Lighting device and projection image display unit

A lighting device, comprising:

• a first light source configured to emit light having a first wavelength;
• a second light source located on a same mount of the first light source and configured to emit light having a second wavelength;
• a third light source located on the same mount of the first and second light sources and configured to emit light having a third wavelength and located so as to emit the light in a direction different from that of the first and second light sources;
• a coupling optical system configured to couple light from the first, second and third light sources;
• and
• a light path synthesizing element configured to synthesize a light path of light from the first, second and third light sources,
• wherein the light path synthesizing element comprises a first surface configured to reflect light from the first light source and transmits light from the second and third light sources, a second surface configured to reflect light from the second light source and transmits light from the third light source and a third surface configured to reflect light from the third light source.

A lighting device, comprising:

• a first light source configured to emit light having a first wavelength;
• a second light source located on a same mount of the first light source and configured to emit light having a second wavelength;
• a third light source located on the same mount of the first and second light sources and configured to emit light having a third wavelength and located so as to emit the light in a direction different from that of the first and second light sources;
• a coupling optical system configured to couple light from the first, second and third light sources;
• and
• a light path synthesizing element configured to synthesize a light path of light from the first, second and third light sources,
• wherein the second and third light sources emit light having different polarization directions, and the light path synthesizing element is at least partly formed of a birefringent material and comprises a first surface and a second surface having a different angle each other, and wherein the first surface is configured to reflect light from the first light source and transmits light from the second and third light sources and the second surface is configured to reflect light from the second and third light sources.