The Analysis And Calibration Of Systematic Errors Of Phase-shifting Interferometer For Flatness Measurement Of MEMS Deformable Mirror

The need for advanced testing technique and devices is increasingly urgent with the development of Micro Electromechanical System (MEMS). MEMS static and dynamic testing technique has become an important part of MEMS testing technology. The traditional testing technique, such as contact measurement, works with low accuracy and inefficiency, and it cannot meet the requirement of entire field precision measurement. Optical interferometry, with the ability of non-contact, whole field measurement, high accuracy and high sensitivity, has a wide application in research and industrial production. In many cases, the measurement parameters have direct relation with the optical phase distribution. A lot of phase measurement methods have already exited, such as Heterodyne Method, Phase-Shifting Interferometry Method (PSI), Speckle Interferometry Method and Holography Method. As we know, PSI is one of the mostly common used optical measurement methods, with the merits of whole field testing, high productivity. This method is currently widely used in testing the static surface and dynamic characteristics of MEMS device.Phase-shifting interferometer can be used in testing the flatness of MEMS deformable mirror (DM) under whole field, whose diameter is 25mm. DM is primarily used as the wavefront calibration in Adaptive Optics, which has a very high requirement on surface flatness and roughness. Although PSI system has a high resolution, it will result in low-accuracy data due to the systematic errors. Thus, the systematic errors should be analyzed and calibrated in quantity. The major works in this thesis are following: 1) Setting up a PSI flatness measurement system as a result of full investigation and study. The thesis has a general explanation for the principle of PSI system and it applies the chosen Phase-shifting and Phase-unwrapping method to obtain the original surface flatness data. 2) This thesis uses an optical flat to calibrate the systematic errors, which has a 300nm P-V value. While the analysis of systematic error indicateds that the major factor is the wave-front aberration of optical system. 3) Wave-front aberration is simulated mathematically by using Zernike polynomials, such as Defocus, Astigmatism, Coma and other high order aberrations, and then separated the simulated values from flatness measurement results. 4) The calibration method shows the approach provide good flatness measurement results ofλ/4 mirror and MEMS deformable mirror.