Chirp optical coherence tomography with high resolution and artifact reduction using tunable near-infrared laser

Chirp optical coherence tomography (C-OCT) has become an alternative solution for imaging scattering media. This technique uses frequency modulated laser sources without a mechanical moving reference mirror as it is necessary in conventional coherence tomography. Images of scattering phantoms using an electrically tunable laser diode with a spatial resolution of about 400 mu m in air had shown the capability of this tomographic principle. The new setup contains an External Cavity Laser (ECL) with a center wavelength of 780 nn. Due to the wide usable tuning range of the ECL an improved spatial resolution could be obtained compared with the electrically tunable laser diode. Having only one reflection in the object the wide bandwidth of the ECL yields a peak with the full width at half maximum less than 20 mu m. Images of phantoms with known dimensions and scattering properties made with this arrangement are presented. Measurement of movement and motion artifacts demands special frequency modulation of the light source. Suitable methods to obtain useful information like location and velocity of moving objects as well as reducing artifacts are proposed. Combining C-OCT with Laser Doppler Perfusion Imaging (LDPI) requires conveniently prepared sweep functions.