Lens distortion in optically coupled digital x-ray imaging.
Lens distortion in optically coupled digital x-ray imaging.
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DOI：
10.1118/1.598956
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发表时间：
2000-05
期刊：
影响因子：
3.8
通讯作者：
H. Liu;H. Jiang;L. Fajardo;A. Karellas;W. Chen
中科院分区：
文献类型：
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作者：
H. Liu;H. Jiang;L. Fajardo;A. Karellas;W. Chen
本研究的目的是分析由光学耦合数字x射线成像系统中的中继透镜引入的几何畸变，并引入一种算法来纠正这种畸变。方法采用透镜耦合CCD （charge coupled device，电荷耦合器件）样机，实验测量了中继透镜在数字x射线成像中的径向和切向误差。提出了一种算法来校正这些畸变。该算法基于标准标定网格的x射线图像，首先确定光轴的位置，然后利用多项式变换技术对径向和切向畸变进行校正。结果对晶状体畸变进行了分类，采用多项式变换对晶状体引起的径向畸变和切向畸变进行了校正。对于所研究的特定镜头- ccd样机，通过校正算法将中继镜头引起的平均位置误差从约8个像素（0.69 mm）减小到小于1.8个像素（0.15 mm）。我们的研究还表明，四阶多项式的校正算法提供了最好的校正结果。结论在位置依赖的定量x射线成像中应考虑透镜畸变，通过适当的算法可以使CCD x射线成像中的透镜畸变最小化，如本文所示。
UNLABELLED The objectives of this research are to analyze geometrical distortions introduced by relay lenses in optically coupled digital x-ray imaging systems and to introduce an algorithm to correct such distortions. METHODS The radial and tangential errors introduced by a relay lens in digital x-ray imaging were experimentally measured, using a lens-coupled CCD (charge coupled device) prototype. An algorithm was introduced to correct these distortions. Based on an x-ray image of a standard calibration grid, the algorithm first identified the location of the optical axis, then corrected the radial and tangential distortions using polynomial transformation technique. RESULTS Lens distortions were classified and both radial and tangential distortions introduced by lenses were corrected using polynomial transformation. For the specific lens-CCD prototype investigated, the mean positional error caused by the relay lens was reduced by the correction algorithm from about eight pixels (0.69 mm) to less than 1.8 pixels (0.15 mm). Our investigation also shows that the fourth order of polynomial for the correction algorithm provided the best correction result. CONCLUSIONS Lens distortions should be considered in position-dependent, quantitative x-ray imaging and such distortions can be minimized in CCD x-ray imaging by appropriate algorithm, as demonstrated in this paper.