====== Thermal sensors ====== ===== Comparison of cameras ===== https://github.com/OpenHD/Open.HD/wiki/Thermal-Cameras ===== Talk with acalbi sales engineer ===== Seine Meinung zu unserer Anwendung Sensorspecs <10° Öffnungswinkel 320x240 Auflösung Quadratsensor vs Zeilensensor Quadratsensor besser weil sehr gutes preisleistungsverältniss / hohe stückzahlen zeilensensor nur bei satelliten kosten höher nicht empfehlenswert laut ihm Flir Sensoren lepton 3.0 datenblat interface sensor SDI Interface selbst entwickeln Kann keine Temperatur messen, nur Unterschiede anzeigen 3.5 kann kan radiometrische information == absolute temperatur ausgeben für uns nicht relevant Wird in Coronatimes gerade sehr gebraucht für Messgeräte... boson 320 640 besser für uns geeignet seiner meinung nach aber 10X so teuer Temperaturunterschied ist entscheident Von oben kuckend ist temepratur bei menschen nicht so hoch Schräg wäre besser weil da mehr warme fläche vom menschen Lepton breakout board V1.0 alte version , kann vlltpaar features nicht, aber hat keine beschwerden gehört, 30$ V2.0 60$ Erkennung mittels sensoren , 3 unterschiedliche stufen Johnson criteria https://www.ecamsecure.com/blog/thermal-cameras/johnsons-criteria-for-thermal-camera-performance/ detektion 2 linienpaare aus = 4 pixel erkennung 6 linienpaare identifikation / klassifikation 12 linienpaare Defekte pixel 1-2% pixel tot Müssen berücksichtigt werden => kann mittels tracking über zeit / bestätigung über zeit gelöst werden ===== Termal situation @ sea ===== {{ ::thermal_situation.png?400 |}} ===== FLIR Lepton 3.0 ===== ==== Specs ==== - 160x120 spacial res - 50 mKelvin temperature res - 71/56° opening angle - not waterproof - more info in this paper: https://www.vutbr.cz/www_base/zav_prace_soubor_verejne.php?file_id=181847 - ~250€ ==== Usage ==== **Flight@300m** {{::lepton_300.png?600|}} **Flight@500m** {{::lepton_500.png?600|}} ==== Buying ==== * https://www.digikey.de/product-detail/en/flir-lepton/500-0726-01/500-0726-01-ND/6163867 * Bought at acalbfi.com * https://www.digikey.de/product-detail/en/flir-lepton/250-0577-00/1577-250-0577-00-ND/10385179 * Bought v1.4 at acalbfi.com Compared to the Lepton 3.5 it doesnt offer temperatur measurements, but we are not interested in it anyway so we can use the 3.0 version. Lepton 3.5 cannot be shipped in corona times anyway. ==== Hardware Interface ==== {{::rpi-flir-diag-fixed.png?200|}} ==== Code ==== * Python Interfacing : https://github.com/groupgets/pylepton/tree/lepton3 * Use lepton3-dev branch for lepton3.x support * Master got only lepton2.x support * Live video: https://github.com/groupgets/LeptonModule/tree/master/software/raspberrypi_video * Paper on the sensor: https://www.vutbr.cz/www_base/zav_prace_soubor_verejne.php?file_id=181847 ==== Case ==== * https://www.thingiverse.com/thing:1563825 * Better imho * https://www.thingiverse.com/thing:2581533 ===== HTI ===== * HT-201 / HT-301 * 320x240 pixel * 32° Opening angle * https://www.amazon.de/Thermal-Infrarot-W%C3%A4rmebildkamera-Mobiltelefone-Aufl%C3%B6sung/dp/B07Y4PJF2S/ref=sr_1_1?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=ht-201+thermal&qid=1607201370&sr=8-1 ===== Seek compact ===== * 206 x 156 Thermal Sensor * 36° Field of View * < 9 Hz Frame Rate * 1,000 ft. Detection Distance (~300m) * not waterproof! * ~250€ * lensmaterial Chalcogenide ==== Usage ==== **Flight@300m** {{::seek_300.png?600|}} **Flight@500m** {{::seek_500.png?600|}} **Flight@700m** {{::seek_700.png?600|}} ==== Code ==== * https://github.com/maartenvds/libseek-thermal ===== Protection Lens ===== ''Needs special material as glas blocks IR. Common materials for LWIR windows include silicon, germanium, and zinc selenide (LWIR absorption in silicon is on the order of 15%/mm, which means NEDT is adversely affected using a silicon window. Bulk absorption in germanium and zinc selenide is negligible, and performance is essentially unchanged provided both surfaces of the window are anti-reflection (AR) coated.)'' ''It should be stated that occasional water, be it fresh or salt, does not damage Germanium lenses if they are rinsed and dried afterwards. Fire fighting cameras regularly get drenched in water and the camera lens protector just needs to be gently cleaned and dried after the shout.'' from https://www.eevblog.com/forum/thermal-imaging/death-of-a-camera-by-drowning-!-flir-vue-its-vulnerabilities-and-death/msg1306467/#msg1306467 From FLIR Lepton Datasheet More Info: * Materials in general: https://www.eevblog.com/forum/thermal-imaging/buying-used-thermal-imaging-lenses-general-buying-guidance-from-fraser/ * Cheap Zinc Selenide ZnSe Lenses @ ebay: https://www.eevblog.com/forum/thermal-imaging/znse-lenses-on-ebay/ * Thermal transparnt plastics: https://miltechlabs.com/index.php?route=product/product&product_id=986 * Cheap PIR thermal transparent windows: https://www.kube.ch/produkte/pir-optics/pir-fenster/ ==== Test thermal transparancy of materials ==== ** Lepton 3.0 Germanium Lens** Bought here: https://de.aliexpress.com/item/32958470241.html * Image {{::img.jpeg?600|}} * Transmission of lens {{::germaninumglas.jpg?600|}} * Without lens {{::0_latest_without.png?600|}} Intensity of hottest point: 210 * With lens {{::0_latest_with_GLAS.png?600|}} Intensity of hottest point: 124 The lens dampens the intensity of the heat by at least ~40%, whis is roughly in line with the chart above. It also created a lens center spot effect in the center of the image. We need to see if this might cause problems. To be tested in real life conditions. **Test different materials for thermal transparancy with Lepton 3.0 @ Pi4** This time i take photos with normalized colors to min and max temperature. Actually a better test would be using absolute value images. Next time... left to right 1. "thick foil" ~ like a paper 2. "superthin foil" 3. transparent ruler ~2mm 4. magnifying glass ~2mm {{::signal-attachment-2020-05-05-000545.rotated.jpeg?400|}} === Outdoor === 0. nothing {{::rgb17.png?600|}} 1. {{::rgb14.png?600|}} 2. {{::rgb13.png?600|}} 3. {{::rgb16.png?600|}} 4. {{::rgb15.png?600|}} === On a static heat source === without {{::rgb26.png?600|}} left to right 1. "superthin foil" 2. "thick foil" ~ like a paper 3. transparent ruler 2mm thick 4. glas {{::rgb22.png?600|}} === Moonshot === {{::rgb18.png?600|}} === Result === Its visible, that thin plastics are a option. The actual thinnest one doesnt protect at all, its too thin. But maybe we can find some cheap fitting material, or we use the professional thermal plastics. ===== Calibration ===== * Images of water are more cold at center than edges * Due to vignetting * https://en.wikipedia.org/wiki/Vignetting * Flat field calibration * Build avg frame over multiple frames and save flat_field_calib * frame_corrected = frame_raw - flat_field_calib * Implementation https://github.com/OpenThermal/libseek-thermal/blob/master/src/SeekCam.cpp#L101