近场衍射图样的抽样定理处理方法

Approach of Near Field Diffraction Patterns by the Sampling Theorem

提出近场衍射图样的抽样定理处理方法。在近场衍射中，孔径和衍射场分布为或近似为空间有界物，在其频域中抽样可以比较精确地恢复衍射场的分布。衍射场频谱带宽的近似值由频谱的幅值大于中心频谱极大幅值的１％的频率范围所确定。在此带宽内对频谱抽样，抽样间距与观察处的带宽成正比，与孔径函数的空间带宽积成反比。对于线度小于波长的狭缝和圆孔的近场衍射图样的计算结果都与他人理论和实验结果相一致。

The method of approaching the near field diffraction patterns by sampling theorem is proposed. In the near field diffraction, the aperture is well defined space function, and approximately so does the diffraction field distribution. The diffraction field can be restored with rather high precision by sampling function in its spatial spectrum. The approximate value of the spectrum bandwidth of the diffraction field is the region in which the spectrum amplitude is larger than 1% of the maximum of its center spectrum. The spatial spectrum is sampled in this bandwidth. The sampling space is proportional to the bandwidth and inversely to the space bandwidth product of the aperture function. The calculation results of the near field diffraction patterns of slit and circle apertures with the size smaller than the wavelength are coincided with other theoretical and experimental results. The sampling method has advantages of direct perceivable and forthright.