vision-circle find and measurement from origin

[Lenox]

I am new to lab view and vision as well. For the first part of my project i want to find a circle and display its center coordinates relitive to a center point on the image file.

Is there a simple routine that i can follow to extract this information. Its a grayscale image and the circle is sorrounded by all black. Once i load a image into vision, first of all it says it is color and it is definatly a monochrome image, second the find circular edge tool is disabled... do i have to create a ROI first and how do i do it? im pretty sure i set up my grid properly so is there a way to measure from the center of the circle to the center of the picture...in the end im looking to move the center of the circle using a xy stepper motor system to the center of the picture for a drilling application...any help would be awesome...i think this concept is probably extremely easy with lab view and vision but this is my first day dealing with the application.....i also work well with visual basic.

              -greg

[Lenox]

ok i got the 8 bit grayscale image to work with the circle tool. is there any way to reconize a circle or the center of a white blob(maybe seperating the regions and using a histogram?) on an image file because the white blob could be in any location of the screen..im not sure if the circle detection is my best option

we are trying to find the center of a circle and move it to the center of the camera

[RManion]

Hi Lenox,

What programming environment are you using?  Are you programming an application in an environment like Labview, VB or C?  Or are you working in one of our other tools, like Vision Assistant or Vision builder for automated inspection?

I believe you are coding in Labview with Vision.  If this is the case and you are using a recent version of IMAQ Vision, you should also have access to Vision Assistant.  Vision Assistant can be helpful to prototype an application similar to this.  You can use a tool called find circular edges.  This tool does precisely what you are looking for and finds the 'best' circle within a region of interest. 

This functionality is also available in LabVIEW in the form of the IMAQ Find Circular Edges VI.  This VI can be found on the Vision - Machine Vision - Find Edges sub palette.

If the object is not a circle, there are several measurement functions that may be useful.  If you threshold your image, it will be made up of many 'particles' that represent different areas of intensity.  You can manipulate the threshold level such that the white blob will be one of those particles.  Afterwards, try the IMAQ Particle Analysis VI, in which you can request certain measurements like a blob's centroid or center of mass.

Good luck on your application!

Robert

[Lenox]

i figured all that out thanks man..now i just gotta find out how to export the center of the circle (both x n y data) to excell cells......i used vision builder with a threshold filter and circle find.....i tried to make real time coordinates using the grid function but the only data i see coming out is in pixels instead of inches which i told it 2 do...any resourse i can look at to export x and y to 2 different cells and chance the data relative to the center of the image? thanks

[RManion]

Hi again Lenox,

In order to get the measurements in inches rather than pixels, make sure you have included a simple calibration at some point prior to the measurement.

As far as exporting to excel, Labview provides some great functions like Write to Spreadsheet File.vi.  These File I/O functions should be all you need.

Good luck!

Robert