Table of Contents

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

FLIR Lepton 3.0

Specs

  1. 160×120 spacial res
  2. 50 mKelvin temperature res
  3. 71/56° opening angle
  4. not waterproof
  5. more info in this paper: https://www.vutbr.cz/www_base/zav_prace_soubor_verejne.php?file_id=181847
  6. ~250€

Usage

Flight@300m

Flight@500m

Buying

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

Code

Case

* https://www.thingiverse.com/thing:1563825

* https://www.thingiverse.com/thing:2581533

HTI

Seek compact

Usage

Flight@300m

Flight@500m

Flight@700m

Code

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:

Test thermal transparancy of materials

Lepton 3.0 Germanium Lens

Bought here: https://de.aliexpress.com/item/32958470241.html

* Image

* Transmission of lens

* Without lens

Intensity of hottest point: 210

* With lens

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

Outdoor

0. nothing

1.

2.

3.

4.

On a static heat source

without

left to right

1. “superthin foil” 2. “thick foil” ~ like a paper 3. transparent ruler 2mm thick 4. glas

Moonshot

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