| 摘要 |
<p>The invention relates to a spectral filter device for filtering an incident beam (20), the device having a window (2) each face of which has a region (4, 8) of a coating which reflects, in the window, radiation at a desired wavelength (?<SUB>1</SUB>) and is transparent to at least one other, undesired wavelength (?<SUB>2</SUB>, ?<SUB>3</SUB>), the coating on one of the faces being located partly opposite the coating on the other face.</p> |
