Algorithm Research Of Full Field Heterodyne White Light Interferometry

White light interferometry is a non-contact measurement method that is widely used in the surface detection and measurement of precision components such as optical components and micro-electro-mechanical systems.However,the lack of movement accuracy of linear displacement mechanisms largely limits the improvement of white light interferometry accuracy.The interferometry method combining heterodyne interference and white light interference can effectively reduce the influence of insufficient accuracy of the linear displacement mechanism,but the interferometry technology still has problems such as large system,complicated algorithm and expensive price.A system of full-field heterodyne white light interferometry was proposed in this paper.,A new signal processing algorithm is proposed to process the data based on this system.The main contents and innovations of this research are as follows:(1)A full-field heterodyne white light interferometry system was designed.The measurement principle of the heterodyne white light interferometry measurement system were described,including the compensation method between the light source and the interference system.The heterodyne white light interference signal was obtained through the measurement system.The system was divided into two parts,heterodyne white light source and Fizeau interferometry system,in order to improve the interchangeability and versatility of the measurement system.(2)Amplitude addressing algorithm for processing measurement signals was studied.A mathematical model of the interference signal was established based on the interference characteristics of the heterodyne white light interference signal,and the existing algorithm was optimized.A new signal processing algorithm was developed by combining two algorithms with strong anti-interference ability and high calculation accuracy.(3)The calculation accuracy and anti-interference of the algorithm were studied.The process of heterodyne white light interferometry may be affected by four factors: white noise error,scan step error,frequency shift error,and scan step size.The influence of each error on the processing algorithm was simulated and analyzed using the control variable method.Compared with the Fourier transform algorithm in the traditional white-light interferometry algorithm,the calculation accuracy was higher and the anti-interference ability was stronger than the Fourier transform algorithm in the traditional white-light interferometry algorithm.(4)Heterodyne white light interference system was established for experimental research.The amplitude addressing algorithm was used to process the experimental data,and the error parameters of the experimental equipment were brought into the simulation model.The experimental results and the simulation calculations reached a consistent calculation accuracy,which verified that the algorithm had a high performance and measurement accuracy under standard experimental conditions..Firstly,the experiments verified that the experimental results and the simulation results had high consistency,and then the simulation results showed that the algorithm was used to measure the 5μm step,the scan step size was 200 nm,the frequency error was 0.005 Hz,and the detector Gaussian noise,the calculation error was still less than 0.1nm when the intensity was 1d B and the step size random error fluctuation was less than 5nm.It was verified that the amplitude addressing algorithm could achieve high-precision surface measurement with a large scanning step,and strong anti-interference ability to the detector’s white noise,frequency shift error and scanning step error.