Generalized Image Acquisition and Analysis

Acquisition and Analysis of Bispectral Bidirectional Reflectance and Reradiation Distribution Functions

In fluorescent materials, light from a certain band of incident wavelengths is reradiated at longer wavelengths, i.e., with a reduced per-photon energy. While fluorescent materials are common in everyday life, they have received little attention in computer graphics. Especially, no bidirectional reradiation measurements of fluorescent materials have been available so far. In this paper, we extend the well-known concept of the bidirectional reflectance distribution function (BRDF) to account for energy transfer between wavelengths, resulting in a Bispectral Bidirectional Reflectance and Reradiation Distribution Function (bispectral BRRDF). Using a bidirectional and bispectral measurement setup, we acquire reflectance and reradiation data of a variety of fluorescent materials, including vehicle paints, paper and fabric, and compare their renderings with RGB, RGB×RGB, and spectral BRDFs. Our acquisition is guided by a principal component analysis on complete bispectral data taken under a sparse set of angles. We show that in order to faithfully reproduce the full bispectral information for all other angles, only a very small number of wavelength pairs needs to be measured at a high angular resolution.


Synchronization and Rolling Shutter Compensation for Consumer Video Camera Arrays

Derek Bradley, Bradley Atcheson, Ivo Ihrke, Wolfgang Heidrich
In: Proceedings of PROCAMS 2009 (2nd best paper).


Two major obstacles to the use of consumer camcorders in computer vision applications are the lack of synchronization hardware, and the use of a "rolling" shutter, which introduces a temporal shear in the video volume. We present two simple approaches for solving both the rolling shutter shear and the synchronization problem at the same time. The first approach is based on strobe illumination, while the second employs a subframe warp along optical flow vectors. In our experiments we have used the proposed methods to effectively remove temporal shear, and synchronize up to 16 consumer-grade camcorders in multiple geometric configurations.
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author = {Derek Bradley and Bradley Atcheson and Ivo Ihrke and Wolfgang Heidrich},
title = {Synchronization and Rolling Shutter Compensation for Consumer Video Camera Arrays},
journal = {International Workshop on Projector-Camera Systems (PROCAMS 2009)},
year = {2009},
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