Patent ID: 6555822
Filing Date: 2003-04-29
Classification: G01N

Abstract:
Method for identification of plastic materials of interest by optical spectroscopic measurements, comprising the steps:measuring a sample and providing a sample spectrum; providing reference spectra for a given group of reference materials of interest, determining spectral distances between sample spectrum and reference spectra, material identification by associating the sample to the material having the reference spectrum with the smallest spectral distance to the sample spectrum, characterized in that a multi-level measurement is conducted, wherein in each level the number of possible materials is further limited, in a first level at least 2 sub-groups (110, 120) and in all levels starting with a second level at least one sub-group (211, 212, 213, 214, 221, 222, 223, 311, 312, 313, 314) of possible materials are defined, wherein one sub-group (110) in the first level comprises all possible materials that are easily distinguishable and at least one further sub-group (120) in the first level comprises materials that are difficult to distinguish from each other, to each sub-group (110, 120, 211, 212, 213, 214, 221, 222, 223, 311, 312, 313, 314) at least one identification frequency range is associated, and said spectral distances are only determined within said at least one identification frequency range in each relevant sub-group (110, 120, 211, 311) of each level and only with respect to reference spectra of materials being comprised in the relevant sub-group (110, 120, 211, 311).