DIY Laser levelling using webcam and laser level

[devmonkey]

Hi John,

It looks like you are using a very old version of the software, I would just download the ready to go latest version, this has the smoothing you need for actual measurements, plus a load of other enhancements, see my previous posts.

When used as a light sensor with a laser and no optics I have testing in pitch darkness and bright light and there is no variation at all, this is because the laser saturates the sensor.

When used as a camera, i.e. focused on an object such as a screen ambient light has to be completely eliminated both front and back of the sensor, you get some shine through the pcb even. I put mine in a black box.

When used as a shadow camera without optics and the shadow generator (wire in your case) very close to the sensor you should be able to just put a very intense light source behind the wire, this will saturate the sensor which is what you want, you will need some diffusion material to even out the light source as I mentioned before.

The software automatically scales the intensity plot, assuming you can generate enough contrast between the thing you are measuring and the background.

You should be able to get very repeatable measurements down to 3um, when using as a shadow camera make sure you tick the invert box in the prefs.

Keep at it!

Joe

[John McNamara]

Hi Joe

I am using the latest software

3um = 0.00011811" (Inches)

I am going to repeat the test tonight, better light control.

Regards
John

[devmonkey]

The picture you attached to the previous post was not the latest version John, the latest version has a table of measurements taken and smoothing when taking a measurement, export to csv, etc. Maybe that photo you took was from some previous experiment?

3um = 0.00011811" (Inches) --> CORRECT

FYI, this is what the latest version looks like:

[John McNamara]

Hi Joe

I ran the tests again this time using a small LED torch as a bright light source.
This gives a very sharp high contrast graph.

Strangely the scaling changed to 119.9 pixel lines with the new light source. I repeated the test a couple of times. the results were the same.

I did not change the gap between the wire and the sensor. it must be caused by the change in light source.

I used the software measure table and recorded every step between zero using 0.05mm steps see image below.

The setup I am using moves the sensor not the wire, Important for a point light source to avoid the shadow elongating like the sun in late afternoon.

This is easy to prove moving the torch by the slightest amount changes the measurement.
I really want to find an evenly dispersed light source.

I have yet to try your smoothing settings, That will be interesting.

Edit just noticed the software has changed a bit more. I will update


Regards
John

[John McNamara]

Hi Joe
Hi All

I downloaded the next version that displays a graph of the measured points. And look how nice and linear the graph is! .05mm measurement steps on the dial indicator.



I ran it 3 times to check.

While testing I moved the light a tiny bit. I had to start again, The light source will have to be rigidly mounted on the platform or you will get errors.

Will the current software work with higher resolution cameras say 1080P? I realize there would be more number crunching for he processor.

Regards
John

[driftspin]

Hey guys,

I have been following this thread with great interest. Really great work.

I really like they way the camera + software is used for this purpose. It smells like a commercial oppertunity in my opinion.

Anyway, Since i bought a new house i am about to move my cnc machine in about a month or two.

I think i could use a laser level device for some of the needed remodelling work so that one could pass investment committee.

I would like to use this technique for a check on my machine after transport.

Actually.. it would be the first time and method i could set up for a half decent check on my machine.



So i would like to buy a new laser device with this in mind.

I only have an 8 mm umbilical type usb HD cam atm. So a really small chip.. i guess not usable for this pupose.

Maybe it could be with the indirect method putting the camera behind the screen.
Is that idea abandoned?

Are you guys using 640x480 on purpose?
Do low res low cost chips have the wanted size / resolution / pixels per mm.
So no need/advantage for throwing a few extra pecunia?

So does a laser level loc in position after setup?

Or do you have to trust the deviation is constant / repeatable.

Greetings Bert


Verstuurd vanaf mijn SM-A320FL met Tapatalk

[devmonkey]

Hi John, Yes with your shadow camera setup you will always have to move the light source with the sensor board, they really need to be bolted together with a gap for the wire. I have used translucent white perspex for led light diffusion before, works really well, you can buy it on amazon.

[devmonkey]

Hey guys,

I have been following this thread with great interest. Really great work.

I really like they way the camera + software is used for this purpose. It smells like a commercial oppertunity in my opinion.

Anyway, Since i bought a new house i am about to move my cnc machine in about a month or two.

I think i could use a laser level device for some of the needed remodelling work so that one could pass investment committee.

I would like to use this technique for a check on my machine after transport.

Actually.. it would be the first time and method i could set up for a half decent check on my machine.



So i would like to buy a new laser device with this in mind.

I only have an 8 mm umbilical type usb HD cam atm. So a really small chip.. i guess not usable for this pupose.

Maybe it could be with the indirect method putting the camera behind the screen.
Is that idea abandoned?

Are you guys using 640x480 on purpose?
Do low res low cost chips have the wanted size / resolution / pixels per mm.
So no need/advantage for throwing a few extra pecunia?

So does a laser level loc in position after setup?

Or do you have to trust the deviation is constant / repeatable.

Greetings Bert


Verstuurd vanaf mijn SM-A320FL met Tapatalk

Hi Bert,

The sensor in your cam is probably fine, although if the overall dimension of the camera is only 8mm it maybe harder to work with. The VGA sensors we are using are 2mm across.

It seems most of the cheap cameras are vga even though they are sold as HD. It is difficult to determine what the actual resolution of the sensors are without a part number, some are probably higher resolution sensor that are binned to get VGA output. We want a reasonable frame rate for averaging so given the bandwidth constraints of USB2 which most of the cameras talk, VGA can be give us 30FPS.

If you take a 2mm sensor with 640 columns of pixels you get 3um per row which is plenty small enough for what we are doing.

My laser doesn't lock in position, but once allowed to stabalise it doesn't move unless knocked. I only need the laser to not move for one measurement run, as I'm not trying to align to the laser rather to get the errors between the laser and whatever i'm measuring to lie in a straight line. From my initial experiments the laser doesn't move at all over say a 10min session. The Dewalt laser I'm using is damped with a magnet, this probably helps. The laser doesn't even need to be self leveling, this just helps getting it setup.

So the process would be switch on the laser (this moves it a bit), wait for a few seconds for it to stabalise, take N measurements along a rail, switch the laser off, shim the rail, repeat. It doesn't matter if the laser moves between runs.

Cheers, Joe

[driftspin]

Hi Joe,

Do you still use it like this?
Or do you also point the laser directly to the sensor now?

Oh btw this is my camera:

https://s.click.aliexpress.com/e/EWnU1gjA

1280x768 i guess.

Hope to put it in the dustshoe later.



Grtz Bert.



Verstuurd vanaf mijn SM-A320FL met Tapatalk

[devmonkey]

Hi Joe
Hi All

I downloaded the next version that displays a graph of the measured points. And look how nice and linear the graph is! .05mm measurement steps on the dial indicator.



I ran it 3 times to check.

While testing I moved the light a tiny bit. I had to start again, The light source will have to be rigidly mounted on the platform or you will get errors.

Will the current software work with higher resolution cameras say 1080P? I realize there would be more number crunching for he processor.

Regards
John

Great result, would be interested to see what it looks like in 0.01mm steps. What does the residual chart look like? I can see your residuals are all less than one pixel which means your step size was very consistent. Also if you put in a scaling factor in the umPerPixel preference you will get your results in um, or tenths or whatever. I need to make these preference persist between runs.

At the moment the software asks the cam for a vga image, so it doesn't matter what the cam resolution is, I can make this more configurable.