[[thermalsensors]]

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thermalsensors [2020/05/05 00:46]
wf68spef 		thermalsensors [2021/02/02 16:10] (current)
wf68spef
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 ====== Thermal sensors ====== ====== Thermal sensors ======
 +
 +===== Comparison of cameras =====
 +
 +https://​github.com/​OpenHD/​Open.HD/​wiki/​Thermal-Cameras
  
 ===== Talk with acalbi sales engineer ===== ===== Talk with acalbi sales engineer =====
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 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. 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 ==== ==== Code ====
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  * https://​www.thingiverse.com/​thing:​2581533  * 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 ===== ===== Seek compact =====
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   * < 9 Hz Frame Rate   * < 9 Hz Frame Rate
   * 1,000 ft. Detection Distance (~300m)   * 1,000 ft. Detection Distance (~300m)
-  * waterproof+  * not waterproof!
   * ~250€   * ~250€
 +  * lensmaterial Chalcogenide
  
 ==== Usage ==== ==== Usage ====
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 ''​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.)''​ ''​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 From FLIR Lepton Datasheet
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   * Cheap PIR thermal transparent windows: https://​www.kube.ch/​produkte/​pir-optics/​pir-fenster/​   * Cheap PIR thermal transparent windows: https://​www.kube.ch/​produkte/​pir-optics/​pir-fenster/​
   ​   ​
-Bought for testing: 
-  * Germanium: https://​de.aliexpress.com/​item/​32958470241.html 
- 
 ==== Test thermal transparancy of materials ==== ==== 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** **Test different materials for thermal transparancy with Lepton 3.0 @ Pi4**
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 {{::​rgb18.png?​600|}} {{::​rgb18.png?​600|}}
 +
 +
 +
  
 === Result === === 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. 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
 +
 +
 +
  • thermalsensors.1588632415.txt.gz
  • Last modified: 2020/05/05 00:46
  • by wf68spef