Speckle Reduction and Three-Dimensional Image Reconstruction of Digital Holography
|School||Zhejiang Normal University|
|Keywords||Digital holography Three-dimensional reconstructed image Laser speckle Strength superposition Synthetic aperture digital holography Phase unwrapping Dual- wavelength digital holographic profilometry|
In recent years, with the advances in computer technology and peripherals, digital holographic research applications in full swing, a very wide range of research involved, mainly covering the shape measurement reconstruction algorithm for digital holographic microscope, the reconstructed images improved image quality a range of areas. Hologram reconstruction algorithm is one of the important issues of digital holography, Numerical Reconstruction of the proposed algorithm is limited to two-dimensional reconstructed image research, and may not fully reflect the complex objects in three-dimensional information lost holography has The biggest advantage. This paper studies the digital holographic three-dimensional reproduction of image reconstruction. The digital holography noise the reconstruction of three-dimensional reproduction like a very big impact. The presence of noise not only affects the image quality reconstructed image, and makes the three-dimensional reconstructed image distortion. Reduce or even eliminate the noise of various three-dimensional image reconstruction. So this article for digital holographic three dimensional reproduction image reconstructed research work is divided into two steps, the first step is to hologram the denoising processing to obtain high quality hologram; The second step is the reconstruction algorithm 3D hologram reproduction like. This thesis is divided into five chapters, the main contents are as follows: the first chapter, the development and implementation of digital holography, digital holography have a general understanding of, and then analyze the digital holography the denoising and digital holographic three-dimensional shape measurement Research. Chapter II of the basic theory of digital holography, lensless Fourier transform digital holography highlights. Chapter III, on the basis of the analysis of laser speckle causes, proposed both reduce laser speckle method: the reconstructed image of strength superposition and synthetic aperture digital holography. We will combine two methods to obtain large-size high-quality hologram, not only to improve the resolution of the reconstructed image, and greatly reduce the impact of laser speckle, which laid the foundation for the next step in this article. Chapter IV, focusing on digital holographic 3D reconstructed image obtained by phase. Chapter on the basis of the research phase with the surface of the object coordinates corresponding relationship, the first through the Fresnel diffraction reproducing algorithm to obtain the phase of the object, but the resulting phase is between (-π, π] wrapped phase commenced in order to obtain continuous phase, we propose two methods, one approach is the Fourier transform of the phase unwrapping algorithm; Another method is the dual-wavelength digital holographic profilometry former better noise immunity, fast calculation, but very complex structure or surface gradient The large object failure; latter eliminating the need for phase unwrapping process, direct access to the real phase, but requires a similar wavelength laser to obtain the equivalent wavelength experiments require a relatively high fifth chapter, the work of the full text Summary and Outlook. innovation of this paper: the first strength superposition method with synthetic aperture digital holography combined with large-size high-quality hologram, then asked the phase of the Fourier transform phase unwrapping algorithm expand and calculated the shape of the three-dimensional surface of the object digital holography and 3D measurement technology is a popular research topic, not only is a major advance in digital holographic research, and further expand the applications of digital holography will give full play to the digital holography The inherent advantages.