| Digital holography,as a digital holographic interferometry technique,enables digital recording and numerical reproduction of three-dimensional morphological features of microstructures.When digital holographic microscopy is performed for microstructured optical elements,the limited depth of field of the microscope objective makes the digital hologram recording poor,which affects the wavefront phase reconstruction results of the hologram diffraction reproduction and leads to the poor measurement accuracy of the 3D morphology of microstructured optical elements.Therefore,in order to improve the quality of wavefront reconstruction of microstructured optical elements,research on wavefront reconstruction method based on compressed sensing digital holographic microscopy is carried out.The main research works and contents are as follows:In order to improve the reconstruction quality of digital holographic wavefront reproduction image,the theory of compressive perception is introduced into the wavefront reconstruction process of digital holography.Based on the imaging model of compression perception,the perception matrix of compressed holographic reproduction of layered objects is constructed,and the object-light waves at different longitudinal depth levels of the hologram are analyzed and processed to realize the simulation recording of 3D samples at longitudinal depth and the layered intensity reconstruction of compressed holograms,which improves the problem that the traditional diffraction reproduction is limited by the information crosstalk between levels.The reconstruction results show that compared with the traditional diffraction reproduction,the compressed perception technique can effectively improve the quality of the reconstructed cross-section,reproduce the original image with only 50% of the hologram information,and reduce the redundancy of the hologram information.In order to obtain three-dimensional information of micro-optical elements from a single hologram,a study of digital focusing reconstruction method based on compressed holography is carried out.The measurement process of digital holography conforms to the observation conditions of compression perception,and the recorded hologram can be represented in the sparse transform domain.Digital focusing is performed during the diffraction reproduction of the compressed hologram,and the reconstructed objects with different reproduction distances are calculated by numerical inverse diffraction propagation;the digital focusing curve is used to find the clearest reconstructed image and obtain the reproduction distance of the best reconstruction plane,so as to obtain accurate phase distribution.The results show that the focus reconstruction method of compression-aware digital holography provides effective information recovery for the measurement of 3D morphology of micro-optical components.A compressed holographic phase reconstruction method based on frequency-domain sparse sampling is proposed.In the process of reproducing traditional digital holography,combined with the fact that the frequency domain contains most of the phase information,the spectral information in the holographic light field is sparsely sampled,and the effective spectrum information of the object light wave is compressed and reconstructed in the transformation domain,and then the phase distribution of the reconstructed object light wave is obtained by the inverse Fourier transform.Our experimental results demonstrated that the method with sparse desampling can achieve effective measurement of wavefront phase and provide more detailed information for 3D phase reconstruction;compared with the phase reconstruction results of conventional digital holography,the peak-to-valley(PV)and root mean square(RMS)values of residuals are reduced by 26.6%和 15.4%,respectively.The reproduction results are obtained by digitally focusing the compressed hologram in a way that is better than the conventional method,and the dynamic testing of the digital holographic wavefront reproduction method is realized to improve the measurement accuracy of the 3D phase of microstructured optical components. |
