Outdoor Scene Reflectance Measurements Using a Bragg-Grating Based Hyperspectral Imager

The acquisition of spectral reflectance factor image data in outdoor environment is a challenging task, mostly due to non-static scene content and illumination. In this work, we propose a work-flow for this task using a commercial Bragg-grating based hyperspectral imager that can capture the visible and near-infrared part of the light spectrum. To our knowledge, we are the first to use this technology for outdoor reflectance imaging. The work-flow involves focus position and exposure time estimation, illumination scaling and image registration, among other procedures. Most of them generally apply to hyperspectral imaging, while some are specific to a Bragg-grating based hyperspectral imaging device when dealing with specific challenges in outdoor environment. We have conducted some experiments to evaluate the quality of the acquired image data and discussed some limitations of the technology for spectral imaging of outdoor scenes. Fourteen urban scene spectral images acquired using the proposed approach are already publicly available to the scientific community under a Creative Commons license.