DIY Laser levelling using webcam and laser level

[devmonkey]

Anyone who used to work down a mine will probably remember Belzona, it was a common and came in a sausage shape plastic packet about 12" long with hardener down the side. You cut it down the middle and mixed it straight away, you had about 10mins before it set like concrete. When I was a young mechanic just about every miner's car in yorkshire had some in the sills or chassis used as filler..Lol

It's come along way since then and the current Belzona is amazing stuff, esp the ceramics. I accidentally used some by mistake and while it was only 3mm thick it hate quality jobber drills for breakfast.

Got a question about this Laser setup.? How wide a beam can it throw and still be accurate.? Could it, for instance, cover a 6mtr x 4mtr area.?

So the way to think about it is as a bunch of rays leaving the laser, each will travel in a straight line. If the optics are good then all these rays will also lie in a plane forming a line on whatever vertical surfaces they hit. I haven't tested the straightness at that distance only that it can be focused to a tight beam at around 10m.

One thing you could try with your large surface plate is setup the laser on the plate, take a bunch of readings in a 1m radius with the sensor sat on the plate, this will tell you whether the laser is planar and if not what the error is for each arc segment, i.e. you can calibrate the optics. Then you can project this error as far as you like to whatever you are actually measuring.

The biggest issue will be whatever you mount the laser on will have to be really solid as just 1 arc second of wobble on the mount will be 0.05mm at 10m. One solution to this is using differential measurement like they do with electronic precision levels, setup one or more fixed sensors and use these to offset any error caused by you breathing near the laser ;-)

This is the part of the system I'm really struggling with. With my laser mounted on that piece of box section with sticks out 400mm from the machine, reasonable finger pressure
is sufficient to bend the box section enough to cause a ~10um deflection in the height of the beam at the other end of the machine say 1.5m away.

When looking at this stuff where the sensor is measuring 3um pixels everything looks like it is made of jelly, at least everything in my garage including the 6 inch concrete slab.

What are you planning that is so large?