Increased absorption-measurement accuracy through windowing of photon-transit times to account for scattering in continuous webs and powders

A sensor for measuring at least one property of a composition of a moving sample that comprises:

• a light source, which emits broadband optical pulses at a moving sample of the composition;
• a receiver operable to detect reflected or transmitted radiation from the moving sample and to provide electrical detection signals wherein the distance between the light source and receiver varies;
• synchronization means for receiving electrical pulses from the light source or optical pulses from the receiver and for providing electrical synchronization signals to a processor;
• and
• wherein the processor receives the electrical detection signals and the electrical synchronization signals and is operable to determine at least one property of the composition with independence of the measurement from the effects associated with scattering in the composition and wherein the processor gates the electrical detection signals to eliminate signals outside a fixed time window relative to the synchronization pulses.

A method of measuring at least one property of a moving sample that comprises the steps of:

• (a) directing radiation from a light source at the moving sample;
• (b) measuring reflected or transmitted radiation from the sample with a receiver and generating electrical signals therefrom such that when the receiver is configured to measure transmitted radiation from the moving sample the light source and the receiver are positioned on opposite sides of the sample and the distance between the light source and the receiver varies and wherein step (b) comprises obtaining absorption as a function of time-of-flight measurements or comprises removing measurements caused by excessive scattering within the moving sample;
• and
• (c) determining at least one property of the moving sample from the electrical signals whereby electrical signals associated with scattering within the sample are processed with the consideration that scattered photons have longer transit times than those of non-scattered photons.

A method of measuring at least one property of a moving sample that comprises the steps of:

• (a) directing radiation from a light source at the moving sample;
• (b) measuring reflected or transmitted radiation from the sample with a receiver and generating electrical signals therefrom such that when the receiver is configured to measure transmitted radiation from the sample the light source and the receiver are positioned on opposite sides of the sample and the distance between the light source and the receiver varies;
• (c) gating the electrical detection signals to eliminate signals outside a fixed time window relative to the synchronization pulses;
• and
• (d) determining at least one property of the sample from the electrical signals whereby electrical signals associated with scattering within the sample are processed with the consideration that scattered photons have longer transit times than those of non-scattered photons.