I got an itch to reproduce MIT Media Lab's Bokode, a really clever optical hack. Their system uses an LED, a diffuser, an image screen, and a pinhole lens. I don't have the components on hand to make something as small as an actual Bokode, but I do have enough camping and cooking gear to smush together a prototype.
My light source was a MAGLITE® LED 3-Cell D Flashlight. I poked some holes in aluminum foil with a mechanical pencil, but I'm not nearly dexterous enough to make an actual QR code. Between the light and the aluminum foil, I inserted a sheet of Kleenex to act as a diffuser. Finally, I reused the pinhole lens I made for a previous experiment as the lens.
I metered, focused at infinity, and took this picture: