An exemplary device includes, on a longitudinal axis, an illumination-light source, an axicon (conic) mirror, an image sensor, and a tilted optical element. The light source provides illumination light propagating forwardly on the axis. The axicon mirror reflects the illumination light radially outward, relative to the axis, to the interior surface of a tube to produce reflected light propagating, from the illuminated interior surface, as imaging light back to the axicon, which reflects the imaging light rearwardly. The image sensor receives at least a portion of the imaging light rearwardly reflected by the axicon mirror. The tilted optical element, situated between the axicon mirror and the interior surface, moves a selected first portion of the imaging light away from being incident on the image sensor, while allowing a second portion of the imaging light to be incident on the image sensor.