【作者】 赵廷玉；

【导师】 余飞鸿；

【作者基本信息】 浙江大学 ， 光学工程， 2009， 博士

【摘要】 波前编码解码系统,一种光学编码和数字解码两步成像系统,可以获得传统光学成像系统无法达到的超大景深。首先,物体通过三次相位掩模调制的光学系统在像面上成中间模糊像,且保证大景深范围内所成的像的模糊程度一致;然后,利用中间像模糊程度一致的特点,利用频域或空间域等各种算法对它们进行图像恢复,从而得到最终清晰像。这项技术无论是在军事还是在民用的光学成像系统上都具有非常广阔的应用前景。首先,本文首次从傅立叶光学的角度分析倾斜入射对光瞳的影响:对点扩散函数(PSF)来说,大视场会造成边扩展效应和扭曲效应;对于调制传递函数(MTF)来说,大视场会直接造成数值的降低。因此,视场效应对最终的解码图像会产生不利影响。其次,本文首次提出了基于主流光学软件的波前编码光学系统的设计思路,首次提出利用控制光瞳面的主光线最大入射角来抑制视场效应。通过两个设计实例,不但印证了理论推导得到的视场效应;而且证明了视场效应的抑制手段在实际的光学系统设计中取得了明显的效果。第三,本文首次提出了基于MTF的TSVD图像恢复算法和基于反镜像边界条件和直积分解的双共轭梯度平方稳定的图像恢复算法。前者是直接法,适用于需要实时显示的场合;后者是迭代算法,速度虽慢却效果很好。两种算法都较传统的算法大大减小了计算量,取得了更好的恢复效果。尤其是后者,在保留了更多图像细节的前提下,有效地抑制了图像边缘和物体边界的振铃效应。然后,我们给出了波前编码解码系统的硬件和软件实现方案。硬件上,本文从光学机械结构和电路两个方面进行详细地介绍。软件上,介绍了以波前解码为核心的图像处理流程。最后,我们通过一个大景深大视场波前编码系统的实际系统给出了实验结果。实验结果表明:基于光学软件的设计手段成功实现了大景深大视场波前编码成像系统。通过双共轭梯度平方稳定算法进行解码,不但消除了维纳滤波算法中存在的振铃效应,而且保留了更多的细节,取得了很好的图像恢复效果。更多还原

【Abstract】 Wavefront coding system, a two-step imaging system including optical encoding and digital decoding, can achieve deep depth of field which is impossible for traditional optical imaging systems. Firstly, intermediate blur images will be obtained in the image plane by the imaging system with a CPM (Cubic Phase Mask) added in the pupil plane. The wavefront coding system has almost the same PSFs (Point Spread Function) within the deep depth of field due to the CPM. Then final sharp images will be obtained based on various image restoration algorithms by using the PSF as the decoding core in frequency or space domain. This technique will be widely used in optical imaging systems for either military or civil use.Firstly, pupil with arbitrary incidence is analyzed for the first time based on Fourier optics theory. The results show that the wide viewing incident angle leads to side-extension and skew-effect for the PSF; it also leads to the decrease of MTF (Modulation Transfer Function). Therefore, it will cause bad effect on the final decoded images.Secondly, we proposed a novel design method for wavefront coding system based on widely-used optical design software. In order to suppress the wide viewing angle effect, we proposed a new method for the first time to control the maximum incident angle of chief rays on the pupil plane. Two design examples show that the wide viewing angle effect is obvious in practical system; and the method we proposed is effective and obvious in practical system design.Thirdly, two novel wavefront decoding algorithms in space domain are proposed. One is image restoration based on TSVD (Truncated Singular Values Decomposition) by using MTF as singular values, and the other is Bi-CGSTAB (BiConjugate Gradient Square Stable Methods) image restoration algorithm based on anti-reflective boundary conditions and Kronecker production approximation. Compared to traditional method, both of them reduce the computation and have better restoration results. The former belongs to direct method, which is suited for real-time restoration; while the latter is iteration method, which suppresses the ringing effect of the image borders and edges with more details maintained.Fourthly, we introduce the hardware and software of the system. Optical-mechanical system and circuit are introduced as hardware; while image process with wavefront decoding as the core is introduced as the software.Finally, we give the experiment results of a wavefront coding system with deep depth of field and large viewing angle. The results show that a wavefront coding imaging system with deep depth of field and large viewing-angle can be obtained successfully by using the design method based on optical design software. Compared to Wiener filter, better restored image has been obtained based on Bi-CGSTAB with ringing effect suppressed and details maintained.更多还原