| Optical interferometry is an important branch of optical detection. Fringe analysis of deformation with interferometry technology have advantages of non-destructive, non-contact and high precision. The numerical reconstruction of the object beam amplitude and phase distribution can be achieved with digital holography. As one of the important areas of modern optics in recent years, Digital holographic technology has broad applications in areas such as imaging and detection. Combination of digital holographic technology and optical interferometry can exert their characteristics and advantages. Based on Digital holographic technology, Optical interferometry and their applications in optical measurement, this dissertation carried out the study of dual-wavelength digital holographic interferometry and its applications in measurement of surface shape and optical inhomogeneity.The contents of this dissertation primary includes the following:(1) Elaborated on the basic principles of digital holography and methods of interferometry. Including the principle of digital holography recording and reproduction, the extraction methods of object wave (in-line digital holography and off-axis digital holography) from the hologram (interferogram) with numerical reconstruction, phase unwrapping methods and so on.(2) Based on the theories of digital holography and interferometry technologies, the measurment of surface shape with dual-wavelength has been proposed. This paper conducted the feasibility analysis and appraisal, given the results of computer simulations and optical experiments. For the optical path difference is less than the equivalent wavelength, dual-wavelength digital holographic interferometry can directly overcome the uncertainty of2n phase, without phase unwrapping. For the optical path difference is greater than the equivalent wavelength, dual-wavelength digital holographic interferometry can simplify the phase unwrapping process which will improve the noise immunity of phase unwrapping algorithms and expand the scope of phase unwrapping algorithms.(3) Traditional measurement of optical inhomogeneity always obtain a globle inhomogeneity including surface parallelism, surface shape and systematic errors. Based on the Lorentz-Lorenz dispersion equation, the relationship between optical inhomogeneity and wavelength is first analyzed in this dissertation. The difference of optical inhomogeneity in different wavelengths is much smaller than the required precision of optical components in practical application. According to the analysis and optical material’s dispersion properties, measurement of optical inhomogeneity with dual-wavelength interferometry is proposed first. We have given the metrical principle and derived the final formula which is confirmed in both computer simulation and optical experiment.The above work laid the foundation for subsequent depth study. |
