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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentTimeJan 14th 2012
    There has often been a few questions about infra-red cameras.
    How about an old 35mm and some infra-red film.
    50mm lens gets around the problem of a narrow field of view and a bit of scanning and photoshopping can soon make it a colour image.

    Now where is my old Zenith EM
    • CommentTimeJan 14th 2012
    It will depend entirely on the glass used in the optics I imagine.

    My Sony digital 35mm-alike seems to take photos in or augmented with (presumably) near-IR in its "nightshot" mode.


    • CommentAuthorJoiner
    • CommentTimeJan 14th 2012 edited
    • CommentTimeJan 14th 2012
    Apparently, according to the font of all knowledge Wikipedia, Sony had a sensor that can cope with IR. Why I thought of pulling my broken Alpha apart.

    I read somewhere that IR film is between 700 and 900 nm, not quite sure how that related to degrees C.
    • CommentAuthorEd Davies
    • CommentTimeJan 14th 2012 edited
    Posted By: SteamyTea: «How about an old 35mm and some infra-red film.»

    What for?

    Not for thermal imaging:


    «In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging.»


    «Black-and-white infrared negative films are sensitive to wavelengths in the 700 to 900 nm near infrared spectrum,...»

    SteamyTea: «I read somewhere that IR film is between 700 and 900 nm, not quite sure how that related to degrees C.»

    Rough rule of thumb is temperature (kelvins) is wavelength divided into 3 mm. So 600 nm (blue-green) is around 5000 K (temperature of the Sun, roughly), 900 nm is around 3333 K. Room temperatures of around 300 K are about 10 µm or 10'000 nm - much longer.

    This has all been discussed pretty recently:

    • CommentTimeJan 14th 2012 edited
    I've just come off the 'phone to an ex-colleague (who rang to tell me he's just retired, too, and isn't it great?!). anyway, it turns out he worked on MEMS (Micro Electronic Mechanical Systems) devices at Malvern years ago and one of the sensors they developed was for imaging long wavelength IR. They made flat plane arrays of microscopic heat-sensitive resistors (thermistors), by etching them from doped silicon wafers. These were then used just like the sensor in a digital camera. The trick to make them sensitive enough to work at room temperature was to etch away the silicon underneath these microscopic sensors, so they looked like tiny flat topped umbrellas. This then thermally decouples them from their substrate and makes them respond almost entirely from the IR that impinges on them.

    He reckoned the technology was now mature (it was around 20 years ago that he worked on it last) and is probably the same as that used in commercial IR cameras now. He did say there was no good reason for the sensors being expensive, as they are, apparently, as easy to fabricate as any other medium scale semiconductor device.

    I'll do some digging around and see if the sensors are available on their own, as if they are then the chances are that a cheap DIY IR imager could probably be put together.
    What kind of technology is required to do that kind of etching of wafers??
    • CommentTimeJan 14th 2012 edited
    <blockquote><cite>Posted By: bot de paille</cite>What kind of technology is required to do that kind of etching of wafers??</blockquote>

    The kit is pretty expensive and needs a hefty investment in things like clean rooms, but the process seems essentially quite simple. The process is a bit like that needed to make semiconductor chips, where bits of silicon are etched away, other materials are impregnated or sputtered on to the silicon wafer and more selective etching takes place, so that a 3D construct can be built on the surface of the silicon. This paper gives and overview of how these things are made: http://www.ee.kth.se/php/modules/publications/reports/2007/IR-EE-MST_2007_132.pdf

    So far I've not found any really cheap sensors, but there are a few DIY thermal imager projects around on the web. In principle it seems pretty easy to make a scanned imager, using a relatively cheap sensor (and I happen to have some Melexis MLX90247 sensors left from another project that might do the job). Looking around the web making an imager to scan a sensor mechanically using a small microcontroller and a pair of model aircraft servos seems very straightforward. The same microcontroller could read the sensor output and store a grid of values for the whole image. I'm reasonably sure I could get this bit to work OK, maybe storing images as a file on an SD card.

    Where I'd come unstuck is in writing the code for a PC to display the stored images.

    I've no doubt that a project like this might well prove useful when investigating house thermal losses, so might be worth playing with.
    Posted By: bot de pailleWhat kind of technology is required to do that kind of etching of wafers??
    Regular silicon processing technology can do the anisotropic etching required for micro-machine devices (MEMS). It's actually pretty mainstream these days - look at all the micro-mirror devices produced for use in projectors etc. Plus the MEMS devices used as accelerometers and so on in things like iPhones.

    Good overview here on the process technologies used: http://en.wikipedia.org/wiki/Microelectromechanical_systems

    [Just to note, work in the semiconductor industry]

    Paul in Montreal
    Isnt it the crystal lense which makes these cameras expensive?
    • CommentTimeJan 15th 2012
    No idea, why I asked. A crystal lens, would that not make me look younger and healthier, money well spent :cool:
    • CommentTimeJan 15th 2012
    <blockquote><cite>Posted By: bot de paille</cite>Isnt it the crystal lense which makes these cameras expensive?</blockquote>

    It can, yes, but there are alternatives, like ceramic lenses, From what I've been reading very recently it seems that the easy and cheap way to do it is to use a scanning mirror instead of a lens, as pretty much any sort of reflective surface will work OK at these long wavelengths. My guess is that an IR optical system like a reflecting telescope might also work well and avoid the need for expensive lenses.
    Traditionally, germanium was used as a lens for IR cameras - very very expensive.

    Paul in Montreal.
    • CommentTimeMay 28th 2013 edited
    • CommentAuthorEd Davies
    • CommentTimeMay 28th 2013
    Infragram is a simple, affordable near-infrared camera…
    So not much use for thermal imaging purposes.
    • CommentTimeMay 28th 2013
    Are plants and houses so different? I do not have a clue but would have thought that plants were pretty close to ambient, just like houses.
    • CommentAuthorSprocket
    • CommentTimeMay 29th 2013 edited
    Near IR is very different to the much longer wavelength IR measured by thermal imagers.
    To have significant near IR a hot body would have ot be very hot (like hundreds of degrees).

    Near IR wavelength is typically 600nm to 1000nm

    Thermal imager measures 7500nm to 14000nm

    The IR imagery you see of plants IN DAYLIGHT is more of a colur/pigment phenomenon. It is very easy (and fun) to make a webcam see near IR, you just remove a little glass filter from the front of the sensor and add a visible light blocker. Images of coloured things then look very different because of whether the pigments reflect or absorb IR (all plants reflect near IR just because the leaves don't absorb it). This has nothing at all to do with the much longer IR *emitted* by warm things.

    The sensors for long IR are pretty much just what JSH describes above - they are micro bolometers ie. a 2D array of tiny thermometers. As someone already mentioned too, the lens to focus long IR onto an image plane is made of expensive Germanium. If you want a cheap thermal imager then we need a cheaper lens.
    • CommentAuthorEd Davies
    • CommentTimeJun 9th 2013
    • CommentAuthorEd Davies
    • CommentTimeJul 12th 2013
    • CommentTimeSep 11th 2013
    Did anyone see this weekends Monza GP.
    I know the cars costs millions and millions, but how much was the IR Camera.
    • CommentTimeMar 20th 2014
    I want some of these (though I am able to see more UV than most now).
    I hope they can see the full spectrum and fit them into phones.
    Posted By: SteamyTeaI want some of these (though I am able to see more UV than most now).
    I hope they can see the full spectrum and fit them into phones.
    http://www.deccanchronicle.com/140320/technology-latest/article/night-vision-contact-lense-developed" rel="nofollow" >http://www.deccanchronicle.com/140320/technology-latest/article/night-vision-contact-lense-developed

    And they are made from........ Graphene! I say again, this material, along with 3D printing is going to revolutionize modern technology.

    The real kicker will be when printable graphene plastic PV panels appear on the market.
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