A diffractive optical element is configured to receive a first patterned light beams, and diffracts the first patterned light beams to project a second patterned light beam outwardly. The second patterned light beam is formed of combined arrangement of a plurality of first patterned light beams, and the combined arrangement includes periodic arrangement in a first direction and a second direction. The first direction and the second direction are not perpendicular to each other. By designing the performance of the diffractive optical element, the outwardly projected structured light pattern is periodically arranged in two directions, and the two directions are not perpendicular to each other, such that spot patterns are highly unrelated in multiple directions, improving accuracy.