Numerical calculation of near field scalar diffraction using angular\n spectrum of plane waves theory and FFT

t is a known fact that near field diffraction or Fresnel diffraction\ncalculations are difficult to perform exactly. It is in general necessary to\nmake some approximations in order to obtain a more suitable form. In this work,\na numerical implementation based on angular spectrum theory for near field\ndiffraction is presented. The method uses Fast Fourier Transforms (FFT) and it\nturns out to be accurate and fast. In order to show the capabilities of the\nmethod, diffraction near field for a circular aperture and a spiral slit are\nstudied. Numerical and experimental results are shown. This method could be\nuseful to implement pc based physical optics learning.\n