IR Receiver/Demodulator [Design]

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From: Dave Platt on 18 Mar 2010 21:22

>> I've taken some interesting photos, using an old Fuji FinePix camera
>> whose Sony sensor has a less-than-efficient IR-exclusion filter,
>> shooting through a simple home-made filter made from black acrylic
>> glued to the end of PVC tubing. The results have the usual IR-photo
>> appearance - the sky is quite dark, green leaves on trees appear
>> almost white.
>>
>
>Hey, couldn't you use that for informal energy audits, find leaks in houses?

I'm not sure that the whole process is anywhere near sensitive enough
for thermal IR, although it's certainly possible that a good digital
SLR, with its internal IR filter entirely removed and an IR-pass
filter added, might do the trick with a long enough exposure and a
cold enough sensor.

--
Dave Platt <dplatt(a)radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

From: JosephKK on 18 Mar 2010 23:33

On Wed, 17 Mar 2010 05:17:58 -0700 (PDT), osr(a)uakron.edu wrote:

>And it seems like you may need a dose of "Hobbs Salts"
>
>
>http://www.electrooptical.net/www/frontends/frontends.pdf
>
>Steve

Mighty good reading.

From: Phil Hobbs on 18 Mar 2010 23:36

On 3/18/2010 9:36 PM, Joerg wrote:
> Phil Hobbs wrote:
>> On 3/18/2010 8:48 PM, Joerg wrote:
>>> Dave Platt wrote:
>>>> In article <2p75q51q8ao2vt8o3vjmoal2c9gcuot9h1(a)4ax.com>,
>>>> Hammy <spam(a)spam.com> wrote:
>>>>
>>>>> As for an IR lens that filters out sunlight and other wavelengths just
>>>>> rip one out of an old TV,STEREO whatever. All IR remote devices in my
>>>>> house have a filter lens in front of the detector. I'm sure you could
>>>>> find a scrap TV or something to scavenge one off for testing.
>>>>>
>>>>> I recall finding sources for the lens you can get it in strip form. I
>>>>> cant find the site anymore but its inexpensive.
>>>>
>>>> Another option is to visit a store which sells sheet plastic (e.g. TAP
>>>> Plastics, Professional Plastics), dig through their scrap bin, and buy
>>>> as thin a piece of black acrylic plastic as you can find. This stuff
>>>> filters out visible light, but the dye in it passes a significant
>>>> amount of IR.
>>>>
>>>> I've taken some interesting photos, using an old Fuji FinePix camera
>>>> whose Sony sensor has a less-than-efficient IR-exclusion filter,
>>>> shooting through a simple home-made filter made from black acrylic
>>>> glued to the end of PVC tubing. The results have the usual IR-photo
>>>> appearance - the sky is quite dark, green leaves on trees appear
>>>> almost white.
>>>>
>>>
>>> Hey, couldn't you use that for informal energy audits, find leaks in
>>> houses?
>>>
>> Not unless the house is on fire. ;0
>>
>
> Seems to be working pretty well here:
>
> http://www.hoagieshouse.com/IR/
>
> He could even see where the veins run underneath the skin and they can't
> possibly be on fire :-)
>

No, it's just that the skin is much more translucent in the IR. There's
almost no temperature contrast between veins and skin, and if there
were, the veins would look brighter since they're carrying heat from
inside the body to the extremities.

Trust me, you can't see thermal luminosity of 300 kelvin objects with a
silicon sensor. Even if you put a microbolometer array or a HgCdTe
sensor there, the glass lens of that camera is completely opaque in the
thermal IR.

Cheers

Phil Hobbs

PS: you get the same sort of view with an S-1 photocathode IR viewer.
It's neat.

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net

From: Tim Williams on 19 Mar 2010 00:06

"Joerg" <invalid(a)invalid.invalid> wrote in message
news:80g1ouFjubU1(a)mid.individual.net...
> http://geektechnique.org/projectlab/254/how-to-turn-a-digital-camera-into-an-ir-camera
>
> This guy's face probably isn't more than 100F.

Yeah, but he's shining an IR flashlight at his face, horror-story style.

I wonder what the inside of an oven looks like? Might be hot enough to
catch the very tail of blackbody radiation.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

From: Martin Brown on 19 Mar 2010 05:01

Joerg wrote:
> Phil Hobbs wrote:
>> On 3/18/2010 8:48 PM, Joerg wrote:
>>> Dave Platt wrote:
>>>> In article <2p75q51q8ao2vt8o3vjmoal2c9gcuot9h1(a)4ax.com>,
>>>> Hammy <spam(a)spam.com> wrote:
>>>>
>>>>> As for an IR lens that filters out sunlight and other wavelengths just
>>>>> rip one out of an old TV,STEREO whatever. All IR remote devices in my
>>>>> house have a filter lens in front of the detector. I'm sure you could
>>>>> find a scrap TV or something to scavenge one off for testing.
>>>>>
>>>>> I recall finding sources for the lens you can get it in strip form. I
>>>>> cant find the site anymore but its inexpensive.
>>>>
>>>> Another option is to visit a store which sells sheet plastic (e.g. TAP
>>>> Plastics, Professional Plastics), dig through their scrap bin, and buy
>>>> as thin a piece of black acrylic plastic as you can find. This stuff
>>>> filters out visible light, but the dye in it passes a significant
>>>> amount of IR.
>>>>
>>>> I've taken some interesting photos, using an old Fuji FinePix camera
>>>> whose Sony sensor has a less-than-efficient IR-exclusion filter,
>>>> shooting through a simple home-made filter made from black acrylic
>>>> glued to the end of PVC tubing. The results have the usual IR-photo
>>>> appearance - the sky is quite dark, green leaves on trees appear
>>>> almost white.
>>>
>>> Hey, couldn't you use that for informal energy audits, find leaks in
>>> houses?

Informal energy audits you can more or less point at any single glazed
windows and the roof as prime suspects...
>>>
>> Not unless the house is on fire. ;0
>
> Seems to be working pretty well here:
>
> http://www.hoagieshouse.com/IR/
>
> He could even see where the veins run underneath the skin and they can't
> possibly be on fire :-)

No but at near IR wavelengths scattering in the skin is low enough that
it is almost transparent. Photon energy for near IR CCDs is
characteristic of a very warm house - about that of molten lead.

Pyrodetector based burglar alarm sensor and a rotating mirror might
allow you to do some ad hoc long wave IR measurments on houses. They
will reliably detect a 37C human against a background ambient of 25C so
you could build an image up line by line.

Regards,
Martin Brown