DIY Laser levelling using webcam and laser level

[Sasquatch]

Did anybody test flatness of the laser beam yet? I'm impressed with results you're getting and just that one question remains unanswered.
I have garde 00 600x400 mm granite plate, one diagonal(720mm) is within 1 micron.
SJ4000 with large sensor and high resolution and can act as webcam.
just no laser...checking ebay...

[John McNamara]

Hi Sasquatch

If you study the two test series I did with two different sensors you will see that the resolved measurements taken with the second sensor were better with the higher density (The pixel lines were closer together), sensor used for the second set of tests.

No lens was used just the wire shadow.

Devmonkey mentioned that the results were better without a lens when he did tests with a laser. Using a lens with the laser generated distortion? I can also confirm this when I tried using a laser with a lens.

Maybe the standard lens supplied with a webcam or action cam is not the ideal for working with a laser. I know industrial laser cutters use lenses made from Germanium and other exotic materials.

A friend who spent his working life as a physics lab tech also mentioned that webcams will probably have a red filter behind the lens and in front of the sensor. He suggested that this should be removed if working with laser light.

These are only study notes on my part, I wish I knew more about optics. Maybe one of the MYCNCUK members here can give a more qualified view?

Regards
John

[Sasquatch]

Hi John.
My action cam lost lenses in shooting accident (air rifle ricochet).
Flare with lenses is an result of partial reflection on each layer of glass/ plastic beam is passing trough.
My action cam had a infrared filter behind the lenses.
Sensor is about 3x4 mm 1080p gives higher pixel density than 2 mm wide VGA sensor. Should be good.

Can't find any lasers with single cylinder lense. No Dewalt dw088 on ebay UK in acceptable price. Any cheap laser recommendations ?
Edit 1:

Figured out easy and cheap way of testing projected line straightness.
Method requires roughly straight surface, aluminium extrusion should do. Surface must only be flat within sensor measurement area.
line laser
pointer laser
2x camera sensors set 90 degrees to each other.
first camera is following pointer aiming along the beam
second camera is following projected line
With some excel magic we can deduct straightness of projected laser line independently of any beam errors.
Given we can get 3-4 microns resolution on both sensors accumulated measurements arrors should be below 0.01mm in worst case ->just a gut feeling, no real maths behind it so feel free to correct me. That should be more accurate than any straight edge one could buy, as 0.01mm over, say 3 meters, is waay beyond din 874/0. and sag on wire could be greater than 0.01mm too?

Edit 2:
Software feature request:
Can we have adjustable capture resolution,since higher res cameras have bigger sensors allowing wider beams and/or wider measurements range?
Or at least run in maximum supported resolution, whichever is easiest.
Also when requesting VGA stream from 1080p sensor camera firmware is scaling each frame introducing errors.

Edit 3:
Created pull request on GitHub with more resolutions possible.
Unfortunately i can't figure out how to add menus to change resolution nor how to pass resolution via command line parameters.
Just edit settigs.java and rebuild to required resolution, supported are 320x240,640x480,800x600, 1280x720 and 1920x1080.
Hope that @devmonkey don't mind and will add settings menu in free time.

[devmonkey]

Sasquatch,

I haven't got one myself but this laser looks very promising with a glass cylindrical lens.
https://banggood.app.link/PPKk7DZpR0

Will integrate your resolution changes when I get time.

Cheers, Joe

[devmonkey]

I've committed a change so that it determines the maximum native resolution of the camera and uses that, please test.

Cheers, Joe

[Sasquatch]

I've committed a change so that it determines the maximum native resolution of the camera and uses that, please test.

Cheers, Joe

You're a star Joe.
But it defaults to 640x480 on SJ4000. "proper" webcam could be working ok, although windows10 camera app detects it as 1280x720(max video output for sj4000)
Saying that, SxrosCamera by default don't support anything above 640x480, hence you have to define custom dimensions for higher resolutions.
It defaulted to maximum resolution supported by SxrosCamera without custom dimensions defined.
Cheers Les.

[devmonkey]

You're a star Joe.
But it defaults to 640x480 on SJ4000. "proper" webcam could be working ok, although windows10 camera app detects it as 1280x720(max video output for sj4000)
Saying that, SxrosCamera by default don't support anything above 640x480, hence you have to define custom dimensions for higher resolutions.
It defaulted to maximum resolution supported by SxrosCamera without custom dimensions defined.
Cheers Les.

So we can't make it automatically pick the max resolution? If we pick the wrong one presumably it crashes the driver? I don't have a higher res camera to test with.

Edit
Ok so it looks like Sarxos is using a driver on Windows that doesn't do resolution detection, are you using windows? We could change it so that we force a specific driver per platform but then it becomes a bit of a nightmare to package. Will have to have a think.

[Sasquatch]

Yes I'm running it under windows.
If I only change resolution to anything above 640x480 in settings.java it crashes saying that correct resolutions are 174xsomething 320x240 and 640x480
Defining custom dimension as per sarxos manual and FAQ(look at my pull request) allows to select any resolution. I tried 4000x3000(max res of my sensor) but image quality suggested it was still 1280x720, makes sense.
Maybe defining custom resolutions and then autos election would work?

[devmonkey]

The trouble with asking for a custom large resolution is the camera encoder chip can choose to scale it for you if it is larger than the sensor. It seems there is no reasonable solution without forcing a windows specific driver which will actually query the camera for the supported resolutions. Will look into this when I have more time. Almost all cheap cameras makers lie about the resolution of their sensors as well so we can't rely on the user inputing whatever resolution is 'written on the box'.

I did look at your pull request, but I don't think it works generally for everyone as if you request a non-native resolution the camera chip can choose to scale it for you.

[Sasquatch]

Totally agree on my pull request, not suited for all(most?) cameras.
My understanding is that sarxos don't support higher resolution at all, unless you define them. At least that's what i understood from quick look at sarxos examples ad faq. I may be completely wrong.
My idea is to try defining "custom" resolutions and then running auto detect. I'll try it tomorrow afternoon, as now i left camera at workshop.
But before that I'll try your auto detection solution under Linux, Ubuntu and PureOs(both debian based).
As for now i can't even check benefits of higher resolution as my laser pointer is extremely noisy and line laser will twke 7-15 days to arrive, absolutely no pressure.