Optical coherence microscopy in gastrointestinal tissues

Optical coherence microscopy (OCM) is a novel technique complementary to optical coherence tomography (OCT), which combines low-coherence interferometry with confocal microscopy to achieve micron-resolution optical imaging deep in highly scattering media. This paper implements an OCM system specifically designed for high-resolution imaging deep in highly scattering tissues by utilizing low-coherence illumination from a superluminescent diode (SLD) source at 1.3-μm center wavelength. High-sensitivity detection of backscattered light (>95 dB dynamic range) is accomplished using heterodyne detection at 1.6-kHz modulation frequency, provided by small-amplitude PZT modulation of the reference arm length. Phase instabilities due to random thermal fluctuations in the fiber lengths are eliminated by digital demodulation of the interferometric signal at dual harmonics of the modulation frequency. Using a 0.65 N.A., 40× water-immersion objective, lateral and axial resolutions of 1.9 and 5 μm FWHM are obtained, respectively.