| 摘要 |
PURPOSE:To obtain a refractive index distribution which is the optimum for changing focal length, by providing an electrode section for moving light condensing point composed of plural electrodes provided in parallel with the advancing direction of light at the front section of a diffraction grating section and power source circuit which applies a voltage across each of the electrodes. CONSTITUTION:On the emissive optical axis of this diffraction grating type light condenser the guided light advanced through an optical waveguide layer 4 is diffracted at a diffraction grating section 5 and condensed to a spatial point P when no voltage is impressed across each electrode of the diffraction grating section 5 and an electrode section 9. When the focal length is to be made shorter, a voltage distribution pattern is given to each electrode 10 of the section 5 and another voltage distribution pattern to each electrode 10 of the electrode section 9. When the focal length is to be made longer, on the contrary, other voltage distribution patterns are respectively given to each electrode 10 of the sections 5 and 9. Therefore, a refractive index distribution which is optimum for changing focal length can be obtained. |
