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How do i find the diameter of a ring in an image?

I'm new to Labview, so i dont know how to use Vision Assistant 7.1 to find the diameter of a ring in the following image. Can someone guide me through the steps?
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Before elaborating a cumbersome solution, is there any chance that you could improve your image.  The lighting is awfull ! Can you try to obtain a more uniform background and a better contrast ? Remember that 90 % of image analysis problems can be solved at shot time ! 😉

Chilly Charly    (aka CC)

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i'm currently working on a better lighting solution, is there any way to work w/ the picture at hand for the time being?
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Hey Mark07,
You will want to use the Circular Edge (Spoke) Step in order to detect the edge of the circle, and give you a center point to your circle. You will probably have to adjust the parameters of the Circular Edge Setup, such as the Gap and the Edge Strength in order to get a best fit circle. Then you can use some other edge detection Step in order to find a point on the edge of the circle. Then you can use the Caliper Step in order to calculate the distance from the center of the circle to the edge of the circle, and then multiply that value by 2 to get the diameter. Again, remember that the Vision Assistant software is not meant to be run as an executable program, so you can do even more once you get into LabVIEW or whatever software you are using and use the other Vision functions. There are multiple ways you can probably do this, but this is just one suggestion that I can think of. Also, Chilly Charlie did have a good point of getting better lighting to clean up your image, so that when you do process a lot of these images, it will be easier to find edges and such. Last, a great way to learn the different aspects of the Vision Assistant Steps is to play around with them and see what they do, or you can read the help documentation, but I think hands on is better. Anyways, let me know if you have any questions or concerns about my suggestion. Thanks, and have a great day.
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