| 摘要 |
PURPOSE:To converge a beam spot sufficiently by varying the aspect ratio of a diffraction grating so that the intensity distribution of projection light has a nearly Gaussian distribution in the traveling direction of waveguide light. CONSTITUTION:The aspect ratio [ratio of grating-array directional thickness d1 of grating to grating pitch (d)] of a Linear Grating Coupler (LGC) 21 for light projection is increased gradually and then decreased gradually in the traveling direction of the waveguide light 13', namely, in the grating array direction of the LGC 21. The light intensity distribution of the light beam 13'' is therefore the nearly Gaussian distribution. Consequently, the light beam projected from the optical waveguide 11 is converged into the small spot W and the accuracy of image recording and reading is improved. |
