Abstract: A method for determining the concentration of individual solutes in a body of liquid, e.g., measuring contaminants in waste water. A sparging IR process is used, in which gas in the form of minute bubbles moves upwardly in a non-flowing body of liquid. The gas remove vaporized samples of the subject solutes and flows to a gas cell, where it is subjected to infrared spectrometer analysis. The true concentration of each subject solute is measured by plotting its concentration values against elapsed time, and then extrapolating back to time zero to determine the initial concentration of the solute. In addition, the rate of depletion is used to determine the ratio of vapor pressure to solubility of the solute. Replotting the original data using logarithm values can simplify the extrapolation.

Abstract: A gas cell for use in spectrometric analysis is disclosed, in which a series of pipes provide both the gas chamber and a light guide for infrared radiation which passes through the gas to accomplish the analysis. The light pipe is designed to provide a maximum radiation throughput of a collimated radiation beam. The same pipe provides laminar gas flow into and out of the gas cell. In other words, the gas when moving is not obstructed or restricted by changes in the cross-sectional area of its passageway.

Abstract: An ATR sample cell is disclosed, of the type incorporating a circular internal reflectance crystal. A flowing liquid sample has input and output ports in the IRE housing, or cell, which are offset from the axis of the circular IRE (or rod) sufficiently to direct the flow of liquid against the internal wall (usually stainless steel) of the flow jacket, rather than against the IRE. This tends to create a helical flow path from the input port at one end of the housing to the output port at the other end of the housing. In order to further control the sample flow path, and augment the spiraling effect, two further improvements are disclosed. The structure through which the sample material enters the sample chamber surrounding the IRE is designed to establish a spiraling motion of the liquid flow before it enters the sample chamber. Also, the inner cylindrical wall of the metal housing has a groove which forms a helical path from the input to the output end.

Abstract: A radiation guiding structure for incoherent radiation is disclosed in which a collimated beam is transmitted through a light pipe having high radition throughput. Radiation losses due to absorbance are minimized by: (1) matching the area of the beam and the light pipe passage; (2) minimizing the number of reflectances of a given ray by reducing the angular divergence of radiation in the beam; and (3) using a reflective coating on the wall of the light pipe which has the low point of its reflectance curve at a relatively high grazing angle.

Abstract: A probe is disclosed for use in internal reflection spectroscopy at locations immersed in containers. Two parallel light pipes, located inside the probe, are used to carry radiation toward and away from an internal reflectance element (IRE) located at or near the bottom of the probe. The IRE, which is exposed to analyte in the container, has a radiation-entering surface and a radiation-exiting surface which permit collimated radiation to fill both light pipes. No beamsplitter is required to separate pre-sample and post-sample radiation. In one embodiment the IRE is a rod having concave conical entering and exiting surfaces, and a separate radiation-direction-reversing element is mounted on the tip of the probe. In another embodiment the IRE is itself a direction-reversing means mounted on the tip of the probe.

Abstract: An external reflectance spectroscopy apparatus and method are disclosed in which maximum radiation througput is obtained by using a beamsplitter which reflects half of a collimated beam and transmits the other half. In order to obtain reliable results, the condition of perpendicular incidence on the sample is approximated (without limiting throughput) by providing a beamsplitter having an uneven number of reflecting blades and the same number of transmitting openings. Each reflecting blade is opposite to an open area having the same size and shape. The result is a substantial equalizing of contributions from rays polarized parallel to the plane of incidence and from rays polarized perpendicular to the plane of incidence.

Abstract: An infrared microscope is disclosed which provides illumination for reflectance by the sample. This illumination follows a path through the objective toward the sample, and again, after reflection, through the objective toward the detector. The reflectance illumination is directed toward the objective and sample by a fully reflective mirror, which injects approximately half of the interferometer beam into the microscope, and permits substantially all of the reflected beam to reach the detector.

Abstract: An apparatus and method for fluid sample analysis are disclosed which use a cylindrical internal reflectance element (IRE) having conical end surfaces. The divergence of rays inside the IRE is minimized by using reflecting cones at each end of the IRE, the structural elements and their dimensions being such that each entering ray strikes the conical IRE end surface at substantially the same angle of incidence. Means are included for providing optical stops at the large end of both the input and output reflecting cones, in order to eliminate any rays which might travel through the IRE without first being reflected by the input cone. Using such stops and properly dimensioning the entering diameter of the reflecting cone, result in a system in which each ray entering the IRE has been reflected once, and only once, by the reflecting cone.

Abstract: A microscopic unit for a multi-station modular FTIR spectrometer system is disclosed. The microscope unit, which has a Cassegrain objective, not only provides the usual optical path for radiation during visual observation, and for infrared radiation in the transmission mode, but also provides a separate optical path for infrared radiation in the reflectance mode and in a macroscopic transmission mode.

Abstract: An infrared microscope is disclosed in which two adjustable field stops are included. One is used to determine the illuminated area at the sample when the microscope is used in the transmission mode. The other is used to determine the illuminated area at the sample when the microscope is used in the reflectance mode. The latter field stop is imaged in the plane of the former; and the radiation in the reflectance mode passes through the former field stop both as it passes to the sample and as it returns from the sample after reflectance.

Abstract: A spectroscopy system is disclosed which obtains analytical information from an internal reflectance element (IRE) deeply immersed in a container. The system is designed to provide adequate radiation throughput under difficult conditions. A plurality of embodiments deal with the optical element(s) at the bottom of the tube and the optical element(s) above the tube which direct post-interference radiation downward in the tube and receive post IRE upward radiation for re-direction to the detector.

Abstract: A spectrometer system is disclosed in which a single ended internal reflectance element (IRE) is readily insertable into, and removable from, liquid samples being analyzed. The IRE is carried by an articulated housing construction having enclosed radiation passages, through which radiation is directed by a plurality of mirrors. The IRE-supporting enclosure is pivotally mounted by means of aligned rotatable members, which permit the IRE to be moved into and out of samples without disconnecting or re-purging the enclosed radiation passages.

Abstract: A spectrmeter radiation transmission system is disclosed which permits concurrent availability of numerous alternative accessory devices by conserving radiation throughput. Parabolic reflectors are used to provide alternating collimated and confocal segments of radiation, thereby largely eliminating the problem of vignetting (i.e., loss of radiation throughput due to beam size expansion). Modular enclosure elements are provided, inside which the radiation path travels between the parabolic reflectors.

Abstract: A modular spectrometer system is disclosed which includes various types of standard building blocks which permit: (a) a multiple accessory system in which experiments can be readily switched from one accessory to another; and (b) easy and cost effective revision of the multiple accessory system as desired. Optical switch components are provided which facilitate steering and switching of the radiation paths, and which are capable of being assembled from standard parts. Modular connecting tubes and interface elements are provided to interconnect components in the system. Component substitutions and position adjustments may be readily accomplished without loss of alignment in the system.

Abstract: An interferometer structure is disclosed which has an integrated central mirror unit, which constitutes an integrated alignment unit permitting complete prealignment before the unit is incorporated into the interferometer. The integrated unit carries the beamsplitter and two folding mirrors. Alignment is accomplished by adjusting the positions of the two folding mirrors around vertical and horizontal axes. Both the stationary mirror and the movable mirror, which control the radiation path lengths in the two interferometer arms, are retroreflectors. Because of the folding miirror effect, resolution of the interferometer spectrometer system is significantly enhanced.

Abstract: An apparatus for spectral analysis of chemical fractions is disclosed in which separate samples are frozen on a substrate, and infrared radiation passes through the sample either before or after it is reflected from a surface on the other side of the substrate from the sample. This permits radiation to move toward and away from the sample at the same side of the sample, thus simplifying the sample-cooling and sample-deposition techniques. The optical system is designed to defocus (and thus avoid detection of) unwanted radiation reflected by the sample.

Abstract: A reflectance/transmittance structure is disclosed, which is adapted to be used in a microscope (primarily for infrared radiation) of a type disclosed in previous common inventor/common assignee applications. Radiation is passed through a Cassegrain objective lens on its way to the sample. It is reflected by a spherical mirror toward a flat mirror, then back to the spherical mirror, and then back through the sample on its way back to the Cassegrain objective lens. This arrangement permits retention of both the redundant aperturing and the injection mirror features of prior patent applications.

Abstract: The present invention provides a radiation source which essentially matches the throughput radiation of the source to the throughput radiation of the interferometer; and it provides the maximum throughput usable by the interferometer with a minimum use of power at the source. The infrared source in this invention combines a radiating element having the optimum area with a hollow, inwardly-reflecting sphere, whose center is at the radiating element and whose exterior has a single aperture which causes radiation to fill the entrance field of view of the spectrometer.

Abstract: A spectrometer system is disclosed in which the sample-containing chamber is a separately constructed, enclosed modular unit which is readily attachable to, and detachable from, one wall of a housing which constitutes the basic unit of the spectrometer, and which contains an interferometer, one or more detectors, and other portions of the system. Various examples of the essentially unlimited types of sampling modules are disclosed. Also, automatic sample loading and unloading devices are disclosed, which are feasible because of the modular construction. And means of loading and unloading samples without purge loss are disclosed, which are feasible because of the modular construction.

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 the "back-to-back" paraboloid reflectors, i.e., their reflecting surfaces face in substantially different, preferably opposite, directions.