由多边形小孔的远场衍射解释灯光的星芒

Explanation of the spikes of light using the far-field diffraction of polygon apertures

用光的衍射理论证实了相机感光元件记录的图样为光圈的远场衍射图样,揭示了灯光星芒的成因.由数值计算可得:当多边形衍射孔的边数n为奇数时,星芒有2n条;n为偶数时,星芒有n条.若光圈的边为直线,则衍射图样为光刺;若光圈的边为圆弧,则衍射图样为光柱.实验观察了正三、四、五、六、八边形孔的远场衍射图样,并对比了正六边形孔衍射条纹到中心的距离、各级衍射条纹的相对亮度的实验和理论结果,两者符合说明了理论分析的正确性和数值算法的有效性.

The diffraction theory of light confirmed that the pattern recorded by the photosensitive element of camera was the far-field diffraction pattern of the aperture,which revealed the origin of the light star.The numerical calculation results indicated that there were 2 nstars when the number of edges of the polygon diffraction hole n was odd;there were nstars when n was even.If the edge of the aperture was straight lines,then the diffraction pattern was light stab;If the edge of the aperture was arc,the diffraction pattern was light beam.The far-field diffraction patterns of trilateral,quadrangle,pentagonal,hexagonal and octagonal holes were observed experimentally,and the experimental and theoretical results of the distance between the diffraction fringes of the hexagonal holes and the relative brightness of the diffraction fringes at all levels were compared.