A laser scanning unit is provided comprising: a housing; a scanning device; a first pre-scan assembly generating a first light beam and directing the first light beam toward the scanning device; a second pre-scan assembly generating a second light beam and directing the second light beam toward the scanning device; a first post-scan assembly receiving the first light beam reflected from the scanning device and causing a first portion of the first light beam to scan along a first scan path; and a second post-scan assembly receiving the second light beam reflected from the scanning device and causing a first portion of the second light beam to scan along a second scan path. The first post-scan assembly further reflects a second portion of the first light beam in a direction away from the first scan path. A shield is associated with the housing for blocking the second portion of the first light beam reflected by the first post-scan assembly during at least a portion of the scan of the first portion of the first light beam along the first scan path so as to prevent the second portion of the first light beam from entering the second post-scan assembly.