Imaging apparatus and method of fiber analysis

A fiber analyzer device for determining fiber deformation and fiber length in a pulp comprising:

• means to provide a fiber suspension in a liquid;
• a flow cell having a first flow passage for a fiber suspension stream, with sheath fluid flow passages on both sides of the first flow passage, the first flow passage tapering to a slit, an exit aperture connecting with the sheath flow passages to form a combined passage, the combined passage having a reduction in area downstream of the exit aperture to align, position and orient fibers in an elongated planar stream;
• an imaging area in the cell downstream of the reduction in area of the combined passage, wherein the elongated planar stream has sheath fluids on both sides;
• an optical system having an optical axis normal to the elongated planar stream, including a visible light source to apply light to one side of the imaging area of the cell, a first circular polarizing filter on the one side of the imaging area and a second circular polarizing filter on an opposite side of the imaging area, the second polarizing filter being in an extinction position with respect to the first polarizing filter,
• an imaging detector on the opposite side of the imaging area to detect fibers in the imaging area imaged from the light source and through the polarizing filters, the imaging detector providing signals representing fiber presence in the imaging area, and
• means to process the signals to determine fiber deformation and fiber length.

A method of determining fiber length for fibers in suspension comprising the steps of:

• passing a fiber suspension stream through a sheath type flow cell wherein the fiber suspension stream is injected into a sheath fluid stream to align and position fibers and form an elongated combined stream;
• projecting a light from one side of the combined stream;
• collecting images of fibers in the combined stream on an opposite side from the light and producing signals representative of fiber images, and
• processing the signals to determine fiber length.

A method of determining fiber deformation and fiber length in a pulp comprising the steps of:

• forming a fiber suspension stream with fibers aligned, positioned and oriented;
• passing the fiber suspension stream through an imaging area in a flow cell with an elongated planar shape with sheath fluids on both sides of the fiber suspension stream to form a combined stream;
• projecting a light with an optical axis normal to the combined stream, through a first polarizing filter, the imaging area followed by a second polarizing filter, the second polarizing filter being in an extinction position with respect to the first polarizing filter, and onto an imaging detector to image fibers in the imaging area and produce signals representative of the fibers, and
• processing the signals from the imaging detector to determine fiber deformation and fiber length.