Research On High-precision Laser Self-mixing System Based On Even-power Phase Modulation

In the 1960s,the birth of the world’s first ruby laser opened a new chapter in optical research.Since then,various lasers and laser detection technologies have sprung up.The laser self-mixing interference effect(SMI)was discovered by researchers during this process.It is an optical feedback phenomenon caused by light reflection or scattering from external objects.With the continuous exploration of a large number of scholars,the mechanism is gradually being Untie,the new type of laser self-mixing interferometer has ushered in a vigorous development.Compared with the traditional double-beam interferometer,it has the advantages of the easy optical path,multiple applicable measurement scenes,and high sensitivity and precision.Its application scope includes motion sensing,terahertz imaging,industrial manufacturing,three-dimensional reconstruction,biomedicine,national defense and many other fields.This paper has launched a series of in-depth discussion and research around SMI.First,through a large number of research and reading literature,we comprehensively sort out its historical background and development process,and classify its applications development in displacement and vibration measurement,absolute distance measurement,speed measurement,etc.After that,based on the classic F-P three-mirror cavity theory,the physical process is deduced and analyzed,and the corresponding mathematical model has been established.The effect of the external cavity phase,linewidth broadening factor and optic feedback intensity factor on the system mode and output signal is studied by simulation.In addition,the commonly used methods in SMI displacement vibration measurement(counting fringe method and de-phase method)are summarized and analyzed,and the effectiveness of the traditional phase unwrapping algorithm and phase modulation method is verified by simulation,which has laid a solid foundation for subsequent research.With the continuous innovation of technology,the requirements for the precision and breadth of nanometer measurement technology are getting higher and higher.Therefore,this paper focuses on the phase-modulated self-mixing interference system,introduces evenpower fast algorithm and multiple reflection structure to broaden the frequency spectrum of the harmonic component,and then realizes the high-precision reconstruction of microdisplacement vibration.A series of experiments under different amplitudes show that the displacement reconstruction errors of even-power phase modulation technology are all less than 17nm.In addition,this paper also proposes a local-spectral energy peak-detection algorithm,which improves the original Fourier analysis demodulation technology.It effectively avoids the failure of frequency domain demodulation and has a high operating efficiency and wide application range,so greatly optimizes the overall performance of the system.At the end of this paper,a variety of methods are combined to construct a highprecision self-mixing interferometric integrated measurement system,and the maximum measurement error is 5nm for a displacement with amplitude of 88nm.The experimental results have proved that the scheme proposed in this paper has achieved a series of outcome in improving reconstruction accuracy,widening the minimum measurable range,and improving system stability.The solution proposed in this paper will have great application potential in the field of nanometer measurement.