Method of comparing spectra to identify similar materials
First Claim
1. A method of determining whether the composition of a test material is the same as the composition of a standard material, said test material and said standard material each having a reflectivity, comprising the steps of measuring the reflectivity of the standard material throughout a range of the near infrared spectrum to produce a measurement of reflectivity, determining from the measurement of the reflectivity of the standard material a first set of n values representing a derivative of any variation of reflectivity with wavelength throughout said range, measuring the reflectivity of said test material throughout said range to produce a measurement of reflectivity, determining from the measurement of the reflectivity of said test material a second set of n values representing a derivative of any variation of the reflectivity of said test material with wavelength throughout said range, defining a first vector having an end point in n-dimensional space represented mathematically by said first set of n values as coordinates of the end point of said first vector, defining a second vector having an end point in n-dimensional space represented mathematically by said second set of n values as the coordinates of the end point of said second vector, and determining the cosine of any angle between first and second vectors as an index of similarity of the composition of said test material and the composition of said standard material.
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Accused Products
Abstract
In a method of identifying or comparing compositions of material, the reflectivity of a material to be identified or compared is measured at index points distributed through the near infrared spectrum. A similar measurement is made for at least one standard or known material. From the reflectivity measurements, sets of values representing the first or higher order derivative curves are determined. These values mathematically define vectors by representing the coordinates of the end points of the vectors and multiple dimensional space. An index of a similarity between the composition of a test sample and a standard material is calculated by determining the cosine of the angle between the corresponding vectors.
100 Citations
10 Claims
- 1. A method of determining whether the composition of a test material is the same as the composition of a standard material, said test material and said standard material each having a reflectivity, comprising the steps of measuring the reflectivity of the standard material throughout a range of the near infrared spectrum to produce a measurement of reflectivity, determining from the measurement of the reflectivity of the standard material a first set of n values representing a derivative of any variation of reflectivity with wavelength throughout said range, measuring the reflectivity of said test material throughout said range to produce a measurement of reflectivity, determining from the measurement of the reflectivity of said test material a second set of n values representing a derivative of any variation of the reflectivity of said test material with wavelength throughout said range, defining a first vector having an end point in n-dimensional space represented mathematically by said first set of n values as coordinates of the end point of said first vector, defining a second vector having an end point in n-dimensional space represented mathematically by said second set of n values as the coordinates of the end point of said second vector, and determining the cosine of any angle between first and second vectors as an index of similarity of the composition of said test material and the composition of said standard material.
- 7. A method of identifying the composition of an unknown material comprising storing a multiplicity of sets of values each determined from and corresponding to a different one of a multiplicity of materials of different compositions, one of which is the same composition as the composition of said unknown material, each set of values representing a derivative of any variation in reflectivity with wavelength of the corresponding one of said multiplicity of materials throughout a range in the near infrared spectrum, measuring the reflectivity of said unknown material througout said range, determining a further set of values from the measurement of the reflectivity of said unknown material, said further set of values representing a derivative of any variation in the reflectivity of said unknown materiall with wavelength throughout said range, defining a vector having an end point for each set of values of said multiplicity and represented mathematically by such set of values as coordinates of the end point of such vector in multidimensional space, thereby defining a multiplicity of vectors, one for each of said multiplicity of materials, defining a further vector having an end point and represented mathematically by the values of said further set of values as coordinates of the end point of said further vector in multidimensional space, determining the cosine of any angle between said further vector and each vector of said multiplicity of vectors to thereby determine a multiplicity of cosine values, one for each of said multiplicity of materials and identifying the composition of said unknown material as the same as that for which a highest cosine value is determined in said step of determining the cosine of the angle between said further vector and each vector of said multiplicity of vectors.
Specification