Patent ID: 7304737

Claim:
A system for monitoring change in: the intensity of; and/or the ratio of and/or the phase between orthogonal components in; a spectroscopic beam of electromagnetic radiation, which is caused by interaction with a sample system (SS); said system comprising: a source of electromagnetic radiation (LS); a beam directing system (BDS) comprising: a substantially planar mirror ( 4 ); a convex spherical mirror ( 10 ); at least one concave spherical mirror ( 5 ) ( 5 ′); and aberation correction system (CL) means; such that in use substantially planar mirror ( 4 ) directs an input beam (IB) of electromagnetic radiation ( 3 ) to reflect therefrom and proceed to reflect from said convex spherical mirror ( 10 ), and from said at least one concave spherical mirror ( 5 ) which focuses it, as incident beam ( 6 ) to a spot (M) on sample (SS), reflected electromagnetic radiation ( 7 ) from said spot (M) on said sample (SS) being collected by said at least one concave spherical mirror ( 5 ′), which reflectively directs it to reflect from convex spherical mirror ( 10 ) and emerge as an output beam (OB); said aberation correction system (CL) means being positioned so that both input (IB) and output (OB) beams pass therethrough; and a detector (DET) of electromagnetic radiation; said system further comprising at least one rotating or rotatable compensator (CMP) (CMP′) positioned so that said beam of electromagnetic radiation transmits therethrough; such that in use, said source (LS) of electromagnetic radiation provides an input beam (EBI) of electromagnetic radiation to said beam directing system (BDS), which in turn causes said input beam (EBI) of electromagnetic radiation to interact with said spot (M) on said sample (SS) and then proceed as output beam (EBO) into said detector (DET) of electromagnetic radiation, as said at least one rotating or rotable compensator (CMP) (CMP′) is caused to continuously rotate or step through sequence of descrete positions.