Abstract
The light field camera provides a robust way to capture both spatial and angular information within a single shot. One of its important applications is in 3D depth sensing, which can extract depth information from the acquired scene. However, conventional light field cameras suffer from shallow depth of field (DoF). Here, a vari-focal light field camera (VF-LFC) with an extended DoF is newly proposed for mid-range 3D depth sensing applications. As a main lens of the system, a vari-focal lens with four different focal lengths is adopted to extend the DoF up to ~15 m. The focal length of the micro-lens array (MLA) is optimized by considering the DoF both in the image plane and in the object plane for each focal length. By dividing measurement regions with each focal length, depth estimation with high reliability is available within the entire DoF. The proposed VF-LFC is evaluated by the disparity data extracted from images with different distances. Moreover, the depth measurement in an outdoor environment demonstrates that our VF-LFC could be applied in various fields such as delivery robots, autonomous vehicles, and remote sensing drones.
Highlights
The initial light field cameras were proposed with two different approaches: placing a pinhole grating inside the camera; placing a micro-lens in front of the image plane [5,6]
micro-lens array (MLA) focal length of 965 μm and the MLA center of depth of field (DoF) distance 4.5 mm, the distance b from the MLA to the image sensor was set to 1.235 mm through the thin lens equation in Equation (1)
A focused light field image was acquired by the focal length 20 mm, whereas in the case of focal length 75 mm, the micro-image itself, which lowers accuracy during image processing, is too large and blur occurs
Summary
A light field camera provides a facile way to capture 3D information (light field or plenoptic function) of an object with only a single image sensor and micro-lens array without any external light source, so it has attracted considerable interest in both academia and industry. The initial light field cameras were proposed with two different approaches: placing a pinhole grating inside the camera; placing a micro-lens in front of the image plane [5,6]. Based on these concepts, Ng introduced the first hand-held plenoptic camera called the standard light field camera (plenoptic 1.0) in 2005 [7], and a focused light field camera (plenoptic 2.0) was proposed by Lumsdaine and Georgiev in
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