Generalized Image Acquisition and Analysis

An evaluation of optical flow algorithms for background oriented schlieren imaging

The background oriented schlieren method (BOS) allows for accurate flow measurements with a simple experimental configuration. To estimate per-pixel displacement vectors between two images, BOS systems traditionally borrow window-based algorithms from particle image velocimetry. In this paper, we evaluate the performance of more recent optical flow methods in BOS settings. We also analyze the impact of different background patterns, suggesting the use of a pattern with detail at many scales. Experiments with both synthetic and real datasets show that the performance of BOS systems can be significantly improved through a combination of optical flow algorithms and multiscale background.


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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