Formation testing with digital image analysis

• US 5,113,454 A
• Filed: 08/19/1988
• Issued: 05/12/1992
• Est. Priority Date: 08/19/1988
• Status: Expired due to Fees

• Current Assignee: Kajaani OY Elektroniika
• Original Assignee: Kajaani OY Elektroniika
• Inventors: Jones, Christopher W., Marcantonio, Jeffrey J.
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): COUSO, YON JUNG
• Application Number:
  US07/234,478
• Time in Patent Office: 1,362 Days
• Field of Search: 382/50, 382/51, 382/52, 382/27, 382/28, 382/8, 382/1, 358/106, 250/562, 250/563, 356/237
• US Class Current: 382/108
• CPC Class Codes: G01N 2021/1772 Array detector
• CPC Class Codes: G01N 2021/8672 Paper formation parameter
• CPC Class Codes: G01N 21/86 Investigating moving sheets G01N21/89 takes precedence
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/30124 Fabrics; Textile; Paper
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06V 10/993 Evaluation of the quality of the acquired pattern

Abstract

A system is disclosed which increases the level of accuracy and precision for quantifying formations in paper. A CCD camera is used to capture data from a large portion of the paper. A diffuse illumination source is used to back light the paper sample. A microcomputer uniquely analyzes digitized image data. In this regard, after the image is stored in memory, a two-dimensional window is created and scanned over the entire frame to two-dimensionally analyze the image intensity level data. Average window intensity levels are generated that are compared to one another. In this regard, smaller local pixel variations are compared to these windows giving both regional and local variation data. Hundreds of thousands of data points are considered in these comparisons which are divided into sixty four difference levels. An array of 64 sample intervals are compiled, each representative of the number of accumulated data points that, when compared to their neighboring region, differ in intensity level by a percentage of the total mean intensity of the entire sample area. An index is generated that accurately reflects the gradient or rate of change over the sample sheet in two dimensions.

Claims

1. A method for determining the uniformity of a medium comprising the steps of:

illuminating said medium by transmitting light through the medium;

generating digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

dividing said digital data into a plurality of relatively large two dimensional windows;

subdividing each of said large windows into a plurality of smaller windows;

determining the average intensity of the data points in at least one large window;

determining the average intensity of he data points in at least one of the smaller windows within the associated large window;

determining the difference in the average intensity level between at least one smaller window and its associated large window; and

generating an index representing the uniformity of said data as a function of the difference in intensity levels between data points in said at least one of the smaller windows and its associated large window.

2. A method according to claim 1, wherein said step of illuminating includes the step of varying the illumination until the mean intensity of the illuminated medium is at a predetermined level.

3. A method according to claim 2, wherein said step of varying includes the step of controllably varying the voltage applied to the light source illuminating said medium until said predetermined level is reached.

4. A method according to claim 1, wherein the step of illuminating includes the step of interposing diffusing material between a light source and said medium to create a diffuse light source.

5. A method according to claim 4, wherein said step of interposing includes the step of disposing two levels of diffusing material between said light source and said medium.

6. A method according to claim 1, wherein said step of dividing said digital data into a plurality of windows includes the step of defining a set of overlapping windows.

7. A method according to claim 1, further including the step of storing the difference between said large window average intensity and said smaller window average intensity for a plurality of windows;

and

organizing the average intensity difference values into a set of difference value storage bins.

8. A method according to claim 7, further including generating said index based on the values in a predetermined number of selected storage bins.

9. A method according to claim 8, wherein said selected storage bins include the highest quantities of difference values.

12. A method according to claim 1, wherein said medium is paper.

13. A method according to claim 12, further including the step of determining whether said paper is fit for a predetermined purpose based on said generated index.

10. A method for determining the uniformity of a medium comprising the steps of:

illuminating said medium;

generating digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

dividing said digital data into a plurality of two dimensional windows;

generating an index representing the uniformity of said data as a function of the intensity levels in a plurality of said two dimensional windows;

wherein said step of dividing includes the step of dividing said digital data into a plurality of relatively large two dimensional windows and subdividing each of said relatively large windows into a plurality of smaller windows;

determining the average intensity of the data points in at least one large window, and determining the average intensity of the data points in at least one of the smaller windows within the large window;

storing the difference between said large window average intensity and said smaller window average intensity for a plurality of windows;

organizing the average intensity difference value into a set of difference value storage bins; and

generating said index based on the values in a predetermined number of selected storage bins, wherein said selected storage bins include the highest quantities of difference values and wherein said step of generating an index includes the step of averaging the intensity values of the predetermined number of selected storage bins and dividing said average value by a predetermined constant.

11. A method for determining the uniformity of a medium comprising the steps of:

illuminating said medium by transmitting light through the medium;

generating digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

dividing said digital data into a plurality of large two dimensional windows;

subdividing each of said plurality of large two dimensional windows into a plurality of smaller windows;

generating an index representing the uniformity of said data as a function of the difference in intensity levels between data points in at least one of said smaller windows and its associated large window;

wherein said step of generating said index includes;

determining the uniformity of the background illumination prior to illuminating the medium to be tested;

storing data relating to said background illumination; and

compensating said generated digital data relating to said illuminated medium based on said stored background illumination data.

14. Apparatus for determining the uniformity of a medium comprising:

means for illuminating said medium by transmitting light through the medium;

means for generating digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

means for dividing said digital data into a plurality of relatively large two dimensional windows and for subdividing each relatively large window into a plurality of smaller windows;

means for determining the average intensity of the data points in at least one large window and for determining the average intensity of the data points in at least one of the smaller windows within the associated large window;

means for determining the difference in the average intensity level between at least one smaller window and its associated large window; and

means for generating an index representing the uniformity of said data as a function of the difference in intensity levels between data points in said at least one of the smaller windows and its associated large window.

15. Apparatus according to claim 14, wherein the means for illuminating includes means for varying the illumination until the mean intensity of the illuminated medium is at a predetermined level.

16. Apparatus according to claim 15, wherein said means for varying includes variable power supply means for generating a variable output voltage and means for controllably varying the output voltage from said power supply means applied to the light source until said predetermined level is reached.

17. Apparatus according to claim 16 wherein said means for illuminating includes diffusing material interposed between a light source and said medium to create a diffuse light source.

18. Apparatus according to claim 17, wherein said diffusing material includes two spaced apart levels of diffusing material between said light source and said medium.

19. Apparatus according to claim 14, wherein said means for dividing said digital data into a plurality of windows includes means for defining a set of overlapping windows.

20. Apparatus according to claim 19, further including means for storing the difference between said large window average intensity and said smaller window average intensity for each of a plurality of window;

and

means for organizing the average intensity difference values into a set of difference value storage bins.

21. Apparatus according to claim 20, wherein said index is based on the values in a predetermined number of selected storage bins.

22. Apparatus according to claim 21, wherein said selected storage bins include the highest quantities of difference values.

23. Apparatus for determining the uniformity of a medium comprising:

means for illuminating said medium;

means for generating digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

means for dividing said digital data into a plurality of relatively large two dimensional windows and for subdividing each relatively large window into a plurality of smaller windows;

means for generating an index representing the uniformity of said data as a function of the intensity levels in a plurality of said two dimensional windows;

wherein said means for dividing said digital data into a plurality of windows further includes means for defining a set of overlapping windows;

means for determining the average intensity of the data points in at least one large window and for determining the average intensity of the data points in at least one of the smaller windows within the large window;

means for storing the difference between said large window average intensity and said smaller window average intensity for each of a plurality of windows; and

means for organizing the average intensity difference values into a set of difference value storage bins;

wherein said index is based on the values in a predetermined number of selected storage bins, wherein said selected storage bins include the highest quantities of difference values; and

wherein said means for generating said index includes means for averaging the intensity values of the predetermined number of selected storage bins and dividing the average by a predetermined constant.

24. Apparatus for determining the uniformity of a medium comprising:

means for illuminating said medium by transmitting light through the medium;

means for generating and storing digital data corresponding to the intensity level of data points in a two dimensional array of data points on said illuminated medium;

means for dividing said digital data into a plurality of large two dimensional windows, said means for dividing including means for subdividing each of said plurality of large windows into a plurality of smaller windows;

means for generating an index representing the uniformity of said data as a function of the difference in intensity levels between data points in at least one of said smaller windows and its associated large window;

said means for generating an index further including;

means for determining the uniformity of the background illumination prior to illuminating the medium to be measured;

means for storing a two dimensional reference image of data relating to said background illumination; and

means for compensating said generated digital data relating to said illuminated medium based on the differences of said stored background illumination data and said generated digital data.

25. A method for determining the uniformity of the physical distribution of solid constituents forming a medium comprising the steps of:

obtaining digital data indicative of the physical distribution of solid constituents forming said medium;

dividing said digital data into a plurality of relatively large two dimensional windows;

subdividing each of said large two dimensional windows into smaller windows; and

generating an index representing the uniformity of said data as a function of the difference between the average of the data in at least one of said large two dimensional windows and the average of data in at least one associated smaller windows.

26. A method according to claim 25, wherein said step of dividing said digital data into a plurality of windows includes the step of defining a set of overlapping windows.

27. A method according to claim 25, further including the step of storing the difference between said large window average and said smaller window average for a plurality of windows;

and

organizing the average difference values into a set of difference value storage bins.

28. A method according to claim 27, further including generating said index based on the values in a predetermined number of selected storage bins.

29. A method according to claim 28, wherein said selected storage bins include the highest quantities of values.

31. A method according to claim 25, wherein said data represents the intensity levels of a predetermined portion of an illuminated medium.

32. A method according to claim 31, wherein said medium is paper.

30. A method for determining the uniformity of data representing a predetermined phenomena comprising the steps of:

dividing said digital data into a plurality of relatively large two dimensional windows;

subdividing each of said large two dimensional windows into smaller windows;

generating an index representing the uniformity of said data as a function of the difference between the average of the data in at least one of said large two dimensional windows and the average of data in at least one associated smaller windows;

storing the difference between said large window average and said smaller window average for a plurality of windows;

organizing the average difference values into a set of difference value storage bins;

wherein said generated index is based on the values in a predetermined number of selected storage bins, wherein said selected storage bins include the highest quantities of difference values and;

wherein said step of generating an index include the step of averaging the values of the predetermined number of selected storage bins and dividing the average by a predetermined constant.