron Ion Concentration Based On Laser Self-mixing Interference

The accurate and rapid measurement of iron ion concentration in water plays an important role and significance in daily production and life.Traditional measurement methods(such as spectrophotometry)have some problems such as complex system and difficulty in improving sensitivity.In order to improve the measurement technology of iron ion concentration,this paper proposes a method of iron ion concentration measurement based on the principle of laser self-mixing interference combined with the simple structure and high sensitivity of laser self-mixing interference.Firstly,the basic principle of laser self-mixing interference is introduced.Combining with the three-mirror cavity model of laser self-mixing interference and considering Lambert Beer’s law,the functional expression of laser self-mixing interference and iron ion concentration is established.Based on the simulation of the amplitude and power spectrum of the laser self-mixing signal in the frequency domain with different iron ion concentration,the influence relationship between the frequency signal with good primary and secondary peak values and iron ion concentration on the laser self-mixing interference is obtained.Then,a laser self-mixing interferometry measurement system is built.According to the absorption spectrum line of the iron ion light source,the appropriate iron ion is selected and the photoelectric conversion process is carried out on the laser self-mixing signal by the photoelectric detector.The influence of different iron ion concentration on the experimental phenomenon is observed.By analyzing the spectral lines of laser self-mixing experiment,the measurement results of iron speparation concentration,measurement limit and sensitivity are obtained.Finally,considering the influence of key parameters such as cuvette angle,and stray light in the system,the laser from mixed experimental error and uncertainty analysis,combining the above laser from the mixed signal spectrum simulation were compared,with the experimental data analysis,the results show that the concentration of the iron ion laser from mixed frequency domain signal simulation and experimental data show the consistent change rule.In this paper,a method of iron ion concentration measurement based on the principle of laser self-mixing interference is proposed.The basic method is that the feedback light is absorbed by the iron ion solution,which has a direct impact on the laser self-mixing interference.The iron ions are obtained by analyzing the frequency domain signal of the laser self-mixing interference.In the measurement range of 1 μg/L～1600 μg/L,it has higher sensitivity than traditional measurement methods.