Tuesday, April 28, 2015

Thermal Diode Array Technology?

Consumer grade thermal cameras keep coming. After FLIR One with microbolometric imager, Seek Thermal came with Raytheon microbolometric sensor, and now Hema Imaging is closing a successful Kickstarter campaign.

Hema Vision camera utilizes 82x62 Heimann Sensor GmbH thermal sensor based on the new "thermal diode array technology." Hema Imaging writes: "Heimann Sensor GmbH is a developer and manufacturer of thermopile arrays for thermal sensing and other infrared sensors, and leads the world in thermopile array technology and now are the experts in thermal diode array technology."

It should be fairly cheap to fit the consumer camera bill, so exotic materials like CMT are probably not an option. So, I wonder how do these "thermal diodes" work?


  1. These thermopiles use Silicon diode junctions. Thermopiles do have a relative stability advantage vs microbolometers (hence mention of the shutter). However they have lower sensitivity (higher NETD), slower speed (time constant, not readout), and worst of all for low-cost modules: large pixel sizes (100um vs 17um for FLIR or 12um for Raytheon). That translates to higher chip cost, but more importantly, much higher optics cost (mid-IR lenses still kind of pricey!).

    So, surprised they launched-- and look like they will successfully complete-- a Kickstarter given the competition that is out there.

    1. The common problem with all these low cost 'Thermal Imagers' is that they are 'Fusion Thermal Imagers' - that would usually be a good thing but the quality of the image presented is almost entirely derived from either a second Device (Cellphones / Tablet) or a second conventional (or IR sensitive) Sensor.

      Those 80x80 pixels get stretched and overlaid onto a 1920x1080 image, and everyone becomes Pixelman http://jeuxcool.com/wp-content/thumbs/mochi/P/pixel-man-rapid-gunner_img1.jpg .

      When people are 100 feet away they are represented by ONE pixel (if your lucky) from the Thermal Imager and probably around 30x120 pixels from a separate image Chip which is overlaid.

      It is a neat toy to mess around with and works OK less than a few feet away (which maximizes the Thermal image content) but it is $250 for a few days of fun.

      For that money NV Binoculars or a Camera with it's IR Filter removed would provide more hours of enjoyment, while (obviously) not providing identical image spectrum capture the result would be similar (for someone who pays under 5K for "Thermal Imagers") and far more satisfying.

      A good (real) Thermal Imager with HD resolution costs a lot but there are recent developments to reduce the pricing; but if the image is 'too good' then you can not buy the equipment (restricted).

      Proper equipment looks like a B/W Photo, sometimes with HD quality multi-spectral fusion which provides false color (that does not mean 'Ironbow', it means 'Tron Outlining'). It can fit in a case so small that it can be helmet mounted.

      My background image at YouTube has a shot of what these images look like and there is a number of Videos on my Channel showing Top of the Line equipment and a few of these low cost Devices.

      I'd rather pay several hundred to get a 'Thermal Image' with the quality of a Cellphone from ten years ago than toss out $250 on a novelty toy that will not be much fun in a week or two.


    2. You're looking from a night vision point of view for which I would agree this makes no sense. However this can be very useful when tracking down where heat is escaping when reviewing home insulation. It can also be used to identify hot spots in machinery and electrical trouble spots. FLIR has sold cameras with this low resolution for many years to industry for quite a bit more money so it can't be that gimmicky.

  2. These thermopiles come with integrated IR windows. So, no need for separate lenses. Together with that window, they are still much cheaper than bolometer based sensors from Flir/Ulis/etc. Keep in mind that when the sensor is sub-standard compared to bolometers, window can also be sub-standard, paving way for cheaper implementation.

  3. wait, how does a "window" eliminate the need for a "lens"? How is the image projected and focused on the FPA? Plus, even it if something comes integrated with the device, someone still had to pay for it along the way

    1. From Window, I meant Ge-optics. Of course, someone had to pay, but I have compared the costs of the two low resolution devices under discussion and there is a clear cut difference in pricing.


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