Three-dimensional Micro-surface Phase Shift Interferometry Studies

Phase-shifting interferometry(PSI) has been considered as a type of opto-electrical measuring interferometry and it has many advantages, such as simple structure,easily modulated,fast and real time,high accuracy and whole field automatic measurement. It has been widely used to test optical element, optical system, and to detect optical surface as well as some physical parameter (such as temperature field, density field) related with optical path difference.In this thesis, the author comprehensively described the research results on the theory and algorithms of phase-shifting interferometry. The study is concentrated on the key problem of phase-shifting interferometry: phase-extracting algorithms and phase-unwrapping algorithms. In order to change the phase of the reference beam in the interfering system, we design a stepping motor control system. Basing on Mirau type microscope interferometer system, we obtain the surface tomography with various types of phase extracting algorithms. We completed the precision phase stepping system as well as the core algorithm design of our system and improved the precision in measuring. This thesis goes in five chapters as follows:Chapter 1: The background of carrying out this thesis. The main methods of surface profile measurement and their comparison are summarized. Then the status of research and development trend is introduced. Finally, the major objective and works are outlined.Chapter 2: The fundamental theoretics of phase-shifting interferometry. First, common interference microscopies and phase measuring techniques are introduced. Then the test principle of phase shifting interferometry,phase shifting techniques(Piezoelectric transducer control technique and Stepping motor control technique),optimum scheme for sampling measurement as well as surface profile of the objects are comprehensively analyzed. Finally, the error in measurement is summarized.Chapter 3: Phase extracting techniques and phase unwrapping algorithms, which is the key chapter in the thesis. This chapter goes as follows: phase stepping algorithms classified into three are comprehensively introduced (include error estimation and performance comparison), our algorithms are put forward, the phase unwrapping algorithms we applied in the thesis—Flynn's Minimum Discontinuity Approach, is introduced. Finally, the experimentresult is showed and analysized.Chapter 4: Experiment result and data analysis. In this chapter, stepping motor control system designed by myself is introduced. Then, basing on the experiment platform of phase shifting interferometry—Mirau type microscope interferometer system, a collection of five interferograms is showed. Next the data is detailly analyzed according to three levels. Finally, we draw the conclusion.Chapter 5: Conclusion and expectation. In this chapter, the conclusions of the thesis are made, and further improvement are also proposed.