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Vision Software Questions

Question Asked:

Hi, i have an application where I need to carry out colour inspection. How to handle such task? What kind of cameras and machine vision algorithms do you recommend? So far I have found out that comparing RGB values is not a good way.

4 Answers

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  • = Answered Questions

Volker Zipprich-Rasch
Baumer Optronic GmbH
vzipprichrasch [at] baumer [dot] com
49 3528 4386 0

Hello, inspecting color is a wide field and the solution heavily depends on your application requirements. If you have a quality inspection task it can be easy as you can see in our video tutorial: "Easy color inspection with a VeriSens vision sensor" https://www.youtube.com/watch?v=iPZXaNcZnZM&list=PL_OqmiTiIbljP75nM4yXPaLrDrJ_lo7AV&index=12 May be it is a starting point.

Robert McConnell - President
WAY-2C Color Machine Vision
rkm [at] way2c [dot] com
(781) 641-0605

Hi Matthew: The first thing to decide is whether the color inspection is concerned with: a) measuring an item's color(s); b) identifying items based on their color(s) or c) identifying items whose colors are anmalous. If the interest is in measuring colors, a spectrophotometer is usually the best bet. These are specially designed for the purpose usually with superior lighting and stability. If the interest is in color-based identification or anomaly detection then color cameras may be used. Unfortunately most published analysis methods have significand difficulties, often because the underlying mathematical assumptions were not well-enough understood by the author. We have extensive experience in color-based identification and anomaly detection built around our WAY-2C software package. You can check out many examples of typical applications at our website. If you'd like to send me a description of your application with some images I'd be happy to take a loo

Kris Balch - President
Vision Systems Technology, LLC
kris [dot] balch [at] visionsystech.com
(858) 449-1562

Please talk to Chromasense

John Salls - Owner/Engineer
Vision ICS, Inc.
john [at] vision-ics [dot] com
(651) 503-0496

Color inspection is a difficult task as it is so lighting dependent. Start with a GREAT really stable White light and Color Balance Target. If you want to verify color quality at the beginning of a run (to make sure your color is perfect), use a spectrophotometer. If you are trying to inspect during production, you would be looking at a color vision system. There is a pretty broad variation in the tools available from one manufacturer to the next. You can usually make RGB systems work, but it can be really confusing. I would look for one that supports HSI (Hue Saturation Intensity) or a variation of this. It makes more sense to human beings that way. For tools Color Histogram or Color meters will generally tell you what color you are looking at in a specific area. Color filters will also help with the tasks looking for variations. Color Blob is great for locating colors (for example sorting Skittles by color). I mostly use Cognex InSight for this. Good Luck!

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