Machine vision NIR polycarbonate

Question

Machine vision NIR polycarbonate

jimbojones1000 (Mechanical)

(OP)

18 Jun 14 05:59

I need to perform some machine vision tasks on small polycarbonate parts in an assembly machine, my problem is that the parts are clear and the slideway is stainless steel, I can easily find features and orient the parts using a GigE camera when they are on a black or any coloured background which is is not reflective, or less reflective, but when they are on the stainless background i get too many reflections to pick up the features accurately. The system is sealed from external light but it still is hard to discount all the reflections as the light is refracted through the part, and as the system is to find the orientation of the part these refractions are not uniform so cant be easily discounted. I was wondering if i could use a NIR camera and an IR source to avoid this problem? I was wondering if someone could tell me what sort of image you get from an NIR camera with polycarbonate and stainless, i dont want to drop £700 on a camera and lens just to find it was a stupid idea. Thanks for any help.

pmrobert (Automotive) · Answer 1 · 2014-06-18 09:28:42

Googling IR + transmission + polycarbonate returns some data that may help you.

IRstuff (Aerospace) · Answer 2 · 2014-06-18 09:56:37

polycarbonates are usually also transparent in the NIR.

You can, however, check the behavior by using any IP camera with an "IR cut filter" option, which is for night operation with the NIR LED illumination. http://foscam.us/foscam-fi8910w-white-wireless-ip-... is one such camera

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tygerdawg (Mechanical) · Answer 3 · 2014-06-18 14:48:16

Perhaps there is a combination of different light colors and/or filters that could solve this. Contact a vision systems vendor / lighting systems vendor. The good ones will have an applications lab that will determine the best lighting / lensing / filtering needed for the camera to capture the features required.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering
www.bluetechnik.com

MikeHalloran (Mechanical) · Answer 4 · 2014-06-18 15:00:35

Perhaps you could get the stainless parts plated with black chrome.

(
It's used to decorate car wheels now, but there is a military spec for when it was used to reduce the observability of missile launcher rails.
)

Mike Halloran
Pembroke Pines, FL, USA

Timelord (Mechanical) · Answer 5 · 2014-06-18 15:52:20

Mike,

My thoughts also. My experience with black chrome is in the solar energy field where it is used for its high emissivity. Black Chrome is MIL-C-14538C

Timelord

jimbojones1000 (Mechanical) · Answer 6 · 2014-06-19 08:25:10

Thanks for the replies, I did try butchering an old webcam to see what id get but to be honest the results just confused me more! I'm using labview to build my vision application as the whole machine is compactRio based, using the FPGA for a lot of the time critical bits. I had considered a coating on the stainless but if i could i would like to avoid it, the parts are for a medical device and the machine will operate in a clean room so any risk of contamination of the parts is a big no no. I think my two options are the surface finish of the slide, its currently polished(by me) and although looks smooth still has some machining marks under high magnification which generate the main reflection problems i guess, so perhaps a duller finish but without any machining marks may help, the second option being to have a glass section in the slide way and illuminate it from below. Shame i was hoping IR would be an easy fix. Thanks for your help.

mcgyvr (Mechanical) · Answer 7 · 2014-06-19 11:09:33

How thick is this material to be inspected?
Could you light it from the side? (like those acrylic signs with LED lights at the bottom shining up through the acrylic)

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Machine vision NIR polycarbonate