| Author | Message | ||
     Paolo (Paulc) |
Hi I'm not experienced with NIR technology and I have a simple question.I have a certain number of alogen lamps in order to analize a generic fruit.Is it better to focus their light on the surface of fruit or on its pseudo-axis? Thank You. PaulC | ||
| David W. Hopkins (Dhopkins) |
Hi Paolo, It depends upon the nature of the fruit. You should arrange your lamps so that you obtain good light intensity returning to the detector(s) and minimize the amount of specular reflection off the surface of the fruit. A 0-45 degree geometry is often used for NIR measurements, 0 degree angle of incidence of the measuring beam, and 45 degree detection. This will be important for fruit like apples, and not so critical with fruit like peaches. Specular reflection is like that from a mirror, and carries no information about the sample; it can seriously degrade the quality of the spectrum, if there is a large amount. | ||
| hlmark |
Paolo - David's advice is good. Implementation of it will involve some of the decisions you make in answer to the larger question of how best to measure the fruit, however. While the question seems simple, in fact there are many considerations to take into account, for example: do you want to measure mostly the skin, the inside flesh, or both? There are many configurations that can and have been used for measuring apples and other fruit (including Karl Norris' original work in the early 1960's on detecting water core in apples, where he used a transmission measurement), and it will probably require some experimentation on your part to decide what configuration that is best for your purposes. So going back to David's advice, how you implement it will depend on whether your detector looks only at a small region on the illuminated surface of the apple, or whether you are looking at the whole fruit, for example. As you can see, there are simply too many possible variables to answer the question by "remote control", so to speak. If you would like to discuss the question further and in more detail, feel free to contact me privately, off the discussion group. Howard \o/ /_\ |