Problem with Ellipse Detection via IMAQ Detect Shapes VI

[PaFl]

Hello,

I have a problem with the IMAQ Detect shapes VI (in particular with detecting ellipses).
I am trying to fit an ellipse to an elliptical droplet after applying a certain threshold to the image, but the detect ellipses VI always only produces circles as the best and only result. The used images show a relatively low resolution owing to the camera - maybe that's the reason.

I tried all input parameter combination I could think of. Does anyone have an idea or solution to fix this?
I will attach my VI and an example image for clarification.

Thank you very much in advance.

PS. please ignore my weird event structure for clearing the stored images - I am pretty new to labview and couldn't think of a better way to clear memory without the program erasing them as soon as its done with ellipse detection.

[Andrey_Dmitriev · Accepted solution]

Yes, the resolution is the problem.

With 10x upsampling (using IMAQ Resample) the results much much better:

(you will need to divide results by 10 to get back to the original size, of course)

Andrey.

[PaFl]

I suspected as much, but wanted to avoid data manipulation due to Pixel interpolation if possible.

Seems like I have no other choice.

Thank you very much for your help Andrey.