Ultrathin fiberscopes typically have an imaging channel and an illumination channel and are available in diameters ranging from 0.5 mm to 2.5 mm. The minimum diameter can be reduced by combining the illumination and imaging paths into a single fiberoptic channel. Constructing a single channel fiberscope requires a technique of illuminating the tissue, while minimizing the Fresnel reflections and scatter within the common illumination and detection channel.;A single channel fiberscope should image diffusely reflected light from tissue illuminated with light filtered for the visible wavelength range (450 - 650 nm). Simply combining the illumination and collection paths via a beamsplitter results in a low object to background signal ratio. The low contrast image is due to a low collection efficiency of light from the object as well as a high background signal from the Fresnel reflection at the proximal surface of the fiber bundle, where the illumination enters the fiber bundle. The focus of the dissertation is the investigation of methods to reduce the background signal from the proximal surface of the fiber bundle. Three systems were tested. The first system uses a coherent fiber bundle with an ar-coating on the proximal face. The second system incorporates crossed polarizers into the light path. In addition, a technique was developed, whereby a portion of the image numerical aperture is devoted to illumination and a portion to image signal detection. This technique is called numerical aperture sharing (NA sharing).;This dissertation presents the design, construction, testing, and comparison of the three single channel fiberscopes. In addition, preliminary results of a study aimed at the usefulness of broadband diffuse reflectance imaging for the identification and tracking of disease progression in mouse esophagus are presented.
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