means the quotient of the luminous intensity reflected by the retro-reflective device in the direction considered, divided by the normal illumination of the retro-reflecting device for given angles of illumination, divergence and rotation, helkurseadme poolt asjaomases suunas peegelduva valgustugevuse jagatis helkurseadmele omase valgustustugevusega antud valgustus-, lahknemis- ja pöördenurga korral
