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infra-red and mirrors

 
 
Adam Chapman
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      10-24-2006
Hello,
I am designing an aircraft for a university project. The specification
states the aircraft needs camera capable of recording IR video, PAL
format, 10cm rsolution.
I am considering using a kind of periscope in stead of those big
spherical "gimball" jobs.
If I used a series of mirrors and the camera was embedded deep within
the aircraft, would the infra-red camera still work?

Any help would be greatly appreciated.
Best Regards,
Adam

 
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Paul Rubin
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      10-24-2006
"Adam Chapman" <(E-Mail Removed)> writes:
> If I used a series of mirrors and the camera was embedded deep within
> the aircraft, would the infra-red camera still work?


If you mean near-IR, then probably yes. Simplest experiment is get
hold of a camcorder with nightshot and point it at your bathroom
mirror on IR and see what happens.
 
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Adam Chapman
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      10-24-2006
The aircraft need to watch the ground from a height of 300m. I do not
quite understant what you mean by near-IR

 
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Paul Rubin
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      10-24-2006
"Adam Chapman" <(E-Mail Removed)> writes:
> The aircraft need to watch the ground from a height of 300m. I do not
> quite understant what you mean by near-IR


IR refers to a range of frequencies. The higher IR frequencies are
near the frequencies of visible light and are called Near IR.
The lower frequencies are further away and are called far IR,
thermal IR, etc. The ones in the middle are called medium IR.

Imaging with thermal IR has traditionally required chilled sensors
though I gather there's ways around that these days. Near IR imaging
is not much different than ordinary photography.
 
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Adam Chapman
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      10-24-2006
Thanks for the help. I really appreciate it.

 
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Scott W
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      10-25-2006

Adam Chapman wrote:
> Thanks for the help. I really appreciate it.

Get a copy of "The Infrared Handbook"
http://www.amazon.com/Infrared-Handb.../dp/096035901X

You are going to need it.

Scott

 
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Don Stauffer in Minnesota
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      10-25-2006

Adam Chapman wrote:
> Hello,
> I am designing an aircraft for a university project. The specification
> states the aircraft needs camera capable of recording IR video, PAL
> format, 10cm rsolution.
> I am considering using a kind of periscope in stead of those big
> spherical "gimball" jobs.
> If I used a series of mirrors and the camera was embedded deep within
> the aircraft, would the infra-red camera still work?
>
> Any help would be greatly appreciated.
> Best Regards,
> Adam


Yes, but you may need to watch the material used for the mirrors. For
near IR normal mirrors should work. For thermal IR, gold is better,
and the mirrors MUST be first surface ones. Glass and aluminum oxide
protective overcoats will strongly absorb thermal IR. Aluminized
mirrors, even first surface ones, will oxidize and eventually dim in
the thermal IR so they are not really recommended. The amount of gold
needed to coat a metal or glass substrate isn't really that much so is
not prohibitively expensive.

 
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Roger N. Clark (change username to rnclark)
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      10-26-2006
Don Stauffer in Minnesota wrote:
> Adam Chapman wrote:
>
>>Hello,
>>I am designing an aircraft for a university project. The specification
>>states the aircraft needs camera capable of recording IR video, PAL
>>format, 10cm rsolution.
>>I am considering using a kind of periscope in stead of those big
>>spherical "gimball" jobs.
>>If I used a series of mirrors and the camera was embedded deep within
>>the aircraft, would the infra-red camera still work?
>>
>>Any help would be greatly appreciated.
>>Best Regards,
>>Adam

>
>
> Yes, but you may need to watch the material used for the mirrors. For
> near IR normal mirrors should work. For thermal IR, gold is better,
> and the mirrors MUST be first surface ones. Glass and aluminum oxide
> protective overcoats will strongly absorb thermal IR. Aluminized
> mirrors, even first surface ones, will oxidize and eventually dim in
> the thermal IR so they are not really recommended. The amount of gold
> needed to coat a metal or glass substrate isn't really that much so is
> not prohibitively expensive.
>

I use aluminum coated first surface mirrors, standard ones off the
shelf, uncooled in spectroscopy from 0.2 to 150 microns,
that covers UV to far infrared. Uncooled mirrors are used
in the thermal IR all the time, in the lab, on aircraft,
on telescopes, and on spacecraft.

Roger
 
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Adam Chapman
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      10-26-2006

Thanks everyone,

I was hoping i could coat the mirror in gold anyway because it will
reduce the chance of being detected by radar

 
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Adam Chapman
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      10-26-2006
The main reason I suggested the mirror periscope idea is because ny
aircraft needs to have a very low radar cross-section.
A spherical gimbal would have the same radar cross section when the
radar is looking at the aircraft from all directions, where as a simple
flat plate mirror pokking out of the bottom would only have a
significant radar signature over a very short range of directions.

Any new ideas would be appreciated

 
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