| 主权项 |
1. A method of calibrating a reflective focusing optics to provide a system that minimizes the effect of multiple beam reflections therewithin on polarization state, comprising the steps of:
a) providing a system for providing a focused beam (FB) of electromagnetic radiation onto a location on a sample (SAM), said system being a reflective optics system (RFO) sequentially comprising first (M1), second (M2), third (M3) and fourth (M4) mirrors, each of said four mirrors (M1) (M2) (M3 (M4) providing reflective surfaces, with said third (M3) and fourth (M4) mirrors providing convex and concave reflective surfaces, respectively; such that in use an input beam (IB) of electromagnetic radiation having a specific polarization state is directed toward said first (M1) mirror and reflects from said reflective surface thereof, such that a first plane of incidence (P1) is formed between said incident beam (IB) and said beam which is reflected from said reflective surface of said first (M1) mirror; and such that said beam reflected from the reflective surface of said first (M1) mirror is directed toward said second mirror (M2) and reflects from said reflective surface thereof toward said convex third (M3) mirror, from which it reflects at an off-center location thereon toward said concave fourth (M4) mirror, wherefrom it is reflected by the reflective surface thereof toward said sample (SAM) as a focused (FB) outgoing beam (OB); said beam reflected from the reflective surface of said convex third (M3) mirror and that reflected from said reflective surface of said concave fourth (M4) mirror forming a second plane of incidence (P2), said first (P1) and second (P2) planes of incidence being orthogonal to one another; the effect of said four reflections from said reflective surfaces of said four (M1) (M2) (M3) (M4) mirrors being to substantially minimize the effects of all said reflections on the specific polarization state of said input beam, and to direct said output beam (OB) and provide it as a focused beam (FB) onto said sample (SAM) at the point it impinges thereupon; b) selecting said first (M1) and second (M2) mirrors from the group consisting of:
a) both (M1) and (M2) are flat mirrors;b) one of (M1) and (M2) is not flat;c) both (M1) and (M2) are not flat; c) while monitoring the polarization state of said focused (FB) outgoing beam (OB) and comparing it to the polarization state of said input beam (IB), variously adjusting the angles of incidence at which the various beams approach and reflect from said first (M1), second (M2), third (M3) and fourth (M4) mirrors; d) selecting the combination of angles of incidence regarding each of first (M1), second (M2), third (M3) and fourth (M4) mirrors that result in the least effect of the presence of said reflecting optics system on the polarization state of said focused (FB) outgoing beam (OB) as compared to that of the input beam (IB). |
