DIY Laser levelling using webcam and laser level

[devmonkey]

I suspect this is not the greatest limitation on the acuracy of your system. Making the concrete floor of your shed more rigid should be a higher priority.

You may think that Kit, however I believe the (presumably linear) interpolation on the sensor is messing with my non-linear intensity fitting algorithms. It makes no sense to resolve down to sub-pixel resolution when 75% of the sensor information is estimated (Nyquist would have a fit).

For example imagine the raw intensity at the peak of our gaussian laser line looks like this:
100, 100, 101, 101, 100, 100
Now if this falls under the bayer filter on a green+red filter line arranged as:
G, R, G, R, G, R, G

With only red laser light, nearest neighbour linear interpolation would look like this:
100, 100, 100, 101, 100, 100

If the bayer filter is offset 1 pixel the other way you would get
100, 100, 101, 100, 100, 100

Therefore you have 1 pixel (3um) uncertainty and this is for a green+red filter line. I think is worse for a green+blue filter line where all the information is interpolated, i.e the information rate is zero.

I have some ideas to detect and strip this out but it is guess work without a datasheet for the camera chip, or maybe just reduce the resolution of the system from 1 pixel to say 4 pixels (6um).

I have a few RPIs here with cameras which I can get the raw bayer data from and just use the red pixels (can't get the raw data from a webcam), might we worth an experiment but would need entirely new code.

An alternative would be to use an IR laser as the bayer filter is transparent to IR therefore the sensor will behave as monochrome at full resolution, but then you couldn't see the laser for rough alignment.

Monochrome usb cameras (that are made without the bayer filter) are expensive as there is no mass demand.