| Optical Computerized Tomography is using laser as light source, to quantitative diagnosis of transparent medium by theory of CT. It has the advantages of non-contact, real time and three-dimensional quantitative detection. And it's an important method to achieve the aerodynamic flow field diagnosis. The moire tomography is based on optical moire method, set deflection angles as projective data, it has the advantages of measurement in large dynamic range and superior ability of anti-error, is appropriated to in aerodynamic flow field diagnosis shaking circumstance. In order to achieve high-precision moire tomography diagnosis, it is an important and key step to collect moire tomography projective data from moire fringe. This paper that mainly based on the scalar diffraction theory analysed forming mechanism of moire fringe and designed triple-grating moire tomography optical path to collect moire tomography projective phase by the method of space phase shit.Main tasks are as follows:1. Analysis of double-grating Moire tomography system by Fourier analysis method, and found that a spatial phase shift of±1 grade projected image.2. Designed the three-grating Moire tomography system, the same using Fourier optics analysis, given the expression of the projection image's light intensity distribution and analysis the spatial phase shift of the projected image.3. Put forward the method of projection data extraction in three-grating Moire tomography system——six-step phase shift method. Test the feasibility of this method by simulation experiment; in the simulation, we make a detailed discussion to the influence of three-grating system's parameters to the phase shift characteristics. The theoretical analysis has great value to the practical application.4. For the actual experiment, set up a three-grating optical tomography system experiment, extract phase information of the projection images by six-step phase shift method, test the feasibility of six-step phase shift method. |
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