| 摘要 |
PURPOSE:To facilitate uniform lighting which does not produce a speckle pattern on a lit surface by a method wherein optical path length differences are given between respective light beams by a light beam forming means and a light beam mixing means such as an optical pipe and, further, the propagation times of the respective light beams are made to be uniform by a light beam swinging means. CONSTITUTION:Some light beams in incident light entering an optical pipe 4 after expanded by a light beam forming means 3 are transmitted as they are and the other light teams are reflected by the inner surface of the optical pipe 4 several times. Then the respective light beams are mixed and guided to a light emitting plane 4. Light path length differences are given between the totally reflected light beams and the non-reflected light beams. Further, the differences in number of total reflections are given between the respective reflected light beams to give the optical path differences between the respective light beams reaching the light emitting plane 4. Further, by turning a light beam swinging means 2, the distribution of the incident angles of the light beams into the optical pipe 4 is changed and the distribution of the light beams totally reflected in the optical pipe 4 is changed so that interference stripes on the light emitting plane is moved and made to be uniform and the radio frequency interference stripes can be satisfactorily eliminated and a lit surface 5 can be lit uniformly. |
