Angular domain spectroscopic imaging of turbid media using silicon micromachined microchannel arrays

We experimentally characterized a novel Angular Domain Spectroscopic Imaging (ADSI) technique for the detection and characterization of optical contrast abnormalities in turbid media. The new imaging system employs silicon micromachined angular filtering methodology, which has high angular selectivity for photons exiting the turbid medium. The angular filter method offers efficient scattered light suppression at moderate levels of scattering (i.e. up to 6 reduced mean free paths). An ADSI system was constructed from a broadband light source, an Angular Filter Array (AFA), and an imaging spectrometer. The free-space collimated broadband light source was used to trans-illuminate a turbid sample over a wide range of wavelengths in the near infrared region of the spectrum. The imaging spectrometer decomposed the output of the AFA into hyperspectral images representative of spatial location and wavelength. It collected and angularly filtered a line image from the object onto the CCD camera with the spatial information displayed along one axis and wavelength information along the other. The ADSI system performance was evaluated on tissue-mimicking phantoms as well as fresh chicken breast tissue. Collected images with the ADSI displayed differences in image contrast between different tissue types.