Optical element, light source device, and projection-type display device

An optical element comprising a hologram layer into which light from a light source is irradiated, said hologram layer comprising:

• a first hologram that diffracts in a predetermined direction, from among light irradiated from said light source, first linearly polarized light in which the polarization component is in a specific direction and emits the result as said first linearly polarized light of a first phase state;
• and
• a second hologram that both diffracts in the same direction as said first linearly polarized light, and moreover, at an equal radiation angle, from among light irradiated from said light source, second linearly polarized light in which the polarization component is in a direction orthogonal to that of said first linearly polarized light and converts it to said first linearly polarized light, and emits the result as said first linearly polarized light of a second phase state that differs from said first phase state.