Analysis of Birefringent Materials to Create Static Polarized Color Patterns for Visible Light Indoor Positioning
N.T. Bhagat (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Marco Zuñiga Zamalloa – Mentor (TU Delft - Embedded Systems)
M.A. Chavez Tapia – Mentor (TU Delft - Embedded Systems)
Andy Zaidman – Graduation committee member (TU Delft - Software Engineering)
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Abstract
Visible Light Positioning (VLP) is an emerging field of research with several possible application. While most state-of-the-art VLP systems work with active modulation of light (switching lights on/off rapidly), this poses issues such as the flickering problem and excessive power consumption. In contrast, passive modulation of light (twisting/bending of light), with the properties of polarizers and birefringent materials, allows cost-effective modulation. This paper analyzes two birefringent materials - plastic (cling-wrap) and transparent adhesive tape - to test them for their usability in a visible light positioning system, in particular, the visibility range, hue-orientation mapping, and ambient light interference. These materials allow to create color patterns visible only to a camera. The patterns can encode data about identifiers of light anchors, while the color detected can be used to find the orientation of the receiver. It was observed that transparent adhesive tape gave much more reliable results, with a step-pattern-like hue-orientation mapping, and low errors ($\pm$ 5) on the hue value detected in the range of 30-250 cm from the light anchor, making it ideal for VLP.