Comparison of defocusing and fractional Fourier transform in spectroholographic storage.
In spectroholographic storage systems the defocusing method is often used for spectrum uniformity and quality improvement of recorded information. The same purpose is served by the fractional Fourier transform (FRFT) storage system. To simplify the numerical analysis, we derive the expressions of the Fraunhofer spectrum and the reconstructed image at the detected plane (CCD) for both cases instead of using the Fresnel spectrum and the FRFT spectrum. The recording aperture, spectrum uniformity, and reconstructed information of both systems are investigated. A numerical comparison is also presented.