Thursday, December 8, 2011

Testing parameter changes

Sometimes it’s necessary to a setting or two on your vision system. Maybe a threshold needs raising to cope with a change in the incoming material, or perhaps a new mold produces a slightly different dimension. Whatever the reason, there you are on the line, tweaking away, but how do you know the long term effect of the change you’re making?

Exeter Engineering, maker of potato grading equipment (and other things too,) has an interesting idea. Their Accu Vision Sorter has a “Last 500” function. This lets an engineer evaluate the effect that a parameter change would have had on the last 500 items inspected.

It’s an interesting idea, though I assume it also means storing the last 500 images, which may not be a trivial undertaking. It may however be a great way to increase both flexibility and robustness.

For details you’ll need to watch their video of the sorter. The inspection part starts at about 6 minutes in. You’ll find there are some other interesting points too, like a color selection tool to “show” the system what needs to be detected. There’s also mention of polarized filters on the color cameras. This last point intrigues me; I’m not sure what polarization would achieve in this application.

So, interesting ideas from looking at potatoes. Whatever next?


Anonymous said...

This seems to be a good idea for tracking how changes can affect a vision system. You may also want to investigate the new TestRun feature from Cognex; something similar but maybe a bit more comprehensive.

As to using polarization on color applications count me as a proponent. One of the advantages is helping to stabilize the effects of ambient light on color applications, which is essential. It also helps to even the effects of light incident on the part. It reduces the likelihood of specular reflection and makes the part appear more two dimensional (by reducing shading). This produces a more even color over the region of interest, which makes color detection more consistent. This is especially useful on items that have significant contours (such as potatoes or fruit), but can help any color applictation.

Simone said...

I can say that Image recording is one of the most important phase of my job, at least in the first stage, maybe one year in case of extensive quality checks (not dimensional checks).
Sometimes, I record more than 20,000 (twenty thousands) images of the production in order to evaluate and propose possibly parameters change, but also algorithm improvements or enhanchements requested by the user: I use to develop my own software using thirdy part libraries, and this is fundamental "way to go" most of the time I think.
In my opinion, embedded systems (except in the rare cases they are really needed... But when!?) are always "late", always too slow, too limited for normal to complex applications, and too expensive for application they can solve... This is my personal opinion of course, maybe because I work in Italy, and always it seems here everything is different...!! Greetengs and compliments for your blog, Simone (