Speckle reducing device and projector

An optical device, comprising:

• a first polarization splitter unit that splits incident light into first light flux that has first polarized light and second light flux that has second polarized light, and outputs the first light flux and the second light flux;
• a first reflecting unit that reflects the first light flux output from the first polarization splitter unit to the first polarization splitter unit;
• a first conversion unit disposed between the first polarization splitter unit and the first reflecting unit, which converts the first polarized light of the first light flux to the second polarized light;
• a second reflecting unit that reflects the first light flux converted to the second polarized light, and which was output from the first polarization splitter unit, entered the first polarization splitter unit and was output from the first polarization splitter unit, to the first polarization splitter unit;
• and
• a second conversion unit disposed between the first polarization splitter unit and the second reflecting unit, which converts the second polarized light of the first light flux to the first polarized light,
• wherein the first polarization splitter unit outputs the first light flux, which was reflected by the second reflecting unit and entered the first polarization splitter unit, and the second light flux along a direction in which the incident light entered the first polarization splitter unit,
• the optical device further comprising:
• a second polarization splitter unit that splits the first light flux and the second light flux, which was output from the first polarization splitter unit and entered the second polarization splitter unit, into third light flux and fourth light flux;
• and
• a third conversion unit disposed between the first polarization splitter unit and the second polarization splitter unit, which converts the first polarized light and the second polarized light included in the first light flux and the second light flux to circularly polarized light.