Abstract: An analytic expression in terms of Bessel＇ s functions or Lommel＇ s functions of two variables, is obtained for the intensity distribution of the Fresnel diffraction by a circular aperture. The Fresnel pattern in any transverse plane at an axial distance from the aperture is then easily computable using commonly available software packages. Comparison with Burch＇s theoretical results（in 1985） is made and satisfactory agreement with experiment is found. The light intensity patterns are recorded by the use of CCD camera, which may be adapted as a student experiment in universities.

Key words: circular aperture, Fresnel diffraction, Bessel function, Lommel function, CCD camera