Fine structure in Fresnel diffraction patterns and its application in optical measurement

The function of light intensity distribution of Fresnel diffraction from an opaque fibre is derived, and the fine structure in the diffraction pattern is theoretically described. In this paper, the relationship between fibre diameter and fine structure in the diffraction pattern is given. The fine structure can be used to measure the diameter of fibres, and measuring subscript limits may be greatly squeezed. Several fibres of different diameters are measured by means of the fine interference fringe in the diffraction pattern, and experimental results show the improved diffraction technique is highly reliable with higher precision compared with the original technique.