A Unifying First-Order Model for Light-Field Cameras: The Equivalent Camera Array

Abstract

Light-field photography is an extension of traditional photography that enables among other effects refocusing, viewpoint change, and aperture synthesis of still images by digital post-processing. It achieves this capability by recording 4-dimensional radiance information rather than 2-dimensional integrated sensor irradiance. Consequently, optical design tools need to change in order to design these new devices. In this article, we propose an optical first-order model that abstracts the architecture of any light-field camera as an Equivalent Camera Array (ECA). This model enables a comparison between different designs and allows for a simulation of the effects of parameter modifications to a design. We present equations for optical properties such as the depth of field, the angle of view, as well as important parameters for algorithmic performance such as the triangulation baseline. We provide an experimental validation of our model by measuring the properties of a real light-field camera. We are able to extract unknown physical parameters of the system such as the focal length of the main lens.

A Vignetting Model for Light Field Cameras With an Application to Light Field Microscopy

“…The previous discussion is on the pixel level, the overall effect is better visible when the system is interpreted as an equivalent camera array as introduced in [1]. In this section, we study the effects of vignetting on the properties of the ECA corresponding to the previously simulated mockup optical system.…”

“…The ECA model is a first-order optical model [1] that represents many different light field camera designs with an equivalent camera array in object space. The motivation behind the model is to set a common ground for a comparison of the optical properties of various light field camera architectures.…”

“…• as an application of the developed techniques, an evaluation of the effect on equivalent camera array [1] properties in a case study involving a custom-built light field microscope.…”

“…A variety of other optically implemented light field camera designs exist that, in principle, are subject to the vignetting effect discussed here since they also have a virtual camera description [1] that is affected by our analysis: External lens arrays placed before the camera achieve a large baseline [10], [11], [12], while mirror arrays are a good way to cover a large field of view [13], [14], [15], [16]. The number of virtual viewpoints in mirror systems can be augmented considerably by utilizing inter-reflections between mirrors [17], [18].…”

“…The equivalent camera array (ECA) model [1] has a similar approach but it decomposes the system into a more accurate set of elementary sampling structures (pairs of apertures) that are also imaged to the object space. In contrast to the SPC model, the ECA model reorganizes these structures into a higher level representation: a virtual camera array (in object space) and it derives the optical properties of these virtual cameras.…”