| 摘要 |
<p>PURPOSE:To miniaturize the projection lens of a projector in an illumination device used for the projector such as a liquid crystal projector. CONSTITUTION:In the illumination device of the projector that light from a point light source 11 is made a parallel light beam, transmission original plates 19R, 19G and 19B(liquid crystal panels) are irradiated with the parallel light beam and the light beams transmitted through the plates 19R, 19G and 19B is projected on a screen, the light from the light source 11 is made the parallel light beam by a parabola reflecting mirror 2 arranged at the back part of the light source 11 and a spherical reflecting mirror 3 arranged in front of the light source except the output part of the parallel light beam. Besides, a parabola reflecting mirror whose diameter of aperture is almost equal to the required illuminating diameter of the parallel light beam and whose focal distance is set so that converging efficiency becomes 50% is used as the mirror 2. As the mirror 3, a spherical mirror whose diameter is somewhat larger than the required illuminating diameter of the parallel light beam is used.</p> |
