Method and apparatus for comparing spectra

Claim 1

A method of analyzing spectral data from an analytical instrument including a spectrophotometer, a spectral detector receptive of spectra from the spectrophotometer, and a data station receptive of transmittance spectrum data points from the detector; the method comprising the steps of: operating the instrument so as to generate and store first and second sets of transmittance spectrum data points for selected frequencies over a selected spectral frequency range; establishing a set of weighting factors, each such factor being proportional to a sum of a first transmittance data point and a second transmittance data point for a selected frequency in the selected frequency range; transforming of the first and second transmittance points respectively to sets of first and second absorbance spectrum data points; converting at least one of the first and second sets of absorbance data points to a weighted data set by multiplying each data point in the at least one set by a corresponding weighting factor; generating a spectral comparison factor as a normalized sum of products for each selected frequency range, each product being formed of a weighting factor squared and corresponding first and second unweighted absorbance data points; and displaying the spectral comparison factor.

Claim 2

A method of analyzing spectral data from an analytical instrument including a spectrophotometer, a spectral detector receptive of spectra from the spectrophotometer, and a data station receptive of transmittance spectrum data points from the detector; the method comprising the steps of: operating the instrument so as to generate and store first and second sets of transmittance spectrum data points for selected frequencies over a selected spectral frequency range; establishing a set of weighting factors, each such factor being proportional to a sum of a first transmittance data point and a second transmittance data point for a selected frequency in the selected frequency range; transforming of the first and second transmittance points respectively to sets of first and second absorbance spectrum data points; converting at least one of the first and second sets of absorbance data points to a weighted data set by multiplying each data point in the at least one set by a corresponding weighting factor; generating a spectral comparison factor as a normalized sum of products for each selected frequency range, each product being formed of a weighting factor squared and corresponding first and second unweighted absorbance data points; and displaying the spectral comparison factor.

Claim 13

A method of analyzing spectral data from an analytical instrument including a spectrophotometer, a spectral detector receptive of spectra from the spectrophotometer, and a data station receptive of spectral signals comprising transmittance spectrum data points from the detector, each of the spectra is formed of at least one spectral band with a typical bandwidth corresponding to a characteristic periodicity; the method comprising the steps of: operating the instrument so as to generate and store first and second sets of transmittance spectrum data points for selected frequencies over a selected spectral frequency range; establishing a set of weighting factors, each such factor being proportional to a square of a sum of a first transmittance data point and a second transmittance data point for a selected frequency in the selected freuqency range, and being further proportional to a black body factor having a value according to the corresponding selected spectral frequency; generating first and second absorbance spectrum data points for each as a logarithm of the corresponding first and second transmittance data points; filter weighting each of a succession of selected absorbance data points of the first and second spectra with a one cycle triangular wave having the characteristic periodicity and a zero crossing substantially at each selected data point, thereby generating respective first and second filtered data points; generating a spectral comparison factor as a normalized sum of products for each selected frequency, each product being formed of a weighting factor squared and corresponding first and second filtered data points; and displaying the spectral comparison factor.

Claim 14

A method of analyzing spectral data from an analytical instrument including a spectrophotometer, a spectral detector receptive of spectra from the spectrophotometer, and a data station receptive of spectral signals comprising transmittance spectrum data points from the detector, each of the spectra is formed of at least one spectral band with a typical bandwidth corresponding to a characteristic periodicity; the method comprising the steps of: operating the instrument so as to generate and store first and second sets of transmittance spectrum data points for selected frequencies over a selected spectral frequency range; establishing a set of weighting factors, each such factor being proportional to a square of a sum of a first transmittance data point and a second transmittance data point for a selected frequency in the selected freuqency range, and being further proportional to a black body factor having a value according to the corresponding selected spectral frequency; generating first and second absorbance spectrum data points for each as a logarithm of the corresponding first and second transmittance data points; filter weighting each of a succession of selected absorbance data points of the first and second spectra with a one cycle triangular wave having the characteristic periodicity and a zero crossing substantially at each selected data point, thereby generating respective first and second filtered data points; generating a spectral comparison factor as a normalized sum of products for each selected frequency, each product being formed of a weighting factor squared and corresponding first and second filtered data points; and displaying the spectral comparison factor.