Display device, organic light emitting display device, and head-mounted display device

A display device comprising:

• a substrate;
• a pixel electrode on the substrate;
• a display element emitting a light and disposed on the pixel electrode;
• a common electrode on the display element;
• an encapsulation layer on the common electrode;
• and
• a plurality of diffraction patterns on the encapsulation layer, wherein:
• the plurality of diffraction patterns include a first diffraction pattern, a second diffraction pattern, and a third diffraction pattern,
• a first duplicate emission pattern and a second duplicate emission pattern are generated from a reference emission pattern by the first diffraction pattern, the second diffraction pattern, and the third diffraction pattern,
• the first duplicate emission pattern is separated from a reference emission pattern by a first diffraction distance, and
• the second duplicate emission pattern is separated from the reference emission pattern by a second diffraction distance.