Study On Phase Shift Drive And Identification Method Of Surface Topography Multiwavelength Interferometry

With the development of modern technology,the application of microcircuit and microstructure surface becomes more and more extensive,which brings new challenges to modern high precision surface topography measurement technology.At present,high precision surface topography measurement methods mainly focus on contact measurement and non-contact measurement.Because of the measuring force between the stylus and the object,the contact measurement will bring great measurement error,which has great limitation in measuring precision and application range.The main method of non-contact high precision measurement is optical phase shift interferometry,it has the characteristics of large measurement range,high precision and wide application prospect.To do this,we designed a multiple wavelength interferometry system across scales based on interferometry and considered about the advantages and disadvantages in phase shift scanning drive.Then,in this paper,the necessity and principle of multi-wavelength interferometry are discussed,and the related formulas of extended measurement range are derived.The main contents of this paper include:First of all,the paper has analyzes the basic principle with current interference measuring technology.Use the principle of phase shift to expand measuring range with more wavelengths.Designed the multi-wavelength interference system based on structure of Mirau interference.Then has deduced relate formula for expand the measurement range.In addition to the open-circuit part,the model selection requirements of other major parts of the system are analyzed,and the whole system linkage adjustment process is described.Secondly,in view of the phase shift and interference in the image acquisition process,write the upper computer software based on the JAVA platform.The phase shift and CCD interference pattern acquisition are controlled by the upper computer to complete the whole measurement process.Then,in this paper,the dynamic and static performance of phase shift is studied.Finally,in view of the phase shift recognition method,based on the least square ellipse fitting method to extract phase interval,and put forward a greyscale image sequence looking for phase difference of ?/2 pixels in the whole field of ways to improve the fitting accuracy,reducing the interference of random error.Then,the effectiveness of this method is proved by simulation and single wavelength experiment.In the case of single-wavelength experiment,the total deviation of phase shift was within + 0.04 radians.For 650 nm monochromatic light,the identification accuracy of phase-shift drive reaches to plus or minus 2nm,which meets the precision requirements of the designed measurement system.