Abstract: The present invention provides a method for monitoring degradation of Hb-based blood substitutes, in a sample. This method comprises determining a concentration of met-Hb within the sample, by applying a calibration algorithm for met-Hb to an absorbance obtained from the sample at one or more than one wavelengths, and using the concentration of met-Hb, as a measurement of degradation of the Hb-based blood substitutes. Using this assay, a concentration of met-Hb that is equal to or greater than 3% may be used as an indicator of degradation of Hb. Alternatively, by obtaining samples over a period of time, the concentration of met-Hb and the concentration of Hb-based blood substitute may be determined in each of these samples, and an increase in the concentration of met-Hb over the period of time is an indicator of degradation of Hb.

Abstract: A method and system for extracting data signals from a scanned image resulting from optical, radiometric, or other types of analysis of a molecular array. The positions of corner features are first located. Then, an initial feature coordinate grid is determined from the positions of the corner features. A refined feature coordinate grid is then calculated based on the positions of strong features, and is used to identify the positions of weak features and the positions of the local background regions surrounding all features. Finally, signal intensity values are extracted from the features and their respective local background regions in the scanned image, and background-subtracted signal intensity values, background-subtracted and normalized signal intensity ratios, and variability information and confidence intervals are determined based on the extracted values.

Abstract: A method and system for measuring properties of a sample are disclosed. At least one source of excitation radiation is used to irradiate the sample's surface. This excites multiple acoustic modes within the sample. A probe source of radiation diffracts off the acoustic modes to generate a signal beam. The signal beam is detected and analyzed to yields a signal waveform, from which a Fourier Transform spectrum is derived. The Fourier Transform spectrum features frequencies corresponding to the multiple acoustic modes. Analysis of the spectrum yields measurements of the sample's properties.

Abstract: An apparatus and system for determining the properties of a sample from measured spectral data collected from the sample by performing a method of multivariate spectral analysis. The method can include: generating a two-dimensional matrix A containing measured spectral data; providing a weighted spectral data matrix D by performing a weighting operation on matrix A; factoring D into the product of two matrices, C and ST, by performing a constrained alternating least-squares analysis of D=CST, where C is a concentration intensity matrix and S is a spectral shapes matrix; unweighting C and S by applying the inverse of the weighting used previously; and determining the properties of the sample by inspecting C and S. This method can be used by a spectrum analyzer to process X-ray spectral data generated by a spectral analysis system that can include a Scanning Electron Microscope (SEM) with an Energy Dispersive Detector and Pulse Height Analyzer.

Abstract: A radiative transport band model algorithm has been developed for prediction and analysis of high spectral resolution radiometric measurements. Atomic and molecular line center absorption is determined from finite spectral bin equivalent widths. A new mathematically exact expansion for finite bin equivalent widths provides high accuracy at any desired spectral resolution. The temperature and pressure dependent Voigt line tail spectral absorption contributing to each spectral bin is pre-computed and fit to Padé approximants for rapid and inaccurate accounting of neighboring-to-distant lines.

Abstract: Described is a method for determining the concentration of an analyte in a future sample that is measured on a second apparatus. This method involves incorporating, in a second apparatus, at least one primary calibration algorithm that is developed using absorbances of samples from a primary calibration set. The absorbances, which are optionally pre-processed prior to primary calibration algorithm development, are obtained from one or more first apparatus. The absorbance values of the future sample are measured on the second apparatus at one or more than one wavelength from a standard set of wavelengths, and a concentration of the analyte in the future sample is calculated by applying the Primary Calibration Algorithm to the optionally pre-processed absorbance of the future sample obtained from the second apparatus.

Abstract: Spectrographic instruments at remote site locations measure near infrared absorbance spectra for unknown materials and transmit the absorbance spectra to a central web site where, the measurements are standardized to be the same as if they were measured by a master instrument. The standardized absorbance spectra are then compared with a library of spectra stored at the central web site to select a subset of absorbance spectra from the library which most closely correlate with the absorbance spectrum received from the remote sites. The library spectra are obtained from measurements on materials, the measurable characteristics of which are known. From the selected subset, equations are developed relating the measurable characteristics of the unknown material to the absorbance spectra and from these equations, the measurable characteristics of the unknown materials are determined. The results of this analysis are then transmitted back to the remote site locations electronically.

Abstract: A system and method of detecting gases in the exhaust of a moving vehicle with a small engine, such as a motorcycle or moped. The system employs a gas analyzer with a beam which makes more than two passes through a detection space. Through multiple passes through the detection space, the gas analyzer generates a signal indicative of the concentrations of one or more components of interest in the exhaust plume. The system also includes a processor for obtaining information about one or more vehicle exhaust components from the generated signal.

Abstract: An oil deterioration diagnosing method and an apparatus for carrying out the same uses an optical sensor capable of determining a degree of deterioration of oil on the basis of transmission losses of near-infrared rays of two different wavelengths and the transmission loss difference between the transmission losses. The degree of deterioration of the oil can be determined without being affected by variable measuring temperature and the original color of the oil.

Abstract: The instant invention relates to improved methods and systems for proteomic analysis using MS (mass spectrometry) data, particularly tandem mass spectrometry (MS/MS) data. The method comprises searching a first level database using sequence information generated by MS/MS obtained from a peptide selected from a digested protein sample. A second level database (which is smaller and contains only the candidate proteins) is then searched to identify the identity of the protein containing the selected peptide. More levels of even smaller databases can be generated for successive rounds of searches if the previous round of search does not unequivocally identify the protein containing the selected peptide(s). The method may be carried out on a range of mass spectrometers including a tandem mass spectrometer (MS/MS), an ion trap mass spectrometer or others capable of generating MS and MS/MS data.

Abstract: A sensitivity encoding method (SENSE) is used to acquire an MR image having a reduced field of view. The number of aliased replicates caused by surrounding object boundaries is calculated for each image pixel location to obtain optimal aliasing artifact suppression without reducing image SNR.

Abstract: A method and a device for measuring the characteristics of a sample by spectral analysis. According to the method, the characteristics are calculated from the spectral data obtained by the spectral analysis, using a calibration model that has been established on the basis of reference samples. In order to improve the stability of the measuring process, an additional calculation of the characteristics (16) of the samples (1) takes place, using at least one additional calibration model (14) that has been established on the basis of additional reference samples (1″). Deviations between the characteristics (12, 16) calculated by the respective calibration models (11, 14) are determined and output.

Abstract: This invention relates to methods and apparatus for determining the multi-dimensional topology of a substance (system) within a volume (space). A method according to a preferred embodiment of the invention comprises the steps of: acquiring a set of relative values for the density (scalar properties) of the volume, each value for a given location (point) within the volume; interpolating a set of functions to generate a continuous relative density for the volume; identifying critical points of the continuous relative density by using an eigenvector following method; and associating critical points with one another by following a gradient path of the continuous relative density between the critical points. The method is applicable to a wide range of data relating to fields such as crystallography, fluid dynamics, edge detection, and financial markets, to determine the topology of structures contained therein.

Abstract: A method for presenting relationships between data from a thrombosis-hemostasis assay on an unknown sample and data from a purality of assays on known samples, which can be in the form of a topological feature map wherein spatial locations within the map correspond to intrinsic features of the known samples. The position of the unknown sample is superimposed on the positions of the known samples. An alternative presentation is showing the distance of each of a purality of predictor variables from an unknown sample to the mean values of a known population.

Abstract: A method that analyzes mass spectra using a digital computer is disclosed. The method includes entering into a digital computer a data set obtained from mass spectra from a plurality of samples. Each sample is, or is to be assigned to a class within a class set having two or more classes and each class is characterized by a different biological status. A classification model is then formed. The classification model discriminates between the classes in the class set.

Abstract: A classification apparatus, notably for uses in recognition or characterisation of odors, comprises a plurality of sensors for generating raw data representing a plurality of instances of a plurality of different classes; and a processing unit for processing said raw data so as to determine an identification model. The identification model comprises definitions of the classes and a particular allocation rule selected dependent upon the application. The class definitions are established by analysing data obtained during a learning phase, the analysis being performed according to a particular information extraction method. During a later identification phase, the identification model enables an instance of unknown class to be allocated to an appropriate class amongst those defined during the learning phase. The information extraction method can be selected dependent upon the application.

Abstract: Systems and methods are described for processing an emission signal, such as a fluorescent signal, to compensate for noise in an excitation beam, such as a laser beam. As one example, a scanning system is described that includes an excitation signal generator that provides an excitation signal having one or more representative excitation values representative of an excitation beam; an excitation reference provider that provides at least one excitation reference value; a normalization factor generator that compares the excitation reference value to at least one representative excitation value, thereby generating a normalization factor; and a comparison processor that adjusts at least one emission value corresponding to the at least one representative excitation value based, at least in part, on the normalization factor.

Abstract: A method and apparatus using a spectral analysis technique are disclosed. In one form of the invention, probabilities are selected to characterize the presence (and in another form, also a quantification of a characteristic) of peaks in an indexed data set for samples that match a reference species, and other probabilities are selected for samples that do not match the reference species. An indexed data set is acquired for a sample, and a determination is made according to techniques exemplified herein as to whether the sample matches or does not match the reference species. When quantification of peak characteristics is undertaken, the model is appropriately expanded, and the analysis accounts for the characteristic model and data. Further techniques are provided to apply the methods and apparatuses to process control, cluster analysis, hypothesis testing, analysis of variance, and other procedures involving multiple comparisons of indexed data.

Abstract: Described is a method for calibrating a spectrophotometric apparatus which is used to measure analytes in plasma and/or serum samples based on the calibration of a First Apparatus, and for recalibrating such apparatus, including recalibration of the First Apparatus all using synthetic calibrators. These apparatus use absorption of radiation to measure analytes in serum or plasma samples. The method described includes using synthetic calibrators which are submitted to the First Apparatus for measurement and compared with measurements of similar calibrators in a Second Apparatus and using the comparison to derive concentrations of analytes in samples measured on the Second Apparatus. As an alternative to making all apparatus identical, in terms of wavelength calibration, the absorbances of all apparatus should be mapped onto a standard set of wavelengths.

Abstract: Methods of compensating for drift in fingerprint spectra of microorganisms caused by changes in their environment are disclosed. These methods of compensating for drift permit identification of microorganisms from their fingerprint spectra regardless of the environment from which the microorganisms are obtained. Furthermore, the disclosed methods may be used to construct coherent databases of fingerprint spectra that may be expanded even though the standard database conditions are no longer experimentally achievable. In particular embodiments, methods of compensating for drift in pyrolysis mass spectra, constructing coherent pyrolysis mass spectral databases, and identifying bacteria from their pyrolysis mass spectra are disclosed.

Abstract: A management method capable of making an accurate decision about a malfunction of the semiconductor manufacturing equipment includes sampling a plurality of data of at least one parameter under normal operating conditions of the semiconductor manufacturing equipment; generating a Mahalanobis space A from a group of sampled data; calculating a Mahalanobis distance D2 from measured values of the parameter under ordinary operating conditions of the semiconductor manufacturing equipment; and deciding that a malfunction occurred in the semiconductor manufacturing equipment when the value of the Mahalanobis distance exceeds a predetermined value.

Abstract: Constituents such as oxy- and deoxy-hemoglobin are monitored non-invasively in an animal organ such as a brain with a spectrometric instrument by passing radiation through the organ. Concentrations are computed from the spectral intensities and from a statistical correlation model. To predetermine the correlation model, the procedures are effected for a plurality of organs of a same type with each organ having established concentrations of the selected constituents, and the correlation model is statistically determined from the concentrations and corresponding intensities. For more accuracy computations are normalized to path length which may be determined by utilizing several discrete wavelengths with RF modulations.

Abstract: An advanced imaging spectrograph system and method are provided for very high throughput identification, sequencing and/or genotyping of DNA and other molecules. The system is based on the integration of improved electrophoresis structures with an imaging spectrophotometer that records the entire emission spectra along an imaging line across a sequencing gel (or capillary array). The system includes spectral shape matching to improve dye identification allowing the use of dyes having nearly any emission spectra and allowing greater than four dye multiplexing.

Abstract: A sensor control and data analysis system (100) for detecting and analyzing various (bio)chemical properties of a given sample substance (107) using an integrated SPR sensor (50) or other miniaturized sensor configuration. In one embodiment, raw sensor data from the sensing device (105) is transferred to a remote processing system (111), such as a desktop computer, having a display (125), keyboard or other user control and data entry device (123), internal storage area (127), internal microprocessor (117) and a communications means (129). The processing system (111) runs a software application program (115) that receives the raw sample data and perform qualitative and quantitative analysis to render meaningful information about the sample substance.

Abstract: Systems and methods using a spectrometer system for real-time automatic evaluation of tissue injury are described. A method of assessing an injury to tissue comprises reflecting an electromagnetic signal from the tissue to produce a reflected electromagnetic signal; producing spectral data pertaining to the intensities of individual wavelengths of the reflected electromagnetic signal; analyzing the spectral data to obtain a set of results; and providing an indication of the nature of the injury to the tissue based upon the set of results.

Abstract: Standard samples including at least a polycrystalline semiconductor film are produced by the energy beam annealing method. Dependencies on wavelength of refractive index and damping coefficients of standard samples are measured by means of a spectral ellipsometer, and grain sizes are measured to be quantified. An estimated sample consisting of a polycrystalline semiconductor film is produced by means of the energy beam annealing method. A dependency on wavelength of a refractive index and a damping coefficient of the estimated sample is measured to be compared with the results of the standard sample. Thus, the optically measured results can be quantified, so that it is possible to accurately measure a mean grain size of a polycrystalline silicon of a sample to be estimated, in a short time of about 5 seconds to calculate mobility to accurately select non-defective from defective in a short time.

Abstract: An oil deterioration diagnosing method and an apparatus for carrying out the same uses an optical sensor capable of determining a degree of deterioration of oil on the basis of transmission losses of near-infrared rays of two different wavelengths and the transmission loss difference between the transmission losses. The degree of deterioration of the oil can be determined without being affected by variable measuring temperature and the original color of the oil.

Abstract: A method for calibration of an IR spectrometry apparatus for providing and evaluating IR spectra in order to determine very low contents of specific components in a fluid, such as milk, and especially low contents of acetone, in a measuring range above 0, such as from 0.5 mM to 2.0 mM acetone in milk, using at least 50, such as from 50-300 known samples including at least 10 samples representing the fluid without any substantial content of the specific component for the calibration. Preferably, a good calibration for acetone shall be based on spectral information including the spectral ranges 1712-1697, 1419-1396, 1378-1353 and 1249-1226 cm−1, or at least a substantial portion/part of said ranges. By use of the new calibration of a FT-IR-spectrometry apparatus it will be possible to determine the acetone content during the sane IR measurement process used for determining other milk parameters such as fat and protein.

Abstract: The inventive system provides a set of human input and output devices such as a video monitor and keyboard, in conjunction with a processing means such as a Personal Computer, an in-circuit microprocessor emulation means, and control software which allows a software developer to interactively and intelligently view the contents of bit-mapped hardware control and status registers in a descriptive manner. Further, the system interacts with the in-circuit emulator and code development environment to automatically create hexadecimal representations of complete register values to be read and written, and performs validity rule checking in order to notify the software developer if disallowed combinations of bit fields have been selected.

Abstract: The properties of a resinous material product are controlled in a manufacturing system by online process parameter monitoring and control. The online monitoring and control incorporates an in-situ measurement system that can monitor product in the process by use of a side stream ultrasonic device. The side stream device advantageously provides online real-time measures of the product's acoustical properties (e.g. velocity, attenuation) under conditions that are independent of process-stream conditions. The side stream device controls the product temperature, pressure, and flow rate while inside the side stream device and the velocity and attenuation are measured under these predetermined temperature, pressure, and flow rate conditions. The acoustical properties (e.g.

Abstract: A data processor used in the overall process of determining meat tenderness which receives, analyses and graphically displays in a dynamic format collected fluorescence emitted by connective tissue as a meat probe passes by such tissue during either insertion or removal of the meat probe from the meat. The data processor also collects and calculates feature variables based on the data collected during the insertion and removal of the meat probe, and through the use of artificial intelligence and artificial neural network processing can be taught to recognize patterns in the meat probe data indicative of tenderness. The data processor also performs an analysis of probe data to make a prediction of meat tenderness.

Abstract: This invention relates to methods and apparatus for determining the multi-dimensional topology of a substance (system) within a volume (space). A method according to a preferred embodiment of the invention comprises the steps of: acquiring a set of relative values for the density (scalar properties) of the volume, each value for a given location (point) within the volume; interpolating a set of functions to generate a continuous relative density for the volume; identifying critical points of the continuous relative density by using an eigenvector following method; and associating critical points with one another by following a gradient path of the continuous relative density between the critical points, The method is applicable to a wide range of data relating to fields such as crystallography, fluid dynamics, edge detection, and financial markets, to determine the topology of structures contained therein.

Abstract: A system and method of detecting gases in the exhaust of a moving vehicle with a small engine, such as a motorcycle or moped. The system employs a gas analyzer with a beam which makes more than two passes through a detection space. Through multiple passes through the detection space, the gas analyzer generates a signal indicative of the concentrations of one or more components of interest in the exhaust plume. The system also includes a processor for obtaining information about one or more vehicle exhaust components from the generated signal.

Abstract: A method is disclosed for predicting the presence of an abnormal level of one or more proteins in the clotting cascade from at least one time-dependent measurement profile. At least one time-dependent measurement on an unknown sample is performed and a respective property of said sample is measured over time so as to derive a time-dependent measurement profile. A set of a plurality of predictor variables are defined which sufficiently define the data of the time-dependent measurement profile. A model is then derived that represents the relationship between the abnormality and the set of predictor variables. Subsequently, the model is utilized to predict which protein or proteins in the clotting cascade are at an abnormal level, with the prediction being a more informative prediction than clot time alone.

Abstract: Methods and apparatus for determining accurate hair color classifications and appropriate coloring agents to bring about a selected change of color include a table of hair color classifications, a color measuring instrument to arrive at Hunter L, a and b values for use in identifying a particular classification from the table and a database that identifies appropriate coloring agents based on a selection of coloring actions from a menu and the classifications of hair color.

Abstract: A system and method for improved image reconstruction of the internal properties of a scattering medium is provided. The reconstruction technique employs a model-based iterative image reconstruction scheme. The reconstruction algorithm comprises a forward and inverse model. The forward model of the present method and system is based on the equation of radiative transfer. The forward model predicts the transport of energy through a medium for a given set of internal properties, source positions, source strengths, and boundary conditions, for a medium to be imaged. The inverse model relates the predicted transport of energy to the actual measured energy transport through the medium to determine the actual properties of the medium.

Abstract: A system method, and computer program product for visualizing and interactively analyzing data relating to chemical compounds. A user selects a plurality of compounds to map, and also selects a method for evaluating similarity/dissimilarity between the selected compounds. A non-linear map is generated in accordance with the selected compounds and the selected method. The non-linear map has a point for each of the selected compounds, wherein a distance between any two points is representative of similarity/dissimilarity between the corresponding compounds. A portion of the non-linear map is then displayed. Users are enabled to interactively analyze compounds represented in the non-linear map.

Abstract: The present invention provides a new analysis based on Differential Spectral Topographic Analysis (DISTA). Using data from the spectral methods known in the art, DISTA is based upon the normalization of the spectra to a fixed topographic space, creating a set of spectral forms, and the summation of the absolute differences in topography between one or more reference spectra and the test spectra taken at different magnitudes of the perturbing parameter. This method allows for a sensitive estimate of the fraction of form A and form B of an entity of interest. This method also allows for the calculation of apparent free energy from the conversion of the entity of interest from a first to a second form where appropriate, and in the alternative, calculation of a fraction of structural changes.

Abstract: A method and apparatus are disclosed for predicting the presence of at least one congenital or acquired imbalance or therapeutic condition associated with thrombosis/hemostasis from at least one time-dependent measurement profile. At least one time-dependent measurement on an unknown sample is performed and a respective property of said sample is measured over time so as to derive a time-dependent measurement profile. A set of a plurality of predictor variables are defined which sufficiently define the data of the time-dependent measurement profile. A model is then derived that represents the relationship between the congenital or acquired imbalance or therapeutic condition, and the set of predictor variables. Subsequently, the model is utilized to predict the existence of the congenital or acquired imbalance or therapeutic condition in the unknown sample.

Abstract: The present invention is a method for optimizing multivariate calibrations such as those used on FT-IR analyzers. The method involves the selection of an optimum subset of samples to use in the calibration from a larger set of available samples. The subset selection is done so as to minimize the bias of the resulting calibration while simultaneously maintaining acceptable standard errors and ensuring maximal range for the model.

Abstract: The present invention discloses testing turfgrass samples in a spectrophotometer. The resulting color output is provided to a processor for determining the quantitative color scale. The resultant output of the processor might be a single number 1 through 9—depending on the relative “greenness” of the tested turfgrass. To determine the standardized number, the processor compares the received color output from the spectrophotometer to a first stored set of values. Additionally, the received color output can be compared to a second stored set of values to predictively determine if adjusting certain nutrients, water, fertilizer, etc. will result in beneficial or other desired results in the turf. The first and second stored set of values or data is empirically established. In addition, a sealed turfgrass sample as a check or calibration sample, in connection with the use of NIRS equipment to determine instrument performance.

Abstract: A fault detection and classification system for wafer etching, tool cleaning, and other fabrication processes employs exhaust gas composition data from a Fourier transform infrared spectrometer in addition to machine-state and other process-state data. Process control may be initiated based upon the classification of a fault.

Abstract: A method for analysis of samples having turbidity and/or high absorption is disclosed. The analysis incorporates several factors that affect transmittance or absorption. These factors may include: absorption as measured in a non-turbid sample, scattering losses due to particles and limitations of the measurement device as measured in a non-absorbing sample, additional scattering losses due to sample absorption, variable path length effects due to the sample, and variable path length effects due to the measurement device. By taking into account additional factors that affect transmittance or absorption, a more accurate analysis is achieved.

Abstract: The present invention relates to a method for determining the mineral composition of an unknown material using both a fuzzy classification system and a confidence measure of substances identified by the fuzzy classification system. The method can be adapted for identification of pore space and sample points containing more than one material.

Abstract: Near-infrared spectroscopic calibration models are developed for the rapid, accurate and non-polluting prediction of the total dietary fiber content in a wide range of cereal products, including mixed grain products, products with high sugar content, products with high crystal sugar content, products with high fat content, and cereal products with high sugar and high fat content.

Abstract: A method and apparatus are disclosed for predicting the presence of at least one congenital or acquired imbalances or therapeutic condition associated with thrombosis/hemostasis from at least one time-dependent measurement profile. At least one time-dependent measurement in a sample is performed and a respective property of sample is measured over time so as to derive a time-dependent measurement profile. A set of a plurality of predictor variables are defined which sufficiently define the data of the time-dependent measurement profile. A model is then derived that represents the relationship between the congenital or acquired imbalance or therapeutic condition, and the set of predictor variables. Subsequently, the model is utilized to predict the existence of the congenital or acquired imbalance or therapeutic condition in a sample.

Abstract: A process plant for the manufacture of halobutyl rubber is provided with online monitoring and control of the process parameters to control the properties of the product. It incorporates an in-situ measurement system that does not require the removal of any sample material from the process. It uses a Fourier Transform Near Infrared (FTNIR) spectrometer, fiber-optic cables, a viscometer for measuring solution viscosity and a Resistance Temperature Device (RTD) for temperature measurement. An online real-time analyzer system using a Constrained Principal Spectral Analysis program predicts the property of the polymer product and provides the process control system with analysis of the data using derived relationships between the physical properties of the polymer and these spectral measurements and the measured values of fluid viscosity and temperature. Differences between the predicted and desired property of the product are used to control process parameters.

Abstract: Systems and methods using a neural network based portable absorption spectrometer system for real-time automatic evaluation of tissue injury are described. An apparatus includes an electromagnetic signal generator; an optical fiber connected to the electromagnetic signal generator; a fiber optic probe connected to the optical fiber; a broad band spectrometer connected to the fiber optic probe; and a hybrid neural network connected to the broad band spectrometer. The hybrid neural network includes a principle component analyzer of broad band spectral data obtained from said broad band spectrometer.

Abstract: A method of operating a laser and a gas analyzer to reduce low frequency and high frequency power non-linearity errors passes a laser beam through a sample gas to a detector. Intensity measurements are taken and compared to a reference set of measurements. The reference set of measurements can be calculated by measuring pressure and temperature of the sample gas. The laser wave number tuning width is locked to tune a high frequency of an absorption path fringe to a predetermined reference value. The analyzer can be operated without taking a reference set of measurements and the analyzer is much smaller than previous analyzers.

Abstract: A method for improving the sensitivity of a Fourier transform infrared (FTIR) spectrometer, especially one which is mounted on a movable platform, includes the step of obtaining a background spectrum and an analytical spectrum from an interferogram, and determining the absorption spectrum from the analytical spectrum and the background spectrum. Then, a classical least squares analysis is applied to the absorption spectrum, with reference to a reference spectrum. The classical least squares analysis removes the bias term, and the first and the second-order correction terms related to frequency from the measured absorption spectrum. The method preferably includes two feedback paths in which the background spectrum used in the analysis is derived from a current background spectrum and previously occurring, co-added background spectra using a weighted average approach. The other feedback path involves using one or more alternative reference spectra should a saturation condition exist.