Abstract: An improved variable rate attenuator (VOA) is disclosed, which is used in an optical signal transmission system for testing (and other) purposes. In an optical fiber data transmission system, the VOA can be used to determine how much attenuation of the light beam can be tolerated without causing excessive bit error rate (BER) in data transmission. The improved VOA is a blocker having a vane-like structure which is gradually rotated into a collimated beam to cause attenuation. Because the movement vector of the edge of the blocker perpendicular to the collimated beam gradually becomes less for a given increment of blocker rotation, resolution of the attenuation is improved.

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: Means for digitizing and averaging the signals in an optical time domain reflectometer are disclosed in which a comparator is used to output a 1 or 0 into an arbitrarily large number of successive time-bins. In each comparator choice, the analog voltage signal from the OTDR receiver is compared to a selected analog voltage value. The selected value is chosen randomly from the range of available signals in the interval of interest; and each such valve is used to provide a comparator input into every time-bin during one waveform recovery.Each comparator output signal (1 or 0) is directed to a separate time-bin (counter), representing the desired time interval (resolution). Subsequent comparator output signals are added to each time bin. The waveform recovery runs are repeated until an acceptable signal-to-noise result is achieved. Each waveform run uses a different voltage for comparison to the receiver voltage.

Abstract: A spectrometer system is disclosed in which a plurality of computers are linked by cable carrying serial electronic signals. At least one control computer, and at least one optical head computer are linked by a local area network system (LAN), which includes means for parallel-to-serial signal conversion of the outgoing signals at each computer, and means for serial-to-parallel signal conversion of the incoming signals at each computer. The system permits remote control of multiple optical heads, a characteristic which is particularly important in process control and environment monitoring situations.

Abstract: This application discloses a system in which a single optical time domain reflector is used to monitor a plurality of cables. In one embodiment two lasers having different wavelengths are separately fired into different cables, and the returning signals are fed into the appropriate port of a wavelength dependent coupler. In another embodiment, each laser simultaneouly checks two cables having different lengths, the length difference permitting identification of the cable in which a fault has occurred.

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 chromatography sample transfer process is disclosed in which fractions on a TLC plate are automatically moved by capillary action from the plate to separate receptacles adapted to retain material for diffuse reflectance measurement. The developed TLC plate is so mounted that its fractions are horizontally spaced, and its lower edge is in a solvent. As the solvent moves upwardly due to capillarity, it dissolves the fraction samples, and transfers them to a plurality of horizontally spaced wicks. The wicks, which are preferably made of sintered stainless steel powder, carry their solvent/sample material upwardly to separate receptacles, each containing transparent powder which retains the sample during diffuse reflectance measurement. The solvent is removed from the receptacles by horizontal airflow (air knife) without requiring significant heating.

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: 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: 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.