Measuring the flatness of a surface with a laser and a webcam to microns over large surfaces.

Because of how image sensor technology has progressed, we can use that as the basis of a highly accurate measurement device. This tool works by reading the laser sensor’s intensity values on a webcam with its camera lens taken off. An image sensor off a typical $15 webcam is about 3mm wide and has a resolution of FHD (1920x1080). This means that each light sensor is in the range of 1-5 microns in size.
The camera sensor is mounted at 90 degree angle so the wide direction is vertical. This gives a high coverage to sense the beam and also reduces power source based noise like PWM noise in switching power supplies.
The laser beam can be a point or a preferred horizontal line (like in a self leveling laser that I am using). We take the mean of each row (ex 1080 pixels wide) reshaping the 2D image into a 1D array. We then take this 1D array and fit a gaussian curve to it to find the center point. Finally converting the pixel position into physical height from calculations based on the physical size of the sensor to its resolution.
Further improvements reaching sub-pixel noise can be done by multisampling the results, smoothing out the luminosity noise in the 1D array, and removal of outliers by percentage.

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Adjusted sample location is done with linear regression and the deviation is the error from the fitted line.

Links:
3d printed Optical Kinematic Mount: https://www.printables.com/model/9515...

Software sources files here:
https://github.com/bhowiebkr/laser-le...

Released binaries of the tool here:
https://github.com/bhowiebkr/laser-le...

PrintNC Discord where the main thread of my experiments and development of the tool are (sign-up is free):
  / discord  

Original thread by the original creator of this workflow (highly recommended reading)
http://www.mycncuk.com/threads/12966-...

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