reproducing spectral signatures

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reproducing spectral signatures

Postby zetreque on October 29th, 2017, 3:47 pm 

Is it possible to artificially reproduce a spectral signature and if so how easy?

say I have some vegetation and I want to reproduce its infrared or thermal signature (the leaves).

How would I go about doing that?

Some thoughts:
-I start out with a full infrared spectrum light and then manufacture a filter somehow?
-I take the leaf of that plant and somehow shine light through it or on it, then project out a more intense light from it.
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Re: reproducing spectral signatures

Postby henriette on February 23rd, 2018, 2:39 pm 

Dear,
There are so many ways to achieve this preliminary engineering issue, would this make sense : http://www.ti.com/lit/wp/dlpa048a/dlpa048a.pdf
A source of light making use of a vegetable as a spectral filter would be as romantic as a weed vaporizer, wouldn't it?
You may consider the spectral range, the spectral sensitivity and the tunability after basics in optics (photometry, geometry, etc.)
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Re: reproducing spectral signatures

Postby zetreque on February 23rd, 2018, 4:05 pm 

Thank you for the response.

Yes, that explains the concept but doesn't help much more than telling me to shine a light through or off of vegetation to a detector.

My goal for this project is to create a light that mimics the spectral finger print of a certain vegetation. Which is difficult given that the light needs to be in the IR spectrum since I am trying to mimic and emit the heat signature of vegetation at night.
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Re: reproducing spectral signatures

Postby henriette on February 24th, 2018, 2:10 am 

Dear,
Yes, you can design the spectrum of a source of light, that is just engineering.
You are maybe a couple of days away from the solution, or years...

Your statement is not clear enough so that a solution can be suggested to you at this step:
My goal for this project is to create a light that mimics the spectral fingerprint of a certain vegetation.

Optical context? : field of view, sensitivity of the recorder, flash rate, optical aperture... all those parameters will be critical here...
Infrared or visible is the same in this context, don't worry.

Basically the frame of such optical source (tunable multispectral source of light) should be :

A- White source S0 (IR in this context)
B- spectral dispersion device (things like prisms, gratings and some lenses, etc.: may resemble monochromator). you get the rainbow image S1 of S0, 1D dispersion
C-spectral coding (the DMD may be convenient, but transmission filter would also do the job, it is a 0-1 filter, you will just have to draw the wished spectrum pattern on the DMD from your spectral database).
you get S2=S1*(mask = spectrum, orientated along the direction of dispersion of B)
D=B-1 : recombine the spectrally dispersed beam (D is the symmetrical of B, this is not Emilie Noether anyway)
E -Projector. Enjoy
All in all the equivalent of : 5 lenses (4+the projector lense) , 2 gratings, the filter and your spectral database.

You can also get a 3D-spectral projector at video rate.
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