Night Vision enhanced by thermal capability

Projects General Guidance
1

Hi Guys I would like to ask you for your opinion and guidance.
I have Gen1 Night vision. This works nicely in low light, and when there is no light I can use 880nm or 940nm IR light to enhance picture quality. When I use this Night vision for airsoft I often see in forest something that looks like human but lots of time it is false alert and there is just strangely shaped tree or something.
So I am wondering, is there any posibility to use cheap thermal sensor like MLX90614 for detectiong temperature changes in front of Night Vision?

I know that using this sensor for creating Thermal Vision is not very good idea because it is very slow and I would need to use servos and mirrors etc.to get full image but my thoughts are diferent.
What I want is just know when there is hot object (car, person, animal ) in front of night vision in distance between lets say 10 to 70m

My idea is to compare ambient temperature and temperature reading from IR sensor. If there is human let say 20m away from sensor and let say that human body will cover 10% of sensor FOV and rest will be just forest I should get higher reading than without that person in FOV. Am I right? Than if I compare reading from IR sensor and ambient temperature around Night Vision I can tell if there is something hotter than surrounding in front of me? If this would be true, I would then use this and represent this compared value by RGB led color in NV ocular to make it user friendly.

Second thing is that I use 880nm and 940nm light as night vision iluminator so I would need to make it go OFF using simple mosfet for example. Otherwise I would be getiing corrupted readings. Am I right ?

So please tell me what You think. Is this plan feasible with IR temp. sensor? Any advices?
Thank You in advance and sorry for my English, as You can see I am not native speaker :smiley: .

2

Go with 4th gen NV, or, try changing your illuminator to 1.3um instead of 880nm.
If you are using 1st gen, you are probably using surplus Russian equipment. They respond much better to 1.3um, with less ghosting and after glare (pretty much the same thing as ghosting, but more intense). Ghosting is a artifact of 1st gen. you can never get rid of it without decreasing lumen intensity.

3

I know that best is to use Gen4 NVG. But ... I am not stealing and I dont have money on anything else than Gen1 so no discussion there. In fact my 880 or 940nm illumination was too just side question like:(Are IR temp sensors influenced by theese wavelengths?).

Whaat I want to know is:
Is it possible to use IR non-contact temp sensor to tell if there is person / animal / running car in 10-70+m distance?

I wonder if 16x4 px sensor like MLX90621 would be able to work on this distances and tell that heat source is for example somewhere on pixel x12y2. Then I would use this one instead and just compare pixels together and not ambient temp.

What I want from finished working system is just to give me back Yes (there is heat source in front of me) or No(there is no heat source), or maybe some percentage of probability that there is something worm in front of sensor. Nothing More, nothing less

4

IMHO, MLX90614 is just a crap, having 90 degree Field of Vision, it can't determine correctly temperature of the human from a distance 0.5 m. Part number mlx90614esf-dci looks better, small lens is narrowing field down to 5 degree, may detect from 10-20 metres, but need to be verified. Price is jumping above 25$ compare to default wide FOV part about 5$
I can see, that part Mlx90621esf-bad has even lower, 2.5 degree/per pixel spacial resolution, same time price tag goes insane.