DIY Laser levelling using webcam and laser level

It could be aliasing from reflections on the lens holder thread, I got much better results with the sensor mounted with nothing close to it in the near field. See picture below, that window started off as a 6mm round hole, it caused aliasing hence I opened it up so no reflected laser light could hit the sensor.
Attachment 26688
I don't know much about dslrs but maybe it could have lens distortion correction built in which would be warping the image non-linearly across the sensor. Have you got a cheap web cam to try with? It is also unlikely that sensor pcb is hard fixed to the body, the ones i've take apart are usually on soft mounts that let the board move around to absorb shocks.

It's cheap Sj4000 clone distortion is massive, if there is correction it does very bad job. I have cheap webcam and 0.08mm steel wire on order. Will try both laser and wire to rule out sensor nonlinearity errors.

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Originally Posted by Sasquatch

It's cheap Sj4000 clone distortion is massive, if there is correction it does very bad job. I have cheap webcam and 0.08mm steel wire on order. Will try both laser and wire to rule out sensor nonlinearity errors.

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One other thing that occurred to me, how did you ensure you moved the sensor/vice assembly absolutely in a straight line? Any deviation in this procedure would show up as non-linear errors in your linearity measure since it would have been impossible to get the laser perfectly planar with the granite. This applies to both types of laser dot and line. I think you need a precision straight edge as well as the reference surface to check the accuracy of the system.

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Originally Posted by devmonkey

One other thing that occurred to me, how did you ensure you moved the sensor/vice assembly absolutely in a straight line? Any deviation in this procedure would show up as non-linear errors in your linearity measure since it would have been impossible to get the laser perfectly planar with the granite. This applies to both types of laser dot and line. I think you need a precision straight edge as well as the reference surface to check the accuracy of the system.

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I used straight edge clamped to the granite, just as you said.

Cheap webcam arrived, useless with lasers, sensor is smaller than the beam, will test it with wire when it gets here.

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Originally Posted by Sasquatch

I used straight edge clamped to the granite, just as you said.

Cheap webcam arrived, useless with lasers, sensor is smaller than the beam, will test it with wire when it gets here.

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Sounds like your laser is no good, can you post a picture of it? Even my dewalt laser level produces a line narrower than the VGA sensor.

Greetings from NorthWest England

I was alerted to this very interesting project by John McNamara [many thanks, John] and have joined the forum to participate in this discussion. ... Hopefully I can be of some help on the optical side of things, but this first post concerns the software:

I have tried running the current version on my 2009 MacBook Pro, under el Capitan, and everything seemed fine except that I could not close the application ... it did not even respond to ‘Force Quit’ and I was obliged to re-boot the machine.

Windows users have a .bat file; so I am wondering if some ‘initialisation’ might be required before Java is happy running the application under OS X

I would be most grateful if anyone can advise.

MichaelG.

Hi Michael,

Welcome! I haven't tried it under OSX, but I'm pretty sure someone in this thread did.

It might well be a driver issue with it not unloading properly, unfortunately I don't have a mac book pro old enough to replicate your system.

Joe

Thanks for the prompt reply, Joe

Hopefully there is someone else out there, limping along with a much-loved but obsolete Mac !

MichaelG.

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Edit: I’ve just tried a little ‘self-help’ and found this:
https://apple.stackexchange.com/ques...vents-shutdown

Unfortunately it is beyond my comprehension.

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Originally Posted by Michael Gilligan

Edit: I’ve just tried a little ‘self-help’ and found this:
https://apple.stackexchange.com/ques...vents-shutdown
Unfortunately it is beyond my comprehension.

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As far as I can see, that's just talking about the issue and other ways to force quit the application.

I'd try uninstalling and reinstalling java on your Mac.

Failing that, you could try running Linux in a virtual machine, and download Java onto that. I'm a fan of Oracle's Virtualbox.

Thanks, Andy

I will try a clean install of Java this evening
... There have been several versions on my Mac over the years, so perhaps there is something unnecessary lurking.

MichaelG.

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Edit:
I removed all trace of Java from the machine [following Oracle's instructions], and installed afresh:
____ You have the recommended Java installed (Version 8 Update 231) ____

For whatever reason: The application now closes as it should. ... Thanks again, Andy