大数值孔径光学镜约束多级衍射机理

Digital holographic microscopy imaging technology is a quantitative phase imaging technology combined with digital holography technology and traditional optical microscopy imaging technology. Owing to there are speckles and parasitic stripe noise in traditional laser off-axis holographic microscopy imaging system and the traditional off-axis digital holographic microscopy of partial coherent light illumination has the problem of poor contrast of coherent fringes, the diffraction phase microscopy imaging system with monochromatic LED illumination is putted forward in this paper. Grating is used to obtain multi-level diffraction of object light. And 0th and +1st order light are separated by 4f system and spatial filter, which are used as reference light and signal light, respectively. Two beams interfere with each other on the CCD and generate off-axis hologram. Thereby a common-path and off-axis holographic imaging structure is formed. Through theoretical analysis and calculation, the optical components used in the experiment are picked to guarantee that the diffracted light spectrum information can be separated and accord with the sampling conditions. In conclusion, the experimental results demonstrate that the proposed system can derive higher imaging accuracy and signal-to-noise ratio than the traditional laser off-axis digital holographic microscopy imaging results.