DIY Laser levelling using webcam and laser level

[Kitwn]

Joe,
I think it would be well worth sharing the app. I know Johm McNamara shared a lot of very useful info regarding the use of electrical sensing of a wire during the earlier pages of this thread. I was inspired by his work to do my tramming with taut wires alignment a couple of weeks ago which proved very sucessful. But the simplicity and low cost of your solution (who hasn't got a laptop these days?) makes it accessible to everyone. I will have to think about how to make the most use of it AFTER I've spent the next couple of weeks tarting my house up to make it more saleable but I suspect another round of alignment could be on the cards in the future thanks to your efforts.

Fitting shims is cheap and easy. Working out WHERE to fit the shims is the trick!

Keep up the good work!

Kit

[John McNamara]

Hi Joe

You just made my day.

Gee using a microscope with your software is a huge step, 3 um = 0.00011811 about a ten thousandth of an inch imperial. accuracy.

Using wire or fishing line allows the measured line to be accurately positioned. By anchoring each end of the wire to the machine frame precisely you can place the linear rail exactly where you want it. A lot easier than pointing a laser from one end. It also allows you to easily place two rails parallel to each other, by simply measuring the space between the ends.

I would really like to try your new software. In fact I am quite excited.
While tweaking it You mentioned that you used black fishing line piano wire is bright and I guess would require a dark background instead of the light background you used to enhance the contrast of the line you used in your experiments.
Maybe the ability to invert the pixel colour in the contrast discrimination code would be a useful addition.

Wire or mono filament fishing line? I can think of a number of applications where the the measuring system will need to be left in place for days or weeks when say a large machine installation or While a DIY machine is being built, All plastics will keep creeping and possibly break. Music wire will retain its elasticity indefinitely if it is not loaded above its elastic limit. I use Roslau music wire with great success. Size 0 is .009 Inches in diameter. I never reuse it (From the coil it is perfectly straight you do not want any kinks) a small coil will last for years of hobby use.

There is another use for this system! A non contact plumb line sensing system or maybe even a pair of plumb lines!!
Two suspended plumb lines will always remain parallel and perfectly vertical in relation to each other (Ignoring the curvature of the earth that is only measurable at great distances.)

The two wires define the edges of a rectangular flat plane that in this case is measurable to .0001 inches using wire and your software. I am going to think some more on this....... I have an idea.

Regards
John

[devmonkey]

Hi John,

I've put up the first version of the wire app here:
https://github.com/betzuka/laserleve...uilds/wire.zip

Extract and run wire.bat, needs java installed as per the laser app. The wire needs to be crossing the rectangular field of view of the sensor in the short dimension, e.g. if your sensor is 640 wide by 480 tall wire should be crossing the sensor from top to bottom.

It doesn't care whether it is looking at a bright wire on a dark background or vice versa, just needs a decent contrast and the microscope focused so that the wire edges appear reasonably crisp. My fishing line is just black mono filament, super cheap kids stuff that I already had. The main reason for the different algo from the laser is that the objective is lit from the front rather than behind, so it isn't acting like a shadow camera, this means you get lots of reflection off of the surface of the wire which would misslead anything searching for a gaussian, or indeed searching for anything other than the wire edges.

Your idea of using it to check for planar surfaces is brilliant ! I could stand my machine on end, drop two plumb lines and measure the relative error between the two lines from each respective rail.

At some point I will integrate it into the laser app so all the other error plotting stuff works. Do you have a microscope to test it with? If not this is the one I'm using, it is also very handy for SMD soldering etc.
https://www.amazon.co.uk/Microscope-.../dp/B07BF86SRP

Cheers, Joe

[John McNamara]

Hi Joe

I do have an optical microscope, A cheap student version I used to align my lathe in 2011 using wire. The is a longish post here that discusses lathe alignment and wire, https://www.model-engineer.co.uk/for....asp?th=136771 In this case I lashed up a measuring stage that allowed me to position the wire centrally in a slot by eye using my bio computer then measure off the error using a micrometer. It worked! Page down the thread to see photos.

In particular note the simple wire positioning stages clamped to the lathe bed made from scrap steel, rock solid.

Using a USB webcam or microscope with your software is clearly a better solution. It eliminates a number of sources of error.

I don't have a working USB microscope I will order one! I cant wait to test the software.

In many ways two cameras will be even more useful, for XY measurement, Ideally using one computer, although old PC's are easy to source for nothing or next to nothing, if two instances of the software could interface to two USB ports on one computer it would be more convenient.

Regards
John

PS stretched wire plumb lines are used to this day by heavy machinery installers, for instance passenger lifts and giant boring mills to align the column. Normally the bob weight is suspended in a container of thick oil to damp out any tendency to sway like a pendulum.