Method and apparatus for witness card statistical analysis using image processing techniques
View Patent ↗A method and apparatus for performing witness card statistical analysis using image processing techniques to quickly and efficiently generate as-sprayed performance statistics for a spray device, or spray, based upon a comprehensive analysis of as-sprayed witness card stains. Calibration and as-sprayed witness cards are scanned to produce images that are processed using image processing techniques to identify stain areas/dimensions. Calibration stain data is associated with known calibration droplet volumes and used to generate a set of calibration equations that model an observed relationship between the area of calibration stains upon a witness card and the volume of the respective fluid droplets that produced the stains. As-sprayed stain area/dimension information is processed using the developed calibration equations to approximate the volume of as-sprayed droplets. The approach provides a direct quantitative assessment of spray device performance based upon a comprehensive assessment of as-sprayed witness cards, resulting in highly accurate, timely spray device performance statistics.
1. A system for assessing a spray using image processing techniques to analyze a scan image of an as-sprayed witness card, wherein the as-sprayed witness card includes a fixed pattern of stains as a result of being sprayed with drops of a selected fluid, the system comprising:
a scanner unit to generate a scan image of a calibration witness card and a scan image of at least one as-sprayed witness card, wherein the calibration witness card includes a plurality of stains, each stain created with a known volume of the selected fluid;
an image analysis unit to identify a plurality of stains within a scan image and to determine a value for a selected dimensional characteristic for each identified stain based upon image processing of the scan image;
a calibration unit to develop a calibration equation based upon values determined for stains identified within the calibration witness card scan image, wherein the calibration equation approximates a relationship between the determined calibration witness card stain values and the respective volumes of the selected fluid that created each respective calibration witness card stain; and
a statistics unit to determine an as-sprayed drop characteristic based upon a value determined for a stain identified within the as-sprayed witness card scan image and the developed calibration equation.
2. The system of claim 1 , wherein the calibration equation includes a non-linear component.
3. The system of claim 1 , wherein the calibration equation includes a set of calibration equations.
4. The system of claim 3 , wherein the set of calibration equations includes at least one non-linear equation.
5. The system of claim 1 , wherein the scanner unit further includes:
a scan color bias unit to increase the sensitivity of the scanner to at least one selected color.
6. The system of claim 1 , wherein the scanner unit further includes:
an image storage unit that stores a generated scan image.
7. The system of claim 6 , wherein the image storage unit is configured to store the scan image as a gray scale image.
8. The system of claim 6 , wherein the image storage unit is configured to store the scan image as a color image.
9. The system of claim 6 , wherein the image storage unit is configured to store the scan image in one of a file and a database.
10. The system of claim 1 , wherein the dimensional characteristic value determined by the image analysis unit for a stain is at least one of:
an area of an identified stain;
a diameter of an identified stain;
a radius of an identified stain; and
a circumference of an identified stain.
11. The system of claim 1 , wherein the image analysis unit further includes:
a value storage unit to store determined witness card stain values.
12. The system of claim 11 , wherein the value storage unit is configured to store values in at least one of a file and a database.
13. The system of claim 1 , wherein the calibration unit further includes:
an equation storage unit to store at least one of a determined equation and a determined equation coefficient.
14. The system of claim 13 , wherein the equation storage unit is configured to store determined equations in at least one of a file and a database.
15. The system of claim 1 , wherein the as-sprayed characteristic determined by the statistics unit is at least one of:
an as-sprayed drop diameter;
an as-sprayed drop volume;
an as-sprayed drop mass;
an as-sprayed drop mass median diameter; and
an as-sprayed spray density.
16. A method for assessing a spray using image processing techniques to analyze a scan image of an as-sprayed witness card, wherein the as-sprayed witness card includes a fixed pattern of stains as a result of being sprayed with drops of a selected fluid, the method comprising:
(a) generating a scan image of a calibration witness card and a scan image of at least one as-sprayed witness card, wherein the calibration witness card includes a plurality of stains, each stain created with a known volume of the selected fluid;
(b) identifying a plurality of stains within a scan image and determining a value for a selected dimensional characteristic for each identified stain based upon image processing of the scan image;
(c) determining a calibration equation based upon values determined for stains identified within the calibration witness card scan image, wherein the calibration equation approximates a relationship between the determined calibration witness card stain values and the respective volumes of the selected fluid that created each respective calibration witness card stain; and
(d) determining an as-sprayed drop characteristic based upon a value determined for a stain identified within the as-sprayed witness card scan image and the developed calibration equation.
17. The method of claim 16 , wherein the calibration equation includes a non-linear component.
18. The method of claim 16 , wherein the calibration equation includes a set of calibration equations.
19. The method of claim 18 , wherein the set of calibration equations includes at least one non-linear equation.
20. The method of claim 16 , wherein step (a) further includes:
(a.1) increasing the sensitivity of the scanner to at least one selected color.
21. The method of claim 16 , wherein step (a) further includes:
(a.1) storing a generated scan image.
22. The method of claim 21 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image as a gray scale image.
23. The method of claim 21 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image as a color image.
24. The method of claim 21 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image in one of a file and a database.
25. The method of claim 16 , wherein the determined dimensional characteristic is at least one of:
an area of an identified stain;
a diameter of an identified stain;
a radius of an identified stain; and
a circumference of an identified stain.
26. The method of claim 16 , wherein step (b) further includes:
(b.1) storing a determined witness card stain value.
27. The method of claim 26 , wherein step (b.1) further includes:
(b.1.1) storing a determined witness card stain value in at least one of a file and a database.
28. The method of claim 16 , wherein step (c) further includes:
(c.1) storing at least one of a determined equation and a determined equation coefficient.
29. The method of claim 28 , wherein step (c.1) further includes:
(c.1.1) storing at least one of the determined equation and a determined equation coefficient in at least one of a file and a database.
30. The method of claim 16 , wherein step (d) the determined as-sprayed characteristic is at least one of:
an as-sprayed drop diameter;
an as-sprayed drop volume;
an as-sprayed drop mass;
an as-sprayed drop mass median diameter; and
an as-sprayed spray density.
31. A program product apparatus having a computer readable medium with computer program logic recorded thereon for assessing a spray using image processing techniques to analyze a scan image of an as-sprayed witness card, wherein the as-sprayed witness card includes a fixed pattern of stains as a result of being sprayed with drops of a selected fluid, said program product apparatus comprising:
a scanner unit to generate a scan image of a calibration witness card and a scan image of at least one as-sprayed witness card, wherein the calibration witness card includes a plurality of stains, each stain created with a known volume of the selected fluid;
an image analysis unit to identify a plurality of stains within a scan image and to determine a value for a selected dimensional characteristic for each identified stain based upon image processing of the scan image;
a calibration unit to develop a calibration equation based upon values determined for stains identified within the calibration witness card scan image, wherein the calibration equation approximates a relationship between the determined calibration witness card stain values and the respective volumes of the selected fluid that created each respective calibration witness card stain; and
a statistics unit to determine an as-sprayed drop characteristic based upon a value determined for a stain identified within the as-sprayed witness card scan image and the developed calibration equation.
32. The program product of claim 31 , wherein the calibration equation includes a non-linear component.
33. The program product of claim 31 , wherein the calibration equation includes a set of calibration equations.
34. The program product of claim 33 , wherein the set of calibration equations includes at least one non-linear equation.
35. The program product of claim 31 , wherein the scanner unit further includes:
a scan color bias unit to increase the sensitivity of the scanner to at least one selected color.
36. The program product of claim 31 , wherein the scanner unit further includes:
an image storage unit that stores a generated scan image.
37. The program product of claim 36 , wherein the image storage unit is configured to store the scan image as a gray scale image.
38. The program product of claim 36 , wherein the image storage unit is configured to store the scan image as a color image.
39. The program product of claim 36 , wherein the image storage unit is configured to store the scan image in one of a file and a database.
40. The program product of claim 31 , wherein the dimensional characteristic value determined by the image analysis unit for a stain is at least one of:
an area of an identified stain;
a diameter of an identified stain;
a radius of an identified stain; and
a circumference of an identified stain.
41. The program product of claim 31 , wherein the image analysis unit further includes:
a value storage unit to store determined witness card stain values.
42. The program product of claim 41 , wherein the value storage unit is configured to store values in at least one of a file and a database.
43. The program product of claim 31 , wherein the calibration unit further includes:
an equation storage unit to store at least one of a determined equation and a determine equation coefficient.
44. The program product of claim 43 , wherein the equation storage unit is configured to store determined equations in at least one of a file and a database.
45. The program product of claim 31 , wherein the as-sprayed characteristic determined by the statistics unit is at least one of:
an as-sprayed drop diameter;
an as-sprayed drop volume;
an as-sprayed drop mass;
an as-sprayed drop mass median diameter; and
an as-sprayed spray density.
46. A method for calibrating a system for assessing a spray using image processing techniques to analyze a scan image of an as-sprayed witness card, wherein the as-sprayed witness card includes a fixed pattern of stains as a result of being sprayed with drops of a selected fluid, the method comprising:
(a) generating a scan image of a calibration witness card, wherein the calibration witness card includes a plurality of stains, each stain created with a known volume of the selected fluid;
(b) identifying a plurality of stains within the scan image and determining a value for a selected dimensional characteristic for each identified stain based upon image processing of the scan image; and
(c) determining a calibration equation based upon values determined for stains identified within the calibration witness card scan image, wherein the calibration equation approximates a relationship between the determined calibration witness card stain values and the respective volumes of the selected fluid that created each respective calibration witness card stain;
wherein the calibration equation is used for determining an as-sprayed drop characteristic based upon a value determined for a stain identified within the as-sprayed witness card scan image and the developed calibration equation.
47. The method of claim 46 , wherein the calibration equation includes a non-linear component.
48. The method of claim 46 , wherein the calibration equation includes a set of calibration equations.
49. The method of claim 48 , wherein the set of calibration equations includes at least one non-linear equation.
50. The method of claim 46 , wherein step (a) further includes:
(a.1) increasing the sensitivity of the scanner to at least one selected color.
51. The method of claim 46 , wherein step (a) further includes:
(a.1) storing a generated scan image.
52. The method of claim 51 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image as a gray scale image.
53. The method of claim 51 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image as a color image.
54. The method of claim 51 , wherein step (a.1) further includes:
(a.1.1) storing a generated scan image in one of a file and a database.
55. The method of claim 46 , wherein the determined dimensional characteristic is at least one of:
an area of an identified stain;
a diameter of an identified stain;
a radius of an identified stain; and
a circumference of an identified stain.
56. The method of claim 46 , wherein step (b) further includes:
(b.1) storing a determined witness card stain value.
57. The method of claim 56 , wherein step (b.1) further includes:
(b.1.1) storing a determined witness card stain value in at least one of a file and a database.
58. The method of claim 46 , wherein step (c) further includes:
(c.1) storing at least one of a determined equation and a determined equation coefficient.
59. The method of claim 58 , wherein step (c.1) further includes:
(c.1.1) storing at least one of the determined equation and a determined equation coefficient in at least one of a file and a database.
60. The method of claim 46 , wherein step (d) the determined as-sprayed characteristic is at least one of:
an as-sprayed drop diameter;
an as-sprayed drop volume;
an as-sprayed drop mass;
an as-sprayed drop mass median diameter; and
an as-sprayed spray density.