基于placido盘的角膜图像采集系统的研制

发布时间：2018-11-21 15:15

【摘要】：角膜地形图仪是现代眼科医学检测中重要的测量仪器，其主要用作人眼角膜表面形貌特征的定量检测，可将眼角膜表面的形貌信息用数据或处理图像的形式给出，为眼科医生对角膜测量提供方便，普遍应用与角膜病症的检查（如圆锥角膜），激光近视手术前的角膜形貌检查，硬性透气性隐形眼镜（RGP）以及角膜塑形镜（OK镜）验配时的角膜测量中。 本课题是基于placido盘的角膜地形图仪开发中的角膜图像采集部分的研究，主要包括：角膜图像采集系统中CCD的选型及驱动设计、图像采集系统中投射系统设计、角膜图像采集系统光学系统设计与实现三个部分。本文将对以上三个部分分别进行探讨。 针对角膜图像采集要求，选用索尼公司ICX424AL面阵CCD作为图像采集系统的图像传感器。分析了ICX424AL的驱动时序要求，在应用高性能模拟前端处理芯片AD9949A和ALTERA公司的MAX2系列EPM240T100C5N共同为CCD提供驱动脉冲信号的基础上，采用Verilog硬件描述语言实现驱动时序的逻辑设计，利用ALTERA公司的软件QuartusⅡ软件进行功能仿真，并针对EPM240T100C5N芯片进行了硬件适配，最终实现了对ICX424AL驱动设计。投射系统设计包括placido盘和背光源的设计，要实现角膜表面形貌的采集首先要使投射系统在人眼角膜上产生清晰、均匀、柔和的圆环像，为此对placido盘的结构和制作工艺进行了深入的探讨，并设计了背光源的电源驱动。 根据系统设计要求选用一种初始的光学透镜结构，用CODEV光学设计软件对该光学结构进行了优化设计，实现了焦距为20mm，视场角20°，入瞳直径为2mm的光学系统。 通过研制的角膜图像采集系统对眼角膜图像进行采集，placido盘在眼角膜上投射的同心圆环满足了上位机对角膜图像进行计算的精度要求。实现了对人眼角膜图的清晰采集，采集图像的分辨率为640（H）×480（V），图像的采集速率为60fps，通过与意大利CSO型角膜地形图仪中的图像采集系统进行对比，证明设计的图像采集系统达到了图像处理软件对角膜表面采样点的提取要求。
[Abstract]:Corneal topography is an important measuring instrument in modern ophthalmological examination. It is mainly used for the quantitative detection of the surface morphology of human cornea. The topography information of the corneal surface can be given in the form of data or image processing. It is convenient for ophthalmologists to measure cornea. It is widely used in the examination of corneal diseases (such as keratoconus), and in the examination of corneal morphology before laser myopia surgery. (RGP) and OK were used to measure the cornea of rigid gas permeable contact lens. This subject is a part of corneal image acquisition in the development of corneal topography instrument based on placido disc. It mainly includes the selection and driving design of CCD in corneal image acquisition system, and the design of projection system in image acquisition system. The optical system of corneal image acquisition system is designed and implemented. The above three parts will be discussed in this paper. According to the requirement of corneal image acquisition, Sony ICX424AL array CCD is selected as the image sensor of the image acquisition system. The driving timing requirements of ICX424AL are analyzed. Based on the application of high performance analog front-end processing chip AD9949A and MAX2 series EPM240T100C5N of ALTERA Company to provide the driving pulse signal for CCD, the logic design of driving timing is realized by Verilog hardware description language. The software Quartus 鈪，

本文编号：2347353