Early cameras and modern cameras work pretty much the same way. A lens (or a pinhole acting as a lens) focuses an image onto a sensor. Of course, sensor, in this case, is a broad term and could include a piece of film that–after all–does sense light via a chemical reaction. Sure, lenses and sensors get better or, at least, different, but the basic design has remained the same since the Chinese built the camera obscura around 400BC (and the Greeks not long after that).
Of course, the lens/sensor arrangement works well, but it does limit how thin you can make a camera. Cell phone cameras are pretty skinny, but there are applications where even they are too thick. That’s why researchers at Rice University are working on a new concept design for a flat camera that uses no lens. You can see a video about the new type of camera below.
The idea is simple: take a conventional sensor and place a mask over it that has a grid-like arrangement of apertures. The resulting image doesn’t match what you would see, but it provides enough information that a computer can reconstruct the picture.