Edge detection - calibrated image

[PetrB]

I have a problem with "IMAQ Find Straight Edges" function, using a calibrated image.

If I find edge on image without calibration, it detect edge fine. If I do calibration, function do not detect edge (same edge parameters).
What is the cause of this behavior?

see "Edge_01.vi"

I use Vision 8.6 and LabVIEW 8.5

Petr 

[Lukas_Bedajanek]

Hi Petr,

the problem is with using Indirect calibration, it is known issue and CAR - Corrective Action Request137424 was created.

The solution is to use DIrect calibration.

Best Regards

Lukas 

[PetrB]

Hi Lukas,
thanks for reply.

But "Direct calibration" find edge on wrong place. Why?

Find edge without calibration works fine.


Results: (same edge parameters)
Point 1.Y = 343.27 pixels  -> No calibration
Point 1.Y = 346.92 pixels  -> Direct calibration

see "Edge_02_Direct.vi"

Petr

[Lukas_Bedajanek]

Hello Petr,

edge detection should be the same in both cases wtih or without calibration.

I will ask my colegues in US how is it possible and keep you posted.

Best Regards

Lukas 

[Lukas_Bedajanek]

Hi Peter,
 
here is the reply.
 
This looks like expected behavior.  I think what is happening is you add calibration information to image, but you don't actually calibrate (correct) the image. When you look for straight edges after adding calibration info the straight edge is placed based on the new calibration information. It places the straight line not just based on the image being displayed but the calibration information associated with it. Try correcting the image after calibrating and you should see a better result.
 
I modified your example to add IMAQ Correct Calibrated Image
 
Best Regards
 
Lukas

[PetrB]

Hi Lukas,

it is a new information for me about need to correct the image.

In NI Vision Concept Manual is other information (see NI_Manual.png) and also in "Perspective Calibration Example.vi" (see NI_Example.png).
Is it a new undocumented feature in NI Vision?

Petr

[Lukas_Bedajanek]

Hi PetrB,

you are right this new feature is not mentioned in Example and Manual but you should use it.

I will report that it is not mentioned in Example and Manual and probably it will be corrected in next version.

Lukas

[PetrB]

Hi Lukas,

I think there's a bug, no new features...

Try to explain your colleagues in US, that this "new" behavior complicates and slows down the vison inspection, if necessary in addition to use time-intensive operation (Image Correction).

Petr

[Lukas_Bedajanek]

Hello Petr,

my colleagues in US are aware of that using IMAQ Correct Calibrated Image is slowing down vision inspection.

I have asked them to correct the example and manual but it seem like there is no need for it.

Best Regards

Lukas

Here is their answer : 

Thank you for the update. The Vision Concepts Manual is language independent (text-based, LabVIEW, etc). There is intentionally no mention of specific functions as it is meant to give more detail about the algorithms in Vision Development Module. Since manual is not targeted directly to a particular language, we cannot give a name to the function as it is differently across languages.

There different manuals for this purpose: IMAQ Vision for LabVIEW User Manual

IMAQ Vision for LabWindows/CVI User Manual

For the example, it does not seem beneficial to add the name of IMAQ Correct Calibrated Image since it is not needed in this example. As stated in the link you sent me, correction is time-intensive and therefore, can sometimes be left out of the process and the calibration information will still be valid.