An optical device has first and second non-parallel optical paths, and a light reflecting surface. The reflecting surface may have a first and second planar portion. The first planar portion receives light from the first path to reflect the light toward the second path. The second planar portion may form an angle .theta.1 with the first planar portion. Angle .theta.1 satisfies a condition of 175.degree..ltoreq..theta.<180.degree. in either clockwise or counterclockwise rotation from the first planar portion.