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Need to produce fake sunlight: power question - Page 3

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Posted by Paul Ciszek on August 20, 2007, 1:47 am
 


I need to measure the transmission (and possibly later, reflection)
of certain materials at those wavelengths that account for most of
the power in sunlight--near UV to about 2um.  I don't need the source
to mimic the spectrum of sunlight per se, so long as there is enough
light present at all these wavelengths to measure transmission fraction
at each wavelength.  Originally, I didn't see any need to reach the
intensity of sunlight, since I was just taking the ratio of two
measurements, and I would have been happy with a halogen work light
as my broad spectrum source.  But now they want the tests to include
things that actually respond to sunlight, and so I may need to match
the actual intensity of sunlight.  I still figure that a black body
with a hot enough color temperature should be good enough as far as
matching the spectral distribution goes, and the references I have
consulted seem to indicate that glass is still transparent at 2um.
I have not had any luck getting reference spectra for light bulbs
that goes outside the visible range; does anyone know if ELH bulbs
emit that far into the IR?  We do not yet have the IR spectrometer
that would allow me to check that directly; I want to take visible
spectra in the meantime and be ready to start taking the IR data
as soon as we get the spectrometer, so I would rather get the light
source right the first time around.

I have heard that some halogen bulbs are coated to reflect the IR
inward, keep the filament hotter with less electricity, and therefore
improve the visible lumens per watt.  While this is a good idea from
a lighting standpoint, it would throw a wrench into my plan for a
cheap artificial sun.

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