Bright streaks move when we present the part differently (Universal Robots UR5e)

GraceBell0668 · 14 May 2026, 22:34 UTC

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GR
GraceBell0668
We're planning planning camera inspection of reflective parts, with Universal Robots UR5e presenting a polished metal cover to a fixed camera in a small finished-parts production cell. Bright streaks move with small presentation changes in our example images, but people keep calling them scratches. We haven't commissioned the cell. How do I sort the references and imaging before we tune thresholds around this mess?

21 replies

SA
SarahBrooks0850
Replying to GraceBell0668

@GraceBell0668 Were those scratches confirmed on the physical samples using your agreed appearance method? Start by linking each image to a sample and its inspection result.

24 points
GR
GraceBell0668
Replying to SarahBrooks0850

Some labels came from the pictures alone. We still have the samples, but those labels aren't tied to physical inspection results. That's irritatingly circular.

21 points
SA
SarahBrooks0850
Replying to GraceBell0668

Mark those labels uncertain and have the samples inspected properly. Then compare images with presentation and lighting controlled; the moving streaks are a useful reflection clue.

22 points
SA
SaraBaker0461
Replying to SarahBrooks0850

A scratch's visibility can change with presentation too. Don't let 'moving streak' quietly become the rule for relabelling something acceptable

2 points
SA
SarahBrooks0850
Replying to SaraBaker0461

Correct. I meant a reason to investigate the imaging, not a new defect label. Physical acceptance stays with the agreed inspection method.

12 points
JA
JackBell0689
Replying to SarahBrooks0850

@SarahBrooks0850 So uncertain isn't the same as good? Where do those images go?

16 points
SA
SarahBrooks0850
Replying to JackBell0689

@JackBell0689 Retain their sample identities and undecided status. They shouldn't become confirmed acceptable or defective examples while the physical review remains unresolved.

23 points
GR
GraceBell0668
Replying to SarahBrooks0850

Our two comparison folders changed exposure and presentation together. I can't tell which change made the images look better. That comparison needs a caveat too.

22 points
DI
DineshBennett0734
Replying to GraceBell0668

On my inspection setup, a folder called 'better lighting' also contained easier samples. The folder name was doing a lot of unearned work.

20 points
GR
GraceBell0668
Replying to DineshBennett0734

Which details did you retain with each image? I can record sample identity and settings, but I'd like a practical record people will actually maintain.

17 points
DI
DineshBennett0734
Replying to GraceBell0668

For my separate setup, sample identity, exposure, lighting arrangement and presentation condition were the useful essentials. They let us understand comparisons without relying on recollection.

3 points
SA
SarahBrooks0850
Replying to DineshBennett0734

Use those details to ask your vision specialist for controlled comparisons on representative surfaces. Keep the sample set fixed when assessing an acquisition change.

10 points
JA
JackBell0689
Replying to SarahBrooks0850

@SarahBrooks0850 Would a learned model just cope with the lighting differences?

14 points
SA
SarahBrooks0850
Replying to JackBell0689

Any learned model still depends on reliable labels and representative evaluation. Changing the method doesn't resolve unconfirmed physical defects or an uncontrolled comparison of image conditions.

13 points
SA
SaraBaker0461
Replying to SarahBrooks0850

Keep physical sample identity in mind when forming evaluation sets. Different images of a sample used for tuning don't provide an independent sample-level evaluation

-2 points
GR
GraceBell0668
Replying to SaraBaker0461

I'll keep all images of one sample together when we split tuning and evaluation sets. Our file names alone wouldn't have caught that overlap.

19 points
SA
SarahBrooks0850
Replying to GraceBell0668

Report missed defects and false rejects separately on the held-out samples. One agreement percentage can hide which mistake your method is making.

21 points
GR
GraceBell0668
Replying to SarahBrooks0850

@SarahBrooks0850 Should undecided physical samples count as misses in that report? I don't want them quietly disappearing just because they're awkward.

23 points
SA
SarahBrooks0850
Replying to GraceBell0668

Report the undecided samples and their number explicitly, but don't include them as confirmed-class errors. This preserves the coverage limitation without assigning an unestablished reference label.

11 points
GR
GraceBell0668
Replying to SarahBrooks0850

@SarahBrooks0850 The reference problem is clearer, but I still can't judge inspection performance from our example images. The physical labels and image comparisons need more work.

25 points

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