Can the laser-scanning detect dampness ?

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Re: Can the laser-scanning detect dampness ?

Post by richard_m »

No.

Depending on the definition of "dampness" then in the lab this is probably possible and indeed an interesting research project.

In the real world tunnels are coated in random degrees of traffic pollution, algae, spiders etc and if the environmental conditions are correct then humidity will condense on the tunnel lining. I would suggest a better line of research is the use of UV or IR imaging?

Good luck.
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Re: Can the laser-scanning detect dampness ?

Post by mzhoum »

Thank you guys, lf2e10,richard_m, and jcoco3.

Jonathan, you mentioned you have some experience with static thermal scans. I am planning experiments combining helical moble 2D scanner with themal camera. Do you have further info as what type of thermal cameras I can consider ?
Michael Zhou, Professor
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Re: Can the laser-scanning detect dampness ?

Post by jcoco3 »

Michael,

When it comes to Thermal cameras there are two basic types. The cheaper and more compact un-cooled microbolometer and the larger more expensive cooled type. Here is an article that does a pretty good job comparing them: http://www.sourcesecurity.com/news/arti ... .2246.html

The cooled type is incredibly sensitive and sometimes able to see vapor and smoke, but I don't think you will need that in this application. I would suggest the more common un-cooled microbolometer type with a temperature range that accommodates the highest and lowest temperatures that you may encounter with the highest resolution you can afford to purchase. Most thermal cameras are extremely low resolution by comparison to any of todays digital cameras and the disparity between a low resolution thermal image and high resolution laser scan can lead to many difficulties. There are also a few other considerations. Because you are conducting a helical scan you may need multiple thermal cameras with wide field of view lenses to cover the area being scanned, and due to the fact that you are in motion you will want to research some on camera frame rates and potential rolling shutter issues. Many of the lower cost point and shoot thermal cameras have observable rolling shutter. Additionally most thermal cameras are manual focus although you can purchase some with autofocus. I doubt you will need autofocus unless the distance changes dramatically. I would think that almost any thermal camera would be sufficient for "detection" of dampness as long as there is enough saturation and evaporation to cause a temperature differential. If you need highly accurate temperature measurement then you may want to be more particular in your choice. You can also ask some of the other members from this thread:http://www.laserscanningforum.com/forum ... 60+thermal

Since I have a thermal camera I would be happy to conduct a simple test for you to see if it is feasible to detect moisture in the tunnel wall material when exposed to a prescribed amount of moisture. Are the tunnel walls concrete, soil, or many things as Richard described?

Some other options:
With regard to UV or IR imaging you might be able to vaporize a chemical that reacts with water into the tunnel preceding your scanner to make it fluoresce or change color. There is a chemical called Bluestar that is used to make blood fluoresce, but I am not sure how well it reacts with water and if it would be practical. You could also use chemicals like lithium chloride, sodium hydroxide, or a mild acid to react with the moisture to cause an exothermic reaction which could assist in thermal detection, but there would be obvious safety concerns along with difficulty in application and practicality.
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Re: Can the laser-scanning detect dampness ?

Post by mzhoum »

Hello, Jonathan,
Thank you for the comments.
http://www.sourcesecurity.com/ is a great site for the article and other related info.
Yes, we plan to detect the tunnel wall that is concrete.
Michael Zhou, Professor
College of Urban Railway Transportation
Shanghai Univ. of Engineering Scence
[email protected]
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Re: Can the laser-scanning detect dampness ?

Post by mzhoum »

Hello, Jonathan, I thank you again for all you info.
For some system reason, I did not see the replay I made at last day, so I put again today.
I appreciate for any info you may have about thermal detction in future.
Michael Zhou, Professor
College of Urban Railway Transportation
Shanghai Univ. of Engineering Scence
[email protected]
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