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为实现角膜地形图仪中实时图像检测,找到一种图像清晰度评价函数对实时角膜图像进行快速、稳定、精确的判别至关重要。基于角膜地形图仪中光学成像系统,分析系统离焦对图像清晰度的影响,并提出一种关于图像清晰度的评价方法。该方法选择拉普拉斯函数作为全局图像粗调的评判参数,通过霍夫圆变换及亚像素边缘检测来确定图像的中心点,并采用Sobel算子与Canny算子相结合的边缘检测方法根据中心点找出最清晰边缘,从而实时获得最清晰的角膜图像。实验表明,该方法具有很好的稳定性和抗噪性,能够准确、有效地评价角膜图像的清晰度,可用于角膜地形图仪中实时图像的精准检测。
In order to realize the real-time image detection in corneal topographer, finding an image sharpness evaluation function is of great importance for the rapid, stable and accurate discrimination of real-time corneal images. Based on the optical imaging system in the corneal topography instrument, the influence of system defocus on image sharpness is analyzed, and a method of evaluating the image sharpness is proposed. The Laplacian function is chosen as the evaluation parameter of the global image coarse adjustment. The center point of the image is determined by Huff’s circle transform and sub-pixel edge detection. The edge detection method based on Sobel operator and Canny operator is adopted. Center to find the clearest edge, so as to get the clearest cornea images in real time. Experiments show that the method has good stability and anti-noise, can accurately and effectively evaluate the clarity of corneal images, and can be used for accurate detection of real-time images in corneal topographers.