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Old Mar 14, 2006, 08:48 AM
Tom Harper is offline
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DIY conversion to infra red


Still looking for wagon tracks, so:

It is possible that IR reflectivity is different for the compacted ground of trackways than it is for surrounding soil. This may be especially true after a rain (if it ever rains again). Lacking BIG bucks for a serious IR camera I chose to modify one of my handhelds. I have standardized on the Olympus C50 5mpx. No particular reason for that camera, but I find that extreme familiarity with one camera lessens problems. I by the broken ones on eBay.

Suddenly there is a ton of info on the web about IR conversions. A few seconds on Google yields a lot. But the simple facts are:

Digital cameras are very sensitive to IR wavelengths

To prevent problems the mfg includes an internal IR blocking filter

Remove the blocking filter and voila - IR camera

Use an IR pass filter in front of the lens to keep out visible light


What you get is a very high contrast false color image that 'sees' things differently than visible light. Probably not useful for Real Estate - but who knows?

The photos show the process. The only tricky part is that you have to cut a replacement for the filter that you remove. I used pieces of the UV filter that was smashed when the Creosote Cruiser pronged into the ground. Just scribed and snapped until I had a piece that fit. I tried to get away without the replacement and the focus was really bad.

No AP yet - the winds have been 40 to 60 mph. But the two ground images show the results. Trees are white. Sky and water are black. Ice on the pond reflects white.

I'm using an IR pass filter in front of the lens. Has some advantages. But I want to cut one to use internal to the camera. Since IR focuses at a different point than visible the thickness of the filter can compensate for the difference. Can one of you experts tell me which way to go. Does thicker glass or thinner glass focus the IR better?
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Old Mar 14, 2006, 09:09 AM
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It almost looks like "night vision", I hope you get this thing worked out. It is very interesting.
Old Mar 14, 2006, 09:23 AM
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Good point! It's night vision that uses the sun for and IR source.
Old Mar 14, 2006, 10:02 AM
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The Glass


Hi Tom-

Neat project. I've thought about attempting this too. I'll have to admit that I don't understand how a flat piece of glass, whether thin or thick, would change a focal point very much. On some old 35 mm film cameras, there were red markings on the focus barrel for IR film, at a little less than visible light infinity setting if I remember right. I'd say if you have a manual focus, just experiment till you find the best focus.

But then again, tell me more. I work with optical systems for a living, and learn something new almost every day.

Rich

P.S. How did you like the CK field paper? Make any sense at all?
Old Mar 14, 2006, 11:57 AM
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Rich,

Really enjoyed the paper. It's one of the reasons I want to try IR. Noticed that you got results from variations in vegetation growth. After a rain I notice a light cover of grasses and low plants. That may suffice. But, once in a while I give fleeting thought to scattering rye grass seed over an area of interest. BLM would probably frown on it.

I assume the focus has to do with the index of refraction of the glass. Seemed odd to me. But, when I left it out the focus was really blurred. The flat glass is .073" thick and the original was .069. It fixes the problem. I'm an electronics and software guy. Optics is magic. Maybe some of your co-workers have an answer.

Tom
Old Mar 14, 2006, 12:01 PM
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Excellent info Tom. I will watch this project very closely!

Are the pics above with or without the IR pass filter?
Old Mar 14, 2006, 12:04 PM
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BTW:

Those IR blocking filters are beautiful. I may have a couple made into earings for my spouse!
Old Mar 14, 2006, 12:53 PM
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Good work, now I know what I'm going to do with my "retired" Olympus D40 - keep us posted on your results. Thanks for sharing!

CJS
Old Mar 14, 2006, 01:03 PM
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IVS.

These pics are with an IR (760nm) pass filter held in front of the camera. It's wierd - when you look through the view finder you see black but there is a picture on the LCD.
Old Mar 14, 2006, 02:20 PM
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Quote:
Probably not useful for Real Estate - but who knows?
How about thermal imaging of buildings - promote cavity wall insulation / Double glazing etc
I know not necessarily industrial spec IR imaging
Old Mar 14, 2006, 02:25 PM
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IR Camera Guru


Tom-

I work mostly with first surface mirrors, either curved or flats. I know an IR camera wizard in Albuquerque. I'll give him a call and see if he has any thoughts on filters and focusses. Good luck finding your roads.

We were shooting a false color IR film at Chaco (some shot by a commercial contractor, some shot by NASA) that had been developed for camouflage detection in Vietnam (Kodak product if I remember right). It was great for seeing subtle differences in vegetation, and especially a few days after a good rain. Active new vegetation looked warm pink in the false color film.

Rich
Old Mar 14, 2006, 02:41 PM
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SMARIC,

IR is not really thermal, just reflective in the IR spectrum.
Old Mar 14, 2006, 02:45 PM
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Rich,

We've found about 3 miles of big frieght wagon trails. They are probably 1800-1850. There is lots of evidence of the earlier trails but we have some learning to do before making any claims. I've posted some stuff here:

http://www.sdc.org/~crane

Tom
Old Mar 14, 2006, 02:45 PM
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Yes, I've seen aerial photography using thermal imaging used to detect leaks in roofs, too. You fly a few days after the rain when the roof is dry, and cold spots show where water is still pooled under the roof.

I wonder if we can do this with our RC AP planes.

-Vince

Quote:
Originally Posted by SMaric
How about thermal imaging of buildings - promote cavity wall insulation / Double glazing etc
I know not necessarily industrial spec IR imaging
Old Mar 14, 2006, 02:47 PM
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vpatron,

Now that's a neat idea!


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