“For the sensor, we make a fine grid of dots that aren't touching each other or anything else. The finer they are, the better you can see.”

Now there is a black fuzz at the far end of the cylinder, barely perceptible as being in a hexagonal grid.

“Then you make the lens. Since you haven't learned to see with this eye yet, open up the side for now and watch how the light falls on the sensor, then reshape the lens until it's as good as you can make it.”

He tweaks the sunshade above their heads to have a pattern of holes in it, then demonstrates holding his simple eye up to the sunbeams and nudging the shape of the lens until there are nicely in-focus dots.