Non-Refractive Modulators for Encoding and Capturing Scene Appearance and Depth
| Citation: | * Veeraraghavan, A.; Agrawal, A.; Raskar, R; Mohan, A.; Tumblin, J., "Non-Refractive Modulators for Encoding and Capturing Scene Appearance and Depth", IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR), June 2008 (IEEE Xplore) |
| MERL Report: | TR2008-028 |
(a) CapturedModulated Image (b) Refocussed Image-Focus in Front (c) Refocussed Image-Focus on the back end (d) Raw Depth labels quantized to 10 depth levels. (e) All in focus image.Supplemental material have additional results including refocussing videos and matlab code.
We analyze the modulation of a light field via non-refracting attenuators. In the most general case, any desired modulation can be achieved with attenuators having four degrees of freedom in ray-space. We motivate the discussion with a universal 4D ray modulator (ray-filter) which can attenuate the intensity of each ray independently. We describe operating of such a fantasy ray-filter in the context of altering the 4D light field incident on a 2D camera sensor.
Ray-filters are difficult to realize in practice but we can achieve reversible encoding for light field capture using patterned attenuating mask. Two mask-based designs are analyzed in this framework. The first design closely mimics the angle-dependent ray-sorting possible with the ray filter. The second design [17] exploits frequency-domain modulation to achieve a more efficient encoding. We extend these designs for optimal sampling of light field by matching the modulation function to the specific shape of the band-limit frequency transform of light field. We also show how a hand-held version of an attenuator based light field camera can be built using a medium-format digital camera and an inexpensive mask.
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