【作者】 黄晨曦；

【导师】 刘华锋；

【作者基本信息】 浙江大学 ， 测试计量技术及仪器， 2013， 博士

【摘要】 沙克哈特曼波前传感器可以用于激光光束质量诊断,激光整形,光学元件和光学系统检查,大气扰动测量,实时控制,以及高功率激光器系统等各个领域。由于它易操作,便于实时探测,而且可以直观地显示波前畸变分布,因而受到学者的广泛关注。科学家哈特曼于1900年首次提出了Shack—Hartmann波前探测技术,后来科学家沙克对其进行了改进,将原来的哈特曼光阑换成微透镜阵列,从而大大提高了探测精度和光能利用率。然而,由于受到背景暗电平,高斯白噪声等因素的干扰,传统的质心算法误差较大,无法得到精确的结果,从而影响到相位图像。另外,由于工艺制作上的约束,其微透镜尺寸大小一直是限制其分辨率的一个瓶颈。它的探测精度以及分辨率的高低,对于整个光学系统的工作性能,将产生非常重要的影响。本文主要尝试对沙克哈特曼波前传感器光学系统所面临的一些技术问题进行研究,并探讨了沙克哈特曼波前传感器在细胞探测上的应用。论文的主要内容及贡献如下：一、初步建立了沙克哈特曼光波传感器的模拟系统,并采用数值模拟方法,分别使用平面波和高斯光束对其进行模拟照射,还计算了不同斜率的高斯光束照射下,通过标准的传统一阶矩质心算法实际测得的斜率,从而验证了本模拟系统的可靠性。接着,在传统一阶矩算法的基础上,使用高阶矩算法、加阈值的一阶矩算法等不同的质心探测方法进行了改进,比较了它们在各种条件下的测量误差与探测精度；同时,还发现各种质心算法的测量精度与畸变程度、以及图像信噪比等实验参数有关。二、搭建了沙克哈特曼传感器的硬件平台,利用空间光调制器产生了各种涡旋光场,并在远场探测到了其强度信息。我们还分析了传统探测算法存在的问题,分别提出了相关匹配算法和混合重心法。我们详细介绍了这两种方法的原理,并将空间光调制器上光涡的位置分别在水平方向和垂直方向平移,分别用这两种方法探测光涡的精确位置。我们对这两种方法进行了比较,从而能在很短的运行时间内,将沙克哈特曼传感器的分辨率从原来的微透镜尺寸级别提高到像素级别。三、将沙克哈特曼波前传感器应用于细胞探测上,用它搭建了定量相位显微镜光学平台。通过我们的改进,光学系统被大大简化,而且由于避免了使用干涉时引入的噪声,从而使探测精度提高。为了测试其对复杂结构样本的成像能力,我们将其应用于多层样本折射率分布的探测,包括单层聚苯乙烯微珠、双层聚苯乙烯微珠等。我们还将产生的三维折射率图像进行了三维可视化处理,搭建了VTK平台,使用了面绘制中的MarchingCube算法和体绘制的Raycasting算法,从而实现了三维相位图像的三维可视化和人机交互。更多还原

【Abstract】 The Shack Hartmann wavefront sensor(SHWS) has been widely applied in laser beam quality diagnosis, laser shaping, optics and optical system diagonals, atmospheric turbulence measurement and real-time control, high power laser system and other fields. Due to the advantages such as easy operation, short response time, and convenience to comprehend the wavefront modes., it received extensive attention of scholars. In1900,Hartmann for the first time proposed the Shack-Hartmann wavefront detection technology. After that, Shack replaced the original Hartmann diaphragm with micro lens array, which greatly improved the detection precision and light energy utilization. However, due to the background level, Gaussian white noise and other factors, the traditional centroid algorithm error is large, which leads to inaccurate results, and finally affect the phase image. In addition, due to the constraints of the production process, the micro lens size has always been a bottleneck of restricting its resolution. Its detection accuracy and resolution, is important for the performance of the whole optical system.We focus on some technology problem that the SHWS optical system has faced, and discuss its application on cell detection. The main contents are as following:Firstly, we constructed a SHWS simulation system, and utilized different centroid detection methods, such as higher moment centroid method, the threshold weighted pixel average algorithm, and compared the detection error and detection accuracy in different situation.Also, we set up a SHWS optical system platform and produces all kinds of vortex light field. After that, we analyzed the problems existing in the traditional detection algorithm, and proposed the correlation matching method and hybrid centroiding method. We can increase the resolution from the level of lenslet size to that of pixel size in a short time.Thirdly, the SHWS was applied in cell detection. We set up a quantitative phase microscope optical platform using SHWS. Through our improvement, the optical system will be greatly simplified, and the detection accuracy was improved. In order to test its imaging ability, we applied it in multi-layer sample detection of the refractive index distribution, including monolayer polystyrene beads, double polystyrene beads, etc. We also set up a VTK platform to process the produced three-dimensional refractive index images. We used MarchingCube algorithm and Raycasting algorithm, respectively, to realize the visualization of the three dimensional phase image and human-computer interaction.更多还原