Displaying Engineering Units in IMAQ display

[BruceMoyer]

In machine vision applications, it is useful to report real world "engineering" units to convey the real size of certain features of the image in an IMAQ display.  Is there a way to apply a pixel to engineering conversion and have the IMAQ display report the engineering units instead of pixels?

Thanks,

Bruce Moyer

[Wes_P]

Hi Bruce,

It sounds like what you are looking for is Image Calibration.  There is definitely a way to do what you are trying to do.  First of all, there is a calibration grid located at the following directory on your computer:

C:\Program Files\National Instruments|Vision\Documentation\calibrationgrid.pdf.

If you go into Vision Assistant, there is a step called "Image Calibration."  This is what you want to do.  If you mount your camera where it will be, then take a picture of the calibration grid, you can run the calibration step.  There are some articles that describe how to do this:

NI Vision Concepts Manual: Chapter 3

Developer Zone Tutorial: System Setup

[BruceMoyer]

Wes,

Thanks for your help.  I pretty much knew that the feature to display engineering units or some other scale besides pixels in the IMAQ display was not possible, I just wanted to give it one final shot to see what people came up with.  The reason doing this is important to me is that I'm trying to use the IMAQ display in order to get very fast display rates instead of having to revert to using the intensity graph (which is slower at updating).  The intensity graph has the ability to convert the axises representation from pixels to some other scale using the graph property "Scaling Factors" in the "Scales" property tab allowing the axises to show real world values.  My application is used for both linescan and area scan cameras, and although creating an undistorted image is useful, this method still does not display the real world units in the resulting image.

Any other suggestions?  Does anyone know if NI has this feature in the development queue for future versions of IMAQ?

Thanks,

Bruce

[Wes_P]

Hi Bruce,

Where exactly on the display are you referring to?  Do you mean when you draw a ROI on the image display, you want the dimensions in real world units as opposed to pixels?  This is still doable with LabVIEW.  It is possible that I have a wrong assumption of what you might be trying to do.  Could you please specify exactly what your desired outcome is?

[BruceMoyer]

Hi Wes,

I was thinking more along the lines of being able to view the cursor location in real world coordinates (shown in the Image Information box of the IMAQ display) based on a conversion value (multiplier and offset).

Additionally, being able to show the scale of the image using rulers similar to the way Word and other programs have rulers would be a benefit to machine vision and scientific applications.  The rulers show the scale based on how zoomed in you are and appear around the edge of the viewable image.  The rulers would also be set based on the conversion value.

Bruce

[BruceMoyer]

Attached is a screenshot from GIMP (a drawing program) that illustrates this.  The rulers on the left and top display distance and the status bar displays the current cursor location in pixels, inches, etc.

Bruce

[Wes_P]

Hi Bruce,

I am not aware of a direct way of doing this for the cursor.  When you calibrate the image, and ROIs that you draw on the screen are reported in real world units.  If you simply want cursor position, you could try creating an overlay of a ruler.  You could do this programmatically using the calibration data.