Patent ID: 6717148
Filing Date: 2004-04-06
Classification: G01N

Abstract:
A method for measuring a coating from paper or board by means of IR radiation, the coating comprising at least two components, said method comprising carrying out the measurement by one detector, measuring at least one component from the coating by using MIR radiation and at least one component being measured by using NIR radiation, whereinin order to measure at least one component by using MIR radiation said method comprises: directing IR radiation at the coating; chopping the IR radiation directed at the coating; bandpass filtering a MIR wavelength band of the component, which is sensitive to the absorption of at least one component from the IR radiation emerging from the coating; measuring the strength of the MIR radiation sensitive to the absorption; bandpass filtering a MIR wavelength band of the component, which is insensitive to the absorption of the component from the IR radiation emerging from the coating; measuring the strength of the MIR radiation insensitive to the absorption; measuring the strength of the absorption of the component by comparing the strength of the MIR radiation sensitive to the absorption and the strength of the MIR radiation insensitive to the absorption with each other; and determining the amount of at least one component of the coating on the basis of the measured strength of at least one MIR absorption; and, in order to measure at least one component by using NIR radiation said method further comprises: bandpass filtering a NIR wavelength band of the component, which is sensitive to the absorption of the component from the IR radiation emerging from the coating; measuring the strength of the NIR radiation sensitive to the absorption; bandpass filtering a NIR wavelength band of the component, which is insensitive to the absorption of the component from the IR radiation emerging from the coating; measuring the strength of the NIR radiation insensitive to the absorption; measuring the strength of the absorption of the component by comparing the strength of the NIR radiation sensitive to the absorption and the strength of the NIR radiation insensitive to the absorption with each other; and determining the amount of at least one component of the coating on the basis of the measured strength of at least one NIR absorption.