Now this is thinking outside the box (or lens in this case). A Caltech engineer has developed a "microscope on a chip" that doesn't use any lenses. Instead, the liquid containing the cells or organisms of interest is run through microscopic fluid channels that pass over a sensor array chip like those in a digital camera. A thin metal layer blocks most of the pixels except for some tiny holes punched in the foil along the fluid channels. The size of these holes (not the pixel size of the detector array) determines the resolution, and the picture is "stitched together" digitally from the changing signals received by the sensors behind the holes. The device will take some time to commercialize, but if the $10 price is realized, optofluidic microscopy (OFM) could allow for small, hand-held, and inexpensive blood analysis devices and probably many other applications.
I've read of some other examples of this sort of radical rethinking of what it means to record an image (can't find a reference at the moment). We've been working from a "fairly large lens and film-like detector that records the whole image all at once" model even in the digital camera age, but it seems there is more than one way to slice and dice light reflected from objects to form images when sensors and computers are cheap and easily configurable. Future cameras and other optical devices may not look anything like a camera does now.
This page has a diagram of the device and some sample images from a prototype. Photo credit: Changhuei Yang, Caltech.