Speckle in optical coherence tomography

Speckle arises as a natural consequence of the limited spatial-frequency ba ndwidth of the interference signals measured in optical coherence tomograph y (OCT). In images of highly scattering biological tissues, speckle has a d ual role as a source of noise and as a carrier of information about tissue microstructure. The first half of this paper provides an overview of the or igin, statistical properties, and classification of speckle in OCT. The con cepts of signal-carrying and signal-degrading speckle are defined in terms of the phase and amplitude disturbances of the sample beam. In the remainin g half of the paper, four speckle-reduction methods-polarization diversity, spatial compounding, frequency compounding, and digital signal processing- are discussed and the potential effectiveness of each method is analyzed br iefly with the aid of examples. Finally, remaining problems that merit furt her research are suggested. (C) 1999 Society of Photo-Optical Instrumentati on Engineers [S1083-3668(99)01401-X].