Fresnel diffraction with small apertures

Fresnel diffraction experiments were conducted with small apertures and a spatially filtered He-Ne beam. The beam was left uncollimated so that a diverging wave was incident on the aperture. This allowed the input radius of curvature to have an effect in determining the location of the Fresnel patterns. The diffraction patterns were magnified onto a 1-in. linear photodiode array of 1024 elements. The imaging system was composed of a 3.8 - mm focal length microscope objective and a 1-m lens. The diffraction-limited entrance f/No.