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--- thermalsensors [2020/05/03 22:12]
wf68spef created
+++ thermalsensors [2020/11/19 02:32]
wf68spef
@@ Line 1: / Line 1: @@
 ====== Thermal sensors ======
-===== Talk with acalbi sales eng =====
+===== Talk with acalbi sales engineer =====
 Seine Meinung zu unserer Anwendung
@@ Line 63: / Line 64: @@
   - 160x120 spacial res
   - 50 mKelvin temperature res
-  - 55° opening angle
+  - 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 ====
-{{ ::300m.png?600 |}}
+**Flight@300m**
-Boat is visible with ~**6x2 Pixel**
+{{::lepton_300.png?600|}}
-{{ ::550m.png?600 |}}
-Boat is visible with ~**3x1 Pixel**
+**Flight@500m**
+{{::lepton_500.png?600|}}
 ==== Buying ====
@@ Line 82: / Line 85: @@
 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
+  * 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 ====
@@ Line 100: / Line 112: @@
   * < 9 Hz Frame Rate
   * 1,000 ft. Detection Distance (~300m)
-  * waterproof
+  * 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 ====
@@ Line 106: / Line 131: @@
   * 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
+. "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 ===
+. nothing
+{{::rgb17.png?600|}}
+.
+{{::rgb14.png?600|}}
+.
+{{::rgb13.png?600|}}
+.
+{{::rgb16.png?600|}}
+.
+{{::rgb15.png?600|}}
+=== On a static heat source ===
+without
+{{::rgb26.png?600|}}
+left to right
+. "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
+====== Low Light cameras ======
+Camera
+https://shop.runcam.com/runcam-night-eagle-2-pro/
+https://hackaday.com/2020/11/12/highly-sensitive-camera-makes-a-great-night-vision-scope/
+http://www.watec-shop.com/en/products/monochrome-cameras.html
+Flight example
+https://www.youtube.com/watch?v=5Rqgn0WI1uo 85€
+Grabber card
+https://www.linuxtv.org/wiki/index.php/Stk1160_based_USB_2.0_video_and_audio_capture_devices