DIY Laser levelling using webcam and laser level

[John McNamara]

Gee Joe.

So many minds around the planet working on a problem generously sharing their ideas.

I Ordered a PI 4 today and will start thinking on the software.

Regards
John

[devmonkey]

Gee Joe.

So many minds around the planet working on a problem generously sharing their ideas.

I Ordered a PI 4 today and will start thinking on the software.

Regards
John

See what I said above about it not working on a PI by default.

[Kitwn]

Hi Kit,

At the moment the app is only performing a gaussian fit in 2D, i.e. one spatial dimension say Z and intensity. I could probably add a 3D fit which would allow you to use a dot laser.

I wasn't thinking of measuring in two dimensions at once, just wondering if the software would cope with just a spot, treating it rather like a short line segment covering only part of the sensor. I would always expect to rotate the sensor to select between horizontal and vertical error measurements. Please don't do even more work just to suit my whims! This was more to do with removing the problems associated with the line-laser lenses. As you would only ever be working with the same central area of the laser line anyway if used as I was thinking, it probably makes no difference.

The camera I've ordered is this one, it looks suitably flimsy at the front and is even cheaper than yours!

[John McNamara]

Hi All

Today I tested the software using a 640 x 480 VGA webcam without a lens and #2 Roslau Music wire (0.0010" thick).

Digging around the workshop I resurrected an accurate XYZ jig table I lashed up with some star linear bearings and preloaded 8mm screws some time ago, this enabled me to precisely position the webcam now stripped from it plastic housing and mounted on in an aluminium bracket securely clamped on the XY stage of the jig. Measurements were taken with a Mitutoyo 0.01mm per division dial indicator.

The wire was positioned about .0015" above the face of the Camera sensor.
Calculated resolution achieved was 130 lines used to measure 0.05m = .003846mm per pixel line 0.000151") see Excel Image below.

This was repeatable I performed the test several times. however there are some issues measuring small values. It was difficult to measure .01 increments repeatably due to the software constantly recalculating very slightly different values. the source of this error needs to be tracked down. It may not be a software issue, I suspect It may be a combination of hardware and software issues.

From various tests I have observed changing light conditions cause the measured value to change in a very substantial way. I also observed this using the laser in earlier tests although to a lesser extent.

In the image below notice the paper tent covering the sensor this is essential to reduce the effect of stray light while providing somewhat even illumination of the sensor. It is not Ideal. I need to enclose the sensor in total darkness apart from an even illumination source behind the wire. I think this light source needs to be variable intensity to provide the correct grey scale balance for the software.

Once the correct lighting conditions are achieved I will run the tests again.

The tests today have proved that the Webcam software is already capable of very good repeatable accuracy. and that there is still plenty of room for improvement. Very exciting!

Regards
John

4 images below:

[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: