高斯核函数在角膜地形图仪图像处理中的应用

Gaussian Kernel Applied to Corneal Topography Image Processing

角膜地形图仪作为角膜检测的重要仪器,采集和分析人眼的Placido图像,检测图像亮环中心线的坐标信息,绘制反映角膜表面形状的角膜地形图.对角膜地形图仪的图像处理技术进行了深入研究,提出一种基于高斯核函数的Placido图像处理方法,用离散的高斯卷积核描述连续高斯核函数,用泰勒多项式描述灰度曲线表达式,建立亮环检测的判别表达式,该方法获得了精确的亚像素点坐标信息.利用标准球验证算法精度,屈光度平均误差小于0.25D,满足人眼角膜检测的要求.

Corneal topography is one of the most important equipments in anterior-segment ophthalmology,particularly in the study of corneal shape.By capturing Placido image,detecting bright circles,corneal topography can be draw with relevant algorithm.A new approach to the extraction of bright circles from Placido images is proposed.The approach is based on computing a second order Taylor polynomial for each sub-pixel in the image by convolution with derivatives of a Gaussian smoothing kernel.Line points are found based on differential geometric properties of this polynomial： they are required to have a vanishing gradient and a high curvature in the direction perpendicular to the line.Accuracy coordinate is obtained and mean deviation of diopter is below 0.25D.