| 摘要 |
An optical element includes a first substrate having a diffractive surface or a surface structure with a surface level difference, a second substrate for covering the diffractive surface or the surface structure to provide a shield therefor, and a groove provided at the diffractive surface or the surface structure, and extending from a central portion to a peripheral portion thereof, for discharging or replacing a gas at the diffractive surface or the surface structure therethrough. |
