Focal shifts in diffracted converging spherical waves
Focal shifts in diffracted converging spherical waves
复制标题
DOI：
10.1016/0030-4018(81)90108-5
复制
发表时间：
1981-10
影响因子：
2.4
通讯作者：
Yajun Li;E. Wolf
中科院分区：
文献类型：
--
作者：
Yajun Li;E. Wolf
从许多出版物中已知，当会聚的单色球面波在圆孔处衍射时，衍射波的最大强度点可能不在入射波的几何焦点处，而是可能位于更靠近孔的位置。本文指出，当入射波为均匀入射，半孔径角较小时，光强最大点的位移Δ f与几何焦点到孔径平面的距离f f的比值仅取决于从几何焦点看孔径的菲涅耳数N。当N ≥ 5时，该效应变得显著。例如，当N = 1时，|Δƒ|最大强度约为几何焦点处强度的两倍。
It is known from a number of publications that when a converging, monochromatic spherical wave is diffracted at a circular aperture, the point of maximum intensity of the diffracted wave may not be at the geometrical focus of the incident wave, but may be located closer to the aperture. In the present note we show that when the incident wave is uniform and the angular semi-aperture is small, the ratio of such a shift Δƒ of the point of maximum intensity to the distance ƒ between the geometrical focus and the plane of the aperture depends only on the Fresnel numberNof the aperture when viewed from the geometrical focus. The effect becomes significant whenN≲ 5. WhenN= 1, for example, |Δƒ| ≈ 0.4 ƒ and the maximum intensity is approximately twice as large as the intensity at the geometrical focus.