Highlighter range finding

After fiddling around with Roborealm, an open source machine vision software, I've made a simple range finder only with the help of vision. Granted that the visual feed is still and that it requires a reference frame that is also relatively stationary in the x-axis, I've setup an easy method to find the range of an object. Here, I've used a highlighter because it stands out from the surroundings and thus easy to track. As one can see from the video, I didn't have a scale of measurement and therefore used a regular A4 sized sheet (which I stole from the computing lab) to measure distances. The range_ratio is the unit of measurement (single A4 sheet) and a range_ratio of 1 corresponds to 297mm in length.

The range finding also involved calibrating the pixels in the visual feed into real world units of measurement and this required writing out a calibration graph.

Here are some pictures of the notes I took to supplement the above.

I ended up with a reasonably good approximation of the range with this formula:
Distance = 2 *Actual distance/# of Pixels

# of Pixels was computed as xdiff in the video

Please let me know if there are any questions.