Patent ID: 6335501
Filing Date: 2002-01-01
Classification: B07C,G01N

Abstract:
A paper sorting device for determining if the dominant colour classification of a piece of paper is white or non-white, comprising:a light source for directing a beam of light at the paper to illuminate the paper; an optical detection system for receiving light diffusely reflected off the paper, isolating three different spectral components of the same reflected light, measuring the intensity of each of the three different spectral components and generating electrical signals representative of the intensity of each of the three different spectral components, the optical detection system comprising a waveguide having a three-way beam splitter comprising a glass trifurcated fibre bundle that blocks ultraviolet light components, for receiving light diffusely reflected off the paper and directing substantially equal intensities of the reflected light to first, second and third optical outputs; a first visible bandpass filter comprising a blue dichroic filter and a photo detector positioned at the first optical output to isolate a first spectral component of light emanating therefrom and measure the intensity of the first spectral component; a second visible bandpass filter comprising a green dichroic filter and a photo detector positioned at the second optical output to isolate a second spectral component of light emanating therefrom and measure the intensity of the second spectral component; and a third visible bandpass filter comprising a red dichroic filter and a photo detector positioned at the third optical output to isolate a third spectral component of light emanating therefrom and measure the intensity of the third spectral component; and a processor responsive to the electrical signals generated by the detection system and operable to (a) determine a relative reflectance for each of the three spectral components; (b) determine a mean of the three relative reflectances; (c) determine a standard deviation of the three relative reflectances; and (d) determine, by comparing the mean and standard deviation to predetermined threshold values, whether the paper is white or non-white.