Abstract: In an infrared analysis instrument, a fiber optic probe, designed to be inserted into a particulate sample, is formed from distal ends of transmitting and receiving optic fibers. The distal ends of the transmitting fibers are located centrally in the probe and the distal ends of the receiving fibers are formed in a ring around the distal ends of the transmitting fibers. The distal ends of the receiving fibers are set back from the distal ends of the transmitting fibers. The receiving fibers carrying diffusely scattered light reflected from and transmitted through the particulate sample to a spectrophotometer housing containing fixed grating and an array of silicon photodetectors arranged to detect the spectrum dispersed by the grating in the range of 500 to 1100 nm.

Abstract: In a flow cell, a flow cell body defines a fluid passageway. Opposed fiber optic cable assemblies with sapphire windows project into the fluid passageway. The fiber optic cable assemblies are axially adjustable in position to provide a capability of varying the path length for the light beam passing between the sapphire windows of the fiber optic cable assemblies in the fluid flowing in the fluid flow path. The path length is precisely settable by means of a feeler gauge which is inserted in a position between the windows of the fiber optic cable assemblies by means of a fixture inserted into the flow path. The fixture is in two parts which engage the fiber optic cable assemblies from opposite ends of the flow path and the fixture is provided with an oblong slot to properly orient the feeler gauge in the flow path between the fiber optic cable assemblies.

Abstract: In a spectroscopic instrument having a spherical grating to disperse incident light into a spectrum, the grating is oscillated on axis to scan the light passing through an exit slit through the spectrum or a portion of the spectrum. The axis of rotation of the grating is shifted to be displaced from tangent to the center of the spherical grating so that the light passing through the exit slit is substantially focused throughout the spectrum scanned by the instrument. The grating is mounted in the holder to shift the center of gravity of the grating and the holder to be on the axis on which the grating is pivoted.

Abstract: In an optical wavelength standard, a concrete matrix embeds wavelength reference material. The concrete matrix is formed from a powdered halogenated polymer (e.g., PTFE) which is mixed with powdered wavelength reference materials, such as rare earth oxides, and the mixture is subjected to sufficient pressure to cause the particles of the halogenated polymer to coalesce into the concrete matrix.

Abstract: In a method for identifying an unknown product a library of absorbance spectra of known products is measured and stored in a library. A quick search using clustering techniques is conducted to narrow the search to a few products, followed by an exhaustive search of the spectra of the few products. More specifically, principal component analysis is applied to the absorbance spectra to generate product score vectors extending into principal component inside model space which are divided into clusters and subclusters in accordance with their relative proximity. Hyperspheres are constructed around each vector and an envelope is constructed to enclose each cluster surrounding the hyperspheres within the cluster. The absorbance spectrum of the unknown product to be identified is measured and an unknown product score vector is determined from the unknown product spectrum projecting in principal component inside model space of the clusters.

Abstract: In an instrument for making an NIR spectrographic transmission measurement of a pharmaceutical tablet, masking structure is provided to prevent or reduce leakage of radiation around the edge of the tablet. The masking structure (30, 44) constricts the boundary of the light beam so that it is within the boundary of the top surface of the tablet where it impinges upon the top surface. The tablet is received in a well slightly larger than the tablet formed in a tablet locator (20). An aperture (39) is formed in the bottom of the well.

Abstract: An infrared spectroscopy instrument having a transflectance type probe with an adjustable path length is disclosed. The instrument is adaptable to take both reflectivity and transmission type measurements. According to a method of use of the instrument discloses a material undergoing a change in viscosity and optical density can be measured by appropriately adjusting the path length to allow a sample of the material to enter. At a first interval, a first measurement is made using the instrument according to a transmission protocol. A second measurement is made of the sample when the sample is viscous and optically dense at a second interval using the same instrument according to a reflectivity measurement protocol.