Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-03-08
2004-08-10
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S339020, C356S051000
Reexamination Certificate
active
06774368
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a Near-infrared (NIR) spectrometer with automatic wavelength calibration without the need of external calibrating. NIR spectroscopy is the measurement of the wavelength and intensity of the absorption of near-infrared light by a sample. Near-infrared light spans the 800 nm-2.5 micrometers (&mgr;m) range and is energetic enough to excite overtones and combinations of molecular vibrations to higher energy levels. NIR spectroscopy is typically used for quantitative measurement of organic functional groups, especially O—H, N—H, and C—H. Analyte detection limits are typically 0.1%.
NIR spectroscopy has been shown to be a powerful analytical tool for the analysis of agricultural products, food products, petroleum products, and pharmaceuticals products. Recently, NIR spectroscopy has been approved for the analysis of pharmaceutical products, a factor that is likely to dramatically extend the number of applications of the technique. In general, when NIR spectroscopy is combined with multivariate calibration procedures, the analytical methodology that results is rapid, accurate, and requires virtually no sample preparation.
1
In conventional NIR spectroscopy, a multivariate statistical model is developed that attempts to correlate subtle changes in the NIR spectrum with known compositional changes determined by standard analytical technology. Once a robust model has been developed, NIR spectroscopic measurements can be substituted for the more time consuming, labor-intensive conventional analytical measurements.
2
To be completely useful, however, a model developed on one spectrometer in the laboratory should be capable of being used on different spectrometers without having to go through the model development all over again with the new instrument. To transfer a model from one spectrometer to another successfully, both instruments must ideally be identical.
3
Many NIR spectrometers in use today employ dispersive systems that use diffraction grating monochromators. For these instruments, accurate wavelength calibration is important if the calibration models developed in the laboratory are to be used successfully on other instruments in the production environment. If the wavelength scales of different spectrometers are miscalibrated (as they inevitably are), problems with calibration transfer will occur.
4
Because of this, the standardization of NIR spectrometers has been pursued. The rational behind this being that if instruments are alike and remain stable enough, calibration transfer no longer becomes an analytical performance issue. Instrument standardization helps ensure that spectra produced from different instruments of the same design are essentially identical. In order to successfully carry out the various instrument standardization protocols, such as those suggested by Workman and Coates
5
and Wang, et al.
6
, it is necessary to develop strategies that would accurately characterize all the instrumental variables of importance (i.e., wavelength and photometric accuracy, spectral bandwidth, and stray light). One way to avoid this problem is to use a wavelength standard to validate the wavelength scale of the spectrometer. Various wavelength standards exist.
7-10
Recently, Busch and co-workers have proposed the use of trichloromethane as a substance with sharper, isolated absorption bands that are suitable for wavelength calibration of spectrometers in the NIR region.
11
The study of the use of trichloromethane as a wavelength standard showed that calibration of the wavelength scale of NIR instruments is absolutely essential, and a typical dispersive NIR spectrometer may be off by as much as 12 nm in the NIR region. Busch and co-workers have also assembled a research-grade NIR spectrometer that has been designed to allow the effect of various instrumental parameters on spectrometer performance to be studied in a systematic fashion. This is the same NIR spectrometer used to study the role of trichloromethane as a wavelength standard for NIR spectroscopy and to evaluate the stray light level in dispersive NIR spectrometers that has been designed to allow the effect of various instrumental parameters on spectrometer performance to be studied in a systematic fashion.
12
This disclosure describes a novel, dispersive, diffraction grating, NIR spectrometer that automatically calibrates the wavelength scale of the instrument without the need for external wavelength calibration materials.
SUMMARY OF THE INVENTION
In accordance with the above and related objects, the present invention is a dispersive, diffraction grating, NIR spectrometer that automatically calibrates the wavelength scale of the instrument without the need for external wavelength calibration materials. In a preferred embodiment, the present invention results from the novel combination of: 1) a low power He—Ne laser at right angles to the source beam of the spectrometer (FIGS.
2
and
3
); 2) a folding mirror to redirect the collimated laser beam so that it is parallel to the source beam (see
FIGS. 1
and
2
); 3) the tendency of diffraction gratings to produce overlapping spectra of higher orders; 4) a “polka dot” beam splitter to redirect the majority of the laser beam toward the reference detector (FIGS.
3
and
4
); 5) PbS detectors and 6) a software routine written in Lab VIEW that automatically corrects the wavelength scale of the instrument from the positions of the 632.8 nm laser line in the spectrum. Methods for making the aforesaid invention are included. In one particular embodiment, the claimed method includes obtaining an enhanced calibration set of NIR spectra by improving a dispersive, diffraction grating NIR spectrometer so that it automatically calibrates the wavelength scale of the spectrometer without the need for external wavelength calibration means. The improvement is further defined as obtaining and installing the novel parts as described above.
REFERENCES:
patent: 5040889 (1991-08-01), Keane
patent: 5394237 (1995-02-01), Chang et al.
patent: 6067156 (2000-05-01), Slater et al.
patent: 6411373 (2002-06-01), Garside et al.
patent: 6452177 (2002-09-01), Feldman et al.
patent: 6480795 (2002-11-01), Bossart et al.
Soyemi, et al, “Design of a modular, dispersive spectrometer for fundamental studies in NIR spectroscopy.” Apr. 2001, 24-33, Spectroscopy.
Blank, et al, “Transfer of near-infrared multivariate calibrations without standards.” Sep. 1, 1996, 2987-2995, Anal. Chem.
Wang, et al, “Multivariate Instrument Standardization.” Dec. 1, 1991, 2750-2756,Anal Chem.
Lowry, et al, “Determination of Wavelength Accuracy in the near-infrared spectral region based on NIST's infrared transmission wavelength standard SRM 1921.”Nov. 3, 2000, 450-455,Spectroscopic Techniques.
Busch, et al, “Wavelength Calibration of a dispersive near-infrared spectrometer using trichloromethane as a calibration standard.” May 2000, 1321-1326,Applied Spectroscopy.
Busch, et al, “Determination of the stray light levels in a dispersive near-infrared spectrometer with trichloromethane.”Aug. 2000, 1759-1766,Applied Spectroscopy.
Wiegenstein, et al, “A virtual instrument approach for automation of temperature programmed desorption.”Oct. 1998, 3707-3708,Am Inst of Physics.
Koenig, et al, “A computer driven crystal spectrometer with charge coupled device detectors for x-ray spectroscopy of laser plasmas.”Jun. 1997, 2387-2392,Am Inst of Physics.
Kirkman, et al, “Software.”Jul. 16, 1991, 869-872,Am Inst of Physics.
Stryjewski, “Macintosh/lab VIEW based control and data acquisition system for a single photon counting fluorometer.”Aug. 1991, 1921-1925,Am Inst of Physics.
de Viteri, Diamond “Virtual Instrument for flow-injection analysis with senor detection.”Aug. 1994, 229-232,Analytical Proceedings.
Workman, et al, “Review of chemometrics applied to spectroscopy: 1985-95, Part 1.”1996, 74-124,Applied Spectroscopy Reviews.
Soyemi, “Design of data acquisition and analysis systems in near infrared spectroscopy: a virtual instrument approach.”May 2000,Dissertation-Doctor
Busch Kenneth W.
Rabbe Dennis H.
Baylor University
Gabor Otilia
Hannaher Constantine
Jackson & Walker, LLP
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