| Author | Message | ||
     P. Keller (Drpaul) |
I want to use NIR (the Inspectra equipment, produced by Hutchinson Technologies) for pressure ulcer research. I want to place healthy volunteers on a glass plate and adjust the NIR probe under the glass plate, on the place where I suspect the highest pressure. My question is, whether glass interferes with the Near Infrared Light and if there is a limit to the thickness of the glass plate I want to use. | ||
| David Hopkins (Hopkins) |
Dr Keller, Yes, glass has Silica that has OH, and the less expensive it is, the more problems due to various thicknesses or imperfections you may have. You can see the bands, by placing a piece of spectralon or Coors ceramic behind a piece of glass you wish to use. The bands are due to the glass OH. You can purchase low hydroxyl quartz from various suppliers, and it is more expensive, the thicker a window you order and the larger the size. You may be able to minimize the problems by going this route. Another problem may be the use of the probe against the glass or quartz, because of the window in the probe. If it has a flat window, and if it is placed nearly flat against the pressure window, you may obtain interference fringes, that appear like regularly spaced absorbance bands in your spectrum. So, my question is, why do you need a window at all? Can you get by with no window, or some thin protective film to protect the probe and be discarded from patient to patient? You have to be careful with fringing with some films too, but very thin film with an irregular surface may be found to give no optical problems. The glass plate will not help much, because the largest part of the scattering problem will be in the human tissue itself, rather than in any windowing material you select. |