通过引入介电常数与吸收常数随膜层厚度非均匀变化函数来计算非理想调制轮廓体全息光栅的衍射效率，分析其衍射特性。根据Kamiya严格的分层计算方法，推导出了非均匀混合调制轮廓等非理想情况下的二阶耦合微分方程，据此考察了吸收常数及其调制度变化时光栅各级次衍射光的衍射特性，分析了衰减系数及相位振幅光栅异相等因素对光栅角度选择性的影响，给出光栅衍射效率对几何分层的响应程度。通过与Kogelnik和Sabol的计算方法对比，进一步论证了严格算法的准确性。结果表明，光栅衍射效率峰值随吸收常数、衰减系数及相位振幅光栅之间相位差的变化而变化；吸收调制度会小幅度增加效率峰值，但因吸收常数的存在，整体效率不高；分层数对光栅角度选择性和角谱宽度影响较小，分层数与衍射效率的收敛性表明取20层较好。该工作对非理想调制轮廓的体全息光栅衍射效率计算及其特性分析具有一定的参考价值。

A method for calculating diffraction efficiencies of non-ideal volume phase holographic gratings is presented by introducing a function between modulation profiles and depths of gratings. By applying Kamiya rigorous delamination-calculation method, rigorous coupled-wave equation for the non-ideal conditions, such as mixed modulation and attenuated modulation profiles, is expressed. The diffraction characteristics of the phase gratings, mixed gratings, out-of-phase gratings and attenuated gratings are investigated. The response degree of diffraction efficiency to the numbers of sub-regions that have been divided is discussed. Comparing with Kogelnik theory and Sabol model, the accuracy of the algorithm is further demonstrated. The results show that, the peaks of diffraction efficiency change over average absorption constants, attenuated constants and the spatial dephasing between the absorption and phase gratings; absorption modulation causes a modest increase of the peak, but average absorption constants drag the efficiencies of the whole transmission orders. The effect of the numbers of sub-regions that have been divided on the angle selectivity and angular spectrum widths of the grating is small, but it decides the accuracy of the algorithm. The work have a certain reference value for calculating the efficiencies and analyzing the diffraction characteristics of the non-ideal modulation of volume holographic gratings.