大数值孔径光学镜约束多级衍射机理

Research on Multi-diffraction Phase Imaging Restricted by Large Numerical Aperture Optical Lens

针对基于激光照明的离轴全息显微成像系统存在散斑和寄生条纹噪声,以及基于部分相干光照明的离轴数字全息显微技术存在相干条纹对比度差的问题,本文提出了一种基于单色LED照明的衍射相位显微成像系统。该系统利用大数值孔径物镜及光栅对物光进行多级衍射,并采用4f系统和空间滤波器分离出0级和+1级信息,分别作为参考光和物光,最终两束光在CCD阵面上干涉产生离轴全息图,从而形成共光路全息成像结构。通过理论分析和计算,对实验用到的光学元器件进行选型,确保衍射光频谱信息能够分开且满足抽样条件。最后与传统激光离轴数字全息显微成像检测结果进行对比,实验结果表明,本文提出的系统能够获得较高的成像准确度和信噪比。

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.