Visible Light Positioning With Lam\'e Curve LEDs: A Generic Approach for Camera Pose Estimation

TL;DR

This paper introduces a unified approach for camera pose estimation using Lamé curve-shaped LEDs in visible light positioning, improving accuracy and robustness across different LED shapes through a novel algorithm and experimental validation.

Contribution

The paper proposes LC-VLP, a generic VLP algorithm utilizing Lamé curve representations for LEDs, enabling effective indoor camera pose estimation across heterogeneous LED geometries.

Findings

Outperforms state-of-the-art methods in simulations with over 40% reduction in position error.

Achieves less than 4 cm average position accuracy in real experiments.

Provides a reliable, initialization-free pose estimation method.

Abstract

Camera-based visible light positioning (VLP) is a promising technique for accurate and low-cost indoor camera pose estimation (CPE). To reduce the number of required light-emitting diodes (LEDs), advanced methods commonly exploit LED shape features for positioning. Although interesting, they are typically restricted to a single LED geometry, leading to failure in heterogeneous LED-shape scenarios. To address this challenge, this paper investigates Lam\'e curves as a unified representation of common LED shapes and proposes a generic VLP algorithm using Lam\'e curve-shaped LEDs, termed LC-VLP. In the considered system, multiple ceiling-mounted Lam\'e curve-shaped LEDs periodically broadcast their curve parameters via visible light communication, which are captured by a camera-equipped receiver. Based on the received LED images and curve parameters, the receiver can estimate the camera pose using LC-VLP. Specifically, an LED database is constructed offline to store the curve parameters, while online positioning is formulated as a nonlinear least-squares problem and solved iteratively. To provide a reliable initialization, a correspondence-free perspective-n-points (FreePnP) algorithm is further developed, enabling approximate CPE without any pre-calibrated reference points. The performance of LC-VLP is verified by both simulations and experiments. Simulations show that LC-VLP outperforms state-of-the-art methods in both circular- and rectangular-LED scenarios, achieving reductions of over 40% in position error and 25% in rotation error. Experiments further show that LC-VLP can achieve an average position accuracy of less than 4 cm.