Abstract: A material which is generally transparent in the visible region of the spectrum but reflective at laser wavelengths reduces undesirable, substrate-induced Raman and fluorescence scattering. A substrate provides a surface for supporting the sample, with the material being disposed between the surface of the substrate and the sample. The material is substantially transparent in the visible region of the spectrum but reflective at the laser wavelength, thereby minimizing unwanted Raman or fluorescence scattering that would be produced by the substrate if the material were not present. The substrate will typically be a glass microscope slide or multi-cell well plate. The optical filter material is preferably a multilayer dielectric filter acting as a “hot mirror” that reflects near-infrared energy. An advantage of visible transmission is that it allows back illumination from behind/underneath the slide or well plate, thereby being visible to a microscope's eyepiece or video camera.

Abstract: Indicator light apparatus and methods associated with a laser beam having a primary wavelength enable an operator to see the indicator while wearing protective eyewear tuned to the primary wavelength. The apparatus includes a source of indicator light other than the primary wavelength, a first optical element for co-injecting the indicator light into the laser beam to form a co-propagating beam, and an optical or physical configuration enabling an operator to view light from the co-propagating beam. The first optical element may be some form of beam splitter or combiner, and the configuration enabling an operator to view light from the co-propagating beam uses a diffuser upon which the co-propagating beam impinges. The indicator light is preferably derived from an inexpensive source, such as a diode laser operating in the 670-690 nm range.

Abstract: A material which is generally transparent in the visible region of the spectrum but reflective at laser wavelengths reduces undesirable, substrate-induced Raman and fluorescence scattering. A substrate provides a surface for supporting the sample, with the material being disposed between the surface of the substrate and the sample. The material is substantially transparent in the visible region of the spectrum but reflective at the laser wavelength, thereby minimizing unwanted Raman or fluorescence scattering that would be produced by the substrate if the material were not present. The substrate will typically be a glass microscope slide or multi-cell well plate. The optical filter material is preferably a multilayer dielectric filter acting as a “hot mirror” that reflects near-infrared energy. An advantage of visible transmission is that it allows back illumination from behind/underneath the slide or well plate, thereby being visible to a microscope's eyepiece or video camera.

Abstract: A material which is generally transparent in the visible region of the spectrum but reflective at laser wavelengths reduces undesirable, substrate-induced Raman and fluorescence scattering. A substrate provides a surface for supporting the sample, with the material being disposed between the surface of the substrate and the sample. The material is substantially transparent in the visible region of the spectrum but reflective at the laser wavelength, thereby minimizing unwanted Raman or fluorescence scattering that would be produced by the substrate if the material were not present. The substrate will typically be a glass microscope slide or multi-cell well plate. The optical filter material is preferably a multilayer dielectric filter acting as a “hot mirror” that reflects near-infrared energy. An advantage of visible transmission is that it allows back illumination from behind/underneath the slide or well plate, thereby being visible to a microscope's eyepiece or video camera.

Abstract: A method and apparatus for encapsulating optical elements, particularly dichromated gelatin (DGC) holographic optical elements (HOEs), exhibits a very high degree of environmental integrity. In broad terms, the optical element is disposed between opposing plates, and a metal seal soldered to the edge(s) of the plates to seal the optical element therewithin. In the preferred embodiment, the metalization includes chrome and nickel, or alloys thereof, followed by gold or platinum. The metallization is preferably applied using a low-temperature process such as vacuum deposition or sputtering. The metal seal may be in the form of a foil or wire. One or both of the plates are compatible with wavelengths of interest, and the technique may be used in transmissive and reflective configurations.

Abstract: Raman measurement apparatus optimized for gaseous and other low-concentration samples includes a focusing objective that uses only first-surface mirrors instead of lenses, thereby dramatically reducing background noise. In the preferred embodiment, the focusing and collimation functions performed by the objective section are performed by an off-axis parabolic mirror. A spherical first-surface mirror opposing the parabolic mirror re-images the counter-propagating beam back through the same focus for re-collimation by the parabolic mirror. A probe-head section operative to generate the counter-propagating beam has substrates and surfaces arranged such that the excitation beam does not pass through any substrates after it is filtered by the bandpass coating, thereby further decreasing background signals.

Abstract: Raman measurement apparatus optimized for gaseous and other low-concentration samples includes a focusing objective that uses only first-surface mirrors instead of lenses, thereby dramatically reducing background noise. In the preferred embodiment, the focusing and collimation functions performed by the objective section are performed by an off-axis parabolic mirror. A spherical first-surface mirror opposing the parabolic mirror re-images the counter-propagating beam back through the same focus for re-collimation by the parabolic mirror. A probe-head section operative to generate the counter-propagating beam has substrates and surfaces arranged such that the excitation beam does not pass through any substrates after it is filtered by the bandpass coating, thereby further decreasing background signals.

Abstract: Optical diffraction configurations provide uniform physical channel spacing in dense wavelength division multiplexing (DWDM) applications. A grating has a dispersed side outputting (or receiving) or a plurality of spaced-apart optical frequencies or wavelengths to (or from) an image plane, and a prism is supported between the dispersed side of the grating and image plane improve the uniformity of the spacing between optical frequencies or wavelengths at the image plane. The diffraction grating may be a transmission or reflection grating. The diffraction grating is preferably a volume-phase holographic (VPH) grating. A second prism may be used such that the input and output beams have a substantially identical aperture.

Abstract: Thermally stable GRISMs comprise a substrate and cover plate composed of a first material keeps the spatial frequency of the grating stable with temperature, and a prism composed of a second material having lower thermal coefficient of refractive index than that of the first material. In the preferred embodiment, the first material is fused silica, and the second material is BK7 glass.

Abstract: A grism based upon a grating with a given line frequency is configured such that a design wavelength will undergo either a specific total bend angle, a zero-degree total bend without lateral displacement, or a zero-degree total bend with a lateral displacement. Each configuration exhibits the same dispersion characteristics. Other design wavelengths, bend angles and displacements are possible through appropriate adjustment of grating frequency, prism geometry, and/or material(s). A specific design is disclosed using light with a +/?delta wavelength around a design wavelength of 795 nm. The invention may be used to disperse light at different wavelengths, including wavelengths associated with optical communications bands.

Abstract: A multi-channel, reconfigurable fiber-coupled Raman instrument uses fiber optic switches for laser and calibration light routing to facilitate automated calibration, diagnosis and operational safety. The system allows wavelength axis calibration on all channels; laser wavelength calibration (including multiple and/or backup laser options); fiber coupling optimization; fault detection/diagnosis; and CCD camera binning setup. In the preferred embodiment, dedicated calibration channels surround data channels on a 2-dimensional CCD dispersed slit image implemented using a unique cabling architecture. This “over/under” calibration interpolation approach facilitates quasi-simultaneous or sequential calibration/data acquisitions. CCD binning between sequential calibration and data acquisitions enables higher density multi-channel operation with tilted images based upon a multiplexed grating configuration.

Abstract: A compact Raman/fluorescence probe is capable of collecting spectra from a relatively large spot size as compared to traditional confocal Raman probes. The inventive probe collects spectra from an area or 1 mm or greater, preferably 3–12 mm or more, compared to current instruments which utilize spot sizes on the order of 2–60 microns. The larger spot size facilitates the collection of statistically useful data from inhomogeneous and laser-sensitive samples, among other applications. Potential pharmaceutical applications include tablet dosage level measurements, as well as online and at-line quality-control (QC) monitoring opportunities. Other applications include tablet identification as a forensic tool to identify counterfeit pharmaceutical products; granulation and blend uniformity for improved formulation via better process understanding, and reactor cleanliness validation.

Abstract: A remote optical measurement suitable for Raman and fluorescence detection uses one or more dielectric components and an optical configuration which affords significant miniaturization, in some cases resulting in a probe with dimensions on the order of one-half inch or less on a side. A primary application is the pharmaceutical market, wherein the reactors vessels are only 1-inch in diameter, causing a scale down of instrumentation due to space requirements.

Abstract: A self-cleaning optical probe includes a probe body having a window with a surface oriented toward a sample under investigation. A sampling beam carrying wavelengths representative of the sample passes into the probe body through the window for analysis. A conduit, preferably forming part of the probe body, is used to carry a fluid to the surface of the window oriented toward the sample, and a partition proximate to the window is used to direct the fluid across the window as a laminar flow. The partition further includes an aperture through which the sampling wavelengths pass. This partition also permits a portion of the fluid to pass though the aperture to ensure that the sample under investigation does not reach the window. The fluid may be a liquid or gas, and is preferably a solvent to maximize window cleaning.

Abstract: An optical configuration suited to the monitoring of a process flow through the wall of a containment vessel for producing a high-quality, high-NA sample focus and reduced residual positive spherical aberration. The invention includes an optical path with a window extending through, and sealed to, the wall of the containment vessel, and an optical surface disposed in the optical path associated with minimizing aberration, increasing numerical aperture, or both. The window has a surface facing into the process flow and a surface facing away from the process flow and, the surface facing away from the process flow is associated with minimizing aberration or increasing numerical aperture. A lens is disposed outside the containment vessel and in the optical path, with the surface of the window facing the lens being substantially spherical. With such an arrangement, the light rays of the optical path are generally normal to the surface of the window facing the lens.

Abstract: A method of monitoring sample crystallization from a solution. The method includes the collection of multiple Raman spectra from a sample dissolved in a solvent as a function of time and under conditions promoting crystallization. Within each of the multiple Raman spectra, a first signal is identified corresponding to the sample associated with the solvent. A second signal corresponding to the sample in a microcrystallite state is also identified. Thereafter, the intensity of the multiple Raman spectra are measured for an increase relating to formation of the sample in a microcrystallite state. A method of monitoring sample crystallization from a solution as a function of turbidity is also disclosed. The method includes the collection of multiple Raman spectra from a sample dissolved in a solvent as a function of time under conditions promoting crystallization.

Abstract: A dispersive optical element and positionable micromirrors are deployed to implement a configurable wavelength routing device for add/drop and other applications. Input light is dispersed and imaged onto a focal plane where there is disposed an array of light redirection elements operative to decenter wavelengths on a selective basis. In the preferred embodiment, the dispersive optical element is a grating or grating/prism featuring a high degree of dispersion allowing the input and return paths to be parallel and counter-propagating, both for a compact size and to facilitate a lateral shifting in a localized area. The inputs and outputs may be implemented in conjunction with optical fibers, with a lens being used to collimate light prior to illumination of the grating. A focusing lens is preferably used to form a nominally telecentric image of the dispersed spectrum at the image plane.

Abstract: In an optical measurement probe of the type which incorporates a window configuration suited to on-line process control and other applications this invention provides an improved technique for bonding such a window to probe body or process vessel. In general terms, the improvement arises through the use of a compression ring around the bonding area to maintain a consistent seal. In terms of apparatus, a hollow probe body terminates in a distal end having a flanged portion with an inner and outer wall that extends back into the body. The outer wall of the window is sealed against the inner wall of the flanged portion, with compression material urged against the outer wall of the flanged portion to pressurize the seal between the window and the inner wall of the flanged portion. In the preferred embodiment, the compression material is ring-shaped and exhibits substantially the same thermal expansion coefficient as the window.

Abstract: Disclosed is a method of positioning a focused image within a sampled medium in an optical measurement probe of the type wherein a focused sampling image is transmitted through a window having a surface facing a sampled medium. A test medium is measured, preferably through the window, and the magnitude of an optical signal associated with the test medium is then compared to the magnitude of an optical signal associated with the window, and the result of the comparison is used to position the focused image. Typically, the magnitudes of optical signals are representative or Raman scattering or another wavelength-selective radiative sampling process such as fluorescence detection. The method is not limited in terms of window composition, and is compatible with sapphire windows commonly used in industry. Nor is the invention limited in terms of test medium though, in the preferred embodiment a fluid hydrocarbon such as isopropyl alcohol is used.

Abstract: Multiplexed grating and grating/prism devices are particularly suited to DWDM optical telecommunications networks, finding utility in optical spectrum analyzers (OSAs) and fiber multiplexer/demultiplexers. The invention may be used to address both single- and dual-band configurations through adjustment of the grating, detector array, and/or inclusion of a fiber-optic switch. As a dual-band OSA covering the C- and L-bands, a device according to the invention may be used to replace two separate OSAs like those currently in production, at only a modest increase in cost relative to a single-band OSA.