Patent ID: 8061877

Claim:
A prism sheet comprising: a transparent main body comprising: a first surface being flat; and a second surface being on another side of the main body opposite to the first surface, the second surface defining a plurality of parallelogram microstructures, each parallelogram microstructure defining four adjacent triangular pyramid depressions in an outline of the parallelogram microstructure, wherein each of the plurality of the parallelogram microstructures borders with four other of the plurality of the parallelogram microstructures, and sidewalls on each side of adjacent triangular pyramid depressions sharing a same edge collectively form a plurality of first V-shaped ridges aligned in a first direction, a plurality of second V-shaped ridge aligned in a second direction, a plurality of third V-shaped ridges aligned in a third direction, and a plurality of fourth V-shaped ridge aligned in a fourth direction, and each triangular pyramidal depression is defined by three of the four V-shaped ridges aligned in four different directions.