Interferometric optical path difference scanners and FT spectrophotometers incorporating them
First Claim
1. Interferometric apparatus comprising:
- (a) a rotary O.P.D. scanning assembly mounting a mirror pair formed by a beam splitter and a folding mirror, said beam splitter having a semi-reflective beam-splitting layer one face of which is the optical input surface in accurately parallel face-to-face relationship with said folding mirror and the other the output surface;
(b) two stationary reversing mirrors co-operating with said mirror pair for defining two interferometric arms, each arm receiving one of the two beams resulting from the splitting of an input beam by the beam splitter, for rotationally scanning successive O.P.D. values between the two beams up to a predetermined maximum, and for recombining the beams at said output surface so that they emerge therefrom as a single beam directed along an output path;
(c) an output mirror mounted at right angles to the output surface of said beam splitting layer, said output mirror being borne by the scanning assembly and positioned to receive the output beam; and
(d) pivotal means arranged to ensure that the scanning assembly rotates around an axis substantially coincident with the line of intersection of the prolongation planes of the semi-reflective beam-splitting layer and the face of the output mirror, respectively.
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Abstract
In an interferometric apparatus the path of the output beam of a rotary Optical Path Difference scanning assembly leading to an electrically responsive detector is maintained substantially fixed in space for any scan angle within predetermined limits, thus obviating a serious drawback of a prior art proposal wherein the output beam translates significantly over the detector face with changes in scan angle, with the result that the detector output is vitiated by totally spurious variations of the energy reaching it.
In one embodiment, the scanning assembly comprises a beam splitter having a semi-reflective layer the output face of which cooperates with the face of an output mirror normal thereto, the axis of rotation being substantially coincident with the line of intersection between the prolongation planes of the two faces. A Fourier Transform spectrophotometer embodying the assembly is also described.
106 Citations
17 Claims
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1. Interferometric apparatus comprising:
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(a) a rotary O.P.D. scanning assembly mounting a mirror pair formed by a beam splitter and a folding mirror, said beam splitter having a semi-reflective beam-splitting layer one face of which is the optical input surface in accurately parallel face-to-face relationship with said folding mirror and the other the output surface; (b) two stationary reversing mirrors co-operating with said mirror pair for defining two interferometric arms, each arm receiving one of the two beams resulting from the splitting of an input beam by the beam splitter, for rotationally scanning successive O.P.D. values between the two beams up to a predetermined maximum, and for recombining the beams at said output surface so that they emerge therefrom as a single beam directed along an output path; (c) an output mirror mounted at right angles to the output surface of said beam splitting layer, said output mirror being borne by the scanning assembly and positioned to receive the output beam; and (d) pivotal means arranged to ensure that the scanning assembly rotates around an axis substantially coincident with the line of intersection of the prolongation planes of the semi-reflective beam-splitting layer and the face of the output mirror, respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification