The present work is to prove the effect of spatial frequency modulation (elimination of the 0$\underline{th}$ spatial frequency spectrum and phase modulation) by comparing the experimental data with the theoretical results derived from Fourier transform optics which is based on Fraunhofer diffraction theory. The optical system used in this experiment consists of the collimating system and the imaging system with unit magnification. The diffraction patterns are observed at the focal plane of the objective where various modulations are conducted.
Each of the intensity distributions(of the spectrum and image) is recorded on the photographic emulsion for photogrammetry. In case of one dimensional phase objects and amplitude objects treated in this work (step, single slit and double slit), the experimental results are in complete agreement with the theoretical results for the schlieren modulation and schlieren plus phase modulation. Among the results, the distinct effect of the elimination of the 0$\underline{th}$ order spatial spectrum is presented with photographs for some materials of special interest (partially polymerized polymer(Nylon 6 + glycol), organic fibre etc.).
