Today i’m goind to design a polarized filter for the rgb camera and light (idea taken from photogrammetry to avoid reflections)
We do that already in the forum last year and works with all scanners , all you need is simple polarized film sheet self sticking , cut it and stick it on the led and camera ( reversed angle ) and it delivers perfect picture . I also use it on my additional lights and works perfect no matter I scan a human or small figurine .
It is easy to remove without damaging or residue…
Simple is beautiful! Because it need to be as closer as possible , other way you will get ghosting .
Also my idea works perfectly on a phone cameras as well if you use it to take picture for photogrammetry.
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Really nice tips!
When you do photogrammetry with phone you apply the reverse polarised filter on the phone flash too or you use an external light source with filter?
As works better for you , you can use on the flash or external light . Depends of what you use . Works both ways .
I use this one : Polarized Film Sheets 2 PCS 7.8x11.8inches/20x30cm https://a.co/d/36kDGNM
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Hello, could you draw on the image where to apply the polarizing filter? Should it be applied only to the RGB camera or also to the Depth cameras?
Hello, this light is intended only for scanning textures, correct? Or does it also affect the scanning of the model?
Only on the LED above and below the RGB camera , maje sure you keep the proper filter angles for the LED and the RGB camera . And if you want to use it on additional lighting source the angle should be the same as you used on the LED . So if you used Vertical on RGB use horizontal on LED or vice versa.
The LED only supports the color texture scanning .
Do not place the filter over the Depth sensors .
Also remove the protective film from the filters if any , one side will be sticky , the other not .
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Why can’t it be placed on Depth sensors? Has anyone ever tried it? Would it also help with reflections?
The Depth sensors need to capture infrared light and not visible light so it don’t need polarizing filters , it uses already special filter , the polarized filter will affect the process and quality of the Depth sensors capture and the filter IOR may affect the smoothness of the surface and proper exposure . NOT recommended.
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Alright, thank you. Do you happen to know what wavelength is used for IR LEDs and projectors? 850nm?"
Let me know if you need anything else!
It is standard Class 1 infrared laser so propably around 850nm for the projector may be just right but not lower than 750 nm or higher than 1mm
IR LEDs are used only for calibration but I never bothered to ask about to be honest , but they should be in the same range .
Could you please ask what wavelengths are there? Thank you
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I’ve always been curious if cross polarization technique could be used in 3D scanning. I remember when I was on a tech scout and visited Gentle Giant studios years ago, when they 3D scanned an actor they would also photograph the actor with cross polarization to remove any scattered light which then could be used to create your albedo color texture maps. At the time, I wondered if using a similar approach to the 3d scanning method itself would help improve the accuracy with scanning semi reflective or translucent materials as light bleed and scatter would cause inaccuracies with 3d scanners that used the visible light spectrum for scanning. Anyrate, glad to hear that the idea of cross polarization is being used.
Hi @kanakaRed
That is correct , cross polarization in photography provide great results , not only for Photogrammetry but also for PBR texturing , it don’t remove all reflections , it removes only fresnel , a light that reflects at opposite direction . So for example if you have reflections from behind and sides of the object , it can only remove one of them at a time .
The scanner Depth sensors capture only infrared light and not visible light so the reflections of the visible light don’t matters , it is different in photogrammetry since it uses the photos for build the model … here only for textures
What is important in structured light scanning is a one color matte surface for the best accuracy .
Any filtering of the infrared light may add or reduce the object’s dimension , that why one color surface is recommended for best accuracy .
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