Abstract: Spectrometer sampling chamber structures are disclosed which avoid purge loss during loading and unloading of samples. In two disclosed versions, a plunger carries the sample, and fits closely inside a fixed tube, into which it is inserted for sample illumination. Sample loading and unloading is accomplished without fully removing the plunger from the tube. Also, an automatic purging flow of gas from the interior of the spectrometer is caused during insertion of a new sample. In a third disclosed version, vertically stacked sample holders move through a vertical chute into which they are inserted to the top of the sample chamber, and from which they are removed at the bottom of the sample chamber.

Abstract: An accessory for use in the sample region of a spectrometer is disclosed which combines a matched pair of off-axis paraboloid reflectors having their focii optically imaged on the sample (either imaged at a common point or at two points which are optically imaged on each other) and having relative locations and orientations such that each ray of radiation strikes the two reflectors at points on the reflectors having approximately the same focal lengths. This arrangement involves the use of collimated optical beams into and out of the accessory. The accessory may function as a transmission-type accessory, in which the radiation passes through the sample, or as an internal reflectance accessory, in which the radiation passes through the sample holder but is reflected by the sample. The focal length relationship set forth is accomplished by having "back-to-back" paraboloid reflectors, i.e., their reflecting surfaces face in substantially different, preferably opposite, directions.

Abstract: A spectrometer is disclosed having an interferometer in which: (a) the variable-length arm has a moving retroreflector (copy A to A in summary). The pivoted linkage comprises three or more arms each having its upper end pivotally connected to a supporting structure and its lower end pivotally connected to a carrier for the retroreflector. The stationary folding mirror blocks approximately half of the open face of the retroreflector, causing the radiation which enters the unblocked half of the retroreflector to be reflected back to the retroreflector after it has traveled diagonally across the retroreflector and then been reflected toward the folding mirror.

Abstract: An interferometer spectrometer aligning apparatus and method are disclosed, in which the laser beam generator, which is in the instrument to provide data controlling clock signals, is also used to accomplish initial (and as needed) alignment of the instrument. The laser beam is directed through a target both on its way from the laser generator to the interferometer, and as it is reflected back from the interferometer, thereby validating the perpendicularity of the reflector to the axis of the interferometer. A semi-transparent mirror, i.e., a small beamsplitter, is used in the path of the laser beam ahead of the interferometer beamsplitter, thereby enabling portions of the laser beam to go into both the interferometer and the sample chamber.

Abstract: A dual beam Fourier-type spectrometer is disclosed in which the collimated output beam of a Michelson type interferometer is divided (post-interferometer) by a reflector which (a) reflects the bulk of said beam to the sample and thereafter a first detector, but (b) transmits part of said beam (preferably through apertures in the reflector) directly to a second detector. The relatively small portion of said beam which is transmitted to the second detector preferably passes through a substantial number of very small apertures in the reflector which are spaced in such a way as to maximize the spatial identity of the beams reaching the first and second detectors.

Abstract: An interferometer, for use in spectrometry, is disclosed in which a more reliable synchronization of the starting points of successive analytical scans is obtained by combining:(a) a moving retro-reflector in the variable-length arm which reflects both the analytical beam and the reference beam;(b) stationary reflecting means in the variable-length arm providing a flat "folding" reflector which causes the path of at least the reference beam from the retro-reflector to be folded on itself and returned to the retro-reflector; and(c) stationary reflecting means for the reference beam in the fixed-length arm so located as to offset the reference interferogram with respect to the analytical interferogram. Two versions of the invention are shown, each having two disclosed embodiments. In one version all three of the beams (clock, reference, and analytical) are "folded" by means of mirrors located adjacent to the moving retro-reflector. In the other version only the reference beam is folded.

Abstract: An accessory for optical spectroscopy is disclosed which combines a matched pair of off-axis paraboloid reflecting surfaces having their focal points at a common location on the reflecting surface of a sample. The entering and exiting beams are collimated. Preferably the paraboloid reflecting surfaces have co-linear, anti-parallel axes, and are part of a unitary structure which is rotatable around the collimated optical beam axis to vary the angle of incidence on the sample without altering the optical alignment, thereby allowing the specular reflectance component to be included or excluded, at will.

Abstract: A refractively scanned interferometer, of the type in which a wedge-shaped prism is moved across one interferometer arm for scanning purposes, in which a similarly shaped fixed prism in the other arm provides optical compensation to avoid aberration problems. The beamsplitter surface is on the fixed wedge-shaped prism, and the two wedge-shaped prisms constitute the only refractive elements in the interferometer arms.

Abstract: An optical apparatus is disclosed which monitors the thickness of a thin film carried by a reflecting substrate. In order to minimize light detection problems caused by inadvertent displacement of the substrate, the light source and detector are located on the same "side" of the optical apparatus, and retro-reflector means are located at the other "side" of the optical apparatus, so that the light is reflected from the substrate to the retro-reflector means, back to the substrate, and thence back to the detector. In the preferred embodiment, the retro-reflector means comprises an array of small retro-reflectors.

Abstract: An interferometer, preferably of the Michelson type, is disclosed, in which the reflectors associated with the interferometer arms are stationary, and scanning is accomplished by displacement of a single wedge-shaped refractive element in one of the arms. The reflectors are preferably retro-reflectors rather than flat mirrors in order to minimize the effects of chromatic dispersion. A Moire scale may be used to measure the position of the wedge-shaped refractive element.

Abstract: A dual beam Fourier-type spectrometer is disclosed incorporating distinct sample and reference beams which enter the Michelson-type interferometer on the same side of the beam splitter and propagate at slightly different angles through the interferometer. The portions of both beams which emerge from the side of the beam splitter opposite the input side are directed to two separate optical detectors, the outputs of which are electronically subtracted. In a preferred embodiment, the interferometer is of the refractively scanned type, wherein the increased field-of-view facilitates the use of beams having different propagation angles.

Abstract: An interferometer is disclosed, preferably of the Michelson type, in which the reflectors associated with the interferometer arms are stationary, and scanning is accomplished by motion of a wedge-shaped refractive element in one of the arms, the orientation of the refractive element and its direction of motion being in specific mathematically derived directions which minimize the translatory displacement of the transmitted optical beam.

Abstract: An optical apparatus is disclosed for measuring and monitoring the thickness of a partially transparent film, or coating, which is either self-supporting or attached to a reflecting substrate. Infra-red radiation strikes the reflecting surface at an angle of incidence which is at or near the Brewster's angle of the film material. The radiation is polarized in its plane of incidence, which must be maintained substantially parallel to any stria in the reflecting surface. The polarization may be provided by germanium plates which receive the radiation at an angle of incidence at or near the Brewster's angle of the germanium.