VISION BUILDER problems identifying circles

[Franitin]

I need to identify some circular shapes in a black&white image (from a microscope), to fix the center of all of them, and to calculate some parameters. The command with works perfectly is "find circular edge", but it only allows me to look for one in each step. Is it possible to use "find circular edge" to locate all the circles (around 100 in each picture) and solve my problem? Is there any other option? As you can find in the attached picture, is not easy to use to deal with it. Could anybody help me? Many thanks in advance.

[Franitin]

Sorry, I forgot the picture. Many thanks again.Regards.

[niNickC]

Hello,

Firstly, can I just absolutely confirm what platform you using - VBAI? (Version?) or Vision Development with LabVIEW? (its just that this was posted on the LabVIEW board)

Next, what information do you need to extract? Is it simply just the centre? and the diameter isn't important?

Having an initial look at this, I think a better approach would be to firstly do some processing (thresholding, maybe convert the image to a binary image) and then 'detect objects' as opposed to finding edges.

Can I ask, do you have access to the Vision Development module? (i.e the vision assistant within VBAI)

Let me know what you think.

Regards,

[Franitin]

Hello,

Thank you for your reply. I have the full version of Labview, with the NI Vision Development Module and VBAI (please, feel free to tell me if this is not the best area for placing my question). The things I need to extract are the following:

- Circles (how many, position, diameter, and area)

- Other geometries found (not circles= impurities), and area.

This information should be OK for my application. I tried to work with the picture, but without any success at the moment (the photograph, due to the geometry of the samples, could have differences in the brightness, as you can find in the attached file --> the threshold and other parameters works only in some areas of the pictures). The characteristic which is clear is that the circles are circles, and least visually are perfecty clear. Could you give me some ideas? Many thanks. Regards.

[niNickC]

Hello,

Sorry it has been so long to get back to you!

There is a 'Machine Vision' board which may be more appropriate next time but don't worry for now.

I can see you point regarding brightness and contrast. However, the Find Circular edges relies of a specified area of interest and it is quite difficult to iterate this across the whole image. I was thinking we could do some destructive thresholding to find the centre of the circles and then use that point to specify our region of interest.

I was having some success using the 'Circle Detection' function from the Vision Assistant, have you had any joy with this?