扩展景深的波前编码系统相位掩膜板研究

发布时间：2018-02-28 15:20

  本文关键词： 波前编码 调制传递函数 相位掩膜板 光学传递函数 点扩散函数　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：大景深(DOF)光学成像系统可以获取物体更为丰富的信息,使获得的景物信息更接近于真实的世界,在过去的近半个世纪里,人们努力寻求着各种各样的方法来扩大光学系统的DOF。波前编码(WFC)技术是近年新兴的光学成像技术,其重要的应用之一便是扩展光学系统DOF。WFC技术作为一种光学数字混合成像技术,其通过在传统非相干成像系统光瞳位置进行相位调制来记录编码图像,并利用数字图像处理技术对编码图像进行解码,以达到系统性能的提升。WFC系统中,相位掩膜板实现波前的相位调制,如何设计及优化相位掩膜板是WFC系统设计的关键。基于此,本文致力于WFC系统的相位掩膜板研究,力求获取更为优越的扩展DOF成像性能。开展了扩展DOF的非对称相位掩膜板研究。从空域和空间频域分析了非对称相位掩膜板WFC系统的成像特性,说明了非对称相位掩膜板设计过程中需考虑的约束条件,建立了非对称相位掩膜板WFC系统像质评价模型。针对非对称相位掩膜板编码和解码特性,为获取更为稳定的编码过程离焦不变的成像特性,并在解码过程有效抑制伪像和噪声,研究了非对称相位掩膜板相位函数。依据相位函数研究结果,获取了四种新形式的非对称相位掩膜板,并展开了性能比对研究,验证了新形式相位掩膜板在扩展DOF成像中的优越性能。开展了扩展DOF的共轭非对称相位掩膜板研究。单一非对称相位掩膜板产生的点扩散函数(PSF)在理论焦面存在偏移,则解码图像中包含伪像,成像质量有一定的下降,这严重影响了系统的扩展DOF性能。基于此,提出了基于共轭非对称相位掩膜板对的扩展DOF成像方法,该方法可产生几乎随离焦不变的PSF,使系统离焦不变特性获得提升。该共轭成像方法可在保证离焦不变特性的同时,有效改正伪像。开展了扩展DOF的径向对称相位掩膜板研究。由于径向对称相位掩膜板产生的PSF具有对称特性,因而复原后的图像不会存在伪像,但其离焦不变特性较径向对称相位掩膜板有所下降。基于此,为提升对称相位掩膜板WFC系统的离焦不变特性,在径向对称相位掩膜板WFC系统成像特性研究的基础上,研究了径向对称相位掩膜板的相位函数,提出了两种新形式的径向对称相位掩膜板,并通过仿真实验验证了提出的相位掩膜板可获取更为稳定的离焦PSF和调制传递函数(MTF)。
[Abstract]:The large depth of Field (DOF) optical imaging system can capture more information about objects and bring them closer to the real world, in the last half century, People are looking for various ways to expand the optical system DOF.Wavefront coding (WFC) technology is a new optical imaging technology in recent years, one of its important applications is the extended optical system DOF.WFC technology as an optical digital hybrid imaging technology. The coded image is recorded by phase modulation in the pupil position of the traditional incoherent imaging system, and the coded image is decoded by digital image processing technology, so as to improve the performance of the system. How to design and optimize the phase mask board is the key to the design of WFC system. Based on this, this paper focuses on the study of phase mask plate in WFC system. In order to obtain better imaging performance of extended DOF, the asymmetric phase mask of extended DOF is studied. The imaging characteristics of asymmetric phase mask WFC system are analyzed in spatial and spatial frequency domain. The constraints to be considered in the design of asymmetric phase mask are explained, and the image quality evaluation model of asymmetric phase mask WFC system is established. The encoding and decoding characteristics of asymmetric phase mask are analyzed. In order to obtain more stable defocus invariant imaging characteristics of the coding process and effectively suppress artifacts and noises in the decoding process, the phase function of asymmetric phase mask is studied. Four new types of asymmetric phase mask are obtained, and the performance ratio studies are carried out. The excellent performance of the new type of phase mask in extended DOF imaging is verified. The conjugate asymmetric phase mask of extended DOF is studied. The point diffusion function generated by the single asymmetric phase mask is offset in the theoretical focal plane. Then the decoded image contains artifacts and the imaging quality decreases, which seriously affects the extended DOF performance of the system. Based on this, an extended DOF imaging method based on conjugate asymmetric phase mask pair is proposed. This method can produce PSF with almost defocus invariance, and improve the system defocus invariance. The conjugate imaging method can guarantee the defocus invariant property at the same time. Effective correction of artifacts. The radial symmetrical phase mask plate of extended DOF is studied. Because the PSF produced by radial symmetric phase mask plate has symmetry characteristics, there is no artifacts in the reconstructed image. However, the defocus invariance is lower than that of the radial symmetrical phase mask. In order to improve the defocus invariance of the symmetrical phase mask WFC system, the imaging characteristics of the radial symmetric phase mask WFC system are studied. The phase function of radial symmetric phase mask is studied and two new types of radial symmetric phase mask are proposed. The simulation results show that the proposed phase mask can obtain more stable defocus PSF and modulation transfer function (MTF).
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN919.81
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本文编号：1547869