| 摘要 |
PURPOSE:To attain cost reduction by adhering the 2nd triangular prism made of an isotropic transparent material to the 1st triangular prism made of a birefringent material, and forming one end surface of the 2nd triangular prism at such an angle that incident light and projection light are parallel to each other. CONSTITUTION:A light beam entering the 1st triangular prism made of the birefringent material travels straight and is separated into an ordinary light beam (o) and an extraordinary light beam (e) by the boundary surface with an adhesive 3. The refractive index of the adhesive 3 is smaller than that of the ordinary light beam (o) and larger than that of the extraordinary light beam (e), so although the extraordinary light beam (e) is transmitted, the ordinary light beam (o) is reflected totally because its angle of incidence exceeds the critical angle, so that both light beams are separated. The refractive index of the 2nd triangular prism 2 to the extraordinary light beam (e) is equal to the refractive index of the triangular prism 1, so projection light is projected from the end surface of the triangular prism 2 in parallel to the incident light. Consequently, the workability and yield are improved because one triangular prism uses the isotropic transparent material such as glass, reducing the cost. |
