Systems and methods for witness card analysis
View Patent ↗A system for and method of assessing fluid spray using image processing techniques of a calibration and one or more as-sprayed witness cards. Calibration and as-sprayed witness cards are exposed to a backlight sufficient to make a plurality of stains thereon electronically visible. At the same time an image of the stains is captured by, e.g., a digital camera. Resulting image data is processed to assess characteristics of the stains of the fluid on the as-sprayed witness card(s) and thereby assess characteristics of the spray, e.g., volume of fluid delivered. In one embodiment, the witness card is a chemically coated semiopaque plate.
1. A witness card analysis method, comprising:
selecting a fluid to be sprayed;
positioning a witness card in an area to be sprayed;
spraying the fluid such that drops of the fluid contact the witness card resulting in an as-sprayed witness card with a pattern of stains of the fluid thereon;
exposing the as-sprayed witness card to a backlight sufficient to make the fixed pattern of stains visible;
capturing an image of the pattern of stains while the as-sprayed witness card is being exposed to the backlight;
processing the image of the pattern of stains to determine characteristics of the drops of the fluid on the as-sprayed witness card, wherein processing comprises using a calibration equation to assess characteristics of the pattern of stains on the as-sprayed witness card by comparing characteristics of the stains of the fluid on the as-sprayed witness card with characteristics of stains of the fluid on a calibration witness card, wherein the calibration equation is developed based on respective dimensions of a plurality of stains and known volume of the fluid for each stain on the calibration witness card; and
generating statistics regarding the as-sprayed witness card using the calibration equation.
2. The method of claim 1 , wherein the fluid is a simulant.
3. The method of claim 1 , wherein the fluid is un-dyed.
4. The method of claim 1 , wherein the witness card is semiopaque.
5. The method of claim 4 , wherein the witness card comprises a coating.
6. The method of claim 5 , wherein the coating chemically reacts with the fluid in such a way as to retain evidence of the fluid having been deposited on the surface of the witness card.
7. The method of claim 1 , further comprising capturing the image of the pattern of stains using a camera.
8. The method of claim 7 , wherein the camera is a digital camera.
9. The method of claim 1 , wherein the characteristics of the stains include 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.
10. A method of assessing a spray using image processing techniques to analyze an image of an as-sprayed witness card, the witness card having been sprayed with drops of a fluid, the method comprising:
preparing a calibration witness card having a plurality of stains, wherein each stain is created with a known volume of a fluid;
exposing the calibration witness card to a backlight sufficient to make the plurality of stains visible and, at the same time, capturing an image of the plurality of stains thereon;
developing a calibration equation that is based on respective dimensions of the plurality of stains and known volume of the fluid for each stain;
obtaining an as-sprayed witness card, wherein the as-sprayed witness card includes a pattern of stains of the fluid;
after the step of exposing the calibration witness card, backlighting the as-sprayed witness card to make the pattern of stains thereon visible and, at the same time, capturing an image of the pattern of stains thereon; and
processing the image of the pattern of stains on the as-sprayed witness card using the calibration equation to assess characteristics of the stains of the fluid on the as-sprayed witness card and thereby assess characteristics of the spray.
11. The method of claim 10 , wherein the fluid is a simulant.
12. The method of claim 10 , wherein the fluid is un-dyed.
13. The method of claim 10 , wherein at least one of the calibration witness card or the as-sprayed witness card comprises a substrate having a coating disposed thereon.
14. The method of claim 13 , wherein the coating reacts with the fluid.
15. The method of claim 10 , further comprising capturing the image of the pattern of stains using a digital camera.
16. The method of claim 10 , wherein the characteristics of the stains of the fluid include 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
17. A system for assessing a spray, comprising:
a witness card image capture unit including a backlit platform configured to backlight a semiopaque witness card having thereon stains created by drops of a fluid and further configured to capture an electronic image of the stains;
a calibration unit to develop a calibration equation based upon characteristic values determined for stains identified in an electronic image of a calibration witness card, wherein the calibration equation approximates a relationship between the determined calibration witness card stain values and respective volumes of the fluid that created each respective calibration witness card stain;
an image analysis unit to identify a plurality of stains within an electronic image of an as-sprayed witness card and to determine a value for a selected dimensional characteristic for each identified stain based upon image processing of the electronic image of the as-sprayed witness card; and
a statistics unit to determine an as-sprayed drop characteristic based upon a value determined for a stain identified within the image of the as-sprayed witness card and the developed calibration equation.
18. The system of claim 17 , wherein the fluid is a simulant.
19. The system of claim 17 , wherein the fluid is un-dyed.
20. The system of claim 17 , wherein the witness card image capture unit comprises a digital camera.
21. The system of claim 17 , wherein the witness card comprises a substrate and a chemical coating disposed on the substrate.
22. The system of claim 21 , wherein the chemical coating is selected so as to react with the fluid.
23. The system of claim 17 , 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.