适用于眼镜片轮廓数据的分段拟合算法

Piecewise fitting for the contour data of the spectacle lens

由于像素精度的限制,从图像中提取的眼镜镜片轮廓数据中存在大量的锯齿形轮廓分段,严重影响轮廓数据的光顺与精度。为了得到光滑的轮廓曲线,对原始的轮廓数据作分段拟合处理:首先根据目标点前后的曲线方向估算轮廓上每一点的曲率,然后将轮廓上曲率大致相同的轮廓段根据最小二乘原理拟合成圆,最后将剩余的轮廓段进行基于Bézier曲线的保形拟合。实验结果表明相较于已有的平滑处理算法,所述分段拟合算法在得到光滑轮廓曲线的同时具有更高的精度,证明了分段拟合算法可用来作眼镜片轮廓曲线的平滑处理。

Due to the limitation of pixel accuracy, there are a large number of sawtooth contour segments in the spectacle lens contour data extracted from the image, which seriously affects the smoothness and accuracy of the contour data. In order to obtain a smooth contour curve, performs segmental fitting processing on the original contour data: firstly, the curvature of each point on the contour is estimated according to the curve direction before and after the target point, and then the contour segments with roughly the same curvature on the contour are calculated according to the least squares. The principle is to fit a circle, and finally the remaining contour segments are conformally fitted based on the Bézier curve. The experimental results show that compared with the existing smoothing algorithm, the segmented fitting algorithm described has higher accuracy while obtaining a smooth contour curve. It is proved that the segmented fitting algorithm can be used to smooth the contour curve of the spectacle lens.