An illumination system comprising, a) a light source; b) a light-directing assembly (1) in close proximity to the light source and comprising a plurality of microprisms (6), each microprism comprising an input surface (7) that admits light radiating from the light source, an output surface (8) distal from and parallel to the input surface (7), and at least one sidewall (9) disposed between and contiguous with the input and output surfaces and forming an obtuse tilt angle with respect to the input surface (7) and further positioned for effecting total reflection of the light rays received by the input surface (7), the sidewalls (9) of the microprisms (6) defining interstitial regions (10) between the microprisms (6); c) at least one blocking means (11) positioned to block the passage of light through the sidewalls (9); and d) an optical means (2, 3, 4) located between the light source and the light-directing assembly (1), with the special feature that e) said optical means (2, 3, 4) comprise a reflective powder (4) to at least substantially shield the blocking means (11) from direct exposure to lig radiated from the light source.
