Development of Microscopic Anti-vibration Surface Profilometry Using Differential Interference Contrast(DIC)
| Autor: | Dinh Thai Bao |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 A microscopic anti-vibration surface profilometry has been developed based on Differential Interference contrast (DIC) technique to examine the 3D profile of the nanoscale reflected samples. Dual-mode design of phase-shifting and phase-scanning DIC is proposed in a single configuration. The system performs high-resolution measurement on samples having the height less than a quarter of the wavelength. In phase-scanning mode, the peak-intensity detection algorithm can reconstruct the contour of samples having the height over a quarter of wavelength without phase-ambiguity. Two configurations using different types of light source are proposed. The first DIC configuration uses a Savart prism as a shear device, which produces two parallel output beams without adding any bias phase error as in conventional Wollaston or Nomarski prism. Because of the self-interference characteristic, all axial vibration influencing to two these beams are canceled out. The system, therefore, introduces high anti-vibration ability. Another proposed configuration of DIC microscopy combines the ability of Michelson module with a pair of retroreflector corner cubes to control the shear distance and shear direction freely. The dual-mode of phase-shifting and phase-scanning also perform excellently with this configuration. A low coherence white light LED replaces the white light laser of the first configuration to remove the speckle noise and diffraction on captured images. The 3D profile of the sample is retrieved from two phase-gradient maps using the Frankot-Chellappa algorithm. The resolution of the system can reach micro or sub-micrometer for lateral axis and nanometer for axial axis. A VLSI step height standard SHS880 of 88(nm) is employed to investigate the precision of phase-shifting mode, while the step height sample of 1.03(μm) is employed to examine ability of phase-scanning mode. The experimental results indicate that the proposed DIC microscopy can be applied to in-line automated optical inspection (AOI). A DIC probe is designed to improve the stability of system. Moreover, the size of probe is estimated based on the Aero Tech stage mounting. The proposed probe will work on the stage as a z-axis profilometry. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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