From
www.photonics.com
--------------------------------------------------------------------------------
'Light Field Camera' Banishes Fuzzy Photos
STANFORD, Calif., Nov. 8 -- Computer scientists are bringing photographic technology into sharper focus.
Ren Ng, a Stanford University computer science graduate student in the lab of Pat Hanrahan, the Canon USA professor in the school of engineering, has developed a "light field camera" capable of producing photographs in which subjects at every depth appear finely tuned. Adapted from a conventional camera, the light field camera overcomes low-light and high-speed conditions that often plague photograph and foreshadows potential improvements to scientific microscopy, security surveillance, and sports and commercial photography.
"Currently, cameras have to make decisions about the focus before taking the exposure, which engineering-wise can be very difficult," said Ng. "With the light field camera, you can take one exposure, capture a lot more information about the light and make focusing decisions after you've already taken the shot. It is more flexible."
The light field camera, sometimes referred to as a "plenoptic camera," looks
and operates exactly like an ordinary handheld digital camera. The difference lies inside. In a conventional camera, rays of light are corralled through the camera's main lens and converge on the film or digital photosensor directly behind it. Each point on the resulting 2-D photo is the sum of all the light rays striking that location.
The light field camera adds an additional element -- a microlens array -- inserted between the main lens and the photosensor. Resembling the multifaceted compound eye of an insect, the microlens array is a square panel composed of nearly 90,000 miniature lenses. Each lenslet separates back out the converged light rays received from the main lens before they hit the photosensor and changes the way the light information is digitally recorded. Custom processing software manipulates this "expanded light field" and traces where each ray would have landed if the camera had been focused at many different depths. The final output is a synthetic image in which the subjects have been digitally refocused.
