Diffraction optical element, lighting device, and projector

A diffraction optical element, comprising:

• a first diffraction pattern which diffracts entering light from a light source device to produce illumination light for illuminating a first area on a side of the first diffraction pattern opposite to the entering light;
• and
• a second diffraction pattern which is disposed adjacent to the first diffraction pattern and contacts the first diffraction pattern, and diffracts entering light from the light source device to produce illumination light for illuminating a second area on a side of the second diffraction pattern opposite to the entering light other than the first area by using at least a part of diffracted light,
• wherein the second diffraction pattern is disposed along a circumference of the first diffraction pattern.