Based on diffraction theory a theoretical method for evaluating the three-dimensional focusing performances of the compound X-ray lenses is presented.

给出了基于衍射理论的评价X射线聚焦组合透镜三维聚焦性能的理论方法。

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But the principle of focusing rays through an aperture onto a two-dimensional surface remains the same.

但其原理通过孔径聚焦光线在一个二维表面是保持不变的。

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Years of focusing on close, two-dimensional work causes most children to become at least slightly nearsighted by the age of 10, say the researchers.

研究者表示，多年的近距离的、二维的课业使绝大多数孩子在10岁之前至少是轻度近视。

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