Linear Volumetric Focus for Light Field Cameras

Abstract

We demonstrate that the redundant information in light field imagery allows volumetric focus, an improvement of signal quality that maintains focus over a controllable range of depths. To do this, we derive the frequencydomain region of support of the light field, finding it to be the 4D hyperfan at the intersection of a dual fan and a hypercone, and design a filter with correspondingly shaped passband. Drawing examples from the Stanford Light Field Archive and images captured using a commercially available lenslet-based plenoptic camera, we demonstrate that the hyperfan outperforms competing methods including planar focus, fan-shaped antialiasing, and nonlinear image and video denoising techniques. We show the hyperfan preserves depth of field, making it a single-step all-in-focus denoising filter suitable for general-purpose light field rendering. We include results for different noise types and levels, through murky water and particulate matter, in real-world scenarios, and evaluated using a variety of metrics. We show that the hyperfan's performance scales with aperture count, and demonstrate the inclusion of aliased components for high-quality rendering.

LiFF: Light Field Features in Scale and Depth

“…We augment this with depth selectivity using a frequency-planar filter H λ . The frequency-planar filter selects for a specific depth in the LF, and can be constructed in a number of ways in the frequency or spatial domains [7], [30]. For this work we consider the direct spatial-domain implementation…”

Deep-learning-based macro-pixel synthesis and lossless coding of light field images

“…The goal of the proposed MP synthesis method is to provide valuable prior information for the proposed MP prediction method used by the MP-wise lossless image codec. The raw LF images are preprocessed by the MATLAB Toolbox [24] to obtain a 5-dimensional data structure denoted by LF(x, y, k, , c), where (x, y) selects a specific light ray propagation angle stored by a MP in an N × N array, (k, ) corresponds to the location of a specific MP in the camera macrolens array of size N mr × N mc , and c is the primary color, c = 1, 2, . .…”

Light Field Blind Motion Deblurring

“…The term γ(z) = (|z|dz/dt) −1 accounts for the 1/|z| factor and change of variables. Intuitively, the motion-blurred light-field spectrum is a double wedge [6,9,11], bounded by slopes z min and z max and containing an infinite number of lines in the frequencydomain. The magnitudes along each line are the same, determined by the original texture W (Ω u ), but every value is uniformly scaled by a factor γ(z), based on the amount of time the camera lingered at that depth (other than W (0), which is constant for all lines).…”