# US 2011/0026026 A1 · Apparatus for characterizing fibrous materials using stokes parameters

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- Number: US 2011/0026026 A1
- Document ID: US20110026026A1
- Status: Published application
- Kind: A1
- Application number: 12/905,150
- Filed: 2010-10-15
- Published: 2011-02-03
- Earliest claimed: 2007-10-23
- Assignees: Honeywell ASCa Inc.
- Inventors: David R. Jez; Frank M. Haran; Graham I. Duck
- Web page: https://patentgrep.com/patent/US20110026026A1

## CPC

- G01N 21/23: Bi-refringence
- G01N 21/86: Investigating moving sheets (G01N21/89 takes precedence)
- G01N 22/00: Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence)
- G01N 33/346: {Paper sheets}
- G01N 21/3581: using far infrared light; using Terahertz radiation
- G01N 2021/8411: {Application to online plant, process monitoring}
- G01N 2021/8416: {and process controlling, not otherwise provided for}
- G01N 2021/8444: {Fibrous material}
- G01N 2021/8681: {Paper fibre orientation}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

An apparatus for determining fiber orientation parameters of a sheet of material during a production process includes a polarized radiation generating system operable for providing polarized radiation having a frequency of at least 1×108 Hz. The radiation is aligned to be incident on a sheet material to be characterized. A polarimeter is aligned to receive the radiation transmitted by the sheet material. A photodetector is provided for measuring radiation received after polarization processing by the polarimeter. A processor is coupled to the photodetector for calculating Stokes parameters of the sheet material based upon intensities of the radiation received and determines at least one parameter relating to fiber orientation of the sheet material based upon the Stokes parameters.

## Claims

### Claim 1

An apparatus for determining fiber orientation parameters of sheet material during production processing, comprising:
a polarized radiation generating system operable for providing polarized radiation having a frequency of at least 1×108 Hz up to 30 THz, said polarized radiation aligned to be incident on a sheet material to be characterized;
a polarimeter aligned to receive radiation transmitted by said sheet material;
a photodetector for measuring radiation received after polarization processing by said polarimeter, and
a processor coupled to said photodetector for calculating Stokes parameters of said sheet material based upon intensities of said radiation received and determining at least one fiber orientation parameter of said sheet material based upon said Stokes parameters.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein said sheet material is processed as a moving sheet by a processing system, further comprising closed loop control between said processor and said processing system for automatically modifying at least one parameter of a production process run by said processing system based on said Stokes parameters or said fiber orientation parameter.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein said closed loop control comprises a wired feedback connection.

### Claim 4 (depends on 2)

The apparatus of claim 2, wherein said closed loop control comprises a transmitter and an antenna coupled to said processor and a receiver coupled to said processing system.

### Claim 5 (depends on 2)

The apparatus of claim 2, wherein said parameter of said production process comprises at least one of jet to wire ratio (Rush/Drag) and slice lip opening.

### Claim 6 (depends on 1)

The apparatus of claim 1, wherein said polarized radiation generating system comprises an unpolarized radiation source optically coupled to a first linear polarizer.

### Claim 7 (depends on 6)

The apparatus of claim 6, wherein said unpolarized radiation source comprises a terahertz source.

### Claim 8 (depends on 6)

The apparatus of claim 6, wherein said polarimeter comprises a rotating quarter wave plate optically coupled to a second linear polarizer, wherein said sheet material is interposed between said first polarizer and said rotating quarter wave plate.

### Claim 9 (depends on 1)

The apparatus of claim 1, wherein said processor determines birefringence of said sheet material and said fiber orientation parameter using a Poincare sphere.

### Claim 10 (depends on 2)

The apparatus of claim 2, wherein an angle between said moving sheet and said polarized radiation is held constant during said production process run by said processing system.