Speckle properties of the logarithmically transformed signal in optical coherence tomography.

We discuss the statistical properties of speckle of the logarithmically transformed signal in optical coherence tomography (OCT) both theoretically and experimentally. OCT signals of Intralipid solution with different volume particle concentrations ρ (correspondingly, scattering coefficient μ(s) ranges from 1.25 to 25.11 mm(-1)) were measured and analyzed under two different focusing conditions [numerical apertures (NAs) of the objective lens of 0.13 and 0.25]. We found that the effect of the speckle noise can be suppressed by displaying OCT images in the logarithmic scale and by using the objective lens with a higher NA. We also found that the speckle properties are correlated with the scattering properties of the sample, which may be used to characterize the scattering properties of biological tissue. The simulated OCT image and the in vitro OCT image of a rat liver are used as examples to demonstrate the feasibility of the method.