通过理论分析，给出了网栅或光源横向偏离束轴、网栅或光源相对束轴有小角度倾斜、光源不在网栅聚焦点上等失聚焦照相条件下的直穿辐射损失率，计算了利用膜片堆叠制造网栅造成的影响。并通过蒙特卡罗数值模拟验证了理论分析结果。结果表明，网栅失聚焦或膜片堆叠制造的影响相当于网栅孔的尺寸减小，孔内其他位置的直穿辐射量保持不变。

The influence of the source out of the focused grid on the image in high-energy X-ray radiography is studied by theoretic analysis and numerical simulation. Direct radiation loss fractions under the conditions, such as the lateral decentering, the inclination and the source out of the focused distance, are calculated by analysis. Direct radiation loss fraction under grid manufacture by the stack of foil sheets is obtained. The theoretical results are validated using Monte Carlo code. The results show that the conditions of the grid out of focus toward the source and grid manufacture by the stack of foil sheets are equivalent to devalue the hole diameter, meanwhile the transmission inside the hole is held the line.