Color high resolution full-field optical coherence microscopy for contrast-enhanced imaging

Abstract

Full-field optical coherence microscopy (FF-OCM) is an established optical technology based on low-coherence interference microscopy for high-resolution non-invasive three-dimensional imaging of semi-transparent samples. We present an extension of the technique setting up an achromatic imaging system over a spectral range extending from 530 nm to 1700 nm, to provide tomographic images in three distinct bands centered at 635 nm, 870 nm and 1170 nm. Image contrast enhancement as well as sample characterization is performed using the conventional RGB color channel representation. Light is emitted by a halogen lamp and then separates into two arms of a Linnik-type interferometer with microscope objectives placed in each arm. The images are projected onto a visible to short-wavelength infrared detector based on an InGaAs photodiode array. <i>Enface</i> oriented tomographic images are obtained by arithmetic combination of four phase-shifted interferometric images. Great care was taken to reach similar performances in the three bands. An axial resolution of ~1.9&mu;m and a transverse resolution of ~2.4&mu;m are achieved in the three bands. A dynamic dispersion compensation system is set up to preserve axial resolution and signal intensity level when the imaging depth is varied. Images of biological samples revealing their spectral properties are shown as illustration of improved detection capability with enhanced contrast.