| 摘要 |
PURPOSE:To minimize the absorption of harmful light and prevent deterioration by providing a light shield layer on the external surface of a light wavelength converting element except in the light incidence area on a light incidence end surface and the light projection area on a light projection end surface. CONSTITUTION:The light wavelength converting element 4 is constituted into an optical fiber type and has a core 41 and a clad 42, and the light shield layer 43 is formed at the outer periphery of the clad 42 except the light incidence and projection end surfaces 44 and 45. In this case, when laser light is made incident on the core 41 of the light wavelength converting element 4, Cherenkov radiation based upon the laser light as a fundamental wave is caused and a generated secondary higher harmonic is projected and emitted while diffused in a ring shape. The projection converted light is collimated, further converged, and used for reading operation. At this time, the outer periphery is covered with the light shield layer 43, so light having wavelength which causes harmful optical deterioration is prevented from entering the core 41 or clad 42 from outside. |
