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Detecting Wrinkled Parts of the paper

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What is the best way to create the program using the NI Vision Builder to detect the wrinkle part of the paper in the middle due to being folded to show that this card fail the inspection status. Still new to this, glad if I can get a baby explanation 🙂

 

 

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I don't have Vision Builder, and it may have a limited set of tools, so I can't help a lot there.

 

However, the image low resolution, which often limits the effectiveness of an inspection process.  If your camera is limited to the resolution, best practices is to fill the entire frame with the image to maximize the number of useful pixels.

 

Color cameras uses a device called a Bayer Filter to interpolate color, the process reduces the camera resolution by as much as 2/3.  Unless color is essential in the inspection, you get more resolution for the $$ with a monochrome camera.

 

If you are stuck with the camera you have, then use the object to take up as much of the sensor as possible.

 

Assuming the object is a rectangle, then it is not flat. Flat is good, as you can use low angle lighting to enhance wrinkles, and then filter using an edge detector.

 

The edge detector will pick up the circular marks as well, although you can choose to ignore them based on geometry. 

 

In some cases, when looking for diffusion on blotting paper, color can be important, because of the chemical reaction between the reagent, and the chemicals imbedded in the paper, but unless the reaction generates different colors that need differentiated, a monochrome camera is still a better choice.

 

This might be a good candidate for the Texture Defects Feature, assuming it's available in vision builder.  It is available in Vision Assistant, and it is ridiculously complicated to set up, but is ideal for finding texture defects in a regular surface.

 

Hopefully better advice / help is forthcoming from this forum.   Improving your resolution will be a good start.

 

And now for a Shameless Plug.. https://www.automate.org/a3-content/cvp-basic-certification offers training and certification.  It would be a great place to get the basics down.  The plug is shameless, because I have been teaching one of the advanced modules for around a decade. These courses are available on line, I think.

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Your card has two (at least) folds, would either be a cause for rejection?

 

altenbach_0-1650314705686.png

 

 

One possibility is the Hough Transform. Obviously, your wrinkles also have local high frequency oscillations, so a FFT based approach might work too. It might also help to have the light source at a very shallow angle, perpendicular to the typical wrinkle direction.

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"I don't have Vision Builder, and it may have a limited set of tools"

 

So what software do you think the best for inspection? 

 

" Unless color is essential in the inspection, you get more resolution for the $$ with a monochrome camera"

 

Color is needed for my inspection but I can change the image to grayscale after the color inspection. Will it be good and does changing my image to grayscale to will effect the resolution?

 

" good candidate for the Texture Defects Feature, assuming it's available in vision builder"

 

Checked and it's available. Will try using your idea

 

Thank you for your help

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"Your card has two (at least) folds, would either be a cause for rejection?"

 

Any wrinkle will lead to rejection and it would not be fix at that place only. It could be anywhere of the card.

 

"One possibility is the Hough Transform. Obviously, your wrinkles also have local high frequency oscillations, so a FFT based approach might work too"

 

I learnt something new.

 

"It might also help to have the light source at a very shallow angle, perpendicular to the typical wrinkle direction."

 

What if I have a problem that my cards will not be in fix position for every inspection to be made

 

Thank you for your help

 

 

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"I don't have Vision Builder, and it may have a limited set of tools"

 

So what software do you think the best for inspection?  It looks like you have Texture defects tools available, I would start there.  Several years ago, vision builder was frustrating limited, and I still do all my work in the standard Labview vision program, although I frequently use Vision Assistant to test ideas.

 

" Unless color is essential in the inspection, you get more resolution for the $$ with a monochrome camera"

 

Color is needed for my inspection but I can change the image to grayscale after the color inspection. Will it be good and does changing my image to grayscale to will effect the resolution?

 

Converting to Grayscale will not affect the resolution, but it may make processing easier.

 

" good candidate for the Texture Defects Feature, assuming it's available in vision builder"

 

Checked and it's available. Will try using your idea.

 

Thank you for your help

 

Good Luck!

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Solution
Accepted by Meliosha

if your card is not in a fixed position, that limits the ability to maximize the resolution of the image and may require an extra step to orient the image in the inspection coordinate system (may not).. Depends of if you want to know where the wrinkles are.

 

Flat card will be easier to inspect.  Low angle lighting will highlight surface texture.

 

you can see an example here: LDR2-LA Series|CCS INC. (ccs-grp.com)

 

Your lighting supplier will have something similar, or you can build something.

 

Cheers

 

Robert

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