Light source device and projector

A light source device comprising:

• a light source unit configured to emit a first light beam having a first wavelength band, a second light beam having a second wavelength band different from the first wavelength band, and a third light beam having a third wavelength band different from the first wavelength band and the second wavelength band;
• a first polarization split element configured to transmit the first light beam and the second light beam having a first polarization direction out of the first light beam, the second light beam, and the third light beam entering the first polarization split element along a first direction from the light source unit toward the first direction, and reflect the third light beam having a second polarization direction different from the first polarization direction toward a second direction crossing the first direction;
• a second polarization split element disposed at the first direction side of the first polarization split element, and configured to transmit the first light beam out of the first light beam and the second light beam, which enter the second polarization split element along the first direction from the first polarization split element, toward the first direction, and reflect the second light beam toward the second direction;
• a first retardation element which is disposed between the first polarization split element and the second polarization split element, and is configured to provide a phase difference to light in the second wavelength band;
• a first diffusion element which is disposed at the second direction side of the first polarization split element, and configured to diffuse the third light beam which enters the first diffusion element along the second direction from the first polarization split element, and emit the third light beam diffused toward a third direction as an opposite direction to the second direction;
• a second diffusion element which is disposed at the second direction side of the second polarization split element, and configured to diffuse the second light beam which enters the second diffusion element along the second direction from the second polarization split element, and emit the second light beam diffused toward the third direction;
• and
• a third diffusion element disposed at the first direction side of the second polarization split element, and configured to diffuse the first light beam which enters the third diffusion element along the first direction from the second polarization split element, and emit the first light beam diffused toward a fourth direction as an opposite direction to the first direction, wherein
• the second polarization split element reflects the first light beam, which enters the second polarization split element along the fourth direction from the third diffusion element, toward the third direction, transmits a part of the second light beam having the first polarization direction out of the second light beam, which enters the second polarization split element along the third direction from the second diffusion element, toward the third direction, and reflects another part of the second light beam having the first polarization direction toward the fourth direction,
• the first retardation element converts the second light beam which enters the first retardation element along the first direction from the first polarization split element and has the first polarization direction into the second light beam having the second polarization direction, and converts the another part of the second light beam which enters the first retardation element along the fourth direction from the second polarization split element and has the first polarization direction into the second light beam having the second polarization direction, and
• the first polarization split element transmits the third light beam which enters the first polarization split element along the third direction from the first diffusion element, and reflects the second light beam which enters the first polarization split element along the fourth direction from the first retardation element and has the second polarization direction.