Development Of A Lensless Digital Holographic Imaging System For Experimental Observation

As the current one kind of popular holographic imaging technology, digital holography is widely used. Lensless digital holographic imaging is improved based on the digital holography,optical system is simplified.It has broad application prospects in the cell observation, microstructure morphology and deformation measurements. At present,there is less study about lensless digital holographic imaging.A small number of experimental studies obtained good imaging results, but lack of regular summary in imaging conditions(such as light color, wavelength, distance from the source to the CCD, etc.),that are important for image quality. In addition, there is no software combined digital holographic reconstruction with image processing in the market to realize some important functions for cell observation,such as holographic reconstruction,reconstructed image feature extraction,measurement, segmentation and so on.Existing methods of image processing is often carried out by MATLAB, low efficiency, manipulation unintuitive, and difficult to achieve commercialization.Based on above problems,a lensless digital holographic imaging hardware devices was built,and corresponding image processing software was developed with Visual C ++.Ultimately,a lensless digital holographic imaging system for experimental observation was formed, and digital holographic imaging lens imaging conditions was explored.The work mainly includes three aspects:①Digital holographic reconstruction algorithm was studied deep,and convolution reconstruction algorithm was select as the holographic reconstruction algorithm.After verifying the accuracy of the algorithm,a lensless digital hologram acquisition and processing system was developed with Visual C ++.The system relized functions of acquisition and reconstruction of digital hologram, measurement, segmentation and so on. The system has high portability and scalability, beautiful interface, and easy to operate.②A experimental platforms was designed and built, the function of controlling the experimental conditions was achieved via combination of stepper motors and sensors and lensless digital holographic acquisition and processing software.Primary functions, such as control of the distance between light source and CMOS,control of the light switch and records of the imaging conditions was completed.③Based on the entire experimental apparatus and software system, three different experiments——exploration of optimal imaging conditions and observation of breast cancer cells and red blood cells was designed to verify the feasibility of the system.The results show that:The best hologram could be acquired when the wavelength was between 465 to 470 nm, brightness was between 8000 to 10000 nit, light source was pink light with angle of 20 degrees and the distance from light source to the CMOS was between 5.5 to 7.5 cm.By lensless digital holography acquisition and processing software, the breast cancer cells and human red blood cells were acquired and reconstructed successfully,and position of cells were clear as well as outline. The results of cell measurement and count with software show:the cell size was similar with the actual size of the cell, and the count results matched well with the microscopic counting, the feasibility and rationality of the whole system was verified.