An optical imaging system incorporates a beam splitter, which is moveable to a beam-splitting position where the beam splitter intercepts the light on an input optical path and a non-beam-splitting position where the beam splitter is located outside of the input optical path. In particular, stent covers having such nanostructures are described, and methods for fabricating these stent covers. Preferred dyes include the common dyes sodium fluorescein, lissamine green, and rose bengal.