| 摘要 |
PURPOSE:To stably control the focus by separating an ordinary-ray luminous flux and an extraordinary-ray luminous flux in directions orthogonal to the prism edge of a Foucault prism. CONSTITUTION:A convergent luminous flux is made incident on a Foucault prism 15. The Foucault prism 15 is made of a birefringence material like crystal and subjects the incident luminous flux to prism action and birefringence action. That is, the incident luminous flux is divided into a pair of luminous fluxes 171 and 172 in directions (upward and downward in the figure) orthogonal to the prism edge 150 (directed orthogonally to the drawing) by the action of Foucault prism 15. Since the incident luminous flux has 45 deg. polarization direction in the linear polarization state, the ordinary-ray luminous flux and the extraordinary-ray luminous flux are separated in directions orthogonal to the prism edge 150 by the birefringence action of the Foucault prism 15. As the result, four luminous fluxes, namely, two ordinary-ray luminous fluxes and two extraordinary-ray luminous fluxes are emitted from the Foucault prism 15, and they are convergent, and ordinary-ray luminous fluxes and extraordinary- ray luminous fluxes constitute pairs of luminous fluxes. |
