An optical source unit includes a first optical source for emitting a P-polarized light beam, a first detector for detecting whether the first optical source is normal or abnormal, a second optical source for emitting an S-polarized light beam, a second detector for detecting whether the second optical source is normal or abnormal, and a light beam combining section including a polarization beam splitter for transmitting the P-polarized light beam and reflecting the S-polarized light beam to combine the P-polarized light beam and the S-polarized light beam into an output light beam of the optical source unit.