Contrast improving sheet and rear projection screen provided with the same

A contrast improving sheet to be used in combination with a display, said contrast improving sheet comprising an optical element adapted to emit image light rays substantially perpendicularly incident on an entrance surface thereof in a direction substantially perpendicular to an exit surface thereof regardless of incidence position on the entrance surface and to absorb stray light rays obliquely incident on the entrance surface and external light fallen on the exit surface,

• wherein the optical element comprises:
• a first optical functional element provided with a plurality of protrusions arranged in a direction or distributed in a plane, each of the protrusions having a pair of opposite total-reflection facets for totally reflecting image light rays substantially perpendicularly incident on an entrance surface thereof and a flat facet extending between front edges, on a side of an exit surface thereof, of the pair of opposite total-reflection facets, and light absorbing layers formed between the adjacent protrusions;
• and
• a second optical functional element attached to a surface, on a viewing side, of the first optical functional element, and provided with a light path correcting layer for correcting light paths followed by the image light rays totally reflected by the total-reflection facets of the protrusions such that the image light rays are emitted through an exit surface thereof substantially perpendicularly to the exit surface.