We understand the concept [Jean] used to create a 3D scan of his face, but the particulars are a bit beyond our own experience. He is not using a dark room and laser line to capture slices which can be reassembled later. Nope, this approach uses pictures taken with several different focal lengths.
The idea is to process the photos using luminance. It looks at a pixel and it’s neighbors, subtracting the luminance and summing the absolute values to estimate how well that pixel is in focus. Apparently if you do this with the entire image, and a set of other images taken from the same vantage point with different focal lengths, you end up with a depth map of pixels.
What we find most interesting about this is the resulting pixels retain their original color values. So after removing the cruft you get a 3D scan that is still in full color.
If you want to learn more about laser-based 3D scanning check out this project.