DIY Laser levelling using webcam and laser level

[devmonkey]

I agree that you could use the output from the sensor to directly plot position.
Using a simple webcam with a 2mm sensor to centre a .008" piano wire or laser, the effective measurement range would be maybe 1mm. The active area of the sensor needs to be found in some way, unless the wire or beam is positioned within the active area all the time.

Hi John,

With a self levelling laser hitting a 2mm square target over the entire machine shouldn't be too hard assuming you have levelling feet on the machine, we all do this or better when we put up a shelf. This assumes we can weld the frame to within 2mm.

Should also be noted that it is only the vga (640x480) web cams that have this small sensor area I think these are 1/6" diagonal sensors, other similarly priced but higher resolution cams have larger sensor areas. For example the raspberry pi camera (1/4") has a 4.6mm diagonal and another sensor I have the OV2640 has 4.5mm. It seems that the sensors are classified by the diagonal size of the sensor of which the active area with the pixels is smaller, this is why 1/4" > 4.6mm.

I like the idea of levelling a jig then grinding the surface as an alternative to shimming. What sort of grinder would you use for this?

I can imagine a jig short jig say 500mm that clamps around a piece of box section that can be micro adjusted for twist and level. I we bolted aluminium to the top of the box section you could probably skim it with a hand router with a small fly cutter in it. Skim the section under the jig then move the jig along, re-align it with the laser/wire then repeat. When you finish one rail then move the assembly to the other without moving the reference laser to bring the other rail into plane. Maybe a wood power planer could be used for the skimming, would be scary though.

The jig itself needs to be planar as you say but this should be straight forward on a milling machine.

What are you thinking for differentiating twist from height variation? I think with the laser two image sensors stuck out each side could detect twist same when you tram a mill with two dial indicators on a T bar in the spindle.

Cheers, Joe