3D imaging of human skin - Optical in vivo tomography and topology by short coherence interferometry

We discuss different modifications of white light interferometry, for the acquisition of human skin morphology. In a first experiment we display the diffusion of light within tissue, versus time. Light is focused onto the surface of the sample, penetrates the sample, is scattered and partly emerges from the surface again. For each point of the surface we can measure a certain run time profile of the emerging photons, via the speckle contrast. The local scattering behavior of the skin is encoded in the run time profile. Further we present a sensor for the acquisition of cross-sectional images of volume scatterers, we call it ''spectral radar''. The scattering amplitude a(z) along one vertical axis from the surface into the bulk can be measured within one exposure. No reference arm scanning is necessary, hence a short measurement time is possible. The depth uncertainty within a range of 1000 mu m is about 10 mu m. In first measurements we distinguished a melanoma maligna from healthy skin, in vitro and we measured the thickness of a fingernail in vivo. We further demonstrate a third method, the ''coherence radar'' for in vivo measurements of skin surface topology, with an accuracy of a few micrometers, and a field of 512 x 512 pixels.