菲涅耳半波带法计算振幅的理论误差讨论

ERROR DISCUSSION IN CALCULATION OF THE DIFFRACTION AMPLITUDE WITH ZONE CONSTRUCTION OF FRESNEL

在利用半波带法计算菲涅尔衍射的振幅时，通常不考虑半波带内的面元到场点之间光程不同引起的相位变化．笔者考虑了这一相位变化，理论推导得到了点光源照明的菲涅尔衍射的振幅表示式，得出了与传统解法不同的结果，发现二者间存在较大的误差，该误差对具体实例有较大的影响．因此，利用半波带法计算振幅时应当注意半波带内的面元到场点之间光程不同的影响．

When calculating the amplitude of Fresnel diffraction with zone construction of Fresnel, we traditionally do not consider the phase changes which are introduced by optical path changes between area elements inside a zone construction of Fresnel and the point at which the light disturbance is determined. The amplitude of Fresnel diffraction is analyzed when the phase change is considered in this paper. The amplitude expression is given when a point source is used. The expression is different from the traditional solution. There are errors between them when they are used to solute examples. Thus the effect of phase change should be considered when zone construction of Fresnel is used to analyze some problems.