DISPERSION INDUCED MULTIPLE SIGNAL PEAK SPLITTING IN PARTIAL COHERENCE INTERFEROMETRY

Dispersion is known to increase the width of the coherence envelope an d therefore to decrease the resolution in partial coherence interferom etry (PCI). If the thickness of a thin foil located behind a dispersiv e medium is to be measured, a further effect occurs. Because of the di fferent refractive indices of different wavelengths in the dispersive medium, the period of the intensity oscillations of the interference f ringes varies within the signal signature. This causes a beat effect w hich can lead to a multiple splitting of the PCI signal peaks. We demo nstrate this effect experimentally and compare the experimental result s with computer simulations. Furthermore, we discuss the implications of this effect for PCI and optical coherence tomography of the human r etina. Care has to be taken to not confuse the peak splitting with rea l 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.