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Vision Systems Questions

Question Asked:

Hello - I need to image a relatively large area (1mx1m) with about 0.5mm resolution. I think this means that the camera/lens system should be no less than about 4 megapixel, but of course higher resolution is preferred. I also need to stand the camera off the part by about 2m. The application is indoors where the lighting can be controlled reasonably well. It can be considered a static application - speed is not a concern. This is essentially a metrology problem where I am trying to measure a roughly 5mm wide x 1m long feature on the part. Are there industrial camera solutions with this type of resolution?

5 Answers

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Andrew Long - CEO
Cyth Systems, Inc.
andy [dot] long [at] cyth.com

Glenn, a couple of questions for you. Are you automating the process of measuring the feature, or is this purely a visual aid to a human? Typically we would look at a resolution of 10 pixels for the smallest item you are trying to see. So using a 0.5mm maps to 1 pixel on the sensor this would give you a resolution in the one dimension of 1000mm / 0.5 mm = 2000 pixels. This will give you approximately a 2000 x 2000 pixels which is nearly equivalent to a 5 MPixel camera which is probably the most common size purchased at the moment. There are a number of camera manufacturers that produce cameras in this space. Remember the other key to a good image is make sure the lens is matched to the sensor, and the lighting that you use to highlight this part is consistent. These are especially true if you are automating the process. For more information about choosing the right components take a look at the AIA Vision Online youtube channel, which is an educational resource for component selection.

Perry West - President
Automated Vision Systems, Inc.
perry [at] autovis [dot] com
(408) 267-1746

Glenn -- You give half the information needed to advise you about the image resolution you need. You mentioned that the feature you want to measure is 5mm wide. You did not describe the measurement accuracy you want to achieve. Both the size of the feature and the measurement accuracy determine the image resolution needed. Would a 4 Mpixel camera work? Assume 2,000 pixels in one direction (rows or columns) across a IM area. That gives a spatial resolution of 0.5 mm/pixel. This is probably enough to image the 5mm wide feature. (I say enough, because I don't have any information on contrast.) It also suggests you might achieve a measurement resolution as good as 0.05mm (again, several maybe's such as contrast and the conformance of your shape to the model used for sub-pixel resolution. Accuracy could range from 0.25mm to 0.5mm depending on more details.) So, yes, there are cameras available. If you share more information, I might be able to help more.

Yury Yakubovich
NSIX Vision Inc.
yury [at] nsixvision [dot] com
(416) 662-3975

There is a variety of industrial cameras that can fit this application. The resolution of 4-5MPx can achieved with $400-$650 camera if you don't have high frame rate requirements. Imaging Source, XIMEA cameras as well as Sentech and other vendors have cameras to serve your application. It should be possible to select a lens with low distortion to accommodate the required accuracy within the Field of View. This considering reasonably controlled lighting. With more advanced accuracy requirements you may need to correct for distortion but in your case it will likely not be necessary.

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

Yes there are industrial camera solutions that will work for you. Many manufacturers do 5MP Industrial Cameras and a few have higher resolution available. You'll want a good lens. Edmund is a good place to start. The rule of thumb you want to be 5x - 10x your resolution. In this case you would get 1M/2448 pixels = 0.4mm/pixel (Target 0.05mm). You might consider 2 lower resolution cameras with a known calibrated distance between them? Unless you need to measure 0m-1m you can save money and get better resolution. The other important thing would be your budget. I'd suggest Cognex because they are relatively easy to program and have the 5MP camera, but you are looking at about $12K of hardware plus. There are lower cost alternatives, but they are harder to program. I'd look at Cognex VisionPro, Data Logic, or Halcon if you want to go that route, particularly multi-camera. No matter what leave some money for good lights. Never Skimp on Lights. Good Luck!!!

Brian Durand - President
I4 Solutions, LLC
bdurand [at] i4solutions [dot] us
(612) 888-6000

Hi Glenn, This reply might be coming a bit late, but nonetheless... Yes, industrial cameras having 2 - 5 MP are pretty typical these days. I included a link to one such camera below. Given this camera's CMV4000 image sensor, a lens having a 25 mm focal length would image 1 x 1 meter from a distance of about 2.2 meters. Depending on the optical characteristics of your object, the 0.5 mm/pixel resolution may, or may not, suffice. https://machinevisionstore.com/catalog/details/722

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