Spectrophotometer

Claim 1

A spectrometer optical system comprising: source means for generating a beam of radiation of preselected spectral wavelengths; an interferometer including a beam splitter having a fixed aperture; means defining a variable aperture adjustable to vary the cross-sectional area of said radiation beam and thus regulate resolution of the spectrometer; means including a first curved reflector for focusing an image of said source means onto said variable aperture, said beam of radiation passing through said variable aperture to said interferometer; means including a second curved reflector directing said radiation beam to illuminate said fixed beam splitter aperture; optical means defining a sample path having a sample position and a substantially identical reference path; a switchable beam path selector; means including a third curved reflector for directing the radiation beam exiting from said interferometer to said beam path selector and focusing an image of said fixed beam splitter aperture at said sample position while imaging the variable aperture at a location remote from said sample position, said beam path selector being constructed and arranged to be switchable between respective positions in which said radiation beam is alternately directed along said sample path and said reference path; photosensitive detector means; and means including a beam path directing mirror for receiving the beam of radiation from either said sample path or from said reference path and focusing said fixed beam splitter aperture on said detector, whereby the detector is uniformly illuminated for all cross-sectional areas of said variable aperture.