To record the light field inside the camera, digital light field photography uses a microlens array in front of the photosensor. Each microlens covers a small array of photosensor pixels. The microlens separates the light that strikes it into a tiny image on this array, forming a miniature picture of the incident lighting. This samples the light field inside the camera in a single photographic exposure. A microlens should be thought of as an output image pixel, and a photosensor pixel value should be thought of as one of the many light rays that
contribute to that output image pixel.
To process final photographs fromthe recorded light field, digital light field photography
uses ray-tracing techniques. The idea is to imagine a camera configured as desired, and trace the recorded light rays through its optics to its imaging plane. Summing the light rays in this imaginary image produces the desired photograph. This ray-tracing framework provides a general mechanism for handling the undesired non-convergence of rays that is central to the focus problem. What is required is imagining a camera in which the rays converge as desired in order to drive the final image computation.