Thermal imager: look at the world through the eyes of a Predator

    I have long wanted to get to the thermal imager - I probably had an ad in my profile for a year. Finally, I managed to find a thermal imager - and I want to share what I managed to remove and a story about how they work.

    The temperature of objects can be determined because the amount of infrared light emitted by objects depends primarily on temperature and already less on material ( emissivity , in correct pyrometers and almost all thermal imagers, you can adjust the correction for emissivity in order to obtain a sufficiently accurate temperature.).

    With increasing temperature - the radiation becomes shorter wavelength, from 700-800 degrees already capturing the region of visible light. Both thermal imagers and pyrometers (infrared thermometers) and motion sensors work on this principle.

    Thermal imagers, like many interesting things in this world, were originally invented for the military. Any warm objects inevitably glow in infrared light (both day and night), air freely transmits infrared light in the range of 7-14 μm, and finally fog, dust traps infrared light much less, i.e. in conditions of poor visibility it can be seen much further.

    Atmosphere Transparency:


    Of course, special optics are required - ordinary optical glass after 1-1.5 microns is no longer transparent, so you have to use germanium, silicon, zinc selenide, table salt (but the optics from it require a protective film because it is destroyed by moisture in the air) or mirror optics ( coated with gold, aluminum, copper or molybdenum). Also, some plastics are transparent to infrared radiation - and for example in plastic pyrometers and motion sensors you can find plastic optics.

    You can see infrared radiation by measuring the heating of a matrix of micro-thermometers (this is called a microbolometer). Each pixel of a microbolometer has a size of the order of 17-45 micrometers (there is nowhere less, the wavelength of infrared light is 7-14 microns).

    The material from which resistances are made can most often be vanadium oxide (requires heating to a phase transition temperature, maximum sensitivity) or amorphous silicon (cheaper and easier to manufacture, but less sensitivity). In motion sensors - the sensor is ferroelectric, it is inconvenient for measuring absolute temperature (because it responds to changes in the radiation flux)

    The military also has IR cameras for a range of 3-4 micrometers - there is usually a semiconductor sensor with much greater sensitivity, but it requires cryogenic cooling (in the best case, with the vigorous Peltier elements, in the worst - with liquid nitrogen). In the civilian sector you will not see this much.

    Thermal imagers are rapidly becoming more affordable - if before they weren’t allowed to enter the threshold without 25 kilobucks, now - the simplest Flir i3 with a matrix of 60x60 pixels can already be found for ~ 50 thousand rubles. The thermal imager that came to me - the UlirVision Ti384 (384 x 288 matrix) is slightly more expensive, about 220 thousand. The most advanced ones - with a 640x480 matrix - are once again 3 times more expensive. And for a simple industrial applications - are already MLX90620 - 16x4 sensor for $ 65, the newly lighted Habré .

    Practical application in the civilian sector - control of heat leaks in homes and at work, control of electrical equipment (if there is poor contact, it will be visible long before the breakdown), production processes. Well, recently there was an article about a thermal imager in a data center.

    Imager itself: UlirVision Ti384



    Telephoto lens, 53mm, similar to germanium:


    The matrix itself. It looks like it is closed with a protective cover that is transparent only for IR, so it's useless to look into an optical microscope:


    Photos by request

    Kitchen

    Fresh pancakes:


    They are from the refrigerator:



    Street (most of which was shot with a “telephoto” 53mm, standard lens 14mm)


    Water bath


    Windows, batteries, etc.


    Electricity
    Shield, consumption 2.35kW:


    Shield, consumption 4.25kW:


    The socket from which is eaten 1.5kw:


    Pilots:


    Wired mess: Any




    iron
    AMD 6990 on the street:




    Dog



    Video

    Unfortunately, this thermal imager is not able to write video "in itself", only to issue it to an analog video output, so I had to blow dust off the TV tuner.

    Some videos are very long and tedious - there you can safely rewind. Sounds and music will have to include your own.

    The dog tramples on the floor
    The kettle is boiling
    Butane burner
    Half an iron dumbbell heated to 90 degrees melts ice

    Thank you for the dumbbell. Kos32
    Flashlight
    Hairdryer
    Li-Ion battery charge - balancing resistors heat up alternately


    Drama

    In general, as in the well-known picture , having both a 40W CO2 laser (emits 11 microns) and a thermal imager (sees radiation 7–14 microns) it is quite natural to try to apply them together :–)

    I turn on the laser at minimum power — I see a point and diffraction rings ... But there’s no beam it is seen. (By itself, only the reflected light, by the laser itself, into the lens is not a candle, and the matrix can be cut). Well, you need to add power ... 5W, 15W, 25W ... And then suddenly I notice that the spot at the point where the laser shines - leaves a loop on the screen of the thermal imager ... With a characteristic knock a couple of bricks fall out.

    I turn off everything, after 5 minutes I turn on the thermal imager again - the “cable” is still on the screen. Here bricks fell not weak. The "train" of course decreased, but it remained the same (lower in the center):

    Following the golden rule of lasers "do not look at the radiation with your left eye", I decided not to take pictures of the laser.

    Fortunately, the loop on the screen gradually passed over time, so everything worked out.
    If you have both a CO2 laser and a thermal imager - I recommend not to do it like me.

    Update: Dave on EEVBlog made a video review in time:

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