An apparatus for recording an image on a sheet comprises a linear array of light sources and an optical element for transmitting light emitted from the light sources. The optical element comprises a light-transmissive member, having an entry surface for disposal near the light sources. The entry surface defines at least one set of prisms. The optical element can further define a DCPC (dielectric compound parabolic concentrator) in cross-section. Collection optics, such as a SELFOC.RTM. lens, receives light reflected from the sheet. Each prism of the optical element defines an angle whereby light exiting the optical element is outside the acceptance angle of the collection optics.