An illumination assembly includes a light-emitting element that emits
light over a light-source numerical aperture and an elongated
light-guiding element including opposed incident and emission ends
between which ends light propagates by total internal reflection. The
light-guiding element includes along a portion of its length a
numerical-aperture alteration taper having opposed small and large ends
exhibiting, respectively, a small-end numerical aperture and a large-end
numerical aperture lower in magnitude than the small-end numerical
aperture. The alteration taper is oriented such that the small end is
more proximate the incident end than the large end. The incident end is
in light-collecting proximity and alignment with the light-emitting
element such that light emitted from the light-emitting element over the
small-end numerical aperture and received into the small end of the
alteration taper is emitted from the emission end of the light-guiding
element at an emission numerical aperture lower in magnitude than the
small-end numerical aperture.