| 摘要 |
PROBLEM TO BE SOLVED: To realize a diffraction grating which can maintain good diffraction characteristics even when the grating is used for a long time in a high humidity environment. SOLUTION: This diffraction grating 1 consists of a transparent substrate 2 and an optical film 3 periodically formed on the surface 201 of the substrate. The surface 201 of the substrate 2 has optical film 3 and exposed part 202 of the substrate surface alternately arranged. A dampproof protective film 4 is formed on the exposed part 202 of the transparent substrate and on the optical film 3. Since the exposed part 202 and the optical film are covered with the dampproof protective film 4, the absorption of moisture in the exposed part and the optical film is suppressed and deterioration of the diffraction characteristics can be prevented. |
