Apparatus and method for measuring caliper of creped tissue paper based on a dominant frequency of the paper and a standard deviation of diffusely reflected light including identifying a caliper measurement by using the image of the paper

Patent metadata

Field	Value
Publication number	US-9303977-B2
Application number	US-201414222251-A
Country	US
Kind code	B2
Filing date	Mar 21, 2014
Priority date	Oct 17, 2013
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A method includes, using at least one processing device, obtaining an image of a web of creped tissue paper and identifying a caliper measurement of the web using the image. The caliper measurement is based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web. The dominant frequency of the web can be based on a number of crepe folds having a dominant crepe fold size that fit within a specified unit distance of the web in the image. The dominant crepe fold size can be determined using a discrete auto-covariance function of the image or a second image of the web. The standard deviation can be based on a variation of reflected light from larger crepe structures in the web.

First claim

What is claimed is:

1. A method comprising:
using at least one processing device:
obtaining an image of a web of creped tissue paper; and
identifying a caliper measurement of the web using the image, the caliper measurement based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web.

2. The method of claim 1 , further comprising:
identifying the dominant frequency of the web based on a dominant crepe fold size of the web within the image.

3. The method of claim 2 , further comprising:
identifying the dominant crepe fold size of the web based on a discrete auto-covariance function of the image or a second image of the web.

4. The method of claim 3 , wherein identifying the dominant crepe fold size of the web comprises:
identifying a first positive local maximum of the discrete auto-covariance function, the discrete auto-covariance function comprising points associated with positive numbers of whole pixels, the first positive local maximum of the discrete auto-covariance function identified at one of the points;
fitting a polynomial curve to the point associated with the first positive local maximum and one or more neighboring points; and
identifying a number of whole and fractional pixels associated with a maximum of the polynomial curve.

5. The method of claim 2 , wherein identifying the dominant frequency of the web comprises:
identifying a number of crepe folds having the dominant crepe fold size that fit within a specified unit distance of the web in the image.

6. The method of claim 2 , further comprising:
identifying the standard deviation of the diffusely-reflected light from the web based on a variation of reflected light from larger crepe structures in the web.

7. The method of claim 6 , wherein identifying the caliper measurement of the web further comprises using a formula of:

C
=

C
0

+

k
⁢

Macro
⁢

⁢
Crepe

Folds
pul

wherein C denotes the caliper measurement of the web;
wherein C 0 denotes a base caliper associated with a grade of tissue paper;
wherein k denotes a grade-dependent constant;
wherein Macro Crepe denotes the variance of reflected light related to the dominant crepe fold size of the web; and
wherein Folds pul denotes a number of crepe folds having the dominant crepe fold size that fit within a specified unit distance of the web.

8. The method of claim 7 , further comprising:
adjusting at least one of the Macro Crepe and Folds pul values based on at least one of uneven illumination and tilt of the web.

9. The method of claim 1 , further comprising:
performing optical, geometrical, or statistical corrections of the image.

10. An apparatus comprising:
at least one memory configured to store an image of a web of creped tissue paper; and
at least one processing device configured to identify a caliper measurement of the web using the image based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web.

11. The apparatus of claim 10 , wherein the at least one processing device is further configured to identify the dominant frequency of the web based on a dominant crepe fold size of the web within the image.

12. The apparatus of claim 11 , wherein the at least one processing device is further configured to identify the dominant crepe fold size of the web based on a discrete auto-covariance function of the image or a second image of the web.

13. The apparatus of claim 12 , wherein the at least one processing device is configured to identify the dominant crepe fold size of the web by:
identifying a first positive local maximum of the discrete auto-covariance function, the discrete auto-covariance function comprising points associated with positive numbers of whole pixels, the first positive local maximum of the discrete auto-covariance function identified at one of the points;
fitting a polynomial curve to the point associated with the first positive local maximum and one or more neighboring points; and
identifying a number of whole and fractional pixels associated with a maximum of the polynomial curve.

14. The apparatus of claim 11 , wherein the at least one processing device is configured to identify the dominant frequency of the web by identifying a number of crepe folds having the dominant crepe fold size that fit within a specified unit distance of the web in the image.

15. The apparatus of claim 11 , wherein the at least one processing device is further configured to identify the standard deviation of the diffusely-reflected light from the web based on a variation of reflected light from larger crepe structures in the web.

16. The apparatus of claim 15 , wherein the at least one processing device is configured to identify the caliper measurement of the web further comprises using a formula of:

C
=

C
0

+

k
⁢

Macro
⁢

⁢
Crepe

Folds
pul

wherein C denotes the caliper measurement of the web;
wherein C 0 denotes a base caliper associated with a grade of tissue paper;
wherein k denotes a grade-dependent constant;
wherein Macro Crepe denotes the variance of reflected light related to the dominant crepe fold size of the web; and
wherein Folds pul denotes a number of crepe folds having the dominant crepe fold size that fit within a specified unit distance of the web.

17. A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code for:
obtaining an image of a web of creped tissue paper; and
identifying a caliper measurement of the web using the image based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web.

18. The computer readable medium of claim 17 , wherein the computer readable program code for identifying the caliper measurement comprises computer readable program code for:
identifying a first positive local maximum of a discrete auto-covariance function of the image or a second image of the web, the discrete auto-covariance function comprising points associated with posi

Assignees

• Honeywell Int Inc

Inventors

• Kellomäki Markku
• Paavola Antti

Classifications

• G01B11/06 Primary

  for measuring thickness {; e.g. of sheet material (thickness measurement by thermal means G01B21/085)} · CPC title

• G01B11/303 Primary

  using photoelectric detection means · CPC title