A total internal reflection prism unit may include a first prism and a second prism. The first prism may include a first total reflection surface, which totally reflect slight incident in a first horizontal direction along a second horizontal direction substantially perpendicular to the first horizontal direction, and a second total reflection surface, which totally reflects the totally reflected light from the first total reflection surface along the first horizontal direction to form a first beam. The second prism may include a third total reflection surface, which totally reflects the light along a third horizontal direction substantially perpendicular to the first horizontal direction, and a fourth total reflection surface, which totally reflects the totally reflected light from the third total reflection surface along the first horizontal direction to form a second beam. The second beam may be discrete from the first beam along the third horizontal direction.