An exemplary prism sheet includes a transparent main body. The transparent main body includes a first surface and a second surface. The first surface and the second surface are on opposite sides of the main body. The first surface of transparent main body defines a plurality of first elongated arc-shaped grooves and a plurality of second elongated arc-shaped grooves. The first elongated arc-shaped grooves intersect with the second elongated arc-shaped grooves. The second surface defining a plurality of rectangular structures. Each rectangular structure defining four adjacent triangular pyramid depressions.