Method and apparatus for classifying articles according to their color

摘要

A method and apparatus for classifying articles according to their color, wherein a first pair of wavelengths is selected on a plurality of light reflection curves in terms of a reflected light wavelength spectrum. An article to be inspected is illuminated with light comprising the first pair of wavelengths and light reflected therefrom is measured to detect light reflection values corresponding to this first pair or wavelengths. A primary signal is produced, which represents a resulting difference between the detected light reflection values, this signal being indicative of the color of the inspected article. At least one secondary wavelength is selected on the reflected light wavelength spectrum, and the inspected article is illuminated with light comprising this secondary wavelength and light reflected therefrom is measured to produce a secondary signal which is further indicative of the color of the inspected article. A computer provides a classification frame comprising a first pattern consisting of a first and second crossing set of lines respectively defined by mathematical analysis, this classification frame defining a plurality of color classes. The computer classifies the inspected article in one of the plurality of color classes defined by the frame whenever the primary and secondary signals comply with a specific condition. The computer rejects the inspected article whenever the primary and secondary signals do not comply with this specific condition.