Sub-pixel resolution in VBAI

[Greg Shearer]

Hi all,

Just hoping someone can clarify for me to what extent sub-pixel resolution is enabled within Vision Builder for Automated Inspection? My experience to-date indicates that it is generally enabled, but I haven't found any clear documentation. The 'NI Vision Concepts Manual' mentions enabling sub-pixel resolution when required, but I assume this refers to LabVIEW, as VBAI doesn't appear to have this facility.

Can anyone clarify the application of sub-pixel resolution within VBAI? I'm particularly interested in its application within pattern matching. I have a functioning 2 camera system using VBAI pattern matching for extensometry (accurate measurement of wire elongation) which works beautifully, but am seeing more 'noise' than expected on another system under development. I'm still looking at various elements of the system which could be contributing, but thought I'd ask about sub-pixel resolution in case it could be relevant.

Are there any automatic 'switches' within VBAI that determine whether sub-pixel resolution should be used? Any information would be appreciated.

Regards,

Greg Shearer

[risheeb]

Hi Greg,

Sub-pixel accuracy is enabled by default in VBAI and cannot be disabled.  I set up a Match Pattern step in VBAI 3.0 to test this.  VBAI returned the location of the pattern I tested with a precision of hundredths of a pixel, confirming that this is the case.

I hope this helps.


Rishee B.
Applications Engineer
National Instruments

[Greg Shearer]

Rishee,

Thanks for checking on this. My previous experience had suggested sub-pixel resolution by default, but the system I'm currently working on has surprised me with an unexpected level of noise. Having said that, several characteristics of the new system are less ideal. Most recently, I think I've overcome the 'noise' issue through implementing a simple filter on the measurements I'm taking. For the next week or so I'm on leave, but was under some pressure to prove the system beforehand. At the moment,all looks ok, but I will be doing further commissioning tests from 21/1.

Thanks again for your help. If I have any further problems, I'll look for other causes.

Greg

[Brad]

Different algorithms have different sub pixel options and if you want to see what VBAI is using, you can generate LabVIEW code and check out the generated code to see exactly what VBAI uses.

Hope this helps,

Brad