Kaiser Optical Systems Inc.

Other

Harry Owen

James M Tedesco

Joseph B Slater

David E Battey

Byung Jin Chang

Michael J Pelletier

Kevin L Davis

David J Strachan

Mark Welch

Achromatically corrected Raman immersion probes minimize chromatic and/or spherical aberration through the use of an achromat, apochromat, refractive/diffractive optics as opposed to a single lens geometry. The improved end optics are adapted for use with a probe body carrying a laser excitation and/or collection beam associated with Raman analysis. The achromatically corrected optic to focus the beam onto or within a sample. The sample may be a gas, a liquid, or a partial liquid such as a slurry. The achromatically corrected optic may be an achromat comprising a lens doublet or an achromat comprising a lens triplet or more optical elements. In one preferred embodiment, the achromatically corrected optic may be an apochromatic optic. A disclosed system includes the achromatically corrected end optic and Raman probehead operative to send and receive counter-propagating laser excitation and collection beams.

Raman immersion probe optics

Immersion Raman probes use collimated light as opposed to a diverging fiber bundle or lens-based focusing geometry to deliver and collect light to and from a sample, thereby eliminating problems associated with chromatic aberration. The probes convey counter-propagating excitation and collection beams to and from a distally sealed, signal-transmissive optical component such as a window immersed, in contact with, or otherwise exposed to a sample volume. The counter-propagating excitation and collection beams pass directly through the sealed optical component and into the sample volume in collimated form for Raman analysis thereof. The probe may further include a baffled sample chamber coupled to the distal end of the probe optic body, with one or more optical elements to reflect the counter-propagating beams. The sample chamber may be fixed or axially movable to facilitate path length adjustment. The invention finds utility in process Raman, microscopy and other applications.

Raman immersion probe systems and methods

Spectroscopic probe light shields coupled to the end of an optical probe improve user safety, reduce unwanted stray light and enhance signal collection from a liquid or gaseous sample. Apertured inner and outer baffles with offset perforations allow a sample to flow through the baffles and past a counter-propagating focused or collimated excitation/collection beam. The spectroscopic probe may be a Raman or fluorescence probe, operating in the UV-visible or mid-IR region of the spectrum. The inner shield may include a retro-reflector to amplify light collection from the sample, or the inner shield may include a light absorber to reduce the intensity of a scattered excitation beam. One or both of the inner and outer shields may be cylindrical, and the apertures in the baffles may be slots, circles or other shapes. The baffle(s) may be adapted for temporary, permanent, or semi-permanent attachment to the distal end of the probe optic.

Probe optic light shields

The present disclosure is directed to a method of particle size determination for particles suspended within a light-transmissive medium. The method includes directing a monochromatic light source into the medium and collecting from the medium a Raman-scattered light spectrum. The method includes analyzing the Raman spectrum to determine an amount of Tyndall scattering of the Raman spectrum caused by particles within the medium, and thus determine the size and the number of particles mediating the Tyndall scattering.

Particle size determination using Raman spectroscopy

A compact Raman analysis system combines a near-infrared (NIR) laser source, a 2D array collecting anti-Stokes Raman spectra, and a probe configured to measure complex solid samples, including pharmaceutical tablets and other large-area targets with reduced background fluorescence at relatively low cost. The system collects spectra from an area of 1-mm or greater, preferably 3-12 mm or more, facilitating 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.

Large-collection-area raman probe with reduced background fluorescence

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&#x2013;12 mm or more, compared to current instruments which utilize spot sizes on the order of 2&#x2013;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.

Large-collection-area optical probe

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. A decrease in intensity is measured across the multiple Raman spectrum over time, the intensity decrease associated with macroscopic crystallization opacity. The decrease in intensity is finely correlated with the onset of macroscopic crystallization of the sample from the solvent.

Raman spectroscopy crystallization analysis method

An optical spectrograph utilizes a plurality of holographic transmission optical gratings operative to receive an incoming source of light to be analyzed and diffract the light such that different spectral components impinge upon spatially separated regions of an opto-electronic detector. Various grating configurations are disclosed, including a physical stack of gratings conducive to extreme compactness, as well as a spaced-apart configuration used to preclude spectral cross talk in certain configurations. Diverging light emerging from a fiber-optic bundle is collimated by a first lens assembly prior to passing through the gratings, and a second lens assembly is used to focus the diffracted light onto the detectors, preferably in the form of a two-dimensional CCD array.

Spectrograph with multiplexing of different wavelength regions onto a

A narrow bandwidth bandpass filter having high transmission efficiency for the passband and excellent out-of-band attenuation employs a transmission holographic grating sandwiched between the oblique faces of a pair of right angle glass prisms. An incoming laser beam to be filtered is incident normal to one of the prism faces so as to intersect the holographic grating at about 45.degree.. The grating frequency is such as to diffract light of the transmission wavelength through substantially 90.degree. so that it exits the cube formed by the two prisms from the right angle face of the second prism. The out-of-band wavelengths of the incident beam are either transmitted unaffected through the grating or diffracted at a different angle than the light of the transmission wavelength. A spatial filter comprising a mask with a central aperture is supported a spaced distance from the output face of the cube so that diffracted light of the transmission wavelength passes through the aperture and the unwanted wavelengths, which are diffracted at different angles than the transmission wavelength, are blocked by the mask.

Holographic transmission bandpass filter

A holographic probe facilitates the measurement of radiative effects such as Raman scattering or fluorescence of a remotely disposed sample. Improving upon prior-art techniques, the probe teaches a substantially in-line path between the sample and an output optic wherein a narrowband reflective element, preferably holographically recorded, is used to fold excitation energy from an illumination path into the collection path and reject any Rayleigh scattering received from the sample. The improved configuration further allows a dispersive filtering element to be placed in the illumination path, which may be used in conjunction with spatial filtering to reject non-excitation wavelengths.

Remote optical measurement probe

The Raman scattering detector of this invention includes a source of collimated monochromatic illumination, a cube formed of two right angle prisms, a holographic optical element disposed between the prisms, a concentrating lens, a focusing lens and one or more photo detectors. The illuminating beam passes through the cube and is concentrated by the concentrating leans to a sample. Scattered light returned to the concentrating lens is substantially collimated upon return to the cube. The holographic optical element diffracts light at desired Raman wavelengths approximately 90 degrees without substantially affecting the original wavelength. The holographic optical element further disperses light at desired Raman wavelengths permitting them to be separated. The diffracted and dispersed wavelengths are focused on one or more detectors by the focusing lens.

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Franklin, MI, United States of America

Harry Owen