QQ客服 官方微博 反馈留言

题名	大焦深光学成像技术的相空间方法研究
作者	阳庆国
学位类别	博士
答辩日期	2007
授予单位	中国科学院上海光学精密机械研究所
导师	刘立人
关键词	焦深 景深 离焦 相空间 波前编码 模糊函数 魏格纳分布函数
其他题名	Optical imaging with extended depth-of-focus by using of phase-space method
中文摘要	成像技术是现代人类获取图像信息的重要途径，然而由于成像系统不完善所引入的像差，特别是离焦像差，使得成像系统限制在一个很小的焦深或景深范围内，在超出成像系统景深范围的物体，因为散焦效应而变得模糊，损失了物体大部分的信息，从而大大降低了成像系统获取更多图像信息的能力。因而突破成像系统的这种局限性，在不改变成像质量的同时，扩大成像系统的焦深，研究大焦深的光学成像技术具有非常重要的意义。 信号的相空间表示是一种空-频（时-频）的联合局域谱表示，它利用相空间表象函数来描述信号的在互成傅里叶变换的变量域中的特性。这种新的数学分析工具与光学系统相结合立刻为光学系统提供一种有价值的信号分析方法。 本论文提出了把相空间分析方法引入到大焦深光学成像技术中，用相空间表象函数来分析和设计大焦深光学成像系统。一方面相空间表象可以十分方便地描述和刻画光学系统的性质，包括系统的焦深特性；另一方面它又可以作为工具用来设计光学系统使之具有大焦深的特点，因而它为研究大焦深光学成像技术提供了一种新的思路和手段。本文围绕大焦深光学成像技术的相空间方法主要开展了如下几个方面的研究： （1）相空间表象模糊函数和魏格纳分布函数应用在圆对称光学系统中时，数学上解析地研究它的形态是不可避免的也是非常具有实际意义的。本文利用级数展开方法求解出了一般圆对称光瞳函数的模糊函数的解析表达式，并同时给出了一种解析近似方法用于简化计算过程。由于光瞳的模糊函数包含了所有的单色离焦光学传递函数，因而模糊函数的解析计算方法可用来有效的计算光学系统的复色光学传递函数，从而为分析圆对称光学系统在复色光照明下的焦深特性提供了手段和依据。 （2）提出了一种扩大焦深的相空间滤波方法。它利用模糊函数作为焦深的设计工具，对光瞳的模糊函数在相空间进行滤波操作，从而使之满足大焦深所应该具有的形态特点。文中从滤波理论出发给出了扩展焦深的滤波函数所应该满足的条件。根据此滤波条件具体设计了几类变迹光瞳函数，并且用一系列的数值分析和模拟成像实验验证了利用此方法设计的光瞳变迹器扩展焦深的有效性。由于滤波器的选择比较方便灵活，并且通过模糊函数的回馈显示又能直接观察到滤波后的效果，因而它是一种直观而便捷的方法。 （3）波前编码成像技术是一项强大的数字成像技术，在扩展成像系统焦深方面有着不凡的表现。先前的理论基础主要是依赖于模糊函数和稳相原理。本文提出了把模糊函数的分析方法扩展到相空间，利用相空间方法分别从几何光学和波动光学的角度详尽的分析了波前编码成像技术的基本原理和成像过程，并且利用相空间表象模糊函数和魏格纳分布函数分别从空域、频域和空-频域充分地展示了波前编码成像系统在扩展焦深方面所具有的优越特性。这项工作弥补了先前理论的不足，有助于更加深入的理解波前编码成像技术的基本思想，对于设计实际的光学成像系统也是非常有益的理论参考。 （4）提出了一种新型的指数相位光瞳掩模板，作为波前编码元件用于扩展成像系统的焦深并对掩模板的关键参数进行了优化设计。为了验证这种元件的在扩展成像系统焦深的可行性，我们把它与经典的三次相位光瞳掩模板在离焦成像时的成像性能做了一系列的比较，比较的结果证明了指数相位调制的波前编码成像系统比三次相位调制的波前编码成像系统在扩展焦深方面有更优的成像性能。
英文摘要	Imaging is an important way to obtain image information for the modern humankind. However, the aberrations, especially the defocus aberration introduced by defects of imaging system, limit the imaging range in a narrow depth of focus. Beyond this range, the image is blurred by the defocus effect and thus most of the image information is lost, this greatly degrades the ability of imaging system for collecting more image information. Therefore, it is significant to break through the limits and to develop an optical imaging system, for which, the imaging quality is maintained while the focal depth is enlarged. The phase-space description of signals is a joint space-spatial frequency representation in local domain. It employ the phase-space representation functions to describe the property of signals between two variables that form a Fourier transform pair and provide a valuable analysis tool for signals when this new mathematical analysis tool applied to an optical system at once. In this thesis, we proposed to introduce the phase-space analysis method to imaging systems and use the phase-space representation functions to analyze and to design the optical imaging system with high focal depth. At one hand, it can conveniently describe and character the optical systems, and at the other hand it can be used as tools to design the optical system so as to own high focal depth property. Therefore, this method provides a new means to study the imaging system with high focal depth. The research works are list as following: (1) It is inevitable and also important to study the analytic form of the phase-space representations, such as the ambiguity function and the Wigner distribution function, on math when these two functions applied to the circularly symmetric optical systems. We solved an analytic expression for the ambiguity function of circularly symmetric pupil function by using the expansion of series and gave an approximate result as well in order to simplify the computation. Since the ambiguity function contains all the monochromatic defocused OTFs, we can use it to efficiently compute the polychromatic OTF of an optical system and thus provide a way to analyze the focal property of an optical system with circularly symmetric pupils under polychromatic illuminations. (2) We proposed a method of enlarging the depth of focus by filtering in phase- space domain. It employs the ambiguity function as design tools to filter the ambiguity function of pupil function in phase-space domain and makes it owning the high focal depth characteristic. From the viewpoint of the filter theory, we roughly give the constraints that the phase-space filter should be satisfied. According these constraints, several sets of apodizers were synthesized and a series of numerical analysis and simulated imaging experiments are performed to verify its effectiveness. Since the filters can be selected flexibly and the results after filtering can also be directly observed by the display of the ambiguity function, it is an intuitionistic and simple method to enlarge the depth of focus. (3) Wave-front coding is a powerful digital imaging technique, it exhibit uncommon performance on extending the depth of focus. The previous theory basis for this technique is mainly the ambiguity function and stationary phase principle. In this thesis, we propose to extend the ambiguity function method to the phase-space and use it to analyze the basic imaging principle and process of wave-front coding from the geometric optics and the wave optics respectively. The excellent characteristic of wave-front coding imaging system on extending the depth of focus are also exhibited by the analysis of the phase-space representation functions, say the ambiguity function and Wigner distribution function, from the space domain, spatial frequency domain and space-spatial frequency domain respectively. This work complements the shortage of the previous theory and can help us comprehensive the basic idea of wave-front coding. It is also beneficial as a theoretical reference to design the actual optical imaging systems. (4) We propose using the exponential phase pupil mask, as a wave-front coding component, to extend the depth of field. The parameters of this mask are optimized by employ an optimization program. In order to attest its effectiveness in extending depth of focus, we compared it with the classical cubic one by a series of evaluations, it is shown that the exponential phase pupil mask provide a slight advantage to cubic one in the performance of extending depth of field.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15438]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	阳庆国. 大焦深光学成像技术的相空间方法研究[D]. 中国科学院上海光学精密机械研究所. 2007.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。