Browsing by Subject "Phase retrieval"
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Item Open Access Complex signal recovery from two fractional Fourier transform intensities: order and noise dependence(Elsevier, 2005-01) Ertosun, M. G.; Atlı, H.; Özaktaş, Haldun M.; Barshan, B.The problem of recovering a complex signal from the magnitudes of two of its fractional Fourier transforms is addressed. This corresponds to phase retrieval from the transverse intensity profiles of an optical field at two arbitrary locations along the optical axis. The convergence of the iterative algorithm, the effects of noise or measurement errors, and their dependence on the fractional transform order are investigated. It is observed that in general, better results are obtained when the fractional transform order is close to unity and poorer results are obtained when the order is close to zero. It follows that to the extent that conditions allow, the fractional order between the two measurement planes should be chosen as close to unity (or other odd integer) as possible for best results.Item Open Access Kesirli fourier dönüşümü genliklerinden karmaşık sinyallerin geri kazanımı(IEEE, 2004-04) Ertosun, M. Günhan; Atlı, Haluk; Özaktaş, Haldun M.; Barshan, BillurBu makalede kesirli Fourier dönüşümü genlikleri kullanılarak karmaşık sinyallerin evrelerinin bulunması üzerinde durulmuştur. Bu aynı zamanda optik eksende enine boyuna rastgele iki yerde yapılan genlik ölçümlerinden evre bilgisinin bulunmasına karşılık gelmektedir. İteratif algoritmanın yakınsaklığı, gürültü ve ölçüm hatalarının etkisi ve bunların dönüşümün kesir değerine olan bağlılığı incelenmiştir. Genel olarak, kesir değerinin ünitere yakın olduğu durumlarda, sıfıra yakın olduğu durumlara göre daha iyi sonuçlar elde edilmiştir. Buna göre, en iyi sonuçları elde etmek için, iki ölçüm düzlemi arasındaki kesir değeri ünitere olabildiğince yakın seçilmelidir.Item Open Access Phase retrieval from electric field intensity for wide angle optical fields(OSA, 2017) Külçe, Onur; Onural, LeventAn intensity preserving scalar to vector electric field mapping, in a wave propagation environment, based on a filtering procedure is proposed. In a phase retrieval problem, the proposed mapping outperforms the conventional mapping.Item Open Access Phase retrieval of sparse signals from Fourier Transform magnitude using non-negative matrix factorization(IEEE, 2013) Salman, M.S.; Eleyan, A.; Deprem, Zeynel; Çetin, A. EnisSignal and image reconstruction from Fourier Transform magnitude is a difficult inverse problem. Fourier transform magnitude can be measured in many practical applications, but the phase may not be measured. Since the autocorrelation of an image or a signal can be expressed as convolution of x(n) with x(-n), it is possible to formulate the inverse problem as a non-negative matrix factorization problem. In this paper, we propose a new algorithm based on the sparse non-negative matrix factorization (NNMF) to estimate the phase of a signal or an image in an iterative manner. Experimental reconstruction results are presented. © 2013 IEEE.