A diffractive optical element (10), comprising a microstructure surface, wherein at least one microstructure pattern unit is provided on the microstructure surface, and the diffractive optical element (10) may receive light beams emitted by a partitioned light source array (20) and project a light field on a target surface (OB), wherein the partitioned light source array (20) comprises a plurality of light source arrays (20-1, 20-2,..., 20-n) spaced apart along a first direction, and the microstructure pattern unit is configured to diverge and evenly modulate light beams emitted by light sources in the plurality of light source arrays (20-1, 20-2,..., 20-n) along the first direction, so that light field regions of adjacent light source arrays (20-1, 20 -2,..., 20-n) on the target surface (OB) adjoin or overlap each other in the first direction. There is a gap between adjacent partitions. Light source partitions are alternately turned on. When each light source partition is turned on, only the region corresponding to the partition in a target light field is uniformly illuminated. Moreover, when all the partitions are turned on together, the entire target light field is uniformly illuminated, and there is no dark region caused by the gap between the partitions, thus achieving the uniform illumination of the partitions of the target light field.
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