Heard of those plenoptic cameras? It may seem to be very rare and actually it has the mini-lenslet array built in between the CCD and the focusing lenses in the camera. The Lytro camera, after taken a picture, you can adjust the focus or what you want to focus on the saved picture. Here's the research paper: Lytro Inc. Plenoptic Camera Research There are a lot of maths here, so you can skip these and read the conclusions instead. here's the preview of the camera:
The tech behind it is definitely very interesting (and actually not new), but at the current state I consider it too be still in a very early infancy stage and not practical for real world use. The file format is proprietary, and the final output resolution is too small for it to be anything other than a fancy toy to play around with. Until they can improve the final output resolution and be more open with the file format, it'll just be an expensive toy for now.
Yeah, it's very experimental stage. The "fly-eye lens" or lenslet array, is very expensive, and the resolution is extremely limited. I had dealt with a bit of a lenslet array simulation during my postgraduate work - the algorithm to reconstruct the image from the array can be complicated! So, the one in the mentioned camera is even a few more times complicated than my work itself. (the camera has to reconstruct a thousand of mini-images and reprocess them!) The same kind of lens is also used in measuring aberrations on the cornea or lens of the human eye, but the reconstruction algorithm is another different thing.
You can actually check out examples of the photos taken with the Lytro at https://pictures.lytro.com/ Incidentally, the founder of Lytro, Ren Ng, was a Malaysian who migrated to Australia when he was very young...