PURPOSE: To make incident light and projection light parallel as to a P- and an S-polarized component and to facilitate to couple with an optical fiber and other various optical parts by bonding the slanting surface of a triangular prism and a glass plate optically and embedding a dielectric multilayered film only in the center part of the adhesion surface between the both.
CONSTITUTION: The slanting surface of the triangular prism 12 whose main cut surface is a right-angled triangle and the glass plate 14 are allowed to adhere optically and the dielectric multilayered film 16 is embedded only in the center part of the adhesion surface between the both. Assuming that incident light is incident from the 1st surface of the triangular prism and reaches the dielectric multilayered film, the S-polarized component of the incident light is reflected by the dielectric multilayered film and projected from the 2nd surface. The P-polarized component, on the other hand, is transmitted through the dielectric multilayered film, reflected totally by the surface of the glass plate, and projected similarly from the 2nd surface. The P- and S-polarized components which are separated as mentioned above are projected as invariably parallel light beams.