Adding Optics to a Consumer Thermal Camera

[David Prutchi] writes in to tell us about his recent experiments with building lenses for thermal imaging cameras, which to his knowledge is a first (at least as far as DIY hardware is concerned). With his custom designed and built optics, he’s demonstrated the ability to not only zoom in on distant targets, but get up close and personal with small objects. He’s working with the Seek RevealPro, but the concept should work on hardware from other manufacturers as well.

In his detailed whitepaper, [David] starts by describing the types of lenses that are appropriate for thermal imaging. Glass doesn’t transmit the wavelengths that thermal camera is looking for, so the lenses need to be made of either germanium or zinc selenide. These aren’t exactly the kind of thing you can pick up at the local camera shop, and even small lenses made of these materials can cost hundreds of dollars. He suggests keeping an eye out on eBay for surplus optics you could pull them out of to keep costs down.

Creating the macro adapter is easy enough, you simply put a convex lens in front of the thermal camera. But telephoto is a bit more involved, and the rest of the whitepaper details the math and construction techniques used to assemble it the optics. [David] gives a complete bill of materials and cost breakdown for his telephoto converter, but prepare for a bout of sticker shock: the total cost with all new hardware is nearly $500 USD. The majority of that is for the special lenses though, so if you can score some on the second-hand market it can drop the cost significantly.

We’ve seen an impressive array of thermal camera hacks and projects recently, no doubt due to the falling prices of consumer-level imaging hardware. Given their utility as a diagnostic tool, a thermal camera might be something worth adding to your bag of tricks.

16 thoughts on “Adding Optics to a Consumer Thermal Camera

        1. Sapphire probably no because its short-pass cutoff is at around 5um, whereas common thermal imagers work in the ~8 to 12 um range. NaCl yes, but I haven’t seen one since I built my first CO2 laser back in highschool some 35 years ago… They degrade very quickly with environmental moisture, and have been almost completely replaced by ZnSe for CO2 lasers, although I know that they are still used in some specialized IR spectroscopy systems. Potassium Bromide (KBr) is another possible choice, although, again, it’s very sensitive to moisture.

          1. Interesting. I recall replacing Nernst Glowers in Beckman spectrophotometers that use optical choppers. Also working on temperature sensors for RTP wafer processing. They looked at the bottom of the wafer through a 100mm sapphire rod. I didn’t think they worked very well at the time, and the people making them did not know how they worked. However, there is one in every Intel “copy exact” RTP setup.

      1. True for macro magnifiers, but I searched high and low for information on telephoto converters, and all I could find is a YouTube video in Russian at: https://www.youtube.com/watch?v=rt4EHTFfKVw&t=38s

        I am not a Russian speaker, and I couldn’t find any other details on how he built the telephoto that he shows in the video, although there are a few pictures with no further explanations at: http://www.eevblog.com/forum/thermal-imaging/yet-another-cheap-thermal-imager-incoming/msg721312/#msg721312. Boris has other videos on his thermal cameras that look very cool: https://www.youtube.com/channel/UCCWd-19-oYdUmPMR8V0TchQ

        The 3D printed parts that Boris shows in his video do look very nice, so I’ll try to get in touch with him to encourage him to post details and maybe stl files.

        Cheers,

        David

  1. Just some things to keep in mind: The laser optics are all designed for 10u, tow peaks 9.4 and 10.6. They are not chromatically adapted for the LWIR range of 7u to 15u. You can build a system using this, but the chromatic aberrations would likely limit performance. Further most of these optics have an F number of >2, typically F3. This is in most cases not suitable for uncooled IR detectors. These bolometric detectors are all designed to work with F numbers below 1.8, ideally F1.4.
    It is an interesting concept, but far from ideal

    R

    1. Agree. One of the pictures in the whitepaper shows the aberrations that you get even when using Ge lenses with AR coating for the thermal IR range. It’s OK for qualitative imaging, but some corrections would be needed for radiometric measurements.
      Cheers,
      David

  2. hi. im a complete newbie to lenses and photography. i do have a seek reveal pro though. i’m trying to find the right lenses but im very unclear what specifications i need in terms of diameter and focal length. i found this one https://www.ebay.com/itm/1-inch-diameter-HAND-POLISHED-Germanium-Metal-Disk-99-999-5grams-Element-Sample/232258898858?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649. Does that work? Can you give me any newbie guidance? thanks!

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