Light source device and projector

A light source device comprising:

• a light emitting device that outputs a first light having a first wavelength in a first polarization direction;
• a first optical element having a first area that reflects the first light and a second area different from the first area;
• a second optical element into which the first light reflected by the first area of the first optical element is entered, converting the first light into a circularly-polarized second light having the first wavelength;
• and
• a diffuser element into which the second light output from the second optical element is entered, wherein
• the second light reflected by the diffuser element and entered into the second optical element is converted into a third light having the first wavelength in a second polarization direction by the second optical element,
• the third light output from the second optical element and entering the first area of the first optical element is transmitted in the first area of the first optical element,
• the second light reflected by the diffuser element and entered into the second area of the first optical element is transmitted in the second area of the first optical element, and
• a fourth light output from the diffuser element and entered into the first area and the second area of the first optical element and having a second wavelength is transmitted in the first area and the second area of the first optical element.