Ck. Hitzenberger et al., Differential phase measurements in low-coherence interferometry without 2 pi ambiguity, OPTICS LETT, 26(23), 2001, pp. 1864-1866
Quantitative phase measurements by low-coherence interferometry and optical
coherence tomography are restricted by the well-known 2 pi ambiguity to pa
th-length differences smaller than lambda /2. We present a method that over
comes this ambiguity. Introducing a slight dispersion imbalance between ref
erence and sample arms of the interferometer causes the short and long wave
lengths of the source spectrum to separate within the interferometric signa
l. This causes the phase slope to vary within the signal. The phase-differe
nce function between two adjacent sample beam components is calculated by s
ubtraction of their phase functions obtained from phase-sensitive interfero
metric signal recording. Because of the dispersive effect, the phase differ
ence varies across the interferometric signal. The slope of that phase diff
erence is proportional to the optical path difference, without 2 pi ambigui
ty. (C) 2001 Optical Society of America.