| 摘要 |
<p>A reflective optical system, in which radiation from a radiation source (e.g. laser produced plasma, or source at infinity) is directed to an image focus or intermediate focus, comprising: one or more mirrors (symmetric about the optical axis), the or each mirror having at least first and second reflective surfaces whereby, in use, radiation from the source undergoes successive grazing incidence reflections in an optical path at said first and second reflective surfaces; and wherein said at least first and second reflective surfaces are formed such that the angles of incidence of said successive grazing incidence reflections at said first and second reflective surfaces are substantially equal. A formula for the preferred geometry of the reflective surface is disclosed. The or each mirror may be formed as an electroformed monolithic component, wherein the first and second reflective surfaces are each provided on a respective one of two contiguous sections of the mirror. The reflective optical system may be embodied in a collector optical system for EUV lithography, or in an EUV or X-ray telescope or imaging optical system.</p> |
