Patent ID: 7537732

Claim:
Apparatus for analyzing pulp fiber, comprising: a flow cell that includes a passageway having an inlet, an outlet and a sample holding region between the inlet and the outlet that has a transparent wall; a conduit for delivering a pulp fiber sample to the inlet of the flow cell, and through the inlet into the sample holding region of the flow cell, said pulp fiber sample including pulp fiber and a fluorescent stain bound to the pulp fiber; a light source and a focused light path positioned to direct light through the transparent wall into the pulp fiber sample to stimulate fluorescence from the pulp fiber sample while it is in the flow cell; means for reducing an amount of stain in solution in the flow cell to an extent desired without undesirably reducing an amount of stain that is bound to the pulp fiber sample; and a fluorescence analyzer to analyze fluorescence emitting from the pulp fiber sample and measure at least one property of the sample.