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Re: [ATM] infra-red
On Sat, 27 Jan 2007, Jarvis Krumbein wrote:
> All CCDs are sensitive to IR. CCD digital cameras have an IR rejection
> filter built in to block the IR.
>
> Jarvis Krumbein
Hi Jarvis, others!
As was explained to me, that filter also reduces red in order
to give more neutral color with respect to blue. The last time
I found absorbance scan of such a filter, it was not a sharp
cutoff/bandpass filter. Absorbance smoothly climbed up from
around 600 nm to a peak around 900 nm.
I am curious about these rejection filters.... can they be removed?
I have wanted to do IR imaging, and dedicated made-for-purpose
hi-res IR cameras cost big time. With my common consumer CCD
camera, I am losing a lot of the signal, albeit I can detect
near IR, like a 15 mW TV remote IR LED (900 nm???) from about
5 meters away (best case scenario). I think without these filters,
these cameras must make excellent IR cameras for scopes.
That being said, I noticed in the States (Fry's Electronics) there
are night security cameras being sold with IR LEDs as a light
source. The ones I saw were B&W CCDs and I would imagine they do
not have these filters since they are intended to be used in the
dark, unknown to the person being imaged. Sadly, none of these had
very high resolution. That was a couple years ago and these cameras
seemed popular, so perhaps newer are are better.
Dominic-Luc Webb
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