| Slightly off-axis digital holography has the advantages of non-contact,high resolution and high efficiency.It can remove the DC component by subtracting two holograms,which increases the lateral resolution and thus improves the reconstruction image quality.Therefore,it is widely used in the fields of microscopic measurement,3D reconstruction,and non-destructive detection.At present time,the slightly off-axis digital holography technology mainly has the following two problems.On the one hand,most slightly off-axis digital holographic optical imaging systems use complex optical components in their design process.This makes the system less flexible in terms of installation and adjustment.On the other hand,the unwrapping is more time consuming during phase reconstruction process.When dealing with large amounts of data,it is impossible to achieve the fast measurement.Therefore,more and more researchers have focused on the above issues in recent years.It has important academic value and practical significance.In this paper,the main research contents for above problems are as follows:Firstly,a slightly off-axis digital holographic imaging system based on grating phase shift is proposed to address complex design and inflexible installation and adjustment of optical imaging system.The imaging system can flexibly adjust the phase shift between the two carrier holograms by moving the transmission grating,thereby the flexibility of setting the phase shift value is enhanced.Since the design does not require the use of complex optical components,it has the advantages of simple installation,flexible adjustment and low cost.Based on this,a slightly off-axis digital holographic phase reconstruction algorithm based on random phase shift is derived.Then the phase reconstruction experiments are carried out for different samples.The results verify the effectiveness and accuracy of the proposed method.Secondly,the parallelization of the slightly off-axis digital holographic phase reconstruction process is designed to address large computation and long operation time.Moreover,the phase reconstruction process is accelerated on the GPU platform by using CUDA programming model.Meanwhile,the shared memory technique is applied in the parallelized implementation of the discrete cosine based least squares unwrapping algorithm.It can improve the efficiency of thread reading data,shorten the algorithm execution time,and further enhance the speed of phase reconstruction.By comparing the running time of the phase reconstruction process on GPU and CPU platforms,it is verified that the parallelized design can effectively improve the speed of the phase reconstruction process.Finally,a slightly off-axis digital holographic optical image processing system is designed based on the software development platforms of Windows 10 and Visual Studio2019.The system includes image reading and display,hologram data processing,image data output and saving,and other functional modules.The visualization of slightly offaxis digital holographic phase reconstruction results is realized. |
