| 摘要 |
PURPOSE:To miniaturize the projection lens and to suppress the aberration fluctuation caused by focusing by moving a lens group of a part of a first lens group of a screen side and executing the focusing. CONSTITUTION:In the projection optical system for projecting an original image to a screen side, a reflecting member for leading the light from an illumination light source to the original image through a second lens group 3 is placed between first lens groups 1, 2 and a second lens group 3 of a projection lens constituted of first lens groups 1, 2 having a positive refractive index and a second lens group 3 having a positive refractive index in order front the screen side. Also, by moving a certain lens in plural lenses for constituting first lens groups 1, 2, focusing is executed. Accordingly, the projection optical system can be miniaturized, and moreover, a focus fluctuation generated at the time of miniaturizing the projection optical system can be suppressed. |
