Mathematical expressions for the irradiance distribution and visibility distribution in the neighborhood of the geometrical image plane of a crossed grating were derived. Two diffracted orders were used as carrier- frequency photography to form the image of the grating. This was achieved by using different spectral profiles for the incident radiations. The profiles of the radiations were considered Gaussian, Lorentzian and Voigte spectral distributions. The results showed that, the visibility of the three profiles have the same behavior and inversely proportional to both the spectral half width of the spectral line and the spatial frequency of the grating. Also the visibility decreases with increasing the number of lines of the grating. Experimental data for the visibility were measured for defocused image at different planes. |
