Variable Aperture Light Field Photography: Overcoming the Diffraction-limited Spatio-angular Resolution Tradeoff | CVPR 2016

Julie Chang, Isaac Kauvar, Xuemei Hu, Gordon Wetzstein

A method to measure light fields with high diffraction-limited resolution using Wigner-based point spread functions and computed tomographic reconstruction.

ABSTRACT

Light fields have many applications in machine vision, consumer photography, robotics, and microscopy. However, the prevalent resolution limits of existing light field imaging systems hinder widespread adoption. In this paper, we analyze fundamental resolution limits of light field cameras in the diffraction limit. We propose a sequen- tial, coded-aperture-style acquisition scheme that optimizes the resolution of a light field reconstructed from multiple photographs captured from different perspectives and f-number settings. We also show that the proposed acquisition scheme facilitates high dynamic range light field imaging and demonstrate a proof-of-concept prototype system. With this work, we hope to advance our understanding of the resolution limits of light field photography and develop practical computational imaging systems to overcome them.

FILES

dof_plot

Photographs captured with different f-number settings exhibit different depths of field and also diffraction-limited resolution for in-focus objects (top row). This effect is most pronounced for macro photography, such as illustrated for a 50 mm lens focused at 200 mm (bottom plot). Using multiple photographs captured from different perspectives and with different f-number settings, the proposed method seeks to recover a light field with the highest possible in-focus and out-of-focus information.

 

 

PSFTable_crop

Wigner point spread functions for an in and out of focus point for different aperture sizes and positions. The larger aperture has better spatial resolution in focus, but because of its decreased angular resolution, it has worse spatial resolution out of focus.

 

 

The experimental setup consisted of a macro camera, a movable, variable radius aperture, and a relay lens. The calibration plots demonstrate that change in PSF size with different aperture radii.

text_v2_reduced

Reconstructed light field displays high resolution in focus in addition to large depth of field.

Acknowledgements

We thank Marc Levoy for fruitful discussions. J. C. and I. K. were NSF Graduate Research Fellowship. X. H. was supported by the NSF of China, awards #61327902 and #61120106003. G.W. was supported by a Terman Faculty Fellowship. This project was supported by NSF awards #1539120 and #1553333, by the Intel Compressive Sensing Alliance, and by the NSF/Intel Partnership on Visual and Experiential Computing.