DIY Laser levelling using webcam and laser level

[AndyUK]

To give you some background, I'm a physicist, and at work I use similar lasers on each wall of the room (ceiling, left wall, right wall, and back wall), all pointing to a single point in space at the middle of the room - part of the job is to ensure these lasers are accurate and are planar with one another.

Assuming the laser is meant to self level. I'd mount it at one end of my garage, with the CNC at the other end. I'd then get a long transparent flexible pipe, and mount one end infront of the laser. I'd then take the other end of the pipe to the other end of the garage past the machine.

Then, fill water into the pipe up to the level of the laser; the meniscus will be at the same height in the room on both ends; the laser should pass through both meniscuses. The deviation (or depth of the meniscus as an error measurement) and distance between the two points will tell you how accurate the laser is self levelling. By moving left to right this will show any 'twist' in the horizontal projection of the laser.

The 'straightness' of the laser isn't an issue - light travels in straight lines unless you're bending it with something in the middle ;) The laser will defocus with distance, but as you're looking at the centre of the profile I don't think its a problem.