Data Processing And Research Of Phase-shifting Interferometer For Micro-surface Profile Measurement

This work concerns the researches in experiments and data processing based on the nanometer phase-shifting interferometer for micro-surface profile measurement. The pretreatment of the collected image, analysis in various phase-shifting algorithms and phase-unwrapping algorithms were realized. Phase-shifting algorithms adapt to this system were found. Two quick phase-unwrapping algorithms were introduced and an improved method to remove the abnormal area on the phase unwrapped image was proposed. The software for the measurement was developed. Through experiments on roughness samples, fiber connectors and the 44nm standard step, the precision and range of measurement for this system were calibrated.Major work of this dissertation:1. Factors affecting the quality of interference pattern and the precision of the system were analyzed. Methods to improve the quality of collected images were adopted. Methods of removing noise were realized and compared. Based on this interferometer, the own algorithm of removing noises was proposed.2. Traditional and improved phase-shifting algorithms were realized in the software. Sensitivity of kinds of phase-shifting algorithms to different errors in the system has been analyzed. The good character in error immunity of the improved phase-shifting algorithms was proved.3. Besides the least-square algorithm, two quick phase-unwrapping algorithms were introduced and an improved method to remove the abnormal area on the phase unwrapped image was proposed. The above phase-unwrapping algorithms were completed in Visual C++ and were validated. The applicable range and processing speed were discussed.4. Experiments on the roughness samples, fiber connectors and the 44nm standard step have been carried out. The functions including data collection, image pretreatment, 3-D and 2-D micro-surface display, adjusting inclination and mensuration of kinds of parameters were realized in the software.5. The precision and range of measurement for this system were calibrated. By compared with the results of the Atomic Force Microscope and a commercial instrument, the precision of height measurement is better than 3nm and the range is larger than 4μm , the resolution in the horizon is better than 4μm .