中子半影成像中椭圆度误差的解析计算
Analytic calculation of ellipticity error effect in neutron penumbral imaging
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摘要: 通过几何光学的方法为双锥孔中子半影成像过程建立了解析计算模型，得到了成像过程中中子吸收路径长度的解析表达式，导出了普适的成像传递函数解析表达式。利用模型数值模拟分析了锥孔加工中的椭圆度误差造成的图像畸变；得到了不同椭圆度偏差下系统传递函数的变化，及其对圆形物成像重建的影响。结果表明，小于0.01的椭圆度偏差对成像重建带来的影响可以忽略。与传统的Monte-Carlo方法相比，解析建模方法在速度上有较大的优势，且能够方便地推广到其他编码成像系统中。Abstract: Using a geometrical optical method, a model for analytic calculation about ellipticity error effect in neutron penumbral imaging is established. An analytic formula of neutron absorbing length is derived from the model, and a general analytical expression for neutron penumbral imaging process is achieved. Based on this model, a numerical simulation of image aberration caused by ellipticity error is realized. The point spread functions under various ellipticity errors and their effects on a round object’s reconstruction are obtained. A semi-quantitative result shows that the effect on imaging quality can be omitted when the ellipticity error is less than 0.01. Compared with the Monte-Carlo method, the analytic model is more effective in computation and easy to apply to other similar code i
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Key words:
- penumbral imaging technique /
- analytic model /
- modulated transfer function /
- ellipticity
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