The Particle Field Holographic Reconstraction And The Image Processing Technology

In particle field holography, the data reconstruction and processing system is a very important part, which gets particle field image from the hologram and processes the image to extract the particle size distribution, the particle location, the particle total number and the particle velocities. To establish a system like that, this thesis conducts theoretical and experimental research in detail.1. On the particle field hologram reconstruction and data processing, the purpose and background have been introduced, and the development has been overviewed. The basic in-line Fraunhofer holography theory and some image processing technologies have been discussed in detail.2. The question about how Jo build an in-line Fraunhofer holography reconstruction system has been discussed in detail. A holography reconstruction system has been constructed with resolution less than 3 micro-meters. In the system, an automatic image reconstructing and capturing program has been developed, which realize the auto control of holographicreconstruction and image capturing firstly in domestic. The system has been used in holography experiment to measure high speed particle field, and many reconstructed results have been obtained.3. Several image processing techniques have been studied and applied in the reconstructed image, including contrast stretching, low-pass filtering, median filtering, and image-subtraction. A new low-pass filter has been designed to restrain the noise in image. By subtracting a background image got by removing hologram in holographic reduction light path, the adding noise induced by the holographic reconstruction system was eliminated.4. The image segmentation technique based on edge detection has been studied and applied in the reconstructed image. Using three threshold evaluation techniques and an error revising method, a new variable threshold technique has been given out. On this base, a region growing technique has been used to re-segment the image. Thus the automatic image processing has been realized, and the question how to segment the image in which there are less particles on some region and more in others, has been solved.5. The real sizes of particles has been achieved by compare the diameters of particles to a criterion silk set up in the particle field in pixels. Moreover, the technique for processing the three-dimension particle field has been researched.6. Seven kinds of particle target with different sizes have been used to detect the error of the holographic reconstruction and data deriving system. The maximum relative error of particle sizes is about ±14%.