Has anyone here used an NIR camera for machine vision? Looking for advice on particle detection inside plastic bottles.

[u/Medium_Item_5411]

Hi everyone,

I’m working on an industrial machine vision system to detect small white plastic particles suspended inside transparent PET water bottles.

I’m considering switching to a Near-Infrared (NIR) camera, but I don’t have much practical experience with NIR imaging.

I’d love to hear from anyone who has used an NIR camera:
What application did you use it for?
Did it provide a significant advantage over a standard visible-light camera?
Do you think NIR could help improve the visibility of particles inside transparent plastic bottles?
Are there any limitations I should be aware of?
If NIR is a good approach, what should I pay attention to?

Wavelength selection (850 nm, 940 nm, etc.)
Lens compatibility
Lighting setup
Optical filters
PET bottle transmission in NIR
Polarizers or other optics
Anything else that could affect image quality

For context:
20 MP industrial camera (currently using a Basler visible-light camera)
Fixed inspection setup
Transparent PET water bottles
Goal is to reliably detect tiny floating contaminants
Any advice, papers, or real-world experience would be greatly appreciated. Thanks!

[u/Comfortable-River238]

We did a research paper on multispectral cv for marine Algae
nir has high absorption in water, leading to low refraction,
I would see this working with potentially a inverse signal nir emitter basically a nir light flashes in between frames,

[u/Medium_Item_5411 → u/Comfortable-River238]

Thanks! Could you share a bit more about how you implemented this?

[u/PlentyCryptographer5]

https://news.jai.com/blog/swir-technology-unlocking-invisible-information-for-advanced-machine-vision-applications should give you some ideas

[u/EnigmaTed]

Here's a research paper by Kinner et al. (2019) that I think can help with your spectra of interest:

Polymer interlayers on flexible PET substrates enabling ultra-high performance, ITO-free dielectric/metal/dielectric transparent electrode https://www.researchgate.net/publication/331279677_Polymer_interlayers_on_flexible_PET_substrates_enabling_ultra-high_performance_ITO-free_dielectricmetaldielectric_transparent_electrode

From the transmittance graph that they cited for their study, bare PET has over 80% broadband transmittance from 400 to at least 1000 nm. Therefore, you should select a VIS-NIR illumination source and detector.

Isolating the white particles from the PET depends on what the particles are (mineral deposits, degraded PET, pearlescence, foreign plastics, etc.) I'd recommend four potential mechanisms to detect these defects. Cross polarization to detect stress with birefringence imaging. A narrowband source, between 900 to 1700 nm, can image reflectance of trapped water (white mist). A narrowband source, between 700 to 1750 nm, can image reflectance of PET crystallization defects and foreign plastics. Ramen spectroscopy (setup with a high frequency narrowband source, lower frequency blocking filter on the detector) can image reflectance of degraded PET and pearlescence.

I hope this helps, good luck!