Dispersion induced multiple signal peak splitting in partial coherence interferometry

Dispersion is known to increase the width of the coherence envelope and therefore to decrease the resolution in partial coherence interferometry (PCI). If the thickness of a thin foil located behind a dispersive medium is to be measured, a further effect occurs. Because of the different refractive indices of different wavelengths in the dispersive medium, the period of the intensity oscillations of the interference fringes varies within the signal signature. This causes a beat effect which can lead to a multiple splitting of the PCI signal peaks. We demonstrate this effect experimentally and compare the experimental results with computer simulations. Furthermore, we discuss the implications of this effect for PCI and optical coherence tomography of the human retina. Care has to be taken to not confuse the peak splitting with real multilayer structures. Finally, we show how this effect can be used to improve the precision of thickness measurements of thin foils. (C) 1998 Elsevier Science B.V. All rights reserved.